DISTRIBUTION AND MANAGEMENT OF THRIPS TABACI (LINDEMAN) (THYSANOPTERA: THRIPIDAE) ON ONION (ALLIUM CEPA) IN SELECTED DISTRICTS OF KHYBER PAKHTUNKHWA PROVINCE, PAKISTAN

Abstract

Onion (Allium cepa L.) is among the cash vegetable crop grown in Khyber Pakhtunkhwa Province, Pakistan. Onion thrips (Thrips tabaci) is the main problem on onions crop which results great losses. However infestation of this pest could be kept below economic injury level with the help of integrated pest management practices. In this connection, firstly field surveys were conducted in the selected onion growing districts of Khyber Pakhtunkhwa Province, Pakistan and recorded infestation/ population of T. tabaci. Highest numbers (57.59) nymphs plant-1 and (15.39) adults thrips plant-1 were recorded in district Swat while lowest (22.37) nymphs plant-1 and (9.69) adults thrips plant-1 were in district Peshawar (East. Part). Regarding the average number of both (nymphs and adults) plant-1, highest (36.49) thrips plant-1 were recorded in district Swat and lowest (16.03) thrips palnt-1 were in district Peshawar (East. Part). Eight onion cultivars (Ambika, Swat-1, Trichmir, Barkel, Macarena, Red ball, Granada Red and Sunset were assessed to determine the most tolerant cultivar against T. tabaci infestation. The results showed that T. tabaci infest all the cultivars more or less, however cultivar Swat-1 showed to be the most tolerant against T. tabaci infestation as well as proved to be a high yielding cultivar among the others. Highest plant height (64.35cm) was observed in cultivar Trichmir and lowest (38.40cm) was observed in Macarena. Highest (13.07) number of leaves plant-1 was recorded in Trichmir and lowest (7.66) was recorded in Granada red. Trichmir was (94.04%) the most succulent cultivar followed by Sunset (91.38%) and Swat-1 (86.49%), Ambika (87.21%) was least succulent cultivars. The maximum yield (18.56 tons ha-1) was obtained from Swat-1 and minimum was from Ambika (9.34 tons ha-1). The studies on Population dynamic revealed that T. tabaci remained a regular pest on onion during the onion growing seasons. The average peak populations were recorded (54.75 thrips plant-1) during the month of April. Population model using the meteorological data showed that average air temperature have a positive correlation with thrips population. The efficacy of Polytrin C® 440 EC (Profenofos + Cypermethrin) and three botanicals extracts (Azadirachta indica, Parthenium hysterophorus and Datura alba) and a combination of selected dose of synthetic insecticide with each botanical were assessed against T. tabaci on onion crop. All the botanicals extracts significantly control T. tabaci at various degrees over the control (untreated plots). Regarding the yield of onion bulbs, synthetic insecticide along with the combination of (half dose of insecticides along with half dose of each botanical) gave the highest yield followed by botanicals as compared xv to control (untreated plots). Results obtained from the laboratory experiments showed that, female western flower thrips Frankliniella occidentalis feed more and caused more feeding damage than that of males. Feeding damage caused by female F. occidentalis increased significantly as the numbers of female leaf-1 disc was increased. Azadirachta indica oil is significantly less effective than Conserve® (spinosad) in killing F. occidentalis. All the concentrations of neem oil significantly deterred F. occidentalis feeding when compared to controls treated with Tween or water. The botanicals Azadirachta indica, Parthenium hysterophorus and Datura alba extracts tested were as effective as Conserve® (spinosad) in killing F. occidentalis. All the botanicals extracts significantly reduced F. occidentalis feeding when compared to the water control. As expected given the very high mortality caused, the least feeding damage was found on spinosad treated leaf discs. Response of Orius laevigatus to chemical insecticide Conserve® (Spinosad) and botanicals extracts on the predation of T. tabaci showed that Conserve® caused negative response to both O. laevigatus and T. tabaci while there were no negative or mortality effects of botanicals extracts on O. laevigatus. The O. laevigatus consumed more T. tabaci in leaf discs treated with water followed by D. alba, A. indica and P. hysterophorus. Botanicals pesticides offer a safer alternative to using synthetic chemicals and have less or no impact on the environment and biological control agent of T. tabaci as well as botanicals can prevent pest resurgence. These findings encourage the use of botanicals extract which is pollution free approaches for onion thrips control.