Effect of biotic and abiotic factors on the population dynamics of wheat greenbug, Schizaphis graminum (Rondani) (Hemiptera: Aphididae) under Sohag governorate conditions.

Abstract

The present study was carried out in the Agriculture Experimental of Shandaweel Agriculture Research Station, Sohag Governorate during two successive seasons of 2015/2016 and 2016/2017. Results of both seasons showed the population fluctuation of S. graminum. The obtained results revealed that greenbug increased from 0.60, 0.63 nymphs/tiller on 3 rd , 4 th week of January respectively, to reach a peak of 82.80, 66.40 nymphs/tiller in 2 nd ,3 rd week of March respectively. Aptera of S. graminum started to appear in 4 th week of January and increased to reach a maximum of 11.00, 4.7 individuals/tiller on both seasons respectively. The peak of alatae reached 3.90, 4.70 individuals/tiller respectively, in the 4 th week of March. The population of all morphs started declining in the last week of March from field and disappeared by 1 st week of April. The grubs and adults of Coccinella septempunctata Linné appeared on the crop during the beginning of February and their population increased with the increase in aphid population. Its abundance was maximum on the 4 th week of March with average of 7.80, 9.06 individuals/tiller on both seasons respectively. The population of aphids had significant positive correlation with maximum, minimum, mean temperature were 0.6524, 0.481, 0.542 in first season and 0.5687,0.472, 0.364 in the second season respectively. But it showed negative correlation with humidity in both seasons-0.454,-0.391 respectively. The studies evaluate in detail the abiotic and biotic factors regulating the wheat aphid populations.

Spatiotemporal distribution of Schizaphis graminum (Rondani) and its natural enemy Coccinella septempunctata (Linnaeus) in graniferous sorghum crops

“…In addition, this reduction in pest density may still be linked to greater precipitation in the area in the reproductive stage, this inverse relationship between aphid population peak and rainfall has been reported in the literature (Schuber et al, 2009). After all abiotic factors may be the most important in the management of cereal aphids under field conditions (Mohanny et al, 2020;Benevenute et al, 2012). The rainfall of the Experimental Farm in the sorghum vegetative stage was 7 mm, whereas 253 mm was recorded for the reproductive stage (Figure 3).…”