• Although cotton is not susceptible to TSWV, it is nevertheless extremely susceptible to mechanical damage from thrips, particularly in the cotyledon to 2 or 3-true leaf stage.
• This feeding can result in maturity delays and high yield losses.
When planning for the upcoming thrips season, a few suggestions come to mind.
• Thrips damage: Several thrips species, especially tobacco thrips, and their damage are a major annual headache for most cotton producers in the Upper Southeast.
On tobacco, peanuts, tomatoes and some other crops, tobacco thrips can vector tomato spotted wilt virus (TSWV), at times resulting in severe damage and crop loss, even with modest thrips feeding.
Although cotton is not susceptible to TSWV, it is nevertheless extremely susceptible to mechanical damage from thrips, particularly in the cotyledon to 2 or 3-true leaf stage. This feeding can result in maturity delays and high yield losses.
• Thrips levels and planting dates: As most cotton producers have found from experience, thrips levels and damage potential can vary from year to year and from field to field.
Additionally, when thrips levels are high and cotton is growing slowly (which happens in both cool and in hot dry weather), the potential for damage to seedlings is greatest due to limited uptake of insecticide.
This high damage potential is often most common in cotton planted during the last week in April through the first week of May.
As a general rule, cotton planted further into May is exposed to warmer average temperatures, resulting in more rapid seedling grow-off and less time in the thrips-susceptible, early stages of development.
For the most part, we have been able to get by with treated seed only (no follow-up foliar spray) with cotton planted from May 15-25.
• At planting options: In applied research trials conducted in North Carolina in 2012, all of the chloronicotinoid cotton seed treatments (Avicta Complete Pac, Poncho/VOTiVO/Aeris and Acceleron) provided very similar levels of control and yields.
If one reads their product labels, these materials tend to have similar or identical insecticides and rates.
One bright spot last season was the high thrips activity and persistence of an in-furrow application of imidacloprid (in this case, Admire Pro) plus a seed treatment (in this case Avicta Complete).
Although more expensive initially, when one considers the added chemical cost, extra tanks and spray rigging, initial results suggest that in many cases, this tactic could provide growers with a one-time at-planting option for “season long” (i.e., getting seedling to the 5 true leaf stage) control of thrips.
Admire Pro applied alone (w/o treated seed) provided thrips control equivalent to a seed treatment alone.
A number of producers are trying this option this year on part of their cotton acreage. This approach will be evaluated in replicated tests throughout the Southeast this season.
• Foliar treatment options for thrips: Based on evaluations of liquid foliar insecticide options for thrips control conducted in North Carolina and Virginia in 2012, it’s safe to say pyrethroids are not the insecticide class of choice: the candidate pyrethroid (Karate at 1.28 oz. product/acre) only provided an average of 22 percent thrips (almost all tobacco thrips) control.
Lannate (74 percent) and Vydate (77 percent) provided intermediate control, while dimethoate (90 percent) and acephate (93 percent) provided the best control.
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A high (and very expensive) rate of Benevia gave 98 percent control, but we just learned last week this product will not be labeled for cotton. Darn!
Compared with the now-rare Temik 15G, the common combination of a seed treatment and a follow-up foliar spray increases the odds of having to deal with subsequent spider mite and/or cotton aphid outbreaks.
Fortunately, we do not contend with economic levels of either pest in North Carolina compared with most other areas of the Cotton Belt, such as the Mid-South and parts of Texas.