There are three neonicotinoid insecticides labeled for plant bug control in cotton. The attached table presents the rates (oz and lb ai/acre). The low and high rates of all products are essentially equal in terms of the amount of active ingredient applied per acre. Although all are neonicotinoides, each of the products is a different compound so activity against plant bug (and stink bug) may differ (Centric contains thimethoxam; Trimax Pro contains imidacloprid, and Belay contains clothianidin). We are in the process of comparing these three for effectiveness in controlling plant bugs in cotton. We will share the results soon. We do have some stink bug control data in both soybeans and cotton, but will wait for another week or so before posting that information.

Additional information: neonicotinoid-insecticide-options-jul-1-2010-v2003-doc

A quick note after a long day—we just completed our annual Early Season Field Tour where we showed about 75 attendees a lot of our cotton and peanut thrips trials. Thrips populations are large and there are dramatic differences in the amount of plant injury between the treatments (which is why we plan this tour for early June). In each trial we have untreated plots where thrips populations are allowed to develop uncontrolled so we see and assess these ‘worst case scenarios’. That is, how bad would they get and what kind of yield loss would you have if you didn’t treat for them. Each week, for about five weeks after plant emergence, we sample thrips populations (adults and immatures) and do plant injury ratings for each treatment. This gives a good comparison of the different treatments, how well they control the thrips, how long they work and of course, ultimately, how much yield they protect.
In our tests, as of this weeks sample we are counting from 113 to 160 immature thrips per 5 plant sample in cotton (that is 22 to 32 per small seedling), and 62 immatures per 10 peanut leaflets. These are very high numbers. The plant injury in these untreated controls is severe. The cotton plants are being killed, and the peanuts are severely stunted with blackened terminals. But the good news is that even under this extreme thrips pressure, most treatments are holding well. Temik, Aeris and Avicta treatments are doing well in cotton, and Temik and several experimental seed and in-furrow applied insecticide treatments are holding in peanuts. Protected plants are green and vigorous. This field tour offers a good opportunity to really see what thrips are capable of in terms of plant damage, and how the many different insecticide options compare.
With the high thrips numbers we are seeing this week, we can expect at least one more week of extreme pressure. Next week we will assess all the plots again and post an update on how things are shaping up.

Just a short update on the thrips situation in Virginia cotton and peanuts – I have gotten several calls from growers and field scouts/consultants with questions about what the thrips are doing, and how the Temik and seed treatments are holding up given this strange season. It was very dry in April and early May to the extent that growers had to stop planting. This week that situation totally reversed itself with some areas (our research Center included) getting over 5 inches of rain. The rain has brought a lot of cotton out of the ground that had been sitting for several days in the dry soil, almost two weeks in some cases. In my plots, as in many growers’ fields, some plants had already emerged and are in the 1– to 2 –leaf stage, while others are just emerging. But the good news is that as of today, the Temik and seed treatments are holding well. I base this on the soapy-sample data (5 cotton seedlings per plot, 10 peanut leaflets per plot) from several tests we sampled this week.

In cotton tests (planted on May 4), Temik treated plots are averaging about 1.5 adults/5 plants and Aeris seed treatment plots are averaging about 2.5 – 3 adults/5 plants. This is compared to about 20-30 adults/5 plants in the untreated controls. So far, there are almost no larvae in any plots, but with these high adult numbers, we expect to see a lot over the next 2 weeks.

In peanut tests (planted on Apr 29), Temik treated plots are averaging about 1 – 2 adults/10 leaflets, compared with 15 – 25 adults/10 leaflets in the untreated controls. Larval numbers are also still very low, less than 1/leaflet even in the untreated controls. Again, these high adult numbers will result in large larval populations over the next couple of weeks.

But, for now, the in-furrow and seed treatments are holding. We are sampling some Avicta seed treated cotton plots later in the week so will have some of that data to share next week.

Until the rain last night (May 13), it was shaping up to be a worst-case-scenario for early season thrips pressure in Virginia cotton. With the prevailing dry conditions, and vacillating between unseasonably hot and cold temperatures, seedlings were either slow to emerge, or if emerged, were standing still. Slow growing plants have reduced root growth and are slow to pick up the systemic insecticides. Couple that with what appears to be, at least so far, a very active thrips population, and it was setting up to be a ‘perfect storm’ for thrips problems.
Last week we began to see adult thrips crawling on cotton seedlings and volunteer peanut plants (peanut seedlings emerging from last year’s crop in cotton, soybean and corn fields). We also set out a series of 3×5 inch sticky cards for monitoring adult thrips. We trapped over cotton and peanut fields, brought the cards in after 3 days, and counted over 100 adult thrips per card (counting both sides). A lot of them were not pest species, but there were plenty of tobacco thrips, our primary cotton and peanut pest. This week we sampled two peanut trials and one cotton trial for thrips (10 peanut leaflets per plot, and 5 cotton seedlings per plot)using our standard soapy-water sampling technique and found an average of about 1 adult and 0.1 larvae per plant in cotton, and 0.5 adults and zero larvae per peanut leaflet. These are very low numbers compared with where it will go from here, but shows that we are definitely at the beginning of what I call ‘Thrips Season’. We are already seeing evidence of thrips feeding damage on untreated cotton and peanut seedlings.
Last night’s rain, about 1 ¼ inches, fell across most of the cotton/peanut counties. Before that rain we were facing the problem of having fields with two crop ages. Cotton planted in rows where moisture was available is up and into the first, even second leaf stage. In areas of the same field where no moisture was available to seeds, plants are not up yet. A long gap between emergence dates results in plants being in different growth stages in the same field which greatly complicates thrips management decisions, that is, when to treat for thrips and where. The rain last night should go a long way towards clearing this up.