Studying the effects of seed treatment with several insecticides against cotton thrips (Thrips tabaci Lindeman, 1889) in field conditions

Cotton thrips is one of the most important pests of cotton in the first season and economically in Iran. Nymphs and mature insects of thrips cause deformation of leaves, reduction of green area, loss of terminal bud, dwarfing and multiple branching of plants, reduced growth and consequently lower yield. One way to prevent pest infestation is to treat the seed with insecticides. In this study, the effects of seed treatment with three insecticides were investigated as a factorial experiment in the form of a randomised complete block trial under field conditions.

This project was conducted in the form of a factorial experiment based on a randomised complete block trial with three replications in the provinces of Khorasan-e Razavi and Khorasan-e South. The main factor (A) was tested in 2 stages of delinated and hairy cotton seeds and the secondary factor (B) in 7 stages with the new insecticide thiomethoxam (Cruiser®) at 5 and 7 mm, imidacloprid (Gaucho®) and thiodicarb at 5 and 7 grammes per kilogramme and the control without insecticide. To treat the seeds, the tested insecticides were mixed in 25 ml of water for each kilogramme of seeds, the cotton seeds were placed in the resulting solution and stirred for 10 minutes. After all surfaces of the seeds were covered with the toxic solution, the treated seeds were placed on a paper sheet until they were completely dry, and then cultivation was carried out in the field. After the cotton plants germinated, the evaluations were collected from the first to the fifth week after germination. The data was analysed using SAS software and the mean values were compared using the Duncan multiple range test.

The results showed that the type of seed (bordered or hairy) had no effect on the efficacy of the seed treatment to control the cotton thrips pest, but the insecticide treatments differed significantly from each other in terms of the number of pests. Of the insecticides tested, Gaucho insecticide at a dosage of 7 grams and Cruzer insecticide at a dosage of 7 ml per kilogram of seed had the greatest effect as a seed treatment in preventing damage from first season cotton pests such as thrips.

According to the results of this test, it can be said that Cruiser® insecticides (7 ml per kg of seed) showed the best results as a seed treatment. To prevent feeding and damage by thrips and even other first season sucking pests in the first five weeks of the plant's growing season, this insecticide is recommended for hairy and non-hairy seeds manually or mechanically in seed treatment farms.