The cotton crop in Virginia looks as good as any in recent years. Recent rains have resulted in lush growth, to the point that growers are starting to make plant growth regulator applications. Along with this lush growth comes an increase in the levels of plant bug populations, but we will take it—and deal with it. Will we see a larger population of stink bugs? Will brown marmorated stink bugs attack cotton? Too soon to tell, but we will be checking and reporting our findings.
Category Archives: Cotton
Plant bug in cotton, product choice and restriction on Bidrin use
We are seeing a few more fields than usual with plant bugs and damage. According to Johnny Parker with Commonwealth Gin, the number of fields reaching the threshold is about 3-5 percent, and that is based on his surveying about 100 fields over the past week. Since fields are still in the pre-bloom stage, thresholds are based primarily on square retention: Do not let fields drop below 80%. Plant bug damage is distinct and pretty easy to see. Bugs prefer to feed on the small pinhead terminal squares causing them to turn black and shed. You can find the tiny black squares (hit the ‘More’ button to see the image) or the scar where the square was shed. We do not have a lot of experience doing insecticide trials with plant bugs so I called one of my colleges in a state that deals with a lot of plant bug pressure. He recommends using only the insecticides in the neonicotinoid class (e.g., Admire Pro @ 0.9-1.7 oz, Belay @ 3-4 oz, Centric, @ 1.25-2.0 oz) and that they are effective. For resistance management and fear of flaring secondary pests, they recommend avoiding use of either pyrethroids (e.g., Bifenthrin, Karate, Baythroid) or organophosphates (e.g., Bidrin, Orthene). And, he reminded me that Bidrin CANNOT be used during this pre-bloom period. These are the statements on the labels (Bidrin: Early Season—Emergence to pre-square; Late Season—First bloom to 30 days prior to harvest) (Bidrin XP: Use only after cotton reaches the ‘First Bloom’ stage of growth).
Additional information: tpb-square-damage-herbert-doc
Thrips update, a tough year
We are definitely having a tough thrips year in cotton, somewhat less in peanut. Growers have reported less control than normal with treatments of Orthene/Acephate, even at rates that used to provide good control. Two things may be happening. One is that treatments did kill a lot of thrips but fields are being continually invaded by adults, especially from nearby grain fields that are drying down. Or, earlier treatments killed most of the tobacco thrips and left or ‘encouraged’ outbreaks of western flower thrips that are much less susceptible to Orthene/Acephate. The only way to confirm a western thrips population is to provide our lab with a soapy/jar sample of clipped seedlings. We rinse them from the plants and ID them using a microscope. Without the knowledge of what species are present, it becomes a question of what insecticide to use. We are rating trips trials daily to generate the data to help guide that decision. For example, in one test we made two foliar applications, the first at bud stage and the second in 7 days. As of this week, we had an average of 71 thrips larvae in the 5-plant sample from the untreated control (definitely a lot of pressure). Orthene 97 at 4 oz provided 87% control, Radiant at 6 oz provided 78% control, Vydate C-LV at 17 oz 77% control, Lannate 2.4LV at 12 oz 67% control, and Karate Z at 1.28 oz 8% control. There were two surprises. Dimethoate 4EC at 8 oz provided 95% control, but this is higher than we have ever seen previously with this product and it may be a ‘misread’. And, the new product Benevia 10OD (Cyazypyr) by Dupont, which is not labeled yet, provided 98% control.
Here are a few thoughts based on these data and what we are seeing in fields. First, cotton in many fields is close to being in the 4-5 true leaf stage, on the other side of the thrips pressure period when no further thrips treatments are needed. With the recent rains and warm-hot weather, we will see a lot of growth in the next week. Second, there does not seem to be a ‘silver bullet’ product for thrips control as some may lead you to believe. Orthene/Acephate is still hard to beat, with the exception of this new Benevia which is not labeled, yet. But there is a risk to multiple applications of Orthene. It is tough on beneficial insects and could lead to a much higher risk to flaring mites and aphids….remember that Temik was providing early season suppression of both of these pests. If a second spray is being considered (still seeing damage to the new bud), it might make good sense cost-wise to shift to Dimethoate at 8 oz, which seems to work pretty well and can provide some control of spider mites (is used by soybean growers for spider mite control in DE and MD). The cotton entomologist at Univ of Georgia also recommends Bidrin at 3.2 oz. I have not tested Bidrin, but trust his knowledge.
We will continue to monitor thrips and our many research trials and look forward to sharing our result at our upcoming field tour on June 2.
Thrips numbers are increasing…’thrips season’ has begun
The following is an advisory from Ames Herbert.
Thrips species captured on sticky cards at the Tidewater AREC in Suffolk, VA, are increasing, and we expect these counts to rise for several more weeks. The adult thrips are migrating into fields from adjacent winter hosts. Counts of adult thrips have risen from about 20 per card during the second week of April to an average of 90 per card for the first week of May. The species complex consists of tobacco (mostly), eastern flower, onion, soybean, and an occasional western flower thrips (based on a subsample of 30 thrips per card). For more details on sticky card thrips captures, please see the attached graph. Sticky cards will catch all thrips species, not just the pests of cotton, therefore we also sample what is present on the cotton plant itself using soapy water thrips samples. Soapy water samples involve cutting cotton plants, submerging them in soapy water (to dislodge the thrips), vacuum filtering the sample, and counting all adult and immature thrips under a stereoscope. Soapy samples were taken on May 9 and 10 from cotton fields planted around April 20 near Boykins and Ivor, VA (cotton plants were at the 1-2 true leaf stage). Additionally, samples were taken from research plots at the Tidewater AREC that were at the 1st true leaf bud stage. In all samples, only adult thrips were present. This is important because foliar insecticide applications should target the thrips larvae which do most of the damage to seedlings. Historically, we have recommended foliar applications when the first true leaf is just expanded (1/4 inch or so). This usually coincides with the onset of larval activity. Cotton planted around April 20 is at or beyond that stage. Cotton planted a week later has not yet reached that stage (bud, only). Each year is different of course, but the many consecutive cool nights are slowing the progress of cotton and slowing the development of thrips. This may be a year to wait a few more days before making a foliar application, wait until a few more larvae are present on the plants. Thanks to my graduate student, Jessica Samler, and my assistant, Sean Malone, for taking the data used to develop this advisory and preparing the draft. Additional information: advisory-thrips-graph-docx
Poncho/VOTiVO seed treatment registered for cotton
Bayer CropScience announces the registration of Poncho®/VOTiVO” seed treatment for use on cotton. Following are quotes from the release statement. Note that this treatment is not a stand-alone for thrips control, but must be used in conjunction with an additional insecticide (e.g., Aeris, Gaucho, or other).
“To control early season insect pests such as thrips, aphids and others, Poncho/VOTiVO should be paired with additional seed-applied insecticides (Gaucho® or Aeris®) from Bayer CropScience.”
“Poncho/VOTiVO protects against damage from a broad range of nematode species, including reniform and root-knot. It provides a new biological mode of action that introduces revolutionary living-barrier science.”
“Employing a new biological mode of action with a unique bacteria strain that lives and grows with young roots, Poncho/VOTiVO creates a living barrier that grows with and protects early season seedlings and roots,” explained product development manager Louis Holloway. “The result means higher cotton yields through a healthier root system and a more vigorous and uniform crop.”
“According to the Cotton Disease Loss Estimate Committee, nematodes remain a major yield-reducing pest of cotton with more than 500,000 bales of yield potential lost to nematode damage in 2009. Poncho/VOTiVO protects against multiple types of nematodes, making it the perfect partner for Integrated Pest Management (IPM) programs.”
For more information, contact your Bayer CropScience field representative or visit: http://www.bayercropscience.us/products/seed-treatments/poncho-votivo/
Bollworm thresholds in conventional cotton
We are finding threshold levels of bollworms (eggs and live worms) in conventional cotton (no Bollgard2 or Widestrike). Those fields should be managed using the old system (treat at egg threshold and retreat in 5-7 days). The best approach for Bollgard2 and Widestrike cotton is the treat one time 5-7 days after the egg threshold, which targets any escaped worms. Not treating Bollgard2 or Widestrike cotton could be a mistake. For the past 2 years, we have seen as much as 2-3% boll damage in some Bollgard2 varieties, and as much as 10% damage in one Phytogen variety. A single pyrethroid application (highest labeled rate) cleaned up the problem. One cautionary note, we have gotten reports of worms escaping pyrethroid treatments in cotton.
Cotton insect update: stink bugs low, bollworm increasing
So far we are not seeing much boll damage from stinkbugs. We think this is due to the overall very hot, dry weather we are experiencing. Week before last I saw 106 degrees on a local bank billboard in my hometown (Franklin, VA), the first time ever according to the ‘old-timers’. This week Johnny Parker with Commonwealth Gin reported that he looked at a couple of thousand acres and found only about 3 bolls total with stink bug damage. He says he has never seen stink bug pressure this low. Yesterday he found a hot spot in an irrigated field approaching 10% boll damage with about 15% dirty blooms. The only insect in the field was tarnished plant bug so he assumed they had caused the boll damage (spots with light internal damage).
Corn earworm/bollworm is on the rise. Trap catches started increasing this week, up from near zero last week, and we are seeing moths flying in soybean, peanut and cotton fields. Stan Winslow with Tidewater Agronomic, Inc. in North Carolina reported today that they were finding an increasing number of bollworm eggs in cotton. We are recommending that growers not react to eggs, but wait to see how they progress and base any sprays on worm escapes. If worm pressure gets high, we can expect some escapes. For example, last year we found 2-4% boll damage on some Bollgard 2 and Widestrike varieties. But time will tell. We may or may not have to treat depending on how many worms break through the Bt and Widestrike toxins.
Cotton insect pest update
Not much is happening in cotton right now in terms of insect pests. The hot, dry weather seems to have things on hold, for the most part. Spider mites are common on a lot of field edges but are not widespread. We are not seeing much evidence of square loss to plant bugs (in untreated fields) and square retention is in the 90% + range. A few stink bugs, mostly brown stink bugs, are beginning to show up and soon we will begin assessing bolls for stink bug damage using our newly released ‘Decision aid for stink bug thresholds in Southeast cotton’ which presents a dynamic internal stink bug damage percentage threshold (changes as the crop matures) that begins with 50% internal damage in the first week of bloom. We will post more details soon.
Neonicotinoid choices for plant bug control in cotton
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
Thrips populations still high but treatments are holding
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.