Host selection behavior of diaeretiella rapae mcIntosh (Hymenoptera : Braconidae)‎ attackingcereal aphids in Upper Egypt

الملخص EN

The present investigation was carried out in Assiut Governorate to study the relative abundance of cereal aphid parasitoids and evaluate the host selection and host-instar preference of Schizaphis graminum(Rondani) and Rhopalosiphum padiL.by the braconid parasitoid, Diaeretiella rapae McIntosh during 2015 wheat growing season.

The obtained results revealed that the dominance percentages of the primary parasitoids were so high and presented by 81.53 % of the total caught parasitoids.

However, the secondary parasitoids showed low dominance percentages and presented by 18.47 %.

The parasitoids, D.

rapaeand Alloxysta australiae (Ashmead)revealed the highest dominance percentage and presented by 76.38 and 47.93 % of the total collected primary and secondary parasitoids, respectively.The aphid, S.

graminumappeared as more relatively preferred for D.

rapae thanR.

padi species.

The development of D.

rapaewas found to be possible in any instar of S.

graminum and R.

padi.

The second and third instars of S.

graminumpresented the optimal response forD.

rapaegrowth and survival, while the third and fourth instars of R.

padipresented the optimal response for parasitization by the same parasitoid species.

The averages of the development times from oviposition until the appearance of the mummified aphid were 7.68and 8.01days forS.

graminum and R.

padi, respectively.

Offspring production per female was high in the adult stage than others.

Nymphs parasitized and mummified by D.

rapae during the first and second instars may be reach to maturity but not produce any progeny.