As of this week, thrips numbers have decreased in cotton, and plants have grown out of the thrips-susceptible window. We have had good rainfall, temperatures are good and most cotton is at the fifth leaf stage or beyond. We have terminated our cotton thrips sampling and ratings for the season. The attached line graph provides the sticky card data and shows the decline in adult catch across the region.
Peanuts are still at risk. As predicted last week, immature thrips numbers have increased in peanut. We are expecting pressure to continue for a least another week to 10 days. In our plots, Temik and Thimet are holding well. For example, in one field trial where we are comparing Temik 15G at 7 lb/acre, Thimet 20G at 5 lb/acres, and some experimental compounds, in the June 9 sample, there were 81 immature thrips/10 leaflets in the untreated plots, 8/10 leaflets in the Thimet treatment, and 7 in the Temik treatment. Untreated peanuts are reaching about a 5.0 on our 0 to 10 plant injury scale (where 0 = no damage and 10 = dead plants). A rating of 5.0 means that almost all leaves are crinkled from thrips feeding and most of the terminals show darkening/blackening. We generally expect yield reductions if ratings get much higher than 5.0, and we will definitely see injury exceed that by next week (given the high number of immatures). But again in our plots, both Temik and Thimet are holding well. We are seeing a big difference among the foliar applied insecticides in terms of thrips control and plant injury. In a nut shell, Orthene 97 and Radiant SC are providing good control as evidenced by the lower plant injury ratings. Karate Z is not performing well in either our cotton or peanut trials.
The thrips situation is very different in soybean. We have several trials across the state assessing both seed and foliar treatments. In soybean, our standard sample consists of 10 leaf trifoliates per plot. As of this week, we are getting averages of about 8 to 15 adults and 30 to 50 immatures per sample. The species break down is also different from what we are used to seeing in cotton and peanut. In those crops we normally see 90% + tobacco thrips. In soybeans, we are finding a mix of about 40% tobacco thrips, 50% soybean thrips and 10% other (eastern, onion, other odd balls). We are taking a lot of data this week and next to track the results of our treatments. Thus far, the seed treatments have a lot fewer thrips compared with untreated plots. Although we are finding a lot of thrips on soybean, we see very little actual plant damage. To date, we have never been able to show a yield response from controlling thrips in soybean. With a coordinated effort, this year we will be able to add several more thrips/soybean yield assessments to our data. We will post these results.
Additional information: stickycards09-ppt