RELATIVE TOXICITY OF SOME INSECTICIDES TO Frankliniella schultzei (THYSANOPTERA: THRIPIDAE) INFESTING TOMATO

Abstract

Tomato is one of the most popular solanaceous vegetable crops. It is attracted by a large number of sucking insect pests like aphid, jassid, thrips, white fly etc. Thrips is one of the most common pests of tomato which is severely responsible for plant growth, crop quality and yield. The insect pest control by chemical insecticides is yet considered as most effective. Relative toxicity of seven selected insecticides (abamectin 1.8 EC, imidacloprid 70 WG, bifenthrin 2.5 EC, deltamethrin 2.5 EC, lambda-cyhalothrin 2.5 EC, spinosad 2.5 SC and thiamethoxam 25 WG) along with untreated control were evaluated to Frankliniella schultzei thrips (Thysanoptera: Thripidae) infesting tomato (BARI TOMATO 4). The effectiveness of treatments was evaluated by two consecutive sprays following randomized complete block design (RCBD) with three replications. Data were recorded at 1, 3, 5, 7 and 14 days after spray (DAS) in each case. After two sprays, among seven insecticides imidacloprid reduced the highest thrips population on leaf (75.73%) followed by thiamethoxam (66.96%) spinosad (61.83%), abamectin (59.34%), lambda-cyhalothrin (54.89%), deltamethrin (52.57%), and bifenthrin (41.90%). In case of flower infestation, the highest reduction of thrips was 77.22% (imidacloprid) followed by 70.77% (thiamethoxam), 64.89% (spinosad), 61.43% (abamectin) 60.27% (lambda-cyhalothrin), 56.20% (deltamethrin), and 53.21% (bifenthrin) compared to untreated control after second spray. Considering the yield of tomato and economics of cultivation, the highest yield (11 kg/plot) was found from imidacloprid treated plot followed by thiamethoxam (9.33 kg/plot), abamectin (8.33 kg/plot), spinosad (8 kg/plot), lambda-cyhalothrin (7.67 kg/plot), deltamethrin (7 kg/plot) and bifenthrin (6.67 kg/plot) treated plot, as compared to untreated control (6 kg/plot). However, from the benefit cost ratio (BCR) the highest BCR (5.79) was recorded in imidacloprid and the lowest was found in bifenthrin (3.61) treated plot. Thus, among the treated insecticides, imidacloprid was the most effective in reducing Frankliniella schultzei and for getting the highest yield and BCR in comparison with other insecticides. So, tomato growers can use imidacloprid as a chemical control against Frankliniella schultzei.