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.