June 18, 2014
The call of the week has been about plant bugs in cotton, and even this early in the game, immatures are already being found. This doesn’t really change my recommendation at this time of year, but it is noteworthy that several people have mentioned it.
Centric or one of the imidacloprid products are still good choices. Excluding when used as a seed treatment, you can only use 0.125 lb AI of thiamethoxam during a season. This means that you can only use a maximum of 5 oz of Centric per season, and the thiamethoxam present in Endigo also counts towards this total use restriction. Thus, alternating between imidacloprid and Centric helps to keep us on the label.
You should use the full labelled rate of whichever imidacloprid product you choose. Alternatively, I often use 1.5 – 1.75 oz of Centric on smaller cotton. Even though immatures are showing up in some cotton, I would refrain from using Diamond until about first bloom or after. The residual control provided by Diamond and most other insecticides on small, rapidly-growing cotton are questionable.
New growth will not be exposed to insecticide, and Diamond does not kill adults (which is most of the population found during early squaring). Diamond is also pretty good at flaring secondary pest outbreaks, so that’s another reason to delay its use for a few more weeks.
One interesting question has come up this week. Should I spray for plant bugs if only part of the field is squaring and at threshold for plant bugs? This has come up where cotton in low spots is stunted and lagging behind other parts of a field that have started squaring. Like any other time of the season, treatments should generally be based on the whole-field average infestation levels.
Of course, you could make a “precision” application to just the infested parts of the field, but that is often easier said then done. Usually, the most practical thing to do is to delay the application for 2-3 days. However, these are situations that require some judgment depending upon what percentage of the field is squaring, how many plant bugs are present is the squaring parts of the fields, etc.
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