Author: Jody Lynn Gangloff

Publisher:

Published: 1999

Total Pages: 144

ISBN-13: 9780599413269

The onion thrips, Thrips tabaci Lindeman (Thysanoptera: Thripidae) is a worldwide pest of onions and other crops. In New York it is an annual threat to the commercial onion industry where populations are managed with regular applications of insecticides. Two peaks of flight activity occurred during the period when T. tabaci infest onions in New York. These flights were composed of both female and males of this species, as well as a smaller number of other species. On-plant populations consisted of both female and male T. tabaci but no other species of thrips. Numbers of thrips on onion plants increased steadily through the growing season, exceeding the economic threshold of three thrips per leaf by mid to late summer in most fields. During the period of population increase, and especially during peaks of flight activity, airborne thrips were captured in equal numbers on traps placed throughout onion fields. Peaks of flight activity and proportions of T. tabaci of all thrips captured in onions did not correspond with peaks, harvest or ratio of thrips captured in neighboring field and forage crops, although T. tabaci was found to be a dominant species in areas outside onion fields. Sexually reproducing strains of T. tabaci were collected from onion fields. These were found to be highly resistant to pyrethroids, including l -cyhalothrin. By contrast, T. tabaci collected in areas adjacent to onions, such as alfalfa fields, reproduced asexually and had low resistance to l -cyhalothrin. It was concluded that neighboring field and forage crops are not the most significant source of T. tabaci that invade onion fields each year and become hard to manage in New York. High levels of insecticide resistance indicate that a resistance management plan and the promotion of integrated pest management in New York's onion industry should be high priorities in the near future.