Insect Strip

Insect Strip

Friday, May 11, 2018

Cotton Pest Report

Cotton Planting
Planting has been underway for awhile now in the Southern High Plains with a few fields north of Amarillo already planted or will be planted soon. Our soil temperatures are quickly rising with our hot dry conditions. The map to the right is from agweb.com and it illustrates soil temperatures at the 4” depth across the U.S for May 9. 

Another source for soil temperatures is at Syngenta’s GreenCast website. These temperatures are also measured to the 4” (0 - 10cm) depth. From this site the current soil temperatures for locations in the Texas Panhandle are: 
Location
Current Soil Temperature
5 Day Avg.
Amarillo
68o
76o
Dalhart
65o
74o
Hereford
69o
77o
Pampa
72o
78o
Perryton
70o
76o
Spearman
70o
76o

Attached is a link to an Extension publication SCS-2005-17, titled Soil Temperature for Cotton Planting. In this publication by Drs. Randy Bowman and Robert Lemon, they discuss the temperature requirements for planting, seed germination and DD60 heat units for emergence. They state that  “At a minimum, soil temperatures in the seed and root zone should exceed 60oF and our five day forecast for daytime maximum temperatures should exceed 80oF. Additionally, nighttime minimum temperatures should be forecast to be above 50oF for the following 5 days.”
We have excellent soil temperatures for planting and cotton emergence. And the outlook for continued warm temperatures is very good. With adequate soil moisture we should have excellent emergence and seedling growth. However, there are two insects that could potentially cause damage to the cotton seed and cotton seedlings. The first insect of concern is the cotton thrips. 
Cotton Thrips
There are primarily two thrips species that infest cotton across the Texas High Plains. They are the western flower thrips, Frankliniella occidentalis, and the onion thrips, Thrips tabaci. Both thrips are very small, approximately 1/15” long, and pale yellowish gray to brownish colored as adults. The immature thrips are whitish to light tan. it is difficult to distinguish between each species without the aid of a hand-lens or microscope. However, the damage caused to cotton leaves is similar. They feed on the tender leaf tissue by rasping, tearing the leaf epidermis, and sucking out the cell contents causing silvering speckling of the leaf, and leaf curling resulting in deformed leaves. This damage will stunt plants, prevent normal plant growth, and delay maturity. In our area delayed maturity from thrips damage means that we loss valuable heat units that could be needed for lint production and lint quality.
Silvering and curled deformed leaf caused by thrips damage to cotton.
Arrows pointing to thrips
Photo: Texas A&M AgriLife Extension Service
We can have problems with thrips during periods of extended cool temperatures and/or heavy migration of thrips from wheat during the first few weeks after cotton emerges. Our threshold is 1 thrips (adult and/or immatures) for each true leaf to the 5th to 7th true leaf stage when treatment is rarely justified. 
Thrips Action Threshold
True Leaf StageTreatment Threshold
Emergence to 1 true leaf1 thrips per plant
2 true leaves2 thrips per plant
3 true leaves3 thrips per plant
4 true leaves4 thrips per plant
5-7 leaves or square initiationTreatment is rarely justified

The first line of defense against thrips have become the use of insecticide seed treatments. These seed treatments generally provide protection for 18 to 21 days. Protection from the time seeds are planted, not from emergence. If immature thrips are found on cotton then the seed treatments are no longer providing protection. Under good growing conditions this will provide protection until the 2nd to 3rd true leaf stage. Therefore, under heavy thrips pressure or cold spell, a foliar insecticide application could be needed to prevent damage. The foliar insecticides, available for use against thrips, only provide no more than 5 days of protection. These insecticides must be applied only when needed and timely to provide effective control after seed treatments are no longer providing thrips control.  The most important period for protection is the first two weeks after emergence because after seedlings have been excessively damaged plants may not recover quickly enough to compensate for the loss in maturity. Therefore, begin scouting and inspecting seedlings once cotton reaches 50% plant stand and scout twice weekly until cotton growth is past the susceptible stages. Carefully pull up plants to prevent adult thrips from flying off the plant. Looks through the terminal grow and all of the true leaves. Use the end of a pencil lead, toothpick or another pointed object to uncurl the deformed leaves to find any adults or immature thrips. Also, pay close attention to where leaf veins connect on both the top and underside of each leaf. Sample 25 plants from four regions of the field, keeping records of the number of thrips per plant and the number of true leaves per plant. Then calculate the average number of thrips per plant and the average number of true leaves per plant. If the number of thrips per plant equals or exceeds the number of true leaves per plant then a foliar insecticide application would be recommended.

Wireworms
The other insect that could be a concern to planted cotton is the wireworm. Admittedly, I am not that familiar with wireworms causing problems in cotton, but Mr. Blayne Reed, Texas A&M AgriLife Extension Agent - IPM for Hale, Swisher, and Floyd Counties, reported an alarming situation of heavy wireworm numbers causing reduced cotton stands in some fields he is scouting. He wrote an article,  “Wireworms Notable in the Area and a Threat to Cotton Establishment” on Monday, May 7, 2018. What is interesting is that before Mr. Reed wrote this article, Dr. Pat Porter had told me that wireworms had completely destroyed his sweet corn seed that had been planted in April at the Agrilife research farm at Lubbock. The seed had not been treated with an insecticide and the seed had been planted in an area that was planted to cotton last year. I cannot say how widespread this may be or if there are pockets of infestations. However, one should consider checking fields for possible plant stand losses and evidence of damage from wireworms. 
There are two different types of wireworms that could be causing damage to the seed and seedlings. These are the true wireworm, Click beetle larvae, and the false wireworm, larvae of the darkling beetle.
Click Beetle
Photo: Pat Porter
True wireworm larvae
Photo: Pat Porter
Darkling Beetle
Photo: Pat Porter
False wireworm larvae
Photo: David Kerns

The Click beetle larvae were the wireworms causing damage to Dr. Porter’s sweet corn seeds. Before cotton emerges larvae feed on the root, hypocotyl (stem) and cotyledon (seed leaves) of germinating plants. This feeding primarily causes plant stunting but can kill plants and reduce plant stands. Scouting for wireworms is difficult and there are no rescue treatments available after planting. Insecticide seed treatments are the most effective way to minimize damage. Additional information is available at: http://agrilife.org/lubbock/files/2017/05/Wireworms_ENTO-068.pdf.

Friday, September 22, 2017

Issues of Fumonison in Corn across the Texas High Plains



Dr. Jourdan Bell writes, In response to elevated reports of fumonison in corn across the Texas High Plains, Texas A&M AgriLife Extension along with Texas Corn Producers has coordinated two emergency meetings for September 27 (9:00 AM in Dimmitt and 6:00 PM in Dumas). Tom Isakeit, Texas A&M Pathologist at College Station who specializes in mycotoxins, will be present to discuss fusarium and the fumonison disease cycle. Other speakers include, Dr. Cat Barr, veterinary toxicologist, Dr. Tim Herrman, Texas State Chemist, and a representative with RMA. Texas Corn Producers news release concerning elevated mycotoxin levels is available at:  http://texascorn.org/2017/09/mycotoxin-levels-high-plains-pose-threat-regions-corn-farmers/

Additional resources concerning mycotoxins in corn and livestock toxicology are at:


Wednesday, August 30, 2017

Predominate Pest Threats in the Texas Panhandle




Photo: TAMU Entomology
      The corn earworm (CEW), aka cotton bollworm, one of the sorghum headworms, and soybean podworm, is probably the primary pest of concern in cotton and a close second behind sugarcane aphids in grain sorghum. The earworm moths prefer corn, then sorghum, and cotton and soybean. There has been an increase in CEW egg lay in grain and forage sorghums all across the Panhandle. In sorghum, both the CEW and the fall armyworm feed on the developing grain kernels. However, fall armyworm numbers have been relatively low this season in our moth trapping sites across the Panhandle. The increased CEW activity in our sorghum crops could spill over to our cotton and soybean fields. A female moth is capable of laying 500 to 2000 eggs singly on cotton leaves, terminals, squares, blooms and bloom tags and bolls and sorghum leaves and heads. Eggs will hatch in 3 to 4 days at an average temperature of 77o F.  Larvae will feed on the cotton and soybean fruiting forms (cotton squares and bolls, soybean pods) and sorghum kernels for 14 to 18 days. The infestations can cause significant yield losses if not controlled.
Bollworm moth on cotton leaf - 8/30/2017,
Sherman County, Photo by John Quillin

Infestations could even reach damaging levels in Bt cotton, including Bollgard II, Widestrike, and TwinLink varieties. The latest Bt cotton traits, Bollard 3, Widestrike 3, and Twinlink Plus, should provide better protection from any Bt resistant caterpillars and from heavier infestation pressure. Historically, the Texas Panhandle rarely has had damaging infestations in cotton, but with the increased cotton acreage and the delayed fruit development this could be a year when we have damaging infestations.  

Bollworm and Tobacco Budworm Action Threshold Based on Boll Damage
Cotton Stage
Action threshold (both Bt and non-Bt cotton
Before bloom
≥ 8 worms (≥1/4 inch) per 100 plants wet populations threaten to reduce square retention below 80 percent

After boll formation
≥ 6% damaged squares and/or bolls and worms are present
Field that have accumulated 350 DD60s beyond 5 NAWF are no longer susceptible to first or second install bollworm/tobacco budworm larvae. Action threshold should be adjusted according to yield potential and production system (dryland vs irrigated).
Tobacco budworms are rarely recorded in substantial numbers in the South Plains and Panhandle areas


Sugarcane aphids (SCA) have been increasing and spreading throughout the Panhandle for last few weeks. In my forage sorghum trials at Bushland, there have been a lot of winged aphids moving into the field the past two weeks and populations are reaching treatable infestations. I am expecting populations to explode this week in my test plots. Currently, there are very few beneficial predators in the field. The predators present are mostly lady beetle adults and larva and minute pirate bug adults and nymphs. There have been an abundant of syrphid flies hovering in the field and more syrphid fly maggots are being found on the leaves this week. Unfortunately, beneficials are not abundant enough to prevent damaging SCA infestations.
Sugarcane aphids, winged and non-winged aphids,
Photo by Pat Porter

Syrphid fly maggot eating sugarcane aphids,
Photo by Ed Bynum

Treatment Thresholds
For cotton, the treatment threshold has been modified and is based on boll damage instead of worm numbers per acre (see new Action Threshold Table). Our old bollworm threshold was 5,000 worms per acre that were larger than !/4 inch long  or 10,000 worms smaller than 1/4 inch long for non-Bt cotton. For Bt cotton, no treatment was not based on worms 1/4 inch or less in size. The threshold for larger than 1/4 inch worms was 5,000 worms per acre with 5-15% damaged fruit. For soybeans, a method of determining infestation is to use a drop cloth laid between the rows and vigorously shaking plants over the cloth. If 1 or more CEW larvae are found per linear foot of sampled row then the infestation is at the economic threshold. Another method is to look for feeding damage to the soybean pods. Treatment levels are recommended if 5% -10% or more pods are damaged from CEW larvae. In grain sorghum, our treatment threshold uses a formula to calculate the number of large (≥ 1/2 inch long) or medium (> 1/4 to 1/2 inch long) sized worm per head to justify treating. This treatment threshold formula factors in the cost of control and the expected market value of the grain. The threshold formula is explained on page 22 of “Managing Insect and Mite Pests of Texas Sorghum”.
Control Options
The majority of insecticides labeled for use to control worms in cotton, grain sorghum, and soybeans are pyrethroid insecticide products. There are a few other products with different modes of action, such as Prevathon, Lannate, Steward, and Blackhawk. Our home-grown worms that overwinter on the Panhandle are most likely susceptible to the pyrethroid products, but the corn earworm/cotton bollworms moths finding their way up here from south Texas could be more resistant to the pyrethroid insecticides. There have been reports of control failures of bollworms down state to the pyrethroid insecticides. Even though we do not know what the frequency of moths we have from south Texas, pyrethroid insecticides should still be effective when using higher label rates of name brand products, not generic pyrethroid products.
One negative impact from using pyrethroid insecticides is that they will be detrimental to the natural beneficial predator and parasitoid populations. This could be an issue where cotton fields have cotton aphids and grain sorghum fields are infested with sugarcane aphids. In these situations, you may want to use some other insecticide that is “soft” on beneficials. Insecticide options for situations with sugarcane aphids are available in Insecticide Selection for Sorghum at Risk to Sugarcane Aphid Infestations”.


Tuesday, August 15, 2017

Another Texas Panhandle County with Sugarcane Aphids

After reporting yesterday of sugarcane aphids in Moore and Sherman Counties, we received an email from Stephen Cox, crop consultant. He is finding sugarcane aphids in Hansford County. We appreciate everyones help letting us know about new findings of sugarcane aphids.

Monday, August 14, 2017

Two more Counties in the Texas Panhandle with Sugarcane Aphids

I received a text today from Kaj Overstreet, crop consultant, that he has been finding sugarcane aphids in fields in Moore County. Then I received another text that he found sugarcane aphids in fields in Sherman County.

Also, last Friday, August 11th, I received a call for Mr. J. R. Sprague, County Extension Agent for Lipscomb County, that crop consultants found sugarcane aphids in a cotton field. I contact Dr. David Kerns, Texas A&M AgriLife Extension Cotton Entomologist, to determine if we should be concerned about sugarcane aphid in cotton. Besides Dr. Kerns being a cotton entomologist he worked on sugarcane aphids in sorghum while with LSU the past few years before coming back to Texas. He stated that sugarcane aphids could be found in cotton, but aphids were not able to survive to cause damage. The sugarcane aphid is indiscriminate as to where or what crops the alate (winged) aphids may land on. After a female aphid lands on a plant she will begin giving birth to live immature aphids.  Since cotton is not a sorghum related plant the aphids are unable to live very long. Therefore, sugarcane aphids should not be a threat to cotton, but other aphids do live and reproduce on cotton.

Friday, August 4, 2017

More Findings of Sugarcane Aphids in the Texas Panhandle

On Friday, July 28th Dr. Brent Bean found sugarcane aphids in a forage sorghum field near Canyon, TX (Randall County). Since this report SCAs were found in Deaf Smith and Parmer Counties in Texas and in DeBacca County in east central New Mexico. And, today the aphids were found in my forage sorghum trial at Bushland in Potter County. Infestations were just beginning to establish. An interesting side note is that in the Texas fields the aphids were found in forage sorghum fields. I am not aware of the type of field in DeBacca County. The official map showing the distribution of the sugarcane aphids can be located at https://www.myfields.info/pests/sugarcane-aphid.
Dr. Pat Porter, Texas AgriLife Extension Specialist - Lubbock, is reporting aphid numbers are increasing in some fields in Crosby and Lubbock counties. Infestations have reached treatable levels on pre-boot to soft dough sorghum. Blayne Reed, Extension Agent-IPM for Hale, Floyd and Swisher counties, is expecting sugarcane aphids will reach treatment thresholds in his grain sorghum experimental fields within the next two weeks.

Monday, July 31, 2017

Update on Moth Trapping

The last of July and two to three weeks in August is typically when southwestern corn borer (SWCB) moths are most active. However, this year we are starting out with very low numbers of SWCB moths in county with moth traps, except moth number in Deaf Smith (trapping locations) and Parmer Counties (John David Gonzales, IPM Extension Agent, light traps) are beginning to increase (See SWCB moth graphs). In Deaf Smith county the high numbers of SWCB moths were in one or two trap locations in the county. Mr. Gonzales has a similar observation that one location in Parmer County has more activity of SWCB moths than other areas in the county. We still have a few more weeks where SWCB moth activity may be a concern. 


Overall, western bean cutworm (WBC) moth activity has not been very high this year, but we have had consistent moth activity in Dallam, Hartley, and Moore counties. WBC trap catches declined this week in Dallam and Hartley, but numbers were fairly high in Moore county (See WBC graph).



Also, fall armyworm (FAW) moth activity continues to be low across the counties being monitored. The was two counties that had an increase in FAWs. These counties were Lipscomb and Randall (see FAW graphs).