Frankliniella fusca activity patterns in wheat

Tobacco thrips (Frankliniella fusca Hinds) are an important seedling pest of many agricultural crops including, but not limited to cotton, tomato, and tobacco. This insect is mobile and completes several generations on both crop and non-crop plants each growing season in the southern United States. We do know that this insect disperses through a predictable sequence of these habitats each spring, however, it is not well known how abundant early season host crops affect population development at a landscape scale.

To better understand how spring crops influence tobacco thrips populations, we conducted a study of tobacco thrips activity in a key early host, winter wheat (Triticum aestivum L.). To do this, we measured larval and adult thrips abundance in 69 wheat fields across 5 North Carolina counties in 2019 and 2020. We first sampled wheat heads weekly to measure how many larvae were present in the crop over approximately 10 weeks before the wheat senesced and harvest occurred. At the same time, we measured the number of tobacco thrips dispersing from the crop into the surrounding landscape using yellow sticky cards placed along the wheat field edge.

We linked these responses to both landscape and weather factors to describe variation in abundance. We also directly related the abundance of larvae found in wheat heads at different crop maturity stages to the number of adult thrips leaving the field. We found that larval counts during the milk and dough stage of wheat maturation related to the adult dispersal patterns two weeks later. This data provides a useful assessment for crop phenology driven dispersal for an economically important pest species in the southern United States.