Thrips pressure ramped up very quickly over the past Memorial Day weekend.
COTTON: In our cotton plots, we’re getting counts of over 100 immatures in some of our 5-plant seeding samples, and injury has reached extreme levels in untreated cotton. So, who cares about data from untreated cotton? I do. These data provide a ground-truth indicator of 1) how the thrips populations compare over the years, and 2) what amount of injury (symptoms) and damage (lint loss) they are capable of causing. We maintain untreated ‘controls’ in our tests for these reasons. Depending on the planting date, variety and soil conditions, the injury in this year’s untreated controls is now ranging from 2.5 of so (on our 0-5 scale) to 4.85 (many plants killed or severely injured). Earlier planted cotton has the most injury and we see more in fields with ‘heavier’ soils. Adult thrips are still present on the plants which tells us that the infestation cycle is not over. Based on past experience, I think the peak will occur next week. So if you have not treated for thrips, now would be a very good time to check fields and make the call. If you see any significant number of seedlings showing injury, especially if the new buds are injured, blackened and deformed, now is the time to treat.
Many treatments in our cotton plots are providing excellent protection. For the most part, seed treatments are not providing the same level of protection as liquid in-furrow treatments. If you are relying on seed treatments, there is a good chance your cotton could benefit from a foliar treatment. The higher rates of the liquid in-furrow treatments are holding well and may not need additional foliar treatments, depending on how fast plants grow to the 3-4 leaf thrips-safe stage.
PEANUTS: Thrips populations are slower to develop in peanuts but untreated plants are beginning to showing significant levels of injury (up to 3.0 on our 0-10 injury scale). There are a lot of adult thrips on peanut seedlings which tells us that the cycle is still in progress and things will get worse over the next couple of weeks, for sure. As in our cotton plots, the seed treatments are showing more injury compared with liquid in-furrow treatments and may need more protection. The decision is not as urgent in peanuts, compared with cotton, as peanuts seem to tolerate thrips injury better—but, there is a point when more protection is a benefit. It is has been hard to pin this down—but in general if I see more 25-30% of the leaves with injury (crinkled leaves) and, especially, if the new terminal leaves are brown and deformed, it is time to apply a foliar treatment.
EARLY SEASON FIELD TOUR—NEXT WEEK—JUNE 5
If you are interested in getting a look at our cotton and peanut thrips trials, or field presentations by our other Tidewater AREC faculty, take advantage of the opportunity to attend our annual Early Season Field Tour Thursday of next week June 5. Registration begins at 8:30am at our Hare Road Farm and we will conclude with a nice lunch. CCA recertification credits will be offered, as well as credits for Private Applicators, Commercial Applicators 1-A, 1-C and 10) and Registered Technicians. Email or call if you need more information (herbert@vt.edu; 757-657-6450).