Temperature development and damage rates of onion thrips

Abstract

Bulb damage caused by onion thrips (Thrips tabaci, Thysanoptera: Thripidae) is a serious problem in New Zealand stored export onions. Understanding the relationships between insect development rates, temperature and damage potential is critical to effective pest management by targeting fewer pesticide applications. Thrips development (egg to adult) was monitored daily on leek leaves, onion leaves or onion bulb discs at constant and variable temperatures. Development rates were not significantly different on different substrates, but survival was lower on onion bulbs. Total development time (egg to adult) ranged from 51.1 days at 12°C to 10.3 days at 30°C. Lower development temperature thresholds ranged from 7.3°C for pupae to 9.1°C for eggs. Accumulation of 221 degree-days above 8.1°C was required to complete development. The temperature development model accurately predicted development time of onion thrips under variable temperature conditions. At 21°C, adults and larvae caused an average of 20.1 and 10.7 mm2 of feeding damage to onion bulbs per day, respectively. © 2012 New Zealand Plant Protection Society (Inc.).