Article by Jack Bacheler
As we have mentioned in previous articles, this could be a big year for stink bugs in cotton and perhaps soybean. It certainly seems to be playing out that way. In some areas we appear to have a perfect storm of high background levels of stink bugs that developed on wheat and other hosts, a high proportion of brown as opposed to green stink bugs, and very attractive and susceptible cotton plants. In most areas of the state, cotton fields are in the 3rd to 5th week of bloom, or “stink bug crunch time” when moderate damage cannot be tolerated and the protective 10% damaged boll threshold is recommended. I think that the potential for stink to cotton bolls is far higher in NC in 2012 than during the past few years, maybe even going back to 2004, our “Year of the Stink Bug”. Many consultants across a wide area are reporting 10 to 20% stink bug damage to quarter-sized bolls. If the 10% threshold is met on consecutive weeks, that finding calls for treating after each of these assessments. If a scout is correctly assessing quarter-sized bolls, a new subset of bolls will be inspected each week and the counting of previous older damage is avoided. Remember to count even slight warting and/or subtle lint staining as a damaged boll. Subtle damage simply means that the damage has occurred recently; this translates into a treatment for a resident stink bugs bug population, not a treatment for old damage.
Although our licensed independent crop consultants have a good handle on managing stink bugs, this year would be a good one for getting additional folks more active in examining approximately 1-inch diameter or quarter-sized bolls for internal damage. Please take the potential significant boll damage from stink bugs seriously.
We are getting many questions about insecticide control options for stink bugs, particularly brown stink bugs. Bidrin and Bidrin-containing combinations are very effective against brown stink bugs, rating a 5 on a 5 point rating system based on the Cotton Insecticide Efficacy Tables developed by entomologists across the cotton belt. However, we should all be reminded that the active ingredient dicrotophos is very toxic to humans and a 6-day reentry interval and appropriate safety safeguards must be observed. Also this material provides no caterpillar activity. Of the pyrethroids, bifenthrin (materials like Declare, Brigade and Discipline) rates a 4.3 out of a possible 5 for brown stink bug effectiveness while the other pyrethroids in general rate approximately 3.3. Adding acephate to a pyrethroid helps with brown stink bug control and lower rates of Bidin plus a pyrethroid is another effective option for stink bugs and provides bollworm control. If green stink bugs predominate, a number of insecticides, including pyrethroids, pyrethroid/chloronic combinations like Endigo and Brigadier, are also effective. Do not use chloronics like Admire Pro, Centric, or Belay alone for stink bugs – members of this chemical class only have ratings in the 1.5 to 3 range out of 5.