Fortunately, much of the cotton is reaching the point where insecticide applications for plant bugs can be terminated.  However, the battle remains pretty intense in later maturing fields (those running 4, 5 6 or more nodes above first-position white flowers).  A number of folks are on their third or fourth consecutive week of spraying.  Consequently, I’ve been getting a lot of questions about whether insecticide sprays are working.  I’ve also had a number of positive and negative comments about the performance of Diamond.  Thus, I’ve put in some data below to make a few points.

1. Bifenthrin products such as Brigade or other pyrethroid insecticides are providing almost no control when used by themselves (see table 1).  We always have some level of pyrethroid resistant tarnished plant bugs, but control this year is the worst ever.
2. Transform (1.5 oz per acre) and Orthene/Acephate (0.75 lb or more per acre) have done a great job in my tests this year.  Bidrin XP II at 10-12 oz per acre has also looked good.
3. Endigo ZC is usually a “go to” product for plant bug control.  It has not been as sharp this year, probably because the pyrethroid component is not adding much (see tables 1, 2 and 3).  Endigo does add protection from stink bugs and bollworm.  There have relatively few reports of stink bugs or bollworm, but there are in the mix.  The frequent plant bugs sprays have covered up problems with these pests.
4. Although not shown in the data below, mixes of pyrethroid insecticides with Orthene/Acephate at 0.5 – 0.67 lbs or Bidrin at 4 oz/acre per acre look pretty good.  These mixes will also cover up background infestations of bollworm and stink bugs.  In table 1, you can see how adding Brigade to Transform at 1 oz/acre gave control of plant bug similar to Transform at 1.5 oz per acre (and it reduced numbers of stink bugs).
5. What about Diamond?  First, I think the benefit of using Diamond this late in the game time is greatly diminished.  This product fits better at the beginning of the spray cycle.  Diamond is an unusual product and is difficult to evaluate.  It rarely looks good the week following a single application, but it has residual benefits down the road.  Table 3 demonstrates some of this slow motion action.  Notice that 4 days following a single application, Transform provided excellent control of plant bugs.  In contrast, plant bug populations following Diamond were still above threshold.  However, control following a single application of Transform or Diamond was nearly identical at 10 days after treatment.   So, Diamond actually performed quite well in the long run.  If used early, it may save an application down the road.  That does not mean you can spray it and think you will not have to spray again, and when fighting high populations you should still plan on two consecutive applications at a 4-5 day interval.

Results of Recent Insecticide Efficacy Trials in Late July and Early August (WTREC, Jackson, TN)

Test 1.  Numbers of plant bugs or stink bugs per 10 row ft (4 days after a first application and 8 or 12 days after a second application).

Test 2.  Number of plant bugs per 10 row ft (5 days after treatment).

Test 3.  Numbers of plant bugs per 10 row ft (4 days after 1^st application and 5 days after a second application).