Seasonal abundance of the cabbage aphid Brevicoryne brassicae (Hemiptera : Aphididae)‎ infesting canola plants in relation with associated natural enemies and weather factors in Sohag governorate

Abstract EN

Canola (Brassica napus L.) is grown in more than 120 countries around the world, including Egypt, hold the third position oil crop after palm and soybean oils .

the cabbage aphid Brevicoryne brassicae (L.) (Hemiptera : Aphididae) is distributed in many parts of the world and is present in Egypt, especially in Upper Egypt.

Its damage occurs on the plant leaves and transmit plant viruses.

The present studies were carried at The Experimental Farm of Shandweel Agricultural Research Station, Sohag Governorate, Egypt during the winter seasons of 2017/2018 and 2018/2019 to investigate the population density of the cabbage aphid B.

brassicae infesting canola in relation to some biotic and abiotic factors in Sohag Governorate.

Data revealed that aphid started to take place in canola fields during the first week of December in both seasons (36 days after planting), then increased to reach its peak in at 20th and 13th February in the two seasons (Between 106 to 113 days after planting), respectively.

The parasitism rate by Diaeretiella rapae (MacIntosh) (Hymenoptera: Braconidae) simultaneously increased as aphid populations increased in both seasons, also, the highest parasitism percentages were synchronization of the aphid numbers reduction in both seasons.

Coccinella undecimpunctata L.

(Coleoptera : Coccinellidae) , Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae) and Syrphus corollae Fabricius (Syrphidae: Diptera) were the main predators inhabiting canola plants, started to take place in canola fields after 2-3 weeks from aphid infestation.

Predators showed their highest abundance during February and simultaneously increased as aphid populations increased in both seasons.

Using simple correlation and simple regression values, the effects of parasitoid and predators showed positive, highly significant and significant effects, respectively, on B.

brassicae during the two seasons.

However, none of abiotic factors (Maximum and minimum temperature and mean relative humidity) showed significant effects in the two seasons.