Effect of Planting Date and Timing of Growth Stages on Damage to Cabbage by Onion Thrips (Thysanoptera: Thripidae)

The same cabbage varieties remain resistant or susceptible to damage by the onion thrips, Thrips tabaci Lindeman, regardless of changes in planting date or synchronization of other growth stages. Thus, varietal resistance observed in previous studies is true resistance, not pseudoresistance caused by differences in timing of maturity or other critical growth stages. Delaying planting from 6 June or 18 June to 2 July significantly reduced damage ratings for susceptible varieties and depth of thrips damage (number of leaves into the head where damage estimated at <1% of leaf area was found) for all four varieties. This result suggests that farmers can reduce thrips damage on their cabbage heads by planting susceptible varieties late in the season, as well as by planting resistant varieties.