Managing Plant Bugs in Cotton That is Just Starting (or About to Start) Bloom: Diamond or Not?

So far, the 2018 cotton crop is off to a good start. Good growing conditions caused cotton to grow off from thrips pretty quick and plant bugs have been fairly light so far this year. A lot of cotton has been sprayed for plant bugs, but we are not hearing about a lot of blow out populations that are difficult to manage. As a result, one of the big questions we have been getting lately is whether or not the pre-bloom Diamond application is still needed in this situation.

To answer that question, we want to first start by saying that we have done a great job with our plant bug IPM program over the last couple of years. There are two main factors why we feel that is the case. The first factor is that we have been successful obtaining a Section 18 for Transform which gives us an additional insecticide that provides very good control of plant bugs.  The second, and probably most important factor has been the use of Diamond during the third week of squaring to first bloom. We feel that widespread use of Diamond has had an overall suppression effect on plant bug populations across the Delta. Also, we feel that the “one-two” punch of Diamond and Transform as sequential applications sets the crop up great as we go into bloom and helps keep populations at a manageable level through bloom.

We have done a lot work in the past looking at the yield benefits of early season Diamond applications in cotton. This link will take you to a summary of some on-farm trials that we did showing the those benefits from a single application of Diamond at this timing (Early Season Diamond Applications). Finally, we feel that the pre-bloom to early-bloom Diamond application is needed and beneficial, even went plant bug populations are relatively low. Most of the applications to this point in the season have included imidacloprid either by itself or mixed with something else because of cost. Once we get close to bloom, it is time to switch it up and move on to some more expensive, but more effective insecticides such as Diamond and Transform. This will set the crop up as we move into bloom and start switching to acephate or Bidrin mixed with bifenthrin once we get into bloom.

Of all the insects we deal with in cotton, tarnished plant bug is the one that drives most of the decisions with spider mites being a very close second.  The last couple of weeks have been fairly wet (or at least not super dry). As you drive around the Delta, it is easy to find a lot of blooming hosts that are full of plant bugs. That suggests the situation can, and likely will, change quickly as dry weather hits and those hosts start to dry down. As a result, it is important to not let your guard down because populations have been low to this point.