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Thursday, March 2, 2017

Preparing for Sugarcane Aphid Part I, Early Season

Sugarcane aphid will most likely return for another run at the High Plains sorghum crop in 2017, and this is the first in a series of articles to compile management suggestions based on what we learned from our 2015 and 2016 research and general field experiences. Contributors to this work include Dr. Ed Bynum, Extension Entomologist in Amarillo, Dr. Katelyn Kesheimer and Blayne Reed, Extension Agents IPM in Lubbock and Crosby counties and Hale, Swisher and Floyd counties, respectively, and Dr. Pat Porter, Extension Entomologist in Lubbock.

Beneficial insects cleaned up the overwintering aphids in 2016

In our 2015/2016 overwintering studies we found successful aphid survival as far north as Tulia. This was a bit of a surprise as our studies the previous year found survivorship only as far north as Hale Center. In 2016 we found SCA on Johnsongrass in Lubbock and Swisher counties in early May. At the time we were concerned that it would be a long aphid season, but fortunately there were abundant aphids in 2016 wheat. These served as food sources for the large number of beneficial insects that went in to overwintering in the fall of 2015 after feeding on sugarcane aphids. After the initial 2016 aphid finds on Johnsongrass we intensified our search, only to discover that the small sugarcane aphid populations were no longer to be found. It seems that the beneficial insects finished eating aphids in wheat and then moved over and wiped out the overwintering and colonizing sugarcane aphids on Johnsongrass.

Eventually sugarcane aphids began to arrive from the east in July, first along the cap in Crosby and Floyd counties. This time they trickled in little by little, and this was fortunately unlike the large clouds of winged aphids that hit the southern High Plains all at once in 2015. Last year's gradual westward movement of aphids meant that they were relatively predictable.

What about this year?

The abundance of beneficial insects early in the season this year will be important in protecting sorghum by preventing aphid movement from Johnsongrass to sorghum fields. Given that we had far less sorghum in 2016 than in 2015, it is the case that we had fewer beneficial insects going into overwintering in 2016. In effect we are starting 2017 with fewer beneficial insects in the system, but fewer sugarcane aphids as well. Katelyn Kesheimer checked some wheat fields today and found that some had high numbers of bird cherry-oat aphids and greenbugs, but there were high numbers of beneficials insects as well. Other wheat fields did not have many aphids or beneficial insects. Ultimately, aphid infestations on the High Plains will depend on overwintering and the earliness of arrival and severity and movement of sugarcane aphids from downstate. This causes a level of unpredictability for our 2017 sugarcane aphid situation. We will monitor populations and report our findings in this newsletter.

Early planting resulted in far less aphid pressure

Our primary recommendation for 2016 was to plant early so that the sorghum was as far along in growth stage as possible by the time aphids arrived. It is well documented that earlier growth stages can suffer more damage, so the idea was to outrun the aphid as much as possible. This strategy paid big dividends in 2016 for those who employed it.

However, to a lesser extent in 2015 we were also suggesting that late planted sorghum might suffer less damage because of all of the beneficial insects in the system that had developed on earlier planted crops. This definitely did not happen in 2016 and the standard and late planted crops were severely damaged by the aphid. So with two years of experience and data, our strongest recommendation is to plant early so as to outrun the aphid as much as possible.

Seed treatments are cheap insurance

We recommend that neonicotinoid seed treatments be used on all sorghum. In 2016, the early planted crop would not have benefitted from the 45 days of protection afforded by seed treatments. However, if we had not had abundant aphids in wheat to serve as food for the large number of beneficial insects that went in to overwintering, it might have been a different story and the early planted sorghum crop might have been infested in May or June. It is too early to tell whether we will have a similar high number of overwintered beneficials to provide protection in 2017. Fields planted in the normal window or late could expect significant aphid pressure within the 45 day window of seed treatment effectiveness. Also, even though seed treatments gradually play out, they still provide some sub-lethal effects on aphid reproduction beyond 45 days and, depending on chance, seed treatments might mean one insecticide application later rather than two. On balance it makes sense to use treated seed to protect against downside risk of infestations in pre-flowering and flowering growth stages. Even for standard and late planted sorghum the ability of seed treatments to provide protection depends largely on when the aphids infest the crop during the season. Therefore, even fields with treated seed need to be scouted for sugarcane aphid.

"Resistant or Tolerant" hybrids are still susceptible

None of the so-called resistant or tolerant hybrids on the High Plains have been shown to be able to keep aphid numbers below treatment thresholds. At best they slow the rate of aphid population increase; when the aphids arrive the threshold will most probably be exceeded and insecticides will be necessary. However, our research at Halfway showed that there is a significant economic benefit to using resistant hybrids even though they still need to be sprayed at the normal threshold. As yet we do not have a list of resistant or tolerant hybrids that we have confidence in, and it will take three years of replicated data from the High Plains before solid recommendations can be made. At present we recommend that growers consult their local seed company for suggestions on resistant or tolerant hybrids.

Coming in Part II

The next article will address treatment thresholds, insecticide rates and efficacy, and an economic threshold for a potential second insecticide application if the first application failed or could not be made.





Monday, February 20, 2017

Short High Plains Sugarcane Aphid Videos Posted



We have just posted nine short videos that encompass our 2015 - 2016 research results and experiences as a primer as we enter the 2017 season. Presenters are Katelyn Kesheimer, IPM Agent in Lubbock and Crosby counties, Blayne Reed, IPM Agent in Hale, Swisher and Floyd counties, Dr. Ed Bynum, Extension Entomologist in Amarillo, and Dr. Patrick Porter, Extension Entomologist in Lubbock.

The videos present data from the Texas High Plains and may not be applicable elsewhere.

1. Aphid overwintering and seasonal abundance (3:41)
2. Early planting is a good idea (3:40)
3. "Resistant" sorghum hybrids and seed treatments (4:23)
4. First insecticide application threshold (3:03)
5. Insecticide application and product efficacy (8:46)
6. Timing of a second insecticide application (4:15)
7. Rate of damage with uncontrolled aphid populations (4:05)
8. Insecticides to prevent sticky harvest problems (5:56)
9. Aphid effects on stalk quality for grazing (3:43)

Wednesday, February 8, 2017

Cotton Variety Selection: More Bt Traits to Choose From

Suhas Vyavhare, Extension Cotton Entomologist, Texas A&M AgriLife Extension Service


Variety selection is the most important decision made during the year. Selecting Bt vs non-Bt or the kind of insect trait package is an important consideration in selecting cotton varieties.
Bt cotton is genetically altered to produce certain proteins which are toxic to specific groups of insects. For example, currently available Bt traits in cotton specifically target worm pests such as cotton bollworm, tobacco budworm, and beet armyworm. On the other hand, conventional, or non-Bt cotton does not produce such insecticidal proteins and as a result it is more vulnerable to worm damage.

Since the introduction of Bt cotton into US agriculture in 1996, the technology has transformed from a single-gene trait to multi-gene trait packages. The 1st generation Bt cotton had only a single Bt gene. The second generation Bt technologies, such as Bollgard 2, TwinLink, and WideStrike produce two Bt toxins. While the most recent 3rd generation Bt is a three-gene trait—Phytogen brand varieties with WideStrike 3 have already been in the market for the last couple of seasons. Recently, Monsanto (Deltapine brand) and Bayer CropScience (FiberMax and Stoneville brands) announced the availability of some of their varieties with Bollgard 3 and TwinLink Plus technologies, respectively.

Bt Technologies
Proteins expressed
Second generation

Bollgard 2
Cry1Ac + Cry2Ab
WideStrike
Cry1Ac + Cry1F
TwinLink
Cry1Ab + Cry2Ae
Third generation

WideStrike 3
Cry1F + Cry1Ac + Vip3A
Bollgard 3
Cry1Ac + Cry2Ab + Vip3A
TwinLink Plus
Cry1Ab + Cry2Ae + Vip3Aa19

Over the years, Bt technologies have been fairly effective controlling worms in cotton. The second generation Bt was more effective than the first one, and the third generation technology is more effective than the second generation due to the addition of toxin(s). Newer traits usually come with additional costs, so if you don’t need these traits, varieties with older trait packages are still competitive in yield and quality.

Some farmers may choose to go with non-Bt cotton to avoid paying tech fees. With non-Bt cotton, field scouting becomes even more important to stay on top of the game. In 2016, worm pressure on the Texas High Plains was so low that many of our non-Bt cotton fields got away without spraying for worms. This doesn’t mean we will have a similar situation in 2017---we may face higher worm pressure—therefore, there is higher risk associated with the non-Bt crop compared to Bt. However, with a good scouting program in place and timely insecticide applications, non-Bt cotton can perform well.

Finally, insect trait is an important consideration in selecting varieties but it should not take priority over agronomic characteristics such as yield, maturity, and fiber quality. I have seen some of the non-Bt cotton varieties performing as well as Bt cotton and sometimes even better (especially on the Texas High Plains where worm pressure is usually light). Therefore, it’s not the transgenic insect trait but the inherent yield potential of a variety which should come first in the decision making.

Monday, December 12, 2016

Sorghum Stalk Nutritional Quality and Sugarcane Aphid Damage

(Because FOCUS on Entomology has a different readership than our Sugarcane Aphid Newsletter, this is a reprint of an article recently posted on the sugarcane aphid news site.)

One of the questions as we end the season is what kind of affect does sugarcane aphid damage have on the nutritional quality of sorghum stalks that are used for stover. We conducted two experiments this season, and both were designed to look at leaf damage and its affect on grain yield. However, in conducting these experiments we ended up with many plots with discreet levels of leaf damage, and The United Sorghum Checkoff Program asked us to harvest stalks from the various plots and send them for nutritional analysis.

To be clear, the results that appear below are for grain sorghum, not forage sorghum. One experiment was conducted at the Lubbock Research and Extension Center using a sugarcane aphid-susceptible hybrid grown under moderate furrow irrigation, and the other was conducted at the Helms Farm near the Halfway Experiment Station. This experiment was conducted on a sugarcane aphid resistant hybrid grown under drip irrigation that supplied relatively more water than was available at Lubbock. Data from the two trials showed very similar trends, so they were combined to generate the following charts.

The Leaf Damage Rating System developed by Blayne Reed goes from 0 to 10, with 1 being very little damage on the lower leaves, to 10 being all the leaves on the plant with observable damage. Sugarcane aphid damages lower leaves first and then moves up the plant, so a leaf damage rating of 5 would suggest the leaves in the lower 50% of the canopy are damaged.

Each dot on a graph represents at least 4 stalks harvested from a plot at a given leaf damage rating. The nutritional analyses were performed at Servi-Tech Labs in Amarillo. A sample report from Servi-Tech is here.

Figure 1. There was a highly significant decrease in Total Digestible Nutrients with increasing levels of leaf damage.



Figure 2. Crude Protein was not significantly different between plots with different levels of leaf damage. 



Figure 3. There was a highly significant increase in Acid Detergent Fiber (non-digestible components) with increasing levels of leaf damage.


Figure 4. There was a highly significant decrease in Digestible Energy with increasing levels of leaf damage.


Figure 5. There was a highly significant decrease in Metabolic Energy, Beef with increasing levels of leaf damage.


Figure 6. There was a highly significant decrease in Net Energy, Lactating with increasing levels of leaf damage.

Thursday, November 3, 2016

Stink Bug Outbreak in Texas High Plains Cotton: What Can We Do Better Next Season?

Suhas Vyavhare and Katelyn Kowles, Texas A&M AgriLife Extension Service

Stink bug infestation in cotton during August-September
Rotten bolls in stink bug infested field 

This season we experienced unusually high numbers of conchuela stink bugs in Texas High Plains cotton (parts of eastern Lubbock and Crosby counties in particular). Stink bug numbers peaked during August-September when plants were loaded with tender bolls that stink bugs feed on with their piercing-sucking mouthparts. Farmers who spotted stink bugs early and took timely action are now reaping the benefits. However, those who missed an insecticide application in infested fields are seeing severe stink bug damage now that bolls have opened. A few infested fields we visited last week have very little to harvest due to the extent of boll damage by stink bugs. During August-September, stink bug numbers were overwhelmingly high in spots—in some fields numbers were over 2-3 stink bugs per boll. When stink bugs feed on tender bolls, it can result in lint staining or allow pathogens to enter and cause boll rot; smaller bolls may be aborted altogether. As we are now towards the end of the growing season, there are many who want to know what can be done differently for the next season.

The fact is there is not much we can do beforehand when it comes to stink bugs as there are no specific effective cultural practices or resistant varieties available. The best thing farmers can do is regular field scouting. Bolls that have been fed on by stink bugs will typically have a black mark on the outside. It is critical to scout fields for stink bugs especially in areas with the known history of this pest. Our field observations indicate that stink bug population build-up started on grain sorghum and as the grain became too hard for the bugs to pierce with their mouthparts, they moved to adjacent cotton. We will provide more information on stink bug scouting and management when we approach the next growing season. Meanwhile, as we wrap up the current season, the best thing we can do is learn from our experience and scout better next time. 


Stink bug infestation in grain sorghum (photo: Pat Porter)


Wednesday, October 5, 2016

Cry1F No Longer Effective Against Western Bean Cutworm

Western bean cutworm is a serious corn pest in the northern Texas Panhandle and occurs in lower numbers as far south as Hale County. Several years ago the insect underwent a major range expansion and is now the primary corn caterpillar pest in several Midwestern states to as far east as New York and as far north as Canada. This year there have been major field failures of Cry1F in these areas, and the Land Grant entomologists have written an open letter to the transgenic seed industry to prompt them to stop claiming that Cry1F corn controls western bean cutworm. Laboratory data confirming resistance to Cry1F are in the scientific publication process.

Given these new developments, we will be modifying our suggestions for Bt corn to control western bean cutworm to include primarily those that contain Vip3a in combination with other toxins. Our now outdated suggestions are in Table A20 (page 32) of Managing Insect and Mite Pests of Texas Corn, 2016. You will easily find the hybrids with Vip3a.

An open letter to the Seed Industry regarding the efficacy of Cry1F Bt against western bean cutworm: October 2016


This open letter was prepared by the undersigned extension entomologists from the Great Lakes Region regarding the efficacy of the Cry1F (Herculex 1, TC1507) trait on western bean cutworm (WBC; Striacosta albicosta). We strongly urge seed companies to remove the designation of “control” for this pest with regard to this toxin.

At the time Cry1F received regulatory approval in 2001, western bean cutworm was found in the far western Corn Belt (Colorado, Idaho, Nebraska, and Wyoming), with occasional movement into western Iowa. Indeed, EPA’s original Biopesticide Registration Action Document (BRAD) for Cry1F Bt corn, published in August 2001, did not even mention WBC. Instead, the following language was used: “The registrant-submitted data indicate that Cry1F protected corn offers excellent control of European corn borer, southwestern corn borer, fall armyworm, black cutworm, and suppression for the corn earworm.” References to Cry1F giving “excellent protection” against WBC began to appear in marketing literature only after Iowa State University entomologists documented its eastward range expansion and the first economic damage in that state. Presumably this rating was based on a limited number of lab assays and field trials done in pure Bt stands, not Refuge-in-a-Bag hybrids.

The rapid eastward range expansion of WBC across the central Corn Belt into the Great Lakes Region resulted in a dramatic increase in the number of WBC-infested acres in a short time period. This created a large-scale ‘efficacy test’ of Cry1F hybrids to (as stated in the BRAD) “provide highly efficacious control of key Lepidopteran pests”, “reduce the use of more toxic chemical insecticides” and “reduce levels of mycotoxin in corn”. In all these regards, Cry1F has failed in our states. This season in particular, the level of larval infestation and damage is troubling in both single and pyramided Refuge-in-a-Bag hybrids from multiple seed companies. Wherever Cry1F is challenged by WBC, it fails to provide observable benefit to producers. We have collectively fielded dozens of phone calls and emails, and visited numerous fields; we know that our agribusiness contacts and seed industry agronomists have responded to many more, and corn acres were sprayed with both insecticides and fungicides (most too late and with little hope of benefit). People are frustrated and angry and, more importantly, yield was lost. Growers purchased Cry1F hybrids with the understanding that the trait provides “control”, thus negating the need to scout for egg masses or larvae in those fields. When the visible manifestations of damage became apparent late in the season, such as the intense ear-feeding we witnessed, it was far too late for rescue treatments. As the fall progresses and damaged corn is harvested, additional issues are sure to arise regarding quality and mycotoxin levels. The severity of the latter will largely be dependent on weather conditions favorable for ear mold development. What is certain is that many damaged ears are primed for fungal colonization and quality loss.

As extension educators and specialists, we can no longer refer to Cry1F as providing WBC control. In fact the opposite is true, and our extension recommendations (including the Handy Bt Trait Table) will be changing to classify Cry1F hybrids for WBC the same as non-Bt, Cry1Ab, or double/ triple pro hybrids, all of which provide no control. In other words, we believe that Cry1F fields must be scouted for egg masses and sprayed with foliar insecticides if needed, the same as a non-Bt corn. Western bean cutworm is now the PRIMARY Lepidopteran ear pest in many parts of the Great Lakes region. For growers in our states, the costs of scouting and spraying Cry1F corn nullifies a major reason they purchased and planted a hybrid with the trait in the first place.

Before growers make seed choices for 2017, we again urge the seed industry to acknowledge the reality of what is happening in the field, and to reclassify Cry1F in hybrid fact sheets, technical use agreements, and other educational materials. This would reduce grower expectations of Cry1F and allow local agricultural professionals to deal with their customers in a more truthful manner, in a way that allows for protection against yield loss. We also urge the industry to regard western bean as a primary, not a secondary, pest. Doing nothing risks alienating those close to the situation, including field agronomists, consultants, university extension staff and (most importantly) corn growers themselves who have a vested interest in finding effective pest management solutions for a growing world.

Sincerely,
Dr. Chris DiFonzo, Michigan State University
Dr. Christian Krupke, Purdue University
Dr. Andy Michel, The Ohio State University
Dr. Elson Shields, Cornell University
Dr. Kelley Tilmon, The Ohio State University
Dr. John Tooker, Pennsylvania State University

BRAD Document:  http://www.ceragmc.org/files/cera/GmCropDatabase/docs/decdocs/brad_006481.pdf)