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 Our now outdated suggestions are in Table A20 (page 32) of Managing Insect and Mite Pests of Texas Corn, 2016.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.

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)

Friday, September 16, 2016

Is There Still Value in GM Crops?

The day after the Bayer/Monsanto agreement was announced this week, The Wall Street Journal had an article entitled "Behind the Monsanto Deal, Doubts About the GMO Revolution" (subscription required or article can be purchased). The paragraph that best summarizes the article was, "Today, farmers are finding it harder to justify the high and often rising prices for modified, or GMO, seed, given the measly returns of the current farm economy. Spending on crop seeds has nearly quadrupled since 1996, when Monsanto Co. became the first of the companies to launch biotech varieties. Yet major crop prices have skidded lower for three years, and this year, many farmers stand to lose money."

The article contained a graphic that showed that since 1996, the year GM soybeans were introduced on a commercial scale, soybean seed prices have risen 305% to $60.75 per acre, but commodity prices have risen only 31% to $9.79.  It is a bit puzzling why the Wall Street Journal did not choose to plot the yield increases per acre since 1996; we all know that higher yields are good but reduce prices, all other things being equal.

This is an entomological newsletter and I won't discuss the benefits to growers that have come from having herbicide tolerant GM crops that allowed greater yields through less weed competition while using a simpler and less expensive herbicide regimen. I will also not discuss the yield losses later incurred when weeds became resistant to those herbicides, or the additional expense of having to go back to a more complicated and expensive herbicide regimen. And I will not discuss the latest generation of herbicide tolerant GM crops that are tolerant to one of two types of older herbicides that have been reformulated to reduce off-target drift. These new crops are being sold in part as the answer to the resistance problem that was caused by the first generation of herbicide tolerant crops. The seed companies will charge on the order of $6 per acre for this trait ($25 - 30 per bag of seed) over and above the cost of current technology, and will additionally profit by selling growers the specific herbicides that must be used on these crops.

GM crops with toxins for insects (Bt crops) have reduced insecticide use and provided environmental benefits. In the Midwest, Bt corn with toxins for European corn borer has reduced the populations of that pest to the point that non-Bt corn can be grown without the need for an insecticide application. Similarly, in my part of the country we no longer fear southwestern corn borer; the planting of Bt corn has greatly reduced the size of the population. Obviously the widespread planting of Bt crops toxic to some insects has resulted in significant benefits.

However, 2016 has been a year of frustration for some farmers who plant GM corn, soybean and cotton. As the Wall Street Journal article said, this is in part because the price of seed seems to be high compared to the value of the commodity at the grain elevator or gin. It is also because some of our insect toxin traits in corn and cotton no longer work as well (or at all) on some of the insects that damage crops and reduce crop quality. This is not the first year for such frustration; resistance to corn rootworm Bt crops was first scientifically documented in 2011 and has spread geographically and to all four Bt toxins used in corn. At least two caterpillar toxins (probably three) have failed due to resistance, as corn growers in the Midwest and Canada are finding out this season due to extensive western bean cutworm damage in their Cry1F corn. This year cotton farmers found themselves having to spray GM crops with insecticides to prevent yield loss.

Our insect-protected Bt crops never were "bulletproof". In fact they never worked very well at all on some pests and were not intended as the sole control for other pests. In the latter case, the word "suppression" or some similar word was usually mentioned in company literature, or no mention was made at all and the grower was left to come to his or her own conclusion.  The job of selling seed being what it is, the nuances between the ability to control one pest and suppress others was often lost and these technologies competed with each other in the sales arena based on being oversold in their abilities. Sales material showed perfect ears of corn and growers were led to believe in the invincibility of the product.

The current frustration then is a result of resistance development in the pests the technologies were meant to control, and resistance in pests for which the technologies formerly provided suppression. In both cases it has become necessary to use traditional insecticides on top of the Bt technologies or suffer significant yield loss. And even when traditional insecticides are used there is often yield loss after the increased expense.

Why are seed prices so high? The Wall Street Journal article said that when GM crops were introduced Monsanto came up with a formula that was quickly adopted by the rest of the industry. "For every dollar that biotech seeds saved farmers in pesticides and labor, Monsanto would keep about 33 cents, in the form of a “technology fee” charged on top of each bag of seed." Seed prices keep going up, but GM crops are no longer saving growers as much in pesticides and labor as they once did. This is to say that in many places GM crops have less value now in terms of insect and weed control. It is not hard to understand the frustration at paying higher prices for something of lesser value.

However, our GM crops are not just herbicide tolerance and insect resistance traits, they are also improved genetics for yield and drought and disease tolerance. These qualities are expensive to produce, and the regulatory system in the US adds significant cost to some of them.

On the surface it would seem that growers could choose to buy non-GM seed and go back to the way we handled insect and weed control prior to 1996. This might work for insects, especially in places Bt crops have driven down populations of major pests. Unfortunately, non-GM crop breeding slowed considerably in the age of GM breeding, and the yield potential of many non-GM crops, even in the absence of pests, is not competitive with GM crops. (This is more true in corn than in cotton.) Another difficulty is that the introduction of GM crops coincided with the Food Quality Protection Act. This was convenient for the EPA because one could rationalize that Bt crops could replace many of the insecticides that would be cancelled. Today there are fewer insecticide options for use in non-Bt crops (or Bt crops with resistant insects), and many of the newer insecticides carry high price tags.

For sure there is still value in GM crops, but right now that value does not seem to be what it once was. It is unclear whether 2016 is the year we will look back on and point to as the start of a movement away from GM crops, or whether improved technologies and higher commodity prices in the future will make them look like a more valuable proposition.


(A  2013 USDA publication called Genetically Engineered Crops in the United States provides a concise summary of the number of GM traits introduced and the economic returns from them. Unfortunately, the publication is somewhat outdated because it does not address the weed and insect resistance to GM crops that has occurred in the last four years.)

Saturday, September 10, 2016

Shuffling the Deck Chairs in Bt Crops

2016 has been a challenging year for our Bt crops. Cotton bollworms did an unusually high amount of damage in many fields of Bt cotton, and corn earworms (which are bollworms by another name) caused a significant amount of damage to corn crops from Texas through Kansas. Western bean cutworm caused severe damage in fields of Cry1F corn in the Midwest and Canada where once the toxin provided a reasonable level of control. Fall armyworm is known to be resistant to Cry1F corn in parts of the country. Corn rootworm is resistant to toxins that once did a good job of control.

One question this fall is whether we have resistance to our Bt toxins targeted at caterpillars and, if so, how far it has spread. Field observations suggest that we do have resistance, but we will have to wait for the results of the laboratory tests on the progeny of the insects collected from the field. We don't have a magic genetic test to detect resistance, so we do things the old fashioned way by crossing field collected insects with laboratory insects and seeing how their offspring survive known doses of Bt toxins as compared to progeny from a colony we know to be susceptible to the toxins.

This article is not about whether we have resistance, it is about why we will have more resistance. When Bt crops were originally registered and deployed some 20 years ago, the seed companies each had their own unique toxins that worked more or less well on specific pests. Effectively the percentage of the pest insect population exposed to any particular toxin depended to a great extent on the market share held by each company.

Over time, however, seed companies began licensing their toxins to their competitors. In addition to financial gain there was a good reason for this; two or three different toxins were far better than one for delaying resistance. If an insect had an allele to survive on toxin 1, it probably did not have different alleles to survive on toxins 2 and 3. The insect would be killed and its allele to survive toxin 1 would die with it and not be passed to the next generation.

This strategy of multiple toxins targeted at the same pest (a pyramid of toxins) was successfully employed when corn rootworm in the Midwest became resistant to Cry3Bb1; the answer was to make plants that expressed both Cry3Bb1 (from company A) and Cry34/35 (from company B). Rootworms resistant to Cry3Bb1 were still exposed to Cry34/35 and many of them died. However, because they were already resistant to one toxin they were really only being challenged by the remaining effective toxin, so they were back to having to overcome one toxin and not two. Astute readers will note that we have four toxins for corn rootworm, so why not add one or both of the other two? The answer is cross resistance; rootworms that are resistant to Cry3Bb1 are also resistant to mCry3a, even if their ancestors never encountered mCry3a. Researchers in Iowa have recently confirmed resistance to the fourth toxin, eCry3.1Ab. A good article on this problem is here, and it says, "Cry3Bb1, mCry3A and eCry3.1Ab all appear fairly similar to the rootworm, and resistance to one is likely to confer resistance to the other two."

The example above illustrates that there is a finite limit to the addition of new Cry toxins and, because companies are licensing their technologies to their competitors, essentially our whole arsenal of Bt toxins is being planted on the vast majority of our corn and cotton acres. On a national level we are effectively selecting several generations of insects, even on different crops, on the same or similar toxins. (Corn rootworm is only on corn, but many of the caterpillar species infest both crops.)

If you want to see an example of cross licensing of toxins, look at Chris DiFonzo's Handy Bt Trait Table for corn. For each company, the products listed toward the bottom of their offerings are the newer types of Bt. Regardless of company they all look pretty much the same. (Cry1A.105 is just a synthetic stack of Cry1Ab, Cry1F and Cry1Ac. Cry1F and Cry1Ac are also used in cotton.)

The newest silver bullet is Vip3a for caterpillars. It is fairly high dose and does a good job of controlling many species. In their latest generation of Bt corn and cotton, all of the seed companies are now adding Vip3a as a pyramid with older toxins. Once again the insects will have adapted, or partially adapted, to the older toxins, so selection for resistance will be on Vip3a.

There does not seem to be a way out of the box with corn rootworm toxins, and increasingly we are relying on Vip3a to protect yield while the other caterpillar toxins are failing. Cry toxins had a good run and will hang on for a while longer, but the era of the Cry toxin seems to be ending.

Thursday, September 8, 2016

Green cloverworms in alfalfa and soybeans

If you are growing soybeans or alfalfa on the Texas High Plains it would be a good idea to scout for green cloverworms. I was in a soybean field near Ralls earlier in the week that had approximately 8 larvae per plant, and I just got a call about soybeans near Clarendon that were heavily infested.

In both cases the people making the reports thought the worms were soybean loopers. It is easy to tell the two caterpillars apart because loopers have two pairs of prolegs on the abdomen while the green cloverworm has three pairs. Loopers are fairly lethargic, but green cloverworms hop around quickly when disturbed.

Green cloverworm larvae near Ralls

Typical defoliation in soybean caused by green cloverworm

Fortunately the green cloverworm is only a leaf feeder in soybean and it does not damage pods. For alfalfa here is a quote the Oklahoma guide, "These defoliators are rarely a significant problem in established alfalfa, although seedling stands can be heavily damaged by their feeding." However, if there are enough of them present they can cause defoliation, which in turn will reduce the amount of nutrients the plants can store for overwintering.

For soybeans, University of Tennessee has good list of insecticides in their publication here. Oklahoma State University has control suggestions for alfalfa here.

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
Before bloom
≥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.
 • 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.