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Tuesday, August 23, 2022

Managing late-season insects in cotton

 As we approach the end of August, one question that has been received lately more often than any other is at what stage do I stop worrying about insects in cotton?  

The major insect activity that I am noticing in South Plains cotton at this stage is around lygus bug and stink bug.  

Stink bugs, on the other hand, will have to be scouted for a bit longer. Although they favor medium-sized bolls, they can feed on any size bolls. Stink bugs may feed on bolls 25 or more days old; bolls of this maturity are relatively safe from yield loss. In larger bolls, stink bug feeding often results in dark spots about 1/16 inch in diameter on the outside of bolls. These dark spots do not always correlate well with the internal damage—callus growths or warts. Once the cotton reaches 450 DD60 beyond 5NAWF, sampling and treating for stink bugs may no longer be necessary since bolls produced after this point will not become fully mature or contribute significantly to the crop yield. Now, it is possible that this value may shift slightly due to factors such as boll shedding, variety, irrigation, presence of pathogens (e.g., boll rot).  Action threshold for stink bugs is based on percentage of bolls with internal injury. For instance, the stink bug threshold during 5th, 6th, 7th, and 8th week of bloom is 10% 20%, 30%, and 50% internal boll damage (lint staining, boll warts), respectively.

Link to updated cotton insects guide: https://lubbock.tamu.edu/files/2022/07/managing-cotton-insects-in-texas.pdf

Thursday, July 21, 2022

Update on the Mozena leaf-footed bug in Texas High Plains cotton

 Suhas Vyavhare and Kerry Siders

Leaf-footed bug, Mozena obtusa (fig. 1) is being spotted on a variety of plants across the Texas High Plains. We have gotten a few inquiries about how damaging this insect is to cotton and what insecticides would be most effective. In cotton, we have spotted this insect in multiple counties across the South Plains region. The numbers remain very low in all the fields where we have seen it except one field in Hockley County where it was found to infest cotton in large numbers (15-20 immatures/plant). In this particular field, insects appeared to be moving from the adjacent fallow field with mesquite trees which are preferred host of Mozena bug. Even the immature stages of this insect are quite agile and can travel some distance in search of new hosts. Fig. 2 shows results from the insecticide efficacy trial being conducted near Sundown, TX. Data collected at 3 and 7 days after treatment application indicate pyrethroids to be the most effective insecticides. We are also collecting data on the impact of Mozena bug on square retention in cotton. Thus far, we have not observed any square loss that can be attributed to this insect. Overall, square retention across the trial area remains over 90%.

Fig. 1. Mozena obtusa adult and nymphs
We are beginning to notice a few egg masses and small immatures on cotton plant indicating its suitability as a host for Mozena bug. With the absence and/or reduction in the availability of preferred hosts such as mesquite and other legumes, this leaf-footed bug can become an issue in cotton. Leaf-footed bugs in general prefer to feed on fruits and seeds and therefore their populations need to be monitored closely as our crop enters the boll development phase.  I would treat them more like stink bugs which feed in the similar manner with their piercing and sucking mouth parts and are mainly boll feeders in cotton. When scouting fields monitor both insect population density and the extent of damage to the crop (fruit retention, external and internal boll injury) and base the treatment decisions accordingly.

Here is a link to our recently updated cotton insect management guide: https://lubbock.tamu.edu/files/2022/07/managing-cotton-insects-in-texas.pdf

  

Fig. 2. Insecticide efficacy against leaf-footed bug, Mozena obtusa in Texas South Plains cotton. Means showing the same letter are not significantly different [Tukey’s HSD; P = 0.4226 (3 days after treatment (DAT)); 0.0302 (7 DAT)].

*Insecticide products were evaluated for research purpose only. When using an insecticide read and follow label directions for safety precautions, rates and preharvest intervals.

 

 

Wednesday, June 22, 2022

Highest Fall Armyworm Numbers in 12 Years of Trapping

The title of the article pretty much says it all; for the week ending today on June 22 I caught 1,242 fall armyworm moths per trap at Lubbock. The prior record, 912, was set in 2021 when FAW caused extensive damage as far as the upper Midwest. 



Thanks to some genetic work done by Ashley Tessnow, a post-doctoral researcher at Texas A&M, we know the vast majority of May moths were "corn strain" fall armyworms. However, she found that our summer flight might be as much as 35% "rice strain" mixed in.  This is not to say the majority of moths from this week won't go to sorghum or pasture grasses, for they surely will - the host preference between strains is not that strong. 

The bottom line is that any of our crops that are susceptible to fall armyworm should be scouted. Our Bt corn will provide good control of these larvae on whorl stage plants. However, sorghum, especially small sorghum, is at significant risk, as are any of the other host crops including vegetables. 

In looking back on my 12 years of data it is apparent that FAW numbers have increased on average over the years. I don't have an explanation for this, but I know what I am seeing. I am using the same pheromone lure year after year, and the traps are in the same place, so I think it is fair to say that increasing fall armyworm is a real phenomenon. 

 


Saturday, April 30, 2022

Insect pest guesses for this strange growing season

As we begin this growing season where most of us have not had appreciable rain in over 200 days, it might be useful to review what things look like on the pest insect front. Of course there is no way to know what will happen and I don’t have a crystal ball. Here is what it looks like through the bottom of a Dr. Pepper bottle. 

Overwintering


Our winter was fairly mild, so we did not get high insect mortality from deep and sudden cold. Winter insect kill is greater when there is rain or melted snow and we had neither. Both things taken together mean that more insects successfully overwintered than in a “normal” year (whatever that is).


Early season host plants


Entomologists think in terms of early season “non-crop host plants”, meaning anything in the system that can support pests until the crop hosts become available. A common example would be tansy mustard that serves as an excellent false chinch bug host. Years with rain and lots of tansy mustard almost always mean we will have more false chinch bugs. Of course the lack of rain has meant a lack of early season hosts, so many of the insects emerging from overwintering will have little to no food. Populations of pests that overwinter here will start the growing season at lower overall levels than in wetter years. 


Fewer insects but fewer crop acres


Starting at lower pest levels is good, but fewer crop acres mean mobile insects will concentrate on those acres. If we cut the number of restaurants in Lubbock by 1/3, then those restaurants still in business would have around 1/3 more customers. Most overwintered insects that find themselves with no food or poor food host plants will leave, either by using their wings or catching a ride on the wind. They are able to detect healthy plants either by color or odor or both, so they will navigate to healthy crops. 


Immigrant pests


Crop conditions in the southern part of Texas are not as bad as ours here, so it is reasonable to expect a somewhat typical northern movement of cotton bollworm (corn earworm), fall armyworm and other migrants. These too will seek out, and concentrate on, the reduced number of healthy crop acres. Moth eggs are fairly susceptible to drying out and dying before they hatch, so high temperatures with low humidities will reduce the next generation to some extent. Those same conditions will affect the health of their crop hosts, especially dryland crops, which might in turn also mean less survival of their larvae. We can expect higher concentrations of migrant pests on our reduced acres, but how well their offspring survive is a tossup. 


Biological control


Most of our beneficial insects overwinter here and build up on our pests slowly at first, then faster as we get more pests. Given that we are starting with fewer pests, it is likely that our beneficial insects will get a much slower start this year. There will be fewer of them around to deal with any large influx of immigrant pests arriving from the south. 


Wildcards


Insects have many ways to survive hard times, and some of them are really good at it. When one species is heavily favored by some climate/host plant condition, it is common that other species that would normally compete with the favored species will be at a big disadvantage. Any insect that is wildly successful on the few weeds and non-crop vegetation that we have in our system can be expected to be at higher levels this year than in a “normal” year. 


Future years


What is happening now will likely affect our insect situation in future years. A good example might be Mozena obtusa, one of those wildcard pests. This big true bug hit us hard in 2013, but in fact its populations started building up in the drought of 2011. Mozena thrives on mesquite, which, all things considered, was not as heavily affected by the drought. Mozena has tough skin and is relatively free from biological control agents, so it got way ahead in 2011, those populations kept getting bigger and bigger on mesquite in 2012, and then they overflowed to our crops in 2013.  


That is what things look like through the bottom of a Dr. Pepper bottle. Field scouting will be very important this year; our overwintered pests might concentrate on the healthy crop acres, and the immigrant pests might be worse than normal. 

Wednesday, August 18, 2021

West Texas Agricultural Chemicals Institute Annual Meeting

West Texas Agricultural Chemicals Institute's 2021 meeting is scheduled for September 14th at the FiberMax Center for Discovery in Lubbock (1121 Canyon Lake Drive).

Link to online registration: https://wtaci.eventsmart.com/

Onsite registration begins at 7:30 am on 14th September.

  




Thursday, July 22, 2021

Sugarcane aphid is here, fall armyworm higher than normal, spider mites on the doorstep

It has been a fairly quiet summer so far in corn and sorghum, but that seems to be changing now. Independent crop consultants reported finding sugarcane aphid colonies in sorghum in southern Hale County earlier in the week, and we had no trouble finding them at the Halfway Experiment Station today. I also found them at the Lubbock Research and Extension Center on the first sorghum leaf I looked at. These were small colonies of 100 or so immature aphids surrounding one adult. At Lubbock we are just now starting to get small amounts of honeydew accumulation. It is time to start scouting your sorghum. 

We had a really big fall armyworm flight five weeks ago as I reported on June 16. The next generation is more numerous than average as well according to the pheromone trap data from Lubbock this week.


Of course we need to scout sorghum for headworms and non-Bt corn setting ears, but this big flight might also be a problem for hay production, and in fact I got a call from a Lubbock County producer yesterday. This is the first such Lubbock County call I have had in several years. The southern and central parts of Texas got slammed by FAW this year, but such high numbers are not as common here. In response to the slamming downstate, my colleagues produced a quick guide to fall armyworm control in pastures

The wet, cool and humid conditions have been good for corn and sorghum and bad for spider mites. However, as the temperatures rise and humidity drops now, spider mite populations are beginning to recover. These populations increase rapidly as corn enters tasseling, and all corn fields should be scouted. 

Things are happening fast in all of our crops. If you want the latest news then consider signing up for our weekly Southern High Plains Pest Management Audio Updates. Area IPM Agents record and distribute this 7-8 minute news report on Wednesday afternoon after they have been scouting, and you will have a text link to the audio file within 30 minutes of finishing the recording. You can sign up here. We don't track you, won't try to sell you an extended warranty on your vehicle, and you can opt out at any time just by sending a text with the with the word "STOP". Relevant news with no commitments. 

Wednesday, July 14, 2021

About those seed treatments .... A really good and balanced article

We live in a time of fake news; coverage designed to mislead and advocate one viewpoint. No, I don't need any scientific citations to back this claim up; we all know it is true. I'm writing tonight to bring a very balanced and well-referenced article to your attention, one that deals with the benefits and downsides of the seed treatments put on our corn, cotton, soybean and other seed. 

Beginning around 15 years ago, seed treatments became commonplace on corn seed, and it is now virtually impossible for High Plains growers to buy any seed without these treatments. Research has shown that the treatments often provide little if any benefit, but sometimes they do, like in our corn that has corn rootworms resistant to Bt toxins. But without the rootworm threat the value of seed treatments is far more questionable. On the other hand, cotton often benefits because of the near-constant thrips pressure early in the year, and the fact that aldicarb is not routinely used at planting anymore. Today we buy a whole package in a bag; crop genetics, Bts, insecticides, fungicides, and more. It is no longer a simple choice, and in most cases there is no longer a choice to buy one component without all of the others. 

In what I consider to be a rare moment of good journalism these days, a writer at Progressive Farmer DTN has written a thoroughly documented article on the issues around seed treatments. She provides web links to many reputable sources that either support seed treatments or argue against them. Spend some time and read it; you will both agree and disagree, but remember that long ago that is what good journalism used to be like: https://www.dtnpf.com/agriculture/web/ag/crops/article/2021/07/13/seed-treatment-overload-unintended. I have suggested to TAMU that this article become required reading for Integrated Pest Management on campus; farming is a complicated business and we have choices, some of which serve us well, and some of which do not, and the difference may depend on whether one is looking at the short term or long term. It is complicated. I am grateful that a real journalist did the hard work to examine all sides of an issue, provide evidence each way, and let the reader decide.