Photo by Lorena Lopez
By Clint Thompson
The impact of tarnished plant bugs (TPB) in North Carolina strawberries is normally low every year. But that has changed this season, due largely to the ongoing drought across the Southeast.
“This year it seems like it’s widespread and not at a moderate level but at a high infestation level in a lot of strawberry farms,” said Lorena Lopez, North Carolina (N.C.) State assistant Extension professor of entomology and plant pathology.
According to N.C. State Extension, tarnished plant bugs can show up as early as the first week of April in fields in the coastal or piedmont areas of North Carolina. The bugs can complete two to three generations per year. Adults and nymphs feed with piercing-sucking mouthparts, injecting enzymes that lead to cell death while disrupting tissue development. This can lead to “button berry” malformation with fruit that is small, uneven or misshapen.
Insecticides are usually the primary tool for managing populations in other areas.
“We have some insecticides, but unfortunately, because most of the growers here in North Carolina usually don’t have issues with (the bugs), they don’t have the (sprays) in the toolkit. They usually just have one which is bifenthrin. That’s one where they already are resistant for. That’s one that the growers use the most,” Lopez said.
“There are options, but they aren’t usually in the toolkit of strawberry growers because it’s not a common issue. It’s becoming a problem now in North Carolina.”
What to Remember
For those implementing insecticides, they should note that pyrethroids should be used sparingly and not as a first option. Growers need to also apply insecticides as late in the day as possible to avoid harmful effects to bees.
Refer to the North Carolina Agricultural Chemicals Manual and the Southern Region Small Fruit Consortium Strawberry IPM Guide for materials recommended against TPB in North Carolina and more details about their management.
It is important for strawberry growers to understand the thresholds for tarnished plant bug impact. They should scout weekly or twice a week, if possible, especially in fields with histories of infestations.
The threshold for TPB in strawberries when sampling using a beat sheet is 4.5 nymphs per 30 clusters (0.15 nymphs per cluster).