header

header

Thursday, August 25, 2016

Cotton on the Texas High Plains: Watch out for Bollworm Activity

Suhas Vyavhare, Texas A&M AgriLife Extension Service

Insect pressure remains light in most parts with cotton ranging from 5 nodes above white flower to hard cutout. We are seeing conchuela stink bug population reaching economic threshold in few fields in Crosby County. However, the infestation is much localized and it is unlikely that we will see economic stink bug infestations in cotton in other areas of the High Plains. I often encounter a few lygus adults and nymphs but the numbers remain well below economic threshold. At this point, one insect that is on our radar is the cotton bollworm. Although much of our cotton has cutout hard and is becoming non-attractive to worms, there are still enough suitable cotton fields out there to worry about.

Earlier this week, Brad Easterling, IPM-agent in Glasscock, Reagan, and Upton counties reported above threshold levels of bollworms in Bt cotton fields near Garden City. Blayne Reed, IPM-agent in Hale, Swisher, and Floyd counties reports that he is seeing increased numbers of bollworm moths in his pheromone traps (http://halecountyipm.blogspot.com/2016/08/late-august-2016-bollworm-threat.html). With the corn and sorghum maturing, we may see increased bollworm movement out of corn into cotton in the next few weeks which makes regular scouting for bollworm larvae essential.
Please report any signs of higher than normal worm damage in cotton (especially Bt cotton) to me at 806-723-8446. We can visit a field and collect insects for resistance and/or old world bollworm screening.

Bollworm larva
When scouting, make sure you do whole plant inspections (squares, white blooms, pink blooms, bloom tags and bolls) for bollworm larvae and injury. Make sure to inspect at least 100 randomly selected plants covering all major areas in the field. Bt toxin is not well expressed in the flower tissues, and as a result bollworm larvae can often be found associated with pink blooms and bloom tags. One should be careful about not oversampling bloom tags while scouting Bt cotton fields. Also, remember bollworms must feed on the cotton plant before they ingest a lethal amount of the Bt toxin, so 1st instar larvae (<1/8-inch) should never be used as a trigger point to spray.

It is often hard to control bollworms with foliar insecticide application once larvae grow larger than ½-inch long. Therefore, it is important to spray for larvae when they are still smaller. If treating a bollworm population that is actively feeding on bolls, consider using a long residual contact insecticide that the worm is more likely to become exposed to when moving from one boll to the next. When targeting bollworms, pyrethroids with good cov
Bollworm damage
erage can still do the trick. However, if fall armyworms are present, the product choices may differ as pyrethroids are weak against fall armyworm, especially larger larvae.

Once cotton plants have an average of 3 nodes or fewer remaining above the uppermost first position white bloom or when the upper bolls that will be harvested have become difficult to cut with a pocket knife, they are normally safe from bollworm injury.

Here is a link to our new video on scouting for bollworms in cotton. (https://www.youtube.com/watch?v=vJhTJ9doDSw

Whole plant inspection method: bollworm action threshold based on number of larvae per 100 plants


Cotton type
Cotton stage
Worm size
Non-Bt
Bt
Before bloom
All
≥30% damaged squares and worms are present
After boll formation
≤1/4 inch
10-15 worms per 100 plants
Do not treat
>1/4 inch
8-12 worms per 100 plants
8-12 worms( >0.25 inch) per 100 plants with >5% damaged fruit
Fields that have accumulated 350 DD60s beyond 5 NAWF are no longer susceptible to first or second instar bollworm.



                                  

Friday, August 5, 2016

Sugarcane aphid update and conditions for using Transform insecticide

As of this writing on Friday, August 5th, sugarcane aphids have been found over much of the Texas High Plains. Tommy Doederlein, Extension IPM Agent in Dawson and Lynn counties, raised the alarm on Monday. Today we know that fields in Floyd, Crosby, Lubbock, Hale and Hockley counties have required insecticide applications. In the northern Panhandle the aphid has been found as far north as Perryton and as far west as Bushland. We are seeing abundant winged adults, so it goes without saying that sugarcane aphids could be anywhere on the High Plains.

Scouting procedures and treatment thresholds are presented in our 2016 sugarcane aphid publication. There are only two good insecticides for sugarcane aphid control; Sivanto and Transform. By "good" I mean high efficacy with little effect on beneficial insects. Sivanto has a full label and Transform can be used through its Section 18 label. This puts some additional restrictions on Transform use, although they are not onerous. Dr. Ed Bynum summarized the conditions of the Section 18 label in his newsletter today, and here is what he said.

"The Section 18 Emergency Exemption label for Transform has some specific information regarding application use and application restrictions. A COPY OF THE LABEL MUST BE IN HAND WHEN APPLICATIONS ARE MADE.

Here are some of the specifics from the Texas Section 18 Label. However, be sure to read the label before applying.
 • Rate range: 0.75 to 1.5 oz. per acre.
 • Application by ground or air (no chemigation).
 • Wind speed not to exceed 10 mph.
 • Droplet Size: Use only medium to coarse spray nozzles (i.e., with median droplet size if 341 μm or greater) for ground and non-ULV aerial application according to ASABE (S 572.1) definition for standard nozzles. In conditions of low humidity and high temperatures, applicators should use a coarser droplet size except where indicated for specific crops.
 • Boom height for ground application: Not to exceed 4 feet.
 • Carrier volume for ground application: A minimum of 5 to 10 gallons per acre - to be increased with increasing crop size and/or pest density.
 • Carrier volume for aerial application: A minimum of 3 gallons per acre, but a minimum of 5 gallons per acre is recommended.
Restrictions:
 • Preharvest Interval: Do not apply within 14 days of grain or straw harvest or within 7 days of grazing, or forage, fodder, or hay harvest.
 • A restricted entry interval (REI) of 24 hours must be observed.
 • Do not make more than two applications per acre per year.
 • Minimum Treatment Interval: Do not make applications less than 14 days apart.
 • Do not apply more than a total of 3.0 oz of Transform WG (0.09 lb ai of sulfoxaflor) per acre per year.
 • Do not apply product ≤ 3 days pre-bloom until after seed set."

----------

The final bullet point about restricting Transform use from three days before bloom until seed set is there to protect honeybees. Extension IPM personnel were asked to make note of honeybees in blooming sorghum this year, so I have been paying close attention. Well, I am highly allergic to bee venom and I always pay close attention because I'm not ready for mortality quite yet. My observations on the AgriLife Research and Extension Center at Lubbock have been that it is very common for large numbers of honeybees to visit sorghum. This usually occurs early in the morning prior to 10:00 am. After that time I seldom see honeybees in blooming sorghum fields. When I get more time I may post video of honeybees in sorghum.


Monday, August 1, 2016

Large Fall Armyworm Flight Underway (8/1/2016, Updated 8/4/16)

Pheromone trapping at the AgriLife Research and Extension Center in Lubbock indicates an unusually large flight of fall armyworm moths is underway. Fall armyworm and corn earworm comprise the "headworm complex" in grain sorghum. Our research in 2011 and 2012 indicated that fall armyworm larvae cause an average per ear loss of 0.2 lbs of yield in non-Bt corn when they puncture the side of an ear. The losses in corn are both from direct kernel feeding and the introduction of fungi that destroy an approximately equal number of kernels.

We normally report trap data on Wednesday but, given the high numbers of moths captured, today's graph (Monday) projects the weekly capture based on 5 of seven nights.

Update on 8/4/16: Here is the official chart which represents a week's worth of moths captured. 



Thursday, July 14, 2016

Southern Plains of Texas: Time to Look for Lygus

Suhas Vyavhare, Texas A&M AgriLife Extension Service


With the daytime highs over 100 degrees almost each day, cotton is squaring with some fields starting to bloom. Although we have received light and spotty showers, we need more over the next couple of weeks for the cotton to continue to grow. Insect pressure remains very low in most places. I know only of a couple of fields that needed to be treated for cotton fleahoppers (Swisher County) so far. Cotton fleahoppers are generally considered a pest in early squaring cotton. As plants increase in size and fruit load, larger numbers of fleahoppers may be tolerated without yield reduction.


With the fields starting to bloom, the next insect pest we
should look for is a lygus bug. Both adult and immature lygus can feed on cotton with their piercing and sucking mouth parts. The damage occurs primarily by insect feeding on the squares and small bolls.  As a result of lygus feeding, small to medium sized squares usually darken, shrivel and fall from the plant, while larger squares may remain on the plant. Flowers that develop from squares damaged by lygus may have tan to brownish colored markings and are referred to as dirty blooms.
 
Lygus feeding on bolls causes small black sunken spots on the outside of the boll.  Small bolls are most susceptible to lygus damage, while bolls that are larger than 1 inch in diameter are generally safe from lygus damage. Bolls that are 1/2 inch in diameter or smaller will often shed due to heavy lygus feeding.  

Alfalfa is a significant source of lygus, and large populations of lygus may disperse into nearby cotton when the alfalfa is cut.  Significant dispersal can often be eliminated by strip or rotational cutting of areas of the alfalfa.  Lygus prefer alfalfa over cotton and if suitable alfalfa is available, lygus will primarily move into the uncut alfalfa rather than the cotton.  Similar tactics can be used for weedy areas.  Avoid mowing or plowing weedy areas infested with lygus, or leave portions for lygus to disperse into rather than the cotton.

We are seeing a good numbers of big-eyed bugs, damsel bugs and collops beetles in cotton that are notable predators of lygus eggs and small nymphs.  Spiders prey on nymphs and adults as well.  Avoiding killing these natural enemies with broad spectrum insecticides will enhance lygus management and may prevent the development of damaging populations. We have just produced a new video on scouting for Lygus in cotton. (https://www.youtube.com/watch?v=gfSM8jF_Rqs )

Lygus Action Threshold

Sampling method
Crop stage
Drop cloth
Sweep net
1st two weeks of squaring
1-2 per 6 ft-row with unacceptable square set
8 per 1oo sweeps with unacceptable square set
3rd week of squaring to 1st bloom
2 per 6 ft-row with unacceptable square set
15 per 100 sweeps with unacceptable square set
After peak bloom
4 per 6 ft-row with unacceptable fruit set
15-20 per 100 sweeps with unacceptable fruit set


Wednesday, July 13, 2016

Sugarcane Aphid Management on the High Plains

Now that sugarcane aphid has been found in Floyd County it is safe to assume that we will shortly find it in surrounding High Plains counties. We all went through the aphid invasion last year and there is no need to go in to great depth on scouting and management, so I will just hit the highlights from lessons learned last year. If you want to read our complete 2016 sugarcane aphid management publication it is here.

Early planting is going to pay off

The earlier the aphid arrives during crop development, the more damage it can do. Infestations prior to boot can cause sterile panicles and decrease yields to essentially zero. Infestations at or after flowering, while still very serious, are somewhat less potentially damaging. This is why our treatment thresholds vary by crop stage.

Treatment threshold:
Pre-boot: 20% of plants with aphids.
Boot: 20% of plants infested with 50 aphids per leaf.
Flowering to Milk: 30% of plants infested with 50 aphids per leaf.
Soft dough through dough: 30% of plants infested, localized areas with heavy honeydew, and established aphid colonies.
Black layer: Heavy honeydew and established aphid colonies with treatment only for preventing harvest problems.

Our earlier planted sorghum has either finished flowering or is now flowering and has moved to the place it can withstand more aphids. In part this might matter because we have a relatively high number of beneficial insects in the system, and they have a better chance of keeping populations below treatment thresholds when those thresholds are higher. And even if one insecticide application is necessary, the need for a second application is far less likely in a much more mature crop.

Weekly scouting is a must

Under hot, dry conditions, the reproductive capacity of this aphid (which is born pregnant) is something approaching Shock And Awe, and everyone who went through the 2015 season will agree.  Missing a weekly scouting might mean missing populations low enough to be brought under control with insecticides. In 2015 we had many fields that were sprayed too late and adequate control was not achieved without a second application. Once the aphid has been found in a field, then twice-weekly scouting is important. Last year I would have linked to our guide to recognizing the sugarcane aphid, but this year I think we all know what the enemy looks like.

"Tolerant" hybrids are susceptible hybrids

There are a few hybrids with resistance to sugarcane aphids, although the seed industry chooses to call these "tolerant" hybrids because they rightly don't want to give the impression they are bulletproof. Our best resistant hybrids are what could be called moderately resistant, and this won't stop the aphids from reaching treatment thresholds. It may slow them down, and it may let the beneficial insects have more time to exert control, but all other things being equal it is merely a delaying action. Fields of "tolerant" hybrids should be scouted and sprayed based on the treatment threshold just like fields of completely susceptible hybrids.

Insecticide choice matters - a lot

Last year saw everything in the book, and some things not in the book, being thrown at sugarcane aphids. Many of these insecticide products were our old aphid standards, and what we found was that they were not very good at killing aphids, but they were very good at killing beneficial insects (the big guns in aphid control after an application). Our insecticide trials confirmed this; we had massive aphid resurgence where we killed the beneficial insects. There are only two good insecticide choices for sugarcane aphid: Sivanto and Transform. Both of these provide high efficacy with minimal impact on beneficial insects.

Make the first application count

Last year we observed insecticide applications of Sivanto and Transform made with high rates and plenty of carrier volume most often did such a good job of control that the few surviving aphids were cleaned up by beneficial insects. Conversely, we observed that fields sprayed with lower rates and/or insufficient carrier volumes frequently did not get control and required a second application.

Experience is a good teacher

This pest is manageable. Last year was a bit of trial and error, but after one growing season of intense aphid pressure we are much better equipped in 2016.

Friday, July 1, 2016

Southern Plains of Texas: Time to Look for Fleahoppers

Suhas Vyavhare and Blayne Reed, Texas A&M AgriLife Extension Service


The high temperatures, high humidity, and the passing of light cotton showers over the last couple of weeks have been very conducive for rapid crop growth and development. Most cotton fields on the Southern High Plains are past the 5th true leaf stage and are sporting pinhead through ¼ grown squares.  This should mean they are no longer vulnerable to economic damage by thrips. There are some late fields and re-planted fields which can still be injured by thrips, however, and we should continue to scout these fields for thrips. With the high temperatures potential for rapid plant growth, and a lessening thrips pressure in general these field might be able to escape from any serious thrips damage.

As the crop is approaching reproductive phase, we should be looking for fleahoppers—many of us scouting regularly in the field are already seeing a few on squaring cotton.  There are already a small handful of regional fields reaching an economic level for this pest.  If you see the smaller and freshly adorned squares turning brown and dropping to the ground, and / or missing from the plant, the problem could be physiological or weather related but most likely the damage was caused by fleahoppers. Fleahoppers can be found in abundance on their preferred weedy hosts like silver leaf nightshade, woolly croton and horsemint. Although cotton is not the primary preferred host, it is a choice secondary host that fleahoppers will move to once weeds are killed by herbicide application, mechanical cultivation, or physical hoeing .

The adult fleahopper is about 1/8 inch long, pale green, and have piercing and sucking mouthparts which they use to suck proteins and other nutrients from the developing squares. Their bodies are flat with an elongated, oval outline and prominent antennae. As their name suggests, they do slightly resemble a whitish or yellowish-green flea, mostly due to the appearance of their hind legs looking much like the hind legs of a common cat flea.  Nymphs resemble adults but lack wings and are initially almost white in color or sometimes pinkish until they feed. After feeding, the immature stage is pale green with prominent, often reddish eyes.

Both adults and nymphs suck sap from the tender portion of the plant, often targeting the smaller squares (immature flower buds).  Matchhead, pinhead, and even smaller size squares are the preferred cotton feeding sites even after the plant develops larger squares.  Unfortunately the all-important first squares put on the plant are at the most risk.  While cotton has the ability to replace some level of early fruit loss, losing too much early fruit set will affect cotton’s growth patterns causing rankness and could impact fiber quality by the end of the season via fruit maturity. When fleahoppers are abundant, heavy early fruit loss may occur. Cotton is particularly susceptible to cotton fleahopper damage during the first three weeks of squaring but remains at risk until the second week of blooming when blooms become widely abundant throughout the field.  At that time, fleahoppers will feed upon readily and easier accessible pollen and be of no economic importance.  Later in the season, fleahoppers are known to even feed upon a few bollworm eggs and small larva as a predator, but early season economic populations should not be ‘saved’ for any beneficial potential. 

The 1st week of squaring economic threshold for fleahoppers in match head stage cotton is 35% infested plants with 90% square set or worse.  This percent fleahopper infested plant calculation can be made via whole plant inspection or beat bucket methods.  As plants get older, many entomologists prefer to scout for fleahoppers with drop cloths or sweep nets.  This allows the field scout to check dozens and hundreds more plants over the same period of time scouting in the field.  The 35% infested economic threshold and treatment level translates into roughly 1 fleahopper / 1.5 – 2.5 row feet for the drop cloth or sweep net method with the same percent square set calculation. 

As cotton plants develop, higher levels of fruit loss to fleahoppers becomes acceptable.  Given sufficient time and if early losses were not heavy enough to impact plant development, cotton is often able to compensate for lost squares during the pre-bloom period with little impact on yield, up to a point.  Thankfully, quite a bit of research has gone into finding those levels.

Cotton fleahopper action threshold is 25-30 cotton fleahoppers/ 100 terminals with:
Week of squaring
Square set
1st week
<90 percent
2nd week
<85 percent
3rd week to 1st bloom
<75 percent
After 1st bloom
Treatment is rarely justified

Sunday, June 19, 2016

Please Report Unexpected Insect Damage to Cotton, Corn and Sorghum


It has been 20 years since Bt corn and cotton were put on the market, and we are now seeing signs that some of the Cry toxins in Bt crops are less effective than they once were. It is certain that fall armyworm is resistant to Cry1F in parts of the country (but not known to be resistant on the High Plains), and corn earworm/cotton bollworm is showing elevated levels of tolerance to several of the toxins in Bt cotton and corn. I want to make it perfectly clear that I am not suggesting we have resistance on the High Plains, but, given what is happening elsewhere in the country, I am saying that it would be prudent to begin watching our fields for elevated levels of damage from fall armyworm, corn earworm/cotton bollworm, southwestern corn borer and western bean cutworm. (This also goes for corn rootworm that is known to be resistant to at least one toxin in Bt corn.)

On top of this we have the old world bollworm, Helicoverpa armigera, knocking on the southern door of the U.S.A., and it may bring with it resistance to some Bt toxins. This species is indistinguishable from our domestic corn earworm/cotton bollworm, except by dissection of the adults. The Texas A&M University Department of Entomology and the AgriLife Extension Service have rapid sampling teams ready to collect from fields that might have H. armigera

This post is a request for growers and consultants to report any signs of higher than normal damage to  corn and cotton regardless of whether they have Bt or not, but especially if they have Bt. We can visit a field and determine whether the damage is within the bounds of "normal" and, if not, we can collect insects for resistance and/or H. armigera screening. My office phone number is (806) 746-6101. Pat Porter.