An Experimental Study of Certain Neonicotinoid Insecticides on the Incidence of Early Infestation of the Spiny and the American Bollworms, Growth and Lint Yield Characteristics of Cotton Plants

Abstract

The cotton bollworms are major pests that reduce yield and quality of the growing cotton crop all over the world. The Spiny bollworm (SBW) Earias insulana (Boisd.) and American bollworm (ABW) Helicoverpa armigera (Hüb) are two common injurious bollworms of cotton in Egypt. A field experiment was conducted at Abo-Homos district, El-Behaira, Governorate during 2015 & 2016 cotton season to determine the efficacy of two neonicotinoid insecticides (imidacloprid and thiamethoxam) as seed dressing and seedling bed at the 3rd true leaf emergence of cotton plants (Giza 86). Reduction in the infestation and larval content/100 green bolls and/or plants of both pests was estimated through 30-90 days of germination. Furthermore, the total chlorophyll content, cotton yield and its fiber quality was determined. The results showed that imidacloprid and thiamethoxam caused a significant larval reduction (79.9, 75.5% & 66.9, 72.7%) of the SBW in both experimental seasons, respectively, at early infestation after 90 days of germination. In case of the ABW, thiamethoxam caused a gradual reduction (79.5, 70.8%) in both seasons, respectively. While, in imidacloprid treatment reduction was fluctuated (54.0-70.8%) after 90 days of germination in 2016 season. Most interestingly, the present results indicated that the application of imidacloprid and thiamethoxam as seed treatments significantly increased the total chlorophyll content in cotton leaves that enhance plant growth and improve cotton properties. In general, the selection of a suitable insecticide for controlling the cotton pests not only depends on its efficacy against the targeted insects but also on their profitable effects on cotton production and fiber quality.