Seasonal variations of onion thrips, <i>Thrips tabaci</i> (L.) on onion in the Central Rift Valley of Ethiopia

Abstract

A field experiment was carried out at Melkassa Agricultural Research Center from 2015 to 2017 to determine the seasonal fluctuation of onion thrips on onion in three consecutive growing seasons. Onion was planted on 10 x 10 m measuring plots and replicated three times. Thrips was counted on fifteen randomly selected plants from the central row of each plot. The thrips population was significantly different in different growth stages of onion. During the bulb enlargement stage, the number of thrips/plant was significantly higher than in the early growth stage, but insignificant differences between bulb enlargement stage and maturation growth stages in both years. Thrips population was significantly varied between the dry and rainy season, with much higher populations in the mid-vegetative growth stage than early growth stages in all seasons. The highest thrips populations were recorded in the dry hot and dry cool seasons, while lower numbers were counted in the rainy season where the highest rainfall recorded season in both years. The population of onion thrips was significantly positively correlated with maximum temperature, while a significantly negatively correlated with rainfall and relative humidity. The population of thrips was not correlated with minimum temperature and wind speed. Future research on the management onion of thrips should consider the growth stage and production season of onions for sustainable integrated thrips management program