Impact of Straw Mulch on Populations of Onion Thrips (Thysanoptera: Thripidae) in Onion

Abstract

Development of insecticide resistance in onion thrips, Thrips tabaci Lindeman (Thysanoptera: Thripidae), populations in onion (Allium spp.) fields and the incidence of the T. tabaci transmitted Iris yellow spot virus have stimulated interest in evaluating alternative management tactics. Effects of straw mulch applied in commercial onion fields in muck areas of western New York were assessed in 2006 and 2007 as a possible onion thrips management strategy. In trials in which no insecticides were applied for thrips control, straw mulch-treated plots supported significantly lower T. tabaci populations compared with control plots. In both years, the action thresholds of one or three larvae per leaf were reached in straw mulch treatments between 7 and 14 d later than in the control. Ground predatory fauna, as evaluated by pitfall trapping, was not increased by straw mulch in 2006; however, populations of the common predatory thrips Aeolothrips fasciatus (L.) (Thysanoptera: Aeolothripidae) were significantly lower in straw mulch plots in both years. Interference of straw mulch in the pupation and emergence of T. tabaci was investigated in the lab and their emergence was reduced by 54% compared with bare soil. In the field the overall yield of onions was not affected by the straw mulch treatment; however, the presence of jumbo grade onions (>77 mm) was increased in 2006, but not in 2007. These results indicate that populations of T. tabaci adults and larvae can be significantly reduced by the use of straw mulch without compromising overall onion yield. The use of this cultural practice in an onion integrated pest management program seems promising.

Onion Thrips (Thysanoptera: Thripidae): A Global Pest of Increasing Concern in Onion

“…: T. tabaci: A WORLDWIDE ONION PEST12-by 12-cm spacing than when planted at 3 by 3 cm and when used at the seedling stage than at plant maturity. Larentzaki et al (2008b) evaluated the impact of straw mulch on T. tabaci in onion. In the Þeld, they observed that straw mulch-treated plots had signiÞcantly less thrips and action thresholds were reached in straw mulch treatments 1Ð2 wk later than in control plots but yield was not signiÞcantly different between plots.…”

Integrated management of Thrips tabaci (Thysanoptera: Thripidae) on onion in north‐western Italy: basic approaches for supervised control

“…Pesticide impact on human and environmental health begs for alternative pest management approaches, such as the use of straw mulch11, 23, 24 or thrips‐resistant onion cultivars25 or the evaluation of new bioinsecticides4 and of biologically active plant volatiles1 against T. tabaci . Moreover, novel chemical and biological control agents appear to be promising for reducing the use of conventional insecticides; in particular, activators of the natural systemic acquired resistance (SAR) response found in most plant species are worthy of attention.…”

Soil conservation practices for insect pest management in highly disturbed agroecosystems – a review

“…In onions grown without pesticides, straw-mulched plots supported significantly lower onion thrips populations compared with control plots, which pushed the action threshold between 7 and 14 days later (Larentzaki et al, 2008). In the same study, the mulch did not reduce yields or impede the use of a mechanical harvester.…”

“…Physical obstruction and alteration of the environment were suggested as mechanisms in suppression of Colorado potato beetle by straw mulch (Zehnder & Hough-Goldstein, 1990;Brust, 1994). Interference of straw mulch in the pupation and emergence of onion thrips was investigated in the laboratory to find that their emergence was reduced by 54% compared with bare soil (Larentzaki et al, 2008). Chemical properties of mulch may play a role as well.…”