Comparative Study of Cereal Aphid Species and Their Associated Predators and Parasitoids In Two Different Wheat Regions In Egypt

Abstract

Wheat is the main crop in cereal group. However, there are many pests attack wheat plants from planting up to harvest, the main insect pests are aphids. Susceptibility of the wheat cultivars Sids 1, Sakha 8, 61 and 69 and Giza 164 and 167 to aphid infestation were studied at two different governorates: Beni-suef in middle Egypt (Sids Agricultural Research Station) and Kafr El-Sheik in Delta,north Egypt (Sakha Agricultural Research Station) during the two successive seasons of 1997/98 and 1998/99.Three main species of aphids were recorded infesting wheat plants: Rhopalosiphum padi,L. Schizaphis graminum Rondani and Rhopalosiphum maidis Fitsh, in both regions. The population densities of aphids in both regions occurred in high numbers during the seasons. Average numbers of aphids/plant for the selected cultivars, Sids 1, Giza 167, Giza 164, Sakha 8, Sakha 61 and Sakha 69 during February were 5.87±2.2, 9.71±2.03, 6.25±1.64, 6.53±1.73, 8.4±2.06 and 9.75±2.67, respectively at Sakha region and 8.87±1.7, 12.11±2.2, 9.65±2.14, 11.68±2.6, 11.8±2.18 and 13.20±1.83, respectively at Sids region. During March they were 7.77±3.54, 9.47±3.91, 6.29±2.71, 6.52±2.67, 7.92±2.91 and 10.62±3.0, respectively at Sakha region and 5.81±2.49, 11.87±4.2, 7.86±2.93, 8.99±3.67, 9.98±3.28 and 12.46±3.99, respectively at Sids region. The results showed that the wheat cultivars were arranged ascendingly according to there susceptibility to infestation levels by aphids as follows: Sids 1 (12.9%), Giza 164 (13.6%), Sakha 8 (15.4%), Sakha 61 (17.3%), Giza 167 (19.7%) and Sakha 69 (21.1%). Survey of the predators associated with wheat aphids revealed the presence of Coccinella undecimpunctata Reiche (36.1% at Sakha and 35% at Sids), Paederus alfierii Koch(19.8% at Sakha and 18% at Sids), Chrysoperla carnea Steph.(16.4% at Sakha and 16% at Sids), Syrphus spp. (9.4% at Sakha and 10% at Sids), Orius spp. (7% at Sakha and 8% at Sids), Scymnus spp. (3.2% at Sakha and 4% at Sids) and true spiders (8.1%, in Sakha and 9% at Sids). The present study showed also five parasitoid species attacking wheat aphids namely; Aphidius matricariae Haliday, Aphidus colemani Viereck, Diaeretiella rapae M'Intosh, Ephedrus sp. and Praon sp. Rate of parasitism on wheat aphids showed low levels (6% at Sakha and 9.62% at Sids) during February and the maximum (14.1% at Sakha and 11.9% at Sids) during March.