Several things have changed since last week’s advisory. Based on our sticky card samples and plant samples (cotton, peanut and soybean), thrips populations have increased a lot since last week. Interestingly, all five sticky card sample sites show the same trend (see the attached line graph), that numbers were very low last Thursday (probably the end of the second generation) and had much higher numbers this past Tuesday. We think this increase marks the beginning of the third and largest generation. Based on previous year’s data, this population will not peak for another 10-14 days.
Cotton treatments (Avicta, Aeris and Temik) are still holding for the most part but are beginning to show some damage. In our plots, there is not a lot of difference among the three except that the seed treatments may be showing just a little bit more damage. For example, in one test in a 5-plant sample, we counted an average of 7 adult and 55 immature thrips in the untreated control, 0.25 adults and 0.25 immatures in the 5 lb Temik treatment, and 4 adults and 4 immatures in the Aeris treatment. The ratings next week will really sort out the treatments, with the heavy and sustained thrips pressure that we expect will occur over the next few days. If seed treatments have not been sprayed, now would be the time to consider doing it, but only if damaged buds are visible, and plants have live thrips.
We have just confirmed western flower thrips in four cotton fields in North Carolina (in Hertford County near Winton). The samples came in yesterday. The fields had been planted with Avicta seed treatment with an additional 3.5 lb of Temik. In addition, they had been treated with 8 oz of Orthene 97 about a week prior to the discovery. In two of the fields, ‘westerns’ comprised close to 100 and 99% of the thrips complex. In the other two fields, they were about 50/50 with tobacco thrips. Each year we see a few fields with the ‘western’ thrips problem. Today, Jack Bacheler and Clyde Sorenson from NC State and me, with the aid of the crop consultant, Chad Harrell, put in a small plot test in the field with the worst damage and largest ‘western’ population. We applied different rates of Radiant SC, Tracer 4SC and Orthene 97. We will take samples next week to see which provide the best control.
As for peanuts, we are still not seeing visible evidence of thrips damage, any leaf crinkling. But based on the leaflet samples we took this week, it won’t be long. In all of the fields we sampled, there were adult thrips in the leaflets but no immatures. When those adults lay eggs and the immatures hatch and begin feeding, damage symptoms will start showing up. This is exactly the right time to apply foliar insecticide treatments to peanuts, if they have not already been protected with in-furrow insecticide treatments. Sprays now would prevent those immatures from developing. If peanuts did receive an in-furrow treatment, then we would recommend waiting a week to determine how well those treatments are holding.
Finally, we were surprised by the number of corn earworm moths that we collected in our local pheromone baited traps. Over the past two nights, we have collected about 200 moths. We have put them into what we call the AVT (adult vial test) to begin monitoring for pyrethroid resistance. Last year the AVT data gave us a good heads up on a potential resistance problem. We do not have vial test results yet, but will begin posting those as we get them.
Additional information: stickycards09-2-ppt