Effects of Thrips (Pseudodendrothrips mori Niwa) Infested Mulberry Leaves on Silkworm Growth and Commercial Cocoon Parameters

In mulberry orchards in northern part of Iran, thrips is a dominant pest and causing a lot of damage to the mulberry. The effect of pest on bio-chemical parameters of mulberry leaf of two varieties viz. Kenmochi and Ichenoise and also the effect of feeding of infested leaves on rearing performances have been studied. For the study, six plots of 200 m2 area of both the varieties were selected and three of them, of each variety, were sprayed with 0.5% Metasystox at a peak period of occurrence of nymph population to obtain the good healthy leaf without thrips infestation. Another 3 plots were left without pesticide spray to obtain infested leaves so as effect of infestation on chemical parameters of leaf and effect of infested leaves on rearing performance could be studied. During rearing, larvae were fed with good quality of mulberry leaf while another lot were fed with infested leaves. The results showed that there was a decrease in nitrogen, phosphorus, potassium and protein contents of leaves by 2.5, 10.8, 18.7 and 12.5%, respectively due to infestation and the decrease in these parameters was more in Kenmochi. There was also a significant decrease in total cocoon production, cocoon weight, pupal weight, and shell weight due to feeding of infested leaves. However, there was no significant difference in shell ratio between the lots fed with healthy and infested leaves.