Cereal Aphids and their Biological Control Agents in Egypt

REVIEW ARTICLE

Cereal Aphids and their Biological Control Agents in Egypt

El-Heneidy, A. H. and D. Adly

Dept. Biological Control, Plant Protection Research Institute, Agriculture Research Center, Giza, Egypt (Received: November 22, 2012and Accepted: December 15, 2012)

Gramineae (grass family) is one of the largest plant families. All cereal species belong to this family. Cereal species include pests or weeds and also economic plants (wheat, barley, corn, sorghum, oat and ray).

The weeds that belong to family Gramineae harbored the highest number of aphid species among the weed families (Megahed, 2000). Aphids are one of the insect groups whose economic importance increases with the development of agriculture (Stary, 1976). All species of aphids nearly reproduce parthenogenetically (Dixon, 1998). Aphids damage the plants roughly through; loss of sap by sucking, reaction of plant tissues stimulated by aphid’s saliva, excreting viscous honeydew on them sooty-molds usually develop and finally transmission of viral diseases to plants.

Cereal aphids are the serious pests attacking cereal crops, particularly wheat, barley and maize (El-Hariry, 1979 and El-Heneidy, 1994). Damages to wheat caused by aphids were estimated by up to 23%, particularly in Upper Egypt, where highest infestation mostly occurs (Tantawi, 1985). Some of the cereal aphids are efficient vectors of different strains (types) of Barley yellow dwarf virus (BYDV). The first reported of this virus in Egypt was in1962 by (Slykhuis, 1962) to be scattered in the delta area near Cairo. The wild plants, Bromus catharticus Vahl, Hordeum murinum, and Panicum sp. were found to be natural BYDV hosts (Elnagar et al., 1980); the virus was identified as economically important in some parts of Egypt (ICARDA, 1995).

Survey of Cereal Aphid Species on Main Cereal Crops and Weeds in Egypt

Aphid species belong to Order: Homoptera and Family: Aphididae). The survey (available literatures) revealed the record of 11 aphid species; Rhopalosiphum padi, Schizaphis graminum, Rhopalosiphum maidis, Sitobion (Macrosiphum) avenae, Diuraphis noxia, Metopolophium dirhodum, Anoecia corni, Geoica phaseoli, G. spatulata, Tetranruraaegyptiace and Rhopalosiphum rufiabdominalis as major cereal aphid species surveyed on cereal and weed plants in Egypt. Egypt, as a country, can be divided to four different agro-ecosystem regions; Delta (Lower Egypt) (Kafr El-Sheikh, Dakhalia, Behera, Gharbia, Menoufia, Sharkia and Qaluobia Governorates), Middle-Egypt (Giza, Fayoum and Beni-Suef Governorates), Upper- Egypt (Menia, Assuit, Sohag and New Valley Governorates) and Sinai (North Sinai Governorate).

1. Bird Cherry-Oat Aphid, Rhopalosiphum padi (Linnaeus, 1758)

The first record of R. padi in Egypt was on the cereal weed plants, Panicum colonum and Phalaris sp. (Hassan, 1958). It was recorded also on other different cereal weed plants in Giza Governorate (Middle Egypt) by many authors (Megahed et al., 1978, Elnagar et al., 1978, Amin, 1979, Abdel-Wahab, 1998 and El-Fatih, 2006) and in Zagazig Governorate (Delta) by Megahed, 2000 on the weed plants; Polypogon monspeliensis, Setaris spp. , Avena fatua, Cynodon dactylon, Punicum coloratum (first record) , Poa annua,Cyperus spp. (first record) , Anagllis arvensis (first record) , Coronopus squamatus (first record), Lolium perenne, Bromus catharticus, Ammi majus (first record) and Diplachne malabarica, in Kafer El- Sheikh (Delta) on the three weed plants; Phalaris paradoxa, Brassica nigra and Malva praviflora by Huda, 2006 and in North Sinai Governorate on beard grass and wild oats (Ahmed et al., 2007).

The first record of R. padi on wheat plants in Egypt was in Cairo (Habib and El-Kady, 1961). Then, it was recorded in different sites in Egypt by (Tantawi et al.,1986), Sharkia (El-Heneidy, 1994, Megahed, 2000, El-Heneidy and Abdel-Samad, 2001), Qaluobia (Al-Ansary, 1993, Hafez, 1994), Menofia and Garbia (Abd-El Wahed, 2003), Giza (Ibrahim, 1990 a, El-Fatih, 2000), Fayoum (El-Heneidy and Attia,1988/89), Beni-Suef El-Heneidy and Attia,1988/89, Mohamed, 1992, El-Heneidy, 1994, El-Lathy, 1999, El-Fatih, 2000, El-Heneidy and Abdel-Samad, 2001), Minia (Mohamed, 1992), Assiut (El-Heneidy, 1991, Mohamed, 1992, Slman, 1993 & 1997, Abdel-Rahman, 1997), Sohag (El-Heneidy, 1991, El-Heneidy, 1994, Mohamed, 1992, El-Heneidy and Abdel-Samad, 2001, AbdEl-Awal, 2005), New Valley (Mannaa, 2000), Sinia (Abd ElSalam, 1999) and North Sinai (Rafah and El-Arish) (Ahmed et al., 2007).

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R. padi was recorded also on barley plants in Giza ( El-Fatih, 2006), Fayoum (Tantawi et al.,1986), Middle Egypt (El-Hariry, 1979), Beni-Suef (Tantawi et al.,1986, Mohamed, 1992), Assiut (Mohamed, 1992), Sohag (Mohamed, 1992, Slman & Ahmed, 2005), Ismailia (Noaman et al., 1992), Marsa Mattrouh (El-Sayed et al., 1995), Sinai (Abd El-Salam, 1999) and North Sinai (Rafah and El-Arish) (Ahmed et al., 2007).

It was recorded also on maize plants in Qalubia Governorate (Yossef, 1990), Giza (El-Heneidy and Abbas, 1984), Darwish,1989), Sinai (Abd El-Salam, 1999) and North Sinai (Rafah and El-Arish) (Ahmed et al., 2007).

2 . Green Bug, Schizaphis graminum (Rondani, 1852)

The first record of S. graminum in Egypt was on cereal weed plants, (Willcocks, 1922). Afterwards, it was recorded on other cereal weeds in Giza (Megahed et al., 1978, Elnagar et al., 1978, Amin, 1979, Abdel- Wahab, 1998 and El-Fatih, 2006), in Zagazig by Mohamed,1984 and on the weed plants; Bromus catharticus and Lolium perenne by Megahed, 2000 and in Kafer El-Sheikh on the three weeds plants; P. paradoxa, B. nigra and M. praviflora by Huda, 2006.

S. graminum was recorded on wheat plants by El-Hariry, 1979, then in different sites in Egypt by (Tantawi et al.,1986) who reported this species as the most predominant in upper Egypt, in Sharkia (El- Heneidy, 1994, Megahed, 2000, El-Heneidy and Abdel-Samad, 2001), Qaluobia (Al-Ansary, 1993 and Hafez, 1994), Menofia and Garbia (Abd-El Wahed, 2003), Giza (El-Fatih, 2000), Fayoum(El-Heneidy and Attia,1988/89), Beni-Suef (El-Heneidy and Attia,1988/89, El-Heneidy, 1994, El-Fatih, 2000, El-Heneidy and Abdel-Samad, 2001), Assiut (El-Heneidy, 1991), Upper Egypt (Slman, 1997), Sohag (El-Heneidy, 1991, Mohamed, 1992, El-Heneidy, 1994, El-Heneidy and Abdel-Samad, 2001, AbdEl-Awal, 2005), New Valley (Mannaa, 2000) and North Sinai (Rafah, Elsheikh Zewaid, El-Arish and Ber El-Abed) (Ahmed et al., 2007).

It was also recorded on barley plants by Abd El-Salam, 1999 in Sinai, El-Sayed et al., 1995, El-Fatih, 2006 in Giza and North Sinai (Rafah, Elsheikh Zewaid, El-Arish and Ber El-Abed) (Ahmed et al., 2007).

3 . Corn Leaf Aphid, Rhopalosiphum maidis (Fitch, 1856)

The first record of R. maidis in Egypt was on the cereal weedplants, Andropogon halepensis (Willcocks, 1922). Afterwards, it was recorded on cereal weeds in Kharga and Dakhla Oases (Hassan, 1957), in Giza (Megahed et al., 1978, Elnagar et al., 1978, Amin, 1979, Abdel-Wahab, 1998 and 2004, and El-Fatih, 2006), Zagazig (Mohamed,1984, Abd Alla, 1985 and Megahed, 2000) on the weed plants; Panicum coloratum (first record) , Echinochloa colonum, Cynodon dactylon, Setaris spp. , Echinocloa crus - galli, Arundo donax, Avena fatua, Bromus catharticus.

R. maidis was recorded also on wheat plants at both of Kharga and Dakhla Oases (Hassan, 1957), in different sites in Egypt by (Tantawi et al.,1986), Sharkia (El-Heneidy, 1994, Megahed, 2000, El-Heneidy and Abdel-Samad, 2001), Menofia and Garbia (Abd-El Wahed, 2003), Giza (Ibrahim, 1990a and El-Fatih, 2000), Fayoum (El-Heneidy and Attia,1988/89),Beni-Suef (El-Heneidy and Attia,1988/89, Mohamed, 1992, El-Heneidy, 1994, Abd El-Salam, 1999 and El-Lathy, 1999, El-Fatih, 2000, El-Heneidy and Abdel-Samad, 2001), Assiut (El-Heneidy, 1991, Mohamed, 1992, Slman, 1993 and 1997 and Abdel-Rahman, 1997), Sohag (El-Heneidy, 1991,Mohamed, 1992, El-Heneidy, 1994, El-Heneidy and Abdel-Samad, 2001, AbdEl-Awal, 2005), New Valley (Mannaa, 2000) and North Sinai (Rafah, Elsheikh Zewaid and El-Arish) (Ahmed et al., 2007).

R. maidis was recorded also on barley plants in Middle Egypt (El-Hariry, 1979), Giza (El-Fatih, 2006) and Sohag (Slman and Ahmed, 2005), Sinai (Abd El-Salam,1999), North Sinai (Rafah, Elsheikh Zewaid and El-Arish) (Ahmed et al., 2007), Ismailia (Noaman et al., 1992), both of Nubaria, Borg El-Arab and Marsa Mattrouh (El-Sayed et al., 1995).

It was recorded also on maize plants (Willcocks, 1922 and Hall, 1926). Afterwards, it was recorded in Kharga and Dakhlia Oases (Hassan, 1957), (Tawfik et al., 1974a), Gharbiah (El-Khouly et al., 1994), Zagazig (Megahed, 2000), Qalubia (Yossef, 1990), Giza (El-Heneidy and Abbas,1984, Darwish,1989), Sohag (El-Gapaly,2007) and Sinai (Abd El-Salam, 1999).

4. English Grain Aphid Sitobion (Macrosiphum) avenae (Fabricius, 1775)

The first record of S. avenae in Egypt was recorded on barley plants by Willcocks, 1922. Afterwards, it was recorded by Hall, 1926, in Giza region by El-Hariry, 1979 and El-Fatih, 2006, in Sinai by Abd El-Salam, 1999 and North Sinai (Rafah, Elsheikh Zewaid, El-Arish and Ber El-Abed) (Ahmed et al., 2007).

S. avenae was recorded also on different cereal weed plants in Giza Governorate by many authors (Hall, 1926, Megahed et al., 1978, Elnagar et al., 1978, Amin, 1979, El-Heneidy, 1991 and El-Fatih, 2006) and in Zagazig, by Mohamed,1984 and Megahed, 2000 and in Kafer El-Sheikh on three weeds plants; P. paradoxa, B. nigra and M. praviflora by Huda, 2006.

The first record of S. avenae on wheat plants was in Cairo (Habib and El-Kady, 1961). Afterwards, it was recorded in different sites in Egypt by (Tantawi et al.,1986), Sharkia (El-Heneidy, 1994, Megahed, 2000, El-Heneidy and Abdel-Samad, 2001), Qalubia (Hafez, 1994), Menofia and Garbia (Abd-El Wahed, 2003), Giza (El-Fatih, 2000), Fayoum (El-Heneidy and Attia,1988/89), Beni-Suef (El-Heneidy and Attia,1988/89, Mohamed, 1992, El-Heneidy, 1994, Abd El-Salam, 1999 and El-Lathy, 1999, El-Fatih, 2000, El-Heneidy and Abdel-Samad, 2001), Assiut (Mohamed, 1992, Slman, 1993 & 1997, Abdel-Rahman, 1997), Sohag (Mohamed, 1992, El-Heneidy, 1994, El-Heneidy and Abdel-Samad, 2001, AbdEl-Awal, 2005), and North Sinai (Rafah, Elsheikh Zewaid, El-Arish and Ber El-Abed) (Ahmed et al., 2007).

It was also recorded on maize plants in Giza (El-Heneidy and Abbas, 1984), (Darwish, 1989) and Qalubia (Yossef, 1990).

5 . Russian Wheat Aphid, Diuraphis noxia (Mordvilko, 1914)

The first record of D. noxia in wheat fields in Egypt was done by (Attia and El-Kady, 1988). Afterwards, it was recorded by many authors on wheat and barley plants in Giza (El-Fatih, 2000 and 2006), Fayoum (El-Heneidy and Attia,1988/89), Beni-Suef El-Heneidy and Attia,1988/89, El-Lathy, 1999), Ismailia (Noaman et al., 1992), Sinai (Abd El-Salam, 1999), North Sinai (Rafah, Elsheikh Zewaid and El-Arish) (Ahmed et al., 2007). Also, it was recorded on the cereal weed plants; Avena fatua and Bromus catharticus by El-Fatih, 2006.

6 . Rose-grass / Rose-grain Aphid, Metopolophium dirhodum (Walker, 1849)

M. dirhodum was recorded first time in Egypt on wheat plants in Beni-Suef Governorate (El-Lathy, 1999), Giza and Beni-Suef (El-Fatih, 2000), and on barley and different cereal weed plants in Giza Governorate (El-Fatih, 2006).

7 . Dog Wood Aphid, Anoecia corni (Fabricius)

The first record of A. corni in Egypt was by Theobald, 1922 on the cereal weed species Cyperus longus. It was recorded also on different cereal weed plants in Giza (Elnagar et al. , 1978 and Amin, 1979) and on Avena fatua and Bromus catharticus in Zagaig by (Megahed, 2000). A. corni was recorded on wheat plants by Habib and El-Kady, 1961 in Cairo, El-Fatih, 2000 in Giza and Megahed, 2000 in Zagaig.

8 . Geoica phaseoli (Passerini)

This aphid species was recorded for the first time in Egypt by (Willcocks, 1922) and then by (Hall, 1926) on barley plants. It was recorded on weed plants Sedge and Portulaca sp. by Habib and E|l-Kady, 1961.

9 . Geoica spatulata Theobald

This aphid species was recorded for the first time in Egypt by Willcocks, 1922) and then by (Hall, 1926) in barley plant field.

10 . Root Aphid, Tetranrura aegyptiace (Theobald)

This aphid species was recorded for the first time in Egypt on weed plant Panicum sp. by Habib and El-Kady, 1961. Afterwards, it was recorded on different weed plants in Giza by (El-Fatih, 2000).It was also recorded on barley fields in Giza by El-Fatih (2000).

11 . Rice Root Aphid, Rhopalosiphum rufiabdominalis (Sasaki)

This aphid species was recorded for the first time in Egypt by (Theobald, 1915) on barley in Giza. It was also recorded on the weed plant Arundo sp. by Hall, 1926 and on Cynodon dactylon in Giza by Hassan, 1958.

Survey of Aphid Species Infest Cereal Weed Plants in Egypt

Available literatures revealed the record of 12 aphid species; Asiphonella dactylonii, Hyalapterus pruni, Melanaphis phyllostachia, Pemphigus napaeus, Saltusaphis scirpus, Schizaphis minuta, Schizaphis rotundiventris, Sipha (Rungsia) maydis, Smynthurodes betae, Tetraneura africana, Tetranruracynodontis and Tetranrurahirsuta as aphid species that infest only cereal weed plants in Egypt.

1. Asiphonella dactylonii Theobald

First record of A. Dactylonii in Egypt was on the cereal weed plant, Cynodon dactylon in Delta and Middle Egypt by (Hassan, 1958).

2. Mealy Plum Aphid, Hyalapterus pruni (Geoffroy, 1762)

H. pruni was recorded for the first time in Egypt by Willcocks, 1916 on twoweedplant species; Arundo donax and Phragmites comnunis and then it was recorded by Elnagar et al., 1978 and Amin, 1979 in Middle Egypt and by Megahed, 2000 on Phragmitis communis in Delta.

3. Melanaphis phyllostachia (Soliman)

This aphid species was recorded first time in Egypt by Habib and El-Kady, 1961 on two weed plant species; Phyllostachus mytis and Phragmites sp. in Middle Egypt and then it was recorded in Delta on Arundo donax by Megahed, 2000.

4. Pemphigus napaeus Buck

First record of the species in Egypt was on the weed plant, Cynodon dactylon in Middle Egypt by Hassan, 1958.

5. Saltusaphis scirpus Theobald, 1915

It was recorded on weed plant on Sedge "Scirpus sp."by Theobald, 1915 and then on Cyperus sp. It was caught on light trap in Middle Egypt by Habib and El-Kady, 1961. Afterwards, it was recorded on Cyperus sp. in Delta (Megahed, 2000) and in Middle Egypt on Cyperus rotundus, Cynodon dactylon and Echinochloa colonum by El-Fatih 2006.

6. Cyperus Aphid, Schizaphis minuta (Van der Goot, 1917)

The species was recorded for the first time in Egypt on weed plants by Habib and El-Kady, 1961 using a light trap. There wasn’t any record about it until it was observed after 39 years on Cyperus rotundus by El-Fatih, 2000 and 2006.

7 . Oil Pulm Aphid, Schizaphis rotundiventris Signoret, 1860

The species was recorded for the first time in Egypt by Theobald, 1922, as a new species under the name of Aphis acori on the weed plant Sedge, Cyperus longus. Then, it was recorded by Hall, 1926 under the name of Toxoptera acori. After approximately 78 years, it was observed in Middle Egypt on different cereal weed plants by Abdel-Wahab, 2004 and El-Fatih 2006 under the name of Schizaphis cyperi. Borner and Heinze (1957) stated that Schizaphis cyperi (Van der Goot) (Ainslie) is a junior synonym of S. rotundiventris Borner and Heinze list (Ainslie) after Van der Goot as the describer, evidently synonymized the two species.

8 . Sipha (Rungsia) maydis Passerini, 1860

First record of the species in Egypt was in Middle Egypt on Aegilops sp. (El-Hariry, 1991). Then, it was recorded on the cereal weed plants; Bromus catharticus Vahl and Sorghum virgatum (Hack.) Stapf.(El-Fatih 2000).

9 . Smynthurodes betae Westwood

This species was recorded on the weed plant, Cyperus rotundus in Middle Egypt by Hassan, 1958.

10 . Tetraneura africana Van der Goot, 1912

This aphid species was recorded for the first time in Egypt on the roots of the weed plant species Cynodon dactylon by Theobald, 1922. Afterwards, it was recorded in Delta and Middle Egypt (Hassan, 1958, Habib & El-Kady, 1961; Elnagar et al.1978and Amin, 1979).

11 . Tetranruracynodontis (Theobald)

It was recorded on the weed plant Cynodon dactylon in Delta and Middle Egypt by Willcocks, 1925, Hassan, 1958, Habib and El-Kady, 1961, Elnagar et al., 1978 and Amin, 1979.

12 . Tetranrurahirsuta (Baker)

It was recorded on the weed plants; Cynodon dactylon, Panicum colonum and Setaria viridis in Middle Egypt by Hassan, 1958 and on Echinocloa colonum in Delta by Megahed, 2000.

Description and Identification of Aphididae in Egypt

Habib and El-Kady (1961) constructed a key to the Egyptian Aphididae (80 species) with biometric data and drawing most of the species. This taxonomical study revealed a revolutionary change in the nomenclature of the Egyptian Aphididae (78 species given by Hall, 1926) and additional records were made by the authors.

Fathi and El Fatih (2009) used morphological characters to make a key to identify apterous viviparous of cereal aphids in Egypt. Helmi, (2011), surveyed, described and illustrated thirteen cereal aphid species represent five subfamilies from different cereal plants in different localities of Egypt. Dichotomous and pictorial keys for apterous viviparous females of these aphid species were included to assist the personnel charged with detection, identification and control of aphids associated with cereals in Egypt. Helmi et al. (2011) reported that classical morphological criteria for aphid species identification may be affected by environmental factors such as; climatic conditions and physiological status of the host plant. So, they used two modern molecular techniques; Random Amplified Polymorphic DNA (RAPD) and Inter Simple Sequence Repeats (ISSRs) to find diagnostic markers for fingerprinting eleven cereal aphid species, those collected from different cereal plants and from different localities in Egypt. Eight RAPD and five ISSRs primers were successfully produced 97 and 69 markers that could be used to differentiate the eleven different cereal aphid species (A. corni, T. africana, R. maidis, R. padi, S. graminum, S. rotundiventris, S. minuta,

S. avenae, M. dirhodum, H. pruni and S. scirpus). Also, these molecular techniques, with 23 diagnostic morphological characters, were used to find the phylogenetic relationship among the different collected species; that divided into two clusters with similarity matrix percentages of 73 and 82%. From these results, it could conclude that these techniques could be successfully used successively to fingerprint and identify these aphid species and differentiate among them.

Seasonal Abundance of Cereal Aphid Species On wheat

As reported in the literatures and in the previous survey, the most important and economic cereal aphid species in Egypt are; R. padi, S. graminum, R. maidis and S. avenae. Highest population of R. padi was recorded on the lower level of wheat plants, while the highest population of R. maidis and S. graminum was presented on the upper level of the wheat plants. Both D. noxia and S. avenae were in the upper and middle levels of the plants but in relatively low numbers. M. dirhodum was found infested both middle and lower levels of the plant (El-Fatih, 2000).

El-Hariry, (1979) and Abdel-Rahman et al. (2000) reported that fluctuations in cereal aphid populations were affected by weather factors. El- Heneidy (1998) stated that relative abundance of different aphid species varied not only from one region to another, but also from one season to another, at the same area, while Ibrahim and Afifi, (1991) and Ali, et al. (1997b) suggested that the fluctuations depended on the activity of natural enemies.

The active period of cereal aphids usually starts from the late-tillering growth stage (mostly during January) and continued through the stem elongation, booting, heading and ends during the ripening (mostly during April) (El-Heneidy and Abdel-Samad, 2001). R. padi starts its occurrence by late December,

S. graminum by early January, R. maidis by early February and S. avenae by early March and all of them usually continue until April (El-Hariry, 1979, Tantawi, 1985, El-Heneidy and Attia, 1988/89, Ibrahim, 1990 a, b El-Heneidy, 1991, 1994, Hafez, 1994, El-Serafy,1999, Abdel-Rahman et al., 2000, El-Heneidy and Abdel-Samad, 2001, Abd-El Wahed, 2003, AbdEl-Awal, 2005 and Slman, 2006).

On barley

El-Hariry (1979) and Tantawi (1985)mentioned that R. padi and R. maidis were the dominant aphid species on barley plants in Middle Egypt. Noaman et al. (1992) recorded that R. maidis was the most abundant aphid species in Northern and North Western coast. Bishara et al., (1997) stated that the weather conditions greatly affected the peak activity of aphids. Marzouk and El-Bawab, (1999) reported that the peak of R. maidis occurred at the weather conditions of 10-11oC and 63-73% RH.

Bishara et al. (1997) and Slman and Ahmed (2005)stated that R. maidis infested barley by late February and early March at Middle and Southern Egypt, respectively. El-Fatih (2006) stated that R. maidis was the most abundant aphid species while the other cereal aphid species were found in few numbers over two seasons at Middle Egypt. Highest records of aphids’ population were found at the plant age of 70 days.

On maize

The maize aphid, R. maidis, the key aphid species on maize , occurs all the year round and its distribution is not limited. It damages a wide range of host plants (mainly maize, sorghum, barley and wheat). It is also a carrier of virus diseases (Hassan, 1957). The infestation with the aphid starts high, on the new tassels and cobs, then decreases gradually during the plant senescence and followed by migration of aphids to younger plants. Occurrence of R. maidis usually starts early in July (at flowering stage), its population increases gradually reaching its peak in August and then decreases to reach its minimum in October (El-Heneidy and Abbas, 1984, Darwish, 1991 and El-Gapaly,2007). El-Gapaly (2007) observed R. padi and S. graminum on the corners of different cultivated corn plots but R. maidis was the most dominant.

On weeds

In agro-ecosystems, weeds are very important hosts (source) of insects and pathogens as they usually disperse from them to economic crops (Van Emden and Wearing, 1965).Hassan (1957) studied the movement of R. maidis throughout the year and noticed that R. maidis migrated from the weeds; Panicum colonum, Digitaria sp., Cynodon dactylon, Setaria sp. and Polygonum sp. to early grown barley by end of December and early January. By mid-January, the aphids migrated to wheat and the infestation remained until March or April. Aphids moved again to gramineous weeds for a short time. R. maidis migrated during May and early June to the sorghum and summer maize plantations. During June and July, the weeds grew on the sides of canals such as; P. colonum were the most favorite host plants for R. maidis. Aphids attacked maize and sorghum at Nile plantations heavily from the end of August until the end of October. The infestation of the Nile maize starts first in the Delta, later in Middle Egypt and ends in Upper Egypt.

Megahed et al. (1978) recorded R. maidis as the most abundant species on wild plants and associated mainly with the plant species, Panicum sp. throughout the year. Three aphid species; R. padi, S. graminum and S. avenae occurred on the wild plants only in March and April. Amin (1979) found that R. padi and S. graminum occurred on their wild host plants from mid-February to late April. R. maidis occurred all the year round on its wild host plants. Tantawi (1985) surveyed a wide range of gramineous weeds attacked by R. padi and R. maidis and concluded that these weed species may play a major role in the ecosystem for the aphid species. Megahed (2000) reported that the total number of surveyed aphids on weed plants was greatly higher (three folds) that recorded on economic crops.

El-Fatih (2000) mentioned that highest population density of cereal aphids on the cereal weed plant, S. cyperi was found by mid-December. D. noxia reached the highest population by early May, while R. padi occurred by early January. The same author in (2006) recorded highest average number of S. cyperi on E. colonum and C. dactylon, during late December and early January. Highest average numbers of R. padi, R. maidis and M. dirhodum were recorded on A. fatua, both R. maidis and M. dirhodum in early April and R. padi in early March. The highest average number of S. avenae was recorded on L. temulentum by early March. D. noxia was recorded on two cereal weed plant species but in remarkably very low numbers. The highest peak was by mid-February. The highest average of S. graminum was recorded on A. fatua, followed by C. dactylon, whereas B. catharticus harbored the lowest numbers. The average numbers of S. minuta and S. scirpus were found by mid-February and early March, respectively.

Biological Studies on Cereal Aphid Species

Biological and life table studies on different cereal aphid species under laboratory conditions were carried out. Only R. padi and S. graminum are considered here as examples.

R. padi:

Life cycle, longevity and fecundity of R. padi on wheat were studied under laboratory conditions by many authors; Mohamed (1992), El- Fatih (2000), Abdel-Rahman, et al. (2002), Agamy, et al. (2003) and El-Heneidy, et al. (2004). They found that the optimum temperature for the development and reproduction of R. padi was 24oC. The life table of R. padi was studied by El- Fatih (2000), Abdel-Rahman, et al. (2002) and El-Heneidy, et al. (2004). The intrinsic rate of increase (rm) ranged (0.241- 0.37) and the net reproductive rate (Ro) ranged (11.77-58.32 at 20-28oC on wheat. Thermal requirement of R. padi was studied by Abdel- Rahman, et al. (2002), who reported that the thermal requirement needed to develop one generation was about 92032 day-degrees, using 8.89oC and El-Heneidy, et al. (2003c) reported that the thermal unit requirements for the time to adult was estimated by 96.15 and 86.2 degree-days for R. padi on wheat and barley. Life cycle, longevity and fecundity of R. padi on barley were also studied by Agamy, et al. (2003) and El-Heneidy, et al. (2004). Its life table was studied by El-Heneidy, et al. (2004) who estimated the intrinsic rate of increase (rm) and the net reproductive rate (Ro) as 0.43 and 63.83, respectively.

S. graminum:

Abdel-Rahman (1997), El-Gantiry et al. (1999), Agamy, et al. (2003) and El-Heneidy, et al. (2004) studied the biology of S. graminum on wheat at different temperatures. El-Ibrashy et al. (1972) showed that the bionomics of R. maidis were considerably influenced by the temperature, food-plant and physiological age of the later. Optimum temperature for rearing was 30ºC. At this temperature, nymphal development was accelerated, complete life-cycle lasted half as long as at 15ºC, and the number of progeny produced/female was high and nymphal mortality was negligible. Barley was more favorable for development of nymphs than great millet (Sorghum vulgare), broad bean (Vicia faba) or maize and young plants 3-5 days old appeared to be the best. In the laboratory, 50 generations could be reared in a year, when the aphid was provided continuously with barley seedlings five days old. Abd-El Wahed, (2003)estimated durations of different nymphal instars and life span of R. padi on barley under the laboratory conditions (23±1ºC and 60±5% R.H.) by 1±0, 1.17±0.38, 1±0, 1.36±0.49 and 23.82 days, respectively. The net reproductive rate Ro and the intrinsic rate of increase rm of R. padi were 63.83 and 0.43, respectively. Agamy et al. (2003) studied the developmental time, longevity and fecundity of R. padi and S. graminum under the laboratory conditions of 20 ±1oC, 50-70 % R.H. and 16: 8 L: D on barley. Longevity and life cycle of R. padi were (12.2 ± 4.85 and 16.2 ± 4.4 days) and for S. graminum they were (19.13 ± 4.3 and 24.33 ± 4.4 days), respectively. Fecundity of R. padi and S. graminum were estimated by (40.33 ± 14.41) and (59.77 ± 13.16), respectively. El-Heneidy et al. (2004) studied the life table of R. padi and S. graminum on barley under laboratory conditions (23±1ºC and 60±5% R.H.). The intrinsic rate of increase (rm) and generation doubling time were 0.43 and 1.61 for R. padi and 0.32 and 2.2 for S. graminum, respectively. El-Fatih (2006) studied the biological parameters of different cereal aphid species; R. maidis, R. padi, M. dirhodum and D. noxia at 15, 20, 25 and 29 OC. Highest fecundity rate was 47.18 progeny/ female for R. maidis at 20OC while the lowest was 5.34 progeny/ female for D. noxia at 25OC. Longest life span for M. dirhodum was 19.1± 2.8 days at 25OC, followed by R. padi 15.65 ± 2.47 days. Life table parameters were studied. R. maidis recorded the highest value of rm (0.32), followed by R. padi (0.23) and then M. dirhodum (0.21). Lowest rm value (0.09) was recorded for D. noxia. The thermal requirement (k) of R. maidis, reared on barley seedlings for each nymphal instar, life cycle and generation time, were 15.167, 20.47, 17.05, 25.53, 87.31 and 88.11 degree-days, respectively.

Economic Threshold (ETL) and Economic Injury Levels (EIL) of Cereal Aphids in Egypt

Use of economic threshold as a basis for decision making is a fundamental component in integrated pest management (IPM). Stern et al. (1959) proposed the concepts of an economic injury level (EIL) and economic threshold (ETL) as a rational comparison of the economic costs and benefits of pesticide use. EIL is defined as the lowest population density (number) that will cause economic damage, where economic damage is the amount of damage that equals the cost of control (Stern et al. 1959 and Pedigo et al. 1986). Implicit in the EIL concept is that not all damage is economically significant and that in many instances a certain level of insect injury may be tolerated. It is also useful to maintain a distinction between injury and damage. Injury can be defined as the effect of insect activities on host physiology, damage as the measurable loss of host utility, which is usually measured by reductions in the commodity yield or quality. Consequently, not all injury causes damage, and damage threshold, or boundary, defines the level of injury where damage occurs (Bardner and Fletcher 1974 and Pedigo et al. 1986).

The EIL and ETL concepts have been successfully and widely applied to generate management guidelines for insect pests in many cropping systems. Also, aphids have been the subjects of much research on ecological relationships and population management. Many workers have contributed to the understanding of host-aphid relationships, and much has been done towards developing economic action levels for cereal aphids' infestation (Wratten, 1978, Robert et al., 1985, Kurppa, 1989, Hole et al., 1994, Li-Jiping et al., 1995 and Wetzel, 1995). However, in Egypt few studies have concerned with development of EIL and ETL recommendations for cereal aphids in Egyptian wheat fields (Ghanem and El-Adl, 1987, El-Serafy et al., 1997 and Ali et al., 1997a).

El- Heneidy et al. (2003b) estimated economic injury (EIL) and threshold (ETL) levels for the key cereal aphid species; R. padi and S. graminum in different wheat locations in Egypt. Tested parameters were: wheat plant growth stage, density and species of aphids and location. The study was carried out in three wheat locations; Sohag, Beni-Suef and Sharkia Governorates, represented Upper-, Middle-Egypt and the Delta, respectively during the wheat growing seasons 2000/01 and 2001/02. Infested plants were divided into two groups; the first was marked for weekly sampling for aphid numbers and the second was left for yield and yield component determinations. ETLs and EILs values fluctuated significantly according to different seasons, sites, growth stages, and aphid species. Respective highest ETLs and EILs values were estimated at Sohag in the growth stages; stem elongation (6.23 and 10.47) and booting (5.38 and 8.52) and at Sharkia in the heading stage (6.13 and 7.17 aphids/plant).Highest EILs were recorded for R. padi during the stem elongation growth stage and decreased in booting and heading stages. An opposite trend was found in ETLs values of the same species. EILs values for S. graminum were almost equal in all locations, where they ranged between 5.7 - 5.9 aphids/plant, while ETLs values increased (3.96 - 4.16 - 4.41 aphids/plant) toward the heading stage. Opposite to the trend of ETLs values in case of R. padi, a negative correlation was found between the grain yields and increase of aphids' numbers/plant in all cases. In all growth stages, the impact of the stress of cumulated aphids’ infestation (reduction in grain yields) caused by R. padi alone was always the lowest, it ranged (21.2 -75%) compared with (21.3 - 80.8%) by S. graminum alone and/or to (22.2 - 84.2%) by the two species together. A recommendation for monitoring cereal aphids' infestation during the stem elongation growth stage (mostly around late January to mid- February) should be considered to take the right decision for the pest control.

Chemical Control and Side Effects

The only control tactic against cereal aphids in cereal field crops available to farmers has been mostly depending upon insecticides. Controlling aphids with insecticides has many risks, including destruction of native natural enemies and accelerated development of insecticide resistance in aphid species. In Egypt, the crop receives an average of 1-2 insecticidal applications during the growing season.

Effect of two mineral oils and five organophosphorous insecticides were tested individually against adults of the cereal aphid R. padi. The most effective combination was pirimiphose-methyl/star oil with a factor of synergism 4.54, while the least was dimethoate/star oil (El-Deeb, 1993). Timing and number of the insecticidal application (Malathion 57%) was very important for control aphids’ population. One spray in the infested spots early in the season decreased aphid population throughout the season and on the other hand, maintained relatively high population of natural enemies (El-Heneidy, 1994). In Delta, the phenomenon of increasing aphid infestation than before in wheat fields required wide use of insecticides that created more problems through disturbing the natural balance between aphids and their natural enemies, which already exist in many wheat fields of the Delta (El-Heneidy, 1994).

El-Heneidy et al. (1991) evaluated the effect of chemical treatments on aphids and their natural enemies in wheat fields during 1990-91 planting season at Sohag Governorate (Upper Egypt). The multiple treatments of insecticides badly affected number of natural enemies. Accordingly, sharp decline in the number of predators (40-48%) and in the percentage of parasitism (66%). The timing of insecticidal application plays a critical role in disturbing the natural balance between aphids and their natural enemies in wheat fields. Early infestation of aphids should be chemically treated only in the infested spots, so less influence on the natural enemies will be occurred. IPM program for aphids control depending on the positive role of predators and parasitoids is always needed to reduce dependence on currently used programs of chemical insecticides.

Biological Control of Cereal Aphids in Egypt

Generally, aphids tend to have three groups of natural enemies; parasitoids, predators, and fungal diseases (Hagen and Van Den Bosch, 1968).

a- Parasitoids

Parasitoid species are mostly specific on a single or certain group of insect hosts. Aphid parasitoids are one of the groups of which utilization in biological control has given significant results in many countries of the world. Aphidiids form the major part of the primary parasitoid spectrum of aphids. As well, the aphelinids form another small group of the primary parasitoids of aphids (Stary, 1976).Eggs of the aphid parasitoids are laid directly into the aphid and the parasitoid may suspend development while the aphid grows and increases in size. As the parasitoid kills the host, it attaches the aphid to subtract by silk, the skin of the aphid drying and becoming a mummy within which the parasitoid pupates. The color and shape of the mummy frequently are characteristic of the genus of parasitoid, (Hafez, 1965 and El-Heneidy and Adly, 2009).

On the biology and morphology of aphid parasitoids

Several studies included biology, life tables and thermal requirements of most common aphid parasitoids in Egypt; Aphelinus asychis (El- Gantiry 1997), Lysiphlebus fabarum (Rezq et al., 2000), Aphidius matricariae (Agamy et al., 2003 and El-Heneidy et al. 2003c), Aphidius colemani (El-Heneidy et al. 2004), Aphelinus albipodus (Adly et al. 2006 and El-Heneidy et al. 2010) and Lysiphlebus testaceipes (Eid, 2012). Besides, some other studies concerned with morphological characteristics of the aphid parasitoids; L. fabarum (Rezq et al. 2000), A. matricariae (El-Heneidy et al., 2003d), A. albipodus (Adly et al., 2010) and L. testaceipes (Eid, 2012).

The phenomenon of hyperparasitism is very common in aphid parasitoids. Primary parasitoid species are usually been attacked by secondary parasitoid species mostly that belong to order: Hymenoptera, Fam.: Cynipidae, Encyrtidae, Pteromalidae and Megaspilidae. Food web studies suggest that most primary parasitoids and hyperparsitoids are relatively specialized so that the community contains a series of relatively compartmentalized aphid - parasitoid - hyperparasitoid interactions. Primary parasitoids only attack a small percentage of the available aphids and this is because their numbers are regulated by secondary parasitoids (Christine et al., 1999).Parasitoid species attack cereal aphids in wheat fields in Egypt were previously recorded by several authors in different locations. On the contrary, few studies concerned with the survey of the cereal aphid species and their natural enemies on barley in Egypt.

Aphid parasitoid species

Survey of both primary and hyperparsitoid species recorded on cereal aphid species in wheat, barley and maize plants in Egypt revealed the presence of:

Primary parasitoids

(Order: Hymenoptera Family: Aphidiidae)

1 . Aphidius spp.: recovered, from specimens of R. padi collected at Middle Egypt in March 1957 (Hassan, 1963, El-Heneidy and Attia, 1988/89, El-Heneidy, 1991 and Hafez, 1994).

- Aphidius matricariae Haliday: was collected by Ibrahim, (1990 a&b), Ibrahim and Afifi, (1991), El-Heneidy, (1994), El-Serafy, (1999), Megahed, (2000), El-Heneidy and Abdel-Samad, (2001), El- Heneidy et al. (2001, 2002, 2003a, 2004), Sobhy et al. (2004), Abdel- Rahman, (2005), El-Fatih, (2006) and Slman, (2006).
- A. colemani Viereck: was surveyed by Ghanim and Adl, (1983), Abdel- Rahman, et al., (2000), Megahed, (2000), El-Heneidy and Abdel-Samad, (2001), El- Heneidy et al. (2001, 2002, 2003a, 2004), Sobhy et al. (2004), El-Fatih, (2006) and Slman,(2006).
- A. rhopalosiphi: was surveyed by Ghanim and Adl, (1983) and El-Serafy, (1999).
- A. uzbekistanicus Luz.: was surveyed by Ibrahim, (1990a) and El-Serafy, (1999).

2. Diaeretiella rapae Mclntosh (Diaeretes dauci): was recovered from specimens of R. padi, collected from Middle Egypt in March 1957, (Hassan, 1963). It was also surveyed by El-Heneidy and Attia, (1988/89), El-Heneidy (1991, 1994), Abdel- Rahman, et al., (2000), Megahed, (2000), El-Heneidy and Abdel-Samad, (2001), El-Heneidy et al. (2001, 2002, 2003a, 2004), Sobhy et al. (2004), Abdel-Rahman, (2005), El-Fatih, (2006) and Slman,(2006).

3. Ephedrus spp.: emerged from specimens of R. padi collected at Middle Egypt in March 1957 (Hassan, 1963).

- Ephedrus persicae Froggatt: was surveyed by Megahed, (2000), El-Heneidy and Abdel-Samad, (2001), El- Heneidy et al. (2001, 2002, 2003a), Sobhy et al. (2004) and El-Fatih, (2006).
- Ephedrus plagiator Ness: was surveyed by Abdel- Rahman, (2005).

4. Praon necans Mackauer: was surveyed by Abdel-Rahman, et al. (2000), El-Heneidy and Abdel-Samad, 2001), El- Heneidy et al. (2001, 2002, 2003a), Sobhy et al. (2004), Abdel- Rahman, 2005) and El-Fatih, (2006).

- Praon gallicum Stary: was surveyed by Ibrahim, (1990 a&b) and El -Serafy, (1999).
- Praon sp.: was surveyed by El- Heneidy, (1991, 1994), Megahed, (2000) and Slman, (2006).
- Praon volcure Hal.: was surveyed by Hafez, (1994).

5. Lysiphlebus sp.: was surveyed by Megahed, (2000).

6. Trioxys spp.: were recorded by El-Heneidy, (1991, 1994), Megahed, (2000), El-Heneidy and

Abdel-Samad, (2001), El- Heneidy et al. (2001, 2002), Abdel- Rahman, (2005) and Slman, (2006).

(Order: Hymenoptera Family: Aphelinidae)

1 - Aphelinus sp .: recovered from specimens of Aploneura lentisci Pass., collected at Middle Egypt in 1953 (Hassan, 1963). It was surveyed by El-Heneidy and Abdel-Samad, (2001), El- Heneidy et al. (2001, 2002), Sobhy et al. (2004), Abdel- Rahman, (2005) and El-Fatih, (2006).
2 - Aphelinus albipodus Hayat and Fatima: native Aphelinus sp. emerged from cereal aphid species, collected from Egyptian wheat fields, were identified by Dr. M. Hayat (the author of the species), Department of Zoology, Aligarh Muslim University, Aligarh, India. The result showed that the native parasitoid species was A. albipodus (Adly,2008).

Hyperparasitoids

Surveyed hyperparasitoid species recovered from primary parasitoid species of cereal aphids in Egypt were found all belong to order Hymenoptera and to five main families:

-Cynipidae: Alloxysta spp., Phaenoglyphis sp . and other cynipids.
-Chalcididae: chalcids.
-Encyrtidae: Aphidencyrtus sp.
-Megaspilidae: Dendrocerus spp.
-Pteromalidae: pteromalids (Asaphes and Pachyneuron)

These hyperparasitoids were recorded by Ibrahim, (1990 a&b), Ibrahim and Afifi, (1991), Hafez, (1994), Megahed, (2000), El-Heneidy and Abdel-Samad, (2001), El- Heneidy et al. 2001, 2002, 2003a), Sobhy et al. (2004), Abdel-Rahman, (2005) and El-Fatih,( 2006).

Seasonal Abundance of Cereal Aphid Parasitoids

1. Primary parasitoids

Highest percentages of parasitism were estimated mostly during the boating and heading growth stages of the wheat plants (late February - mid- April) to coincide more or less with the highest population of cereal aphids on wheat and barley(El-Heneidy and Attia, 1988/89, Ibrahim, 1990 a,b, El-Heneidy, 1991, 1994, Hafez, 1994, El-Serafy, 1999, Abdel- Rahman et al., 2000, El-Heneidy et al., 2001, Abdel-Rahman, 2005 and Slman,2006). Percentages of parasitism were increased by plantations of flowering plants surrounding wheat fields. That mean, planting some flowering plants surrounding wheat fields enhanced the attraction of parasitoids for controlling the cereal aphids (Hafez, 1994). Increase rate of aphid parasitoids usually follows the increase in the aphid population. Peak of the aphid parasitoids was recorded two weeks post the peak of the aphid species (El-Serafy, 1999 and Megahed, 2000).

Numbers of surveyed parasitoids emerged from aphids attacking weeds were much higher than those emerged from aphids infesting cultivated economic plants such as wheat plants. High population of parasitoids occurs on weeds in October due to the lack of crop plantations during this period between summer and winter seasonal crops, during May due to the decrease of aphids’ infestation in wheat and barley fields, when the crops became senescent and during July and August when the chemical control measures sometimes are practiced on maize plantations. These periods may be unsuitable and unadvisable to weed elimination (Megahed, 2000).

2. Hyperparasitoids

Aphid hyperparasitoids are mostly obligate because they are restricted to being secondary parasitoids whose progeny can develop only in or on primary parasitoids. Hyperparasitoids have an ecological impact on both the primary parasitoids and host aphid population dynamics. For instance, hyperparasitism has practical ecological implications in any biological control program because of the negative effect on the beneficial primary parasitoids. Generally, few studies have been carried out on hyperparasitism of aphid’s primary parasitoids in Egypt (EL- Heneidy et al. 2002).

Hyperparasitism has traditionally been viewed in the context of applied ecology as being harmful and so it is believed to have usually a negative impact on beneficial primary parasitoids. There is a contrary speculation as to hyperparasitoids' possible positive role in maintaining a proper balance between the primary parasitoids and their hosts by preventing an excessive buildup of parasitoid numbers (Stary, 1970, May, 1973 and Van den Bosch et al., 1979).

Hyperparasitoid species were observed by late February until end of April (Ibrahim, 1990 a,b, El- Heneidy et al., 2001,2002 and Abdel- Rahman, 2005).Highest percentage of hyperparasitism (51.5%) was found in the New Valley (Upper Egypt) during 1997/98 season, while the lowest (2.8%) was recorded in the Delta at the same season (El- Heneidy et al., 2001).

Generally, diversity of species and number of the parasitoids and their potential to control cereal aphids in wheat fields in Egypt has been adversely influenced by:

1- Regular pesticides treatments. A sharp decline (66%) in the number of the parasitoids in wheat fields, following pesticides applications was recorded (El-Heneidy, et al., 1991).
2- Significant role of hyperparasitoids species in suppressing the primary parasitoids. Maximum percentage of naturally occurring parasitism, recorded on the cereal aphids was 36% in Upper Egypt (El-Heneidy and Abdel-Samad, 2001).

b- Predators

Aphids are subject to predation by number of groups of relatively specific predators, as well as by more generalist species that also feed on other groups of insects. The most important specialists are ladybird beetles (Coccinellidae, both adults and larvae), lacewing larvae (Chrysopidae), hoverfly larvae (Syrphidae), midge larvae (Cecidomyiidae) and certain genera of true bugs (Heteroptera)(Christine et al., 1999).

Recorded predatory species associated with cereal aphids in Egypt were:

Order: Coleoptera Family:Coccinellidae

- Coccinella undecimpunctata L .: was recorded associated with cereal aphid species; R. padi, R. maidis, S. graminum and S. avenae by Hassan, (1957), Tawfik et al. (1974 a,b), El-Heneidy and Abbas, (1984), El-Heneidy and Attia, (1988/89), Salem and Megahed, (1990), Darwish, (1991), El- Heneidy et al. (1991), Ibrahim and Afifi, (1991), El- Heneidy, (1994), Hafez, (1994), Ali and Abdel-Rahman, (2000), Megahed, (2000), El-Heneidy and Abdel-Samad, (2001), El-Heneidy, (2004), Slman and Ahmed, (2005), El-Fatih, (2006) and El-Gapaly, (2007).
- C. septempunctata L.: was recorded associated with cereal aphid species; R. padi, S. graminum and S. avenae by Hafez, (1994).
- Scymnus interruptus L.: was recorded associated with cereal aphid species; R. padi, R. maidis,
- S. graminum and S. avenae by Hassan, (1957), Tawfik et al. (1974 a,b), El-Heneidy and Abbas, (1984), El-Heneidy, (1994), El-Heneidy and Abdel-Samad, (2001) and El-Fatih, (2006).
- S. gilvifrons Muls.: was recorded associated with R. maidis by El-Gapaly, (2007).
- S.pallidivestis Muls.: was recorded associated with R. maidis by El-Gapaly, (2007).
- Scymnus spp .: were recorded associated with different cereal aphid species by El-Heneidy and Attia, (1988/89), Darwish, (1991), Hafez, (1994), Ali and Abdel-Rahman, (2000), Megahed, (2000) and El-Gapaly, (2007).
- Cydonia vicina var. nilotica Muls.: was recorded associated with R. maidis by Hassan, (1957), Tawfik et al. (1974 a,b), El-Heneidy and Abbas, (1984) and the aphid species; R. padi, S. graminum and S. avenae by Hafez, (1994).
- Cydonia vicina var. isis Muls.: was recorded associated with cereal aphid species; R. padi, S. graminum and S. avenae by Hafez, (1994).

Order: Coleoptera Family: Staphelinidae

- Paederus alfierii Koch: was recorded associated with different cereal aphid species by Hassan, (1957), Tawfik et al. (1974 a,b), El-Heneidy and Abbas, (1984), El-Heneidy and Attia, (1988/89), Salem and Megahed, (1990), El-Heneidy, (1994), Hafez, (1994), Megahed, (2000),El-Heneidy and Abdel-Samad, (2001), El-Fatih, (2006) and El-Gapaly, (2007).

Order: Neuroptera Family: Chrysopidae

- Chrysoperla carnea Steph.: was recorded associated with cereal aphid species; R. padi, R. maidis, S. graminum and S. avenae by Hassan, (1957), Tawfik et al. (1974 a,b), Ghanim and El-Adl, (1983), El-Heneidy and Abbas, (1984), El-Heneidy and Attia, (1988/89), Salem and Megahed, (1990), Darwish, (1991),Ibrahim and Afifi, (1991), El- Heneidy, (1994), Hafez, (1994), Ali and Abdel-Rahman, (2000), Megahed, (2000), El-Heneidy and Abdel-Samad, (2001), El-Fatih, (2006) and El-Gapaly, (2007).

Order: Diptera Family: Syrphidae

- Syrphus corolla Fab.: was recorded associated with cereal aphid species by Ghanim and El-Adl, (1983), Salem and Megahed, (1990), Ibrahim and Afifi, (1991), Hafez, (1994), Ali and Abdel-Rahman, (2000) and El-Fatih, (2006).
- Syrphus spp.: were recorded by Hassan, (1957), Tawfik et al. (1974 a,b), El-Heneidy and Abbas, (1984) El-Heneidy and Attia, (1988/89), El-Heneidy, (1994), Megahed, (2000) and El-Heneidy and Abdel-Samad, (2001).
- Lasiophthicus flavicauda Zetterstedt: was recorded associated with cereal aphid species byEl-Fatih, (2006).
- L. pyrastri L.: was recorded associated with cereal aphid species by Efflatoun, (1922).
- L. albomaculatus Macq.: was recorded associated with cereal aphid species by Efflatoun, (1922).
- Xanthogramma aegyptium and Sphaerophoria flavicauda Zett. were recorded associated with R. padi, S. graminum and S. avenae by Hafez, (1994) and with R. maidis by El-Gapaly, (2007).
- Sphaerophoria flavicauda Zett.: was recorded associated with R. maidis by El-Gapaly, (2007).
- Paragus aegyptium Macq.: was recorded associated with R. padi, S. graminum and S. avenae by Hafez, (1994).

Order: Hemiptera Family: Anthocoridae

- Orius albidipennis Reut.was recorded associated with R. maidis by El-Gapaly, (2007).
- Orius laevigatus: was recorded associated with R. maidis by El-Gapaly, (2007).
- Orius spp.: were recorded by Hassan, (1957), Tawfik et al. (1974 a,b), El-Heneidy and Abbas, (1984), El-Heneidy and Attia, (1988/89), Darwish, (1991), El- Heneidy, (1994), Megahed, (2000) and El-Heneidy and Abdel-Samad, (2001).

Spiders

Acrina: spiders (several species) were recorded by El-Heneidy and Abbas, (1984), Darwish, (1991), El-Heneidy, (1991&1994), El-Heneidy and Abdel-Samad, (2001).

Seasonal Abundance of Predators Associated with Cereal Aphid Species:

In wheat fields, population of aphidophagous predators increased gradually towards the end of the season reached their maximum during April. C. undecimpunctata was the dominant predator in the two seasons 1987 and 1988 on wheat fields (El-Heneidy and Attia, 1988/89 and Hafez, 1994). Predatory numbers increased in wheat treatments surrounded with flowering plants (Hafez, 1994). Peak numbers of predators in wheat fields occurred during March and by mid-April (El-Heneidy and Attia, 1988/89, El-Heneidy, 1991, Hafez, 1994, El-Heneidy and Abdel-Samad, 2001), while Ghanem and El-Adl,1983, Ibrahim and Afifi 1991, Hafez 1994 and El-Heneidy, 1994) reported that the peak number of predators occurred during April, which was later than the highest infestation period of cereal aphids in wheat, usually in March. Decrease of population numbers of the predators occurred after pesticide applications (El-Heneidy et al., 1991).

In maize fields, highest numbers of predators associated with cereal aphids were recorded in August and October, while the lowest was recorded in September. P. alferii dominated in August, Oruis spp. and C. undecimpunctata mainly occurred in September and October. The population of predatory species follows that of the preys (El-Heneidy and Abbas, 1984).

Occurrence of C. undecimpunctata, Syrphus spp., C. carnae, Orius spp., P. alfierii were observed on weeds all over the year, on wheat (February - April), on maize (August - September) but Orius spp. on weeds during (October - November), (March), and (June -September), P. alfierii on weeds during (October - November) and (February - September) (Megahed, 2000).

c- Entomopathogenic Fungi

Entomopathogenic fungi are principal pathogens among Homopteran piercing sucking insects (Hajek and St. Leger, 1994). Several species of entomopathogenic fungi; Beauveria bassiana, Verticillium lecanii,Pandora neoaphidis, Conidiobolus thromboides, C. obscurus, C. coronatus, Entomophthora planchoniana were recorded infecting cereal aphid species; R. padi,R. maidis and S. graminum in wheat fields in Egypt, particularly at Upper Egypt (Abdel-Rahman et al., 2006).El-Fatih, (2006) recorded four entomopathogenic fungal species; P. neoaphidis and C. thromboides (Order: Entomophthoraceae) and V. lecanii and Paecilomyces farinosus species (Order: Moniliales) infected R. maidis and M. dirhodum in Egypt.

Fungal infections to cereal aphids in wheat fields were found startingby mid-March, while the peak was counted in April (Hafez, 1994).

Biological Control Applications

Diversity and populations of parasitoids and predators seem to be relatively low to play a significant role for aphid management of cereal aphids in Egypt. Additional work should be done to make the agro-ecosystem more favorable to the natural enemies (El-Heneidy and Attia, 1988/89).

El-Heneidy et al. (2006) imported through an Egyptian/American collaborative project (1997-2002), four cereal aphid exotic parasitoid species from different countries to provide additional mortality factors to the indigenous ones, against key cereal aphid species in Egyptian and American wheat fields. The exotic cereal aphid parasitoid species were collected from Syria, Morocco, and Iran, in localities near the reported areas of the origin of cereal species and from habitats of climatic patterns similar to those in Upper Egypt and Southern California, USA. A. matricariae, D. rapae, A. rhopalosiphi and A. albipodus were the parasitoid species introduced and evaluated under laboratory, field cages and open wheat field conditions. The exotic parasitoid species showed different performances under several tested conditions. The most promising species for its potential field effectiveness against cereal aphids was A. matricariae imported from Syria as it showed efficiency against wheat aphids in hot areas in Upper Egypt.

Sabbour, (2007) evaluated different species of fungi and the predator C. septempunctata under laboratory and field conditions against cereal aphids’ species R. padi and R. maidis for two successive wheat growing seasons 2005 and 2006. The fungus B. bassiana showed significantly best result, followed by Paecilomyces fumosoroseus, Metarhizium anisopliae, V. lecanii and Nomuraea rileyi against R. padi and R. maidis. Under field conditions, the treatments with the different fungi after releasing the predator (C. septempunctata) decreased the infestations with the cereal aphids. Also, the percentage of yield loss was significantly decreased to 17% after predators releasing and fungal treatments, as compared to 51% in untreated plots.

A. albipodus was released as mummies, collected from the laboratory stock culture, in field cages and open field at Giza Governorate (Middle Egypt) during the season 2005/06. Evaluation of the release of the parasitoid in the field cages and open field were carried out. Percentage of parasitism in the control was higher (27.49% ±2.58) than that in the field cages (21.96% ± 2.45), which might be due to the competition among different other parasitoid species. A. albipodus had the lowest percentages in both open field and the control and with no difference between the percentages of the A. albipodus before and after releases (Adly, 2008).

ACKNOWLEDGEMENT

The authors are very grateful to Dr. Petr Stary, Institute of Entomology, Academy of Science of the Czech Republic for his continuous assistance for identifying of parasitoid species and for his technical support when needed.

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