Aphids, Bollworms, Stink Bugs, & Tarnished Plant Bugs Complicating Insecticide Management
Well it is definitely mid-season cotton management time here in North Carolina. Lots of questions on a complex of insect pests present in the Coastal Plain. Bollworm flight activity has picked up on cue (link to light trap information) and any management decisions made for other pests should also revolve around this pest. To avoid flaring bollworm and other pests, it is critical that we maintain as many natural enemies as possible. This can be accomplished by using more selective insecticides and avoiding broad spectrum insecticides unless they are needed. As a rule of thumb, carbamates (e.g., Vydate) and organophosphates (e.g., Bidrin, Lorsban, Orthene) are the harshest on natural enemies, followed by pyrethroids (e.g., bifenthrin, Karate/Warrior).
Aphids have been widespread and problematic. Generally they are held back by natural enemies and a fungus, but we haven’t yet spotted fungal activity in our state (generally associated with warm and moist conditions). Aphids can be a problem if cotton is stressed and especially when it is planted late. We can hold off on a dedicated aphid spray unless they are clearly stressing the cotton. Transform is a good choice for aphid control since many populations in our state are resistant to neonicotinoids (e.g., Admire, Belay, Centric). It also has the added advantage of preserving most natural enemies and is the product of choice during a bollworm flight.
Stink bugs have been heavy in both Georgia and South Carolina, but are one pest complex that we should be able to stay on top of. Bifenthrin or Bidrin are effective for brown stink bugs and pyrethroids, in general, are good for greens. As stated in the first paragraph, avoid Bidrin or Orthene during bollworm flights unless a major cleanup is needed or if you are prepared to spray Prevathon or Besiege in Bollgard II, TwinkLink, or WideStrike varieties.
Tarnished plant bugs are still around in some spots and should be considered when insecticide applications are made. Transform is a good choice during bollworm flights because natural enemies will help hold them back. If tarnished plant bug pressure is heavy, pyrethroids + Orthene might be needed in severe cases.