ISHS Acta Horticulturae 708: V International Strawberry Symposium
GETTING A GRIP ON THRIPS IN STRAWBERRIES |
| Authors: | M.Y. Steiner, S. Goodwin |
| Keywords: | Action thresholds, trapping, natural enemies, pest management |
| Abstract:
Results from a three-year study in a hydroponic strawberry crop near Sydney, New South Wales, on management of western flower thrips, Frankliniella occidentalis (Pergande), resulted in a better appreciation of the nature of thrips damage, thresholds for action, the interaction of the environment and damage severity, and tools for managing populations below economic threshold levels. Western flower thrips was the dominant species in the first year, but only plague thrips, Thrips imaginis Bagnall, and onion thrips, Thrips tabaci Lindeman, were present in the second and third year, with plague thrips dominant and causing damage similar to that of western flower thrips. Damage to fruit occurred during two distinct development phases, and resulted in different symptoms. The most severe damage occurred on young green fruit about two weeks post-flowering, evident as a network of surface russeting, with secondary damage caused to older green and red fruit, in the form of browning around the seeds. Action thresholds and monitoring methods were developed that are based primarily on critical numbers of thrips in flowers, though for western flower thrips, counts on yellow sticky traps can provide supporting information. An action threshold of 45% of flowers with 5 or more adult western flower thrips, or 40% with 10 or more plague thrips was established, with a greater tolerance during cool wet periods. For western flower thrips, the action threshold also corresponded with a sexual bias on traps of 60-65% females (20-30 females per trap). While pesticides are likely to remain necessary to protect crops against invasive species, those with least risk to natural enemies should be selected where possible, as the latter may play an important role in regulating late season populations. Overhead misting during hot dry periods was found to reduce damage severity and thrips population density. Familiarity with local thrips species and natural enemies and their seasonal occurrence is important, as management approaches will need to be adapted to them. | |
Download Adobe Acrobat Reader (free software to read PDF files) | |
