New Jersey blueberry growers are often concerned about thrips in their farms. These insects are difficult to detect on plants because of their small size (see picture). Also, thrips injury appears similar to that caused by nutrient deficiencies and diseases. To ensure that thrips are the causal agent of injury to your crop, you will need to inspect the injured sites for presence of thrips. This can be achieved by using a white beating tray. Most grower concerns come from the potential of thrips injury to blueberry flowers. This injury is usually caused by flower thrips in the genus Frankliniella. In New Jersey blueberries, the eastern flower thrips, F. tritici, is commonly found on plants in and around farms and can feed on blueberry flowers, and thus imposes a potential threat. This thrips species can be monitored using white sticky traps. Our recent data also show that after bloom, most thrips feed on young blueberry foliage, causing curling of the leaves. This type of injury is mainly caused by another thrips species, Scirtothrips ruthveni. It remains unknown whether injury to leaves causes yield reductions. Injury to fruit by thrips is low and becomes undetectable as the fruit matures.
We have collected data on thrips captures on white sticky traps and recently developed a degree-day model to predict thrips abundance on blueberry fields. This model is available at the Degree Day Calulator (Blueberry and Cranberry Research Station).
Scouting and Control
White sticky traps and beating trays are used to monitor thrips. If you find thrips causing injury to your crop, you may use Entrust (OMRI approved) or Delegate. These products are highly toxic to bees so, if used during bloom, they need to be applied at dusk, when bees are not actively foraging. We recommend avoiding the use of these products during bloom unless it is extremely necessary.