The stink bug complex is now getting the most attention from crop consultants working cotton in Alabama.
Based on calls from consultants, this would be appropriate since there are no other widespread problems being reported in cotton and there is a high number of stink bugs in all the major row crops.
This began with wheat during the spring months. Stink bug numbers later shifted to corn. High numbers have been reported in recent weeks in peanuts, with increasing numbers being reported in both cotton and soybeans.
If we back up and review the situation since the end of the 2012 season, this is as expected. Stink bugs built high numbers on soybeans late last season resulting in a high level entering over-wintering sites. This past winter was mild and we did not have the excessive high temperatures or extended drought this spring to limit a 2013 population build up.
This complex included both the brown and the southern green species. In the more southern counties within Alabama, the leaf footed bug is also in the mix. Leaf footed bug damage is identical to stink bug damage to cotton bolls.
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The important thing here is that, control wise, they are more like the brown stink bug. Phosphide insecticides do a much better job in controlling brown stink bugs and leaf footed bugs than do pyrethroids.
Growers will need to keep this in mind as they select their chemical for treatment decisions.
In Alabama, escaped bollworms on Bollgard and Widestrike cotton varieties have not presented a big enough problem to select a pyrethroid over a phosphate for stink bug control.
Field monitoring between July 20 and Aug. 10 will determine if that trend holds true for the 2013 season.
In a few weeks, as we begin to make more stink bug control decisions in soybeans, we will have to work more with the pyrethroid chemistry to suppress the brown stink bugs in the complex.
Research trials across the south point to bifenthrin as the superior pyrethroid for brown stink bugs in soybeans. We can improve the percent control by using the higher labeled rates.
Treatment decisions in cotton
Back to cotton. Here is how we suggest making treatment decisions.
First, select a minimum of 25 10 to 12 day old bolls that are still soft to the touch and can be crushed by hand. Select more bolls from at least two locations from larger fields. Crush these bolls and observe for internal injury.
Note, it may make this process faster by first separating the bolls with external feeding signs from those that have none.
First, crush the bolls with external feeding only and determine the percent that have internal injury. If a threshold is reached, then the remainder of the bolls with no external feeding signs will not need to be crushed.
Internal damage may consist of one or more warts on the inside of the boll wall, damaged seed or stained lint.
Second, the decision maker needs to know how long that particular field has been in the blooming stage. Most stink bug injury and loss is coming during weeks three though five or six of bloom. This is the period when most harvestable bolls are being set.
In Alabama, I suggest using a 10 percent internal damage threshold during weeks three though six of bloom.
An insecticide application will usually suppress stink bug numbers for seven to 10 days unless a field borders another untreated crop with high numbers of stink bugs. If has been my experience that stink bugs do not move rapidly across fields like plant bugs as they re-infest. The first four to 10 rows adjacent to corn or peanuts seem to get most of the migration initially.
In our heaviest stink bug years, cotton in the Coastal Plains of the southeast have required up to four applications. Under most conditions however, only two or three sprays may be warranted.
One last thing I will mention today is that, in the past, stink bugs seem to cause more internal boll damage in wet seasons than in dry seasons. That being the case, and unless the weather changes, we need to be extra cautious of stink bug damage to cotton in 2013.