With cotton moving into squaring it’s a good time to think about a game plan for tarnished plant bugs. In recent years, tarnished plant bug infestations have extended far into the blooming period. Because insecticide resistance is a real issue for this pest, planning a solid insecticide rotation will be important for long-term control in cotton.
Before bloom, our goal is to keep 80% of the squares on the plant. If squares are dropping off pre-bloom, it’s a good bet that plant bugs are to blame. However, use a combination of plant bug presence (8 plant bugs in 100 swooshes of the net) plus 80% square retention as a threshold to trigger sprays.
Specific scouting details can be found in the tarnished plant bug sampling section in the NC Cotton Insect Scouting Guide.
We are now past the point in the season where neonicotinoids (Admire and Centric) should be applied alone. We have pyrethroid-resistant plant bugs in the northeastern part of the state and this should serve as a wake-up call to rotate insecticides.
Try to avoid using more disruptive insecticides (e.g., Bidrin, pyrethroids [including bifenthrin], Orthene, etc.) until later on in the season when we need to manage both stink bugs and possibly plant bugs. Beneficial insects are a residual management strategy after insecticide applications (think of them as bio-residual).
If we preserve them in the field, their populations should continue to build and eat pests as they show up. Now is the time to use insecticides like Transform (I recommend 2 oz and above) and Vydate (10 to 12 oz). Admire or Centric can be tank-mixed with either of these insecticides to add an additional mode of action to target plant bugs.
Finally, if nymphs are present, Diamond (4 to 6 oz) should be tank-mixed to provide extended control.