Texas South Plains Cotton: Shifting Gears Towards Cotton Fleahopper

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

Showers over the last week should help cotton that was struggling earlier to stay alive and catch up with the progress. Most fields should fairly be safe from thrips at this stage. Many fields have already started squaring and becoming more attractive to flower feeding plant bugs such as the cotton fleahopper. Cotton fleahoppers prefer to feed on small squares (pinhead size) and can drastically reduce the fruiting sites in no time when in large numbers. When scouting for fleahoppers one should pay attention to both number of insects in field and the percent square retention especially during the first three weeks of squaring. I haven’t seen any major cotton fleahopper activity yet as numbers still remain scarce. This may be due to earlier hot and dry spell and the unavailability of alternate host plants to buildup fleahopper populations. However, fleahopper populations are unpredictable and can rise quickly in spots which is why it is important to keep a close watch on them. If you are seeing any square loss but no signs of plant bugs—that could just be the hot and dry weather causing it.

 Here is a link to access our new fact sheet for more information on the management of cotton fleahopper.

http://lubbock.tamu.edu/files/2017/06/Cotton-fleahopper_ENTO073.pdf

Also, check out our video to learn more about the cotton fleahopper and how to scout for it:

https://www.youtube.com/watch?v=epVctkRkTHs

Fall Armyworm 2x Normal and May Be On Fast Increase

After a very quiet spring, fall armyworm trap captures shot up this week to twice the 6-year average. The average trap capture this week was 228, but significantly, 106 of these were caught in the last two nights. This indicates that a possible very rapid population increase might be underway.

I was taking data this morning in a corn trial near Ralls. The corn was at V8 growth stage, and the non-Bt corn in the trial ranged from 20 - 50% of the plants per plot with fall armyworm damage. In the plots with the most damage, the average damage rating was 5 on a 1-9 scale. This is still below the level of concern, but if we are indeed in a time of rapid fall armyworm increase then noticeable damage in sorghum and non-Bt corn will be appearing soon.

Fall Armyworm Numbers Rebuilding, Sugarcane Aphid Moves Closer

After what has been a wonderfully quiet spring, the first day of summer brings news that fall armyworm numbers are on the increase. The trap captures at Lubbock jumped in the last week and are now near the 6-year average. Expect to start seeing damage on whorl stage corn and sorghum.

Additionally, sugarcane aphid has been confirmed in Tom Green and Nolan counties. This is discussed on the Sugarcane Aphid News site here.

Texas High Plains Cotton: Keep an Eye for Grasshoppers

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

Early planted cotton with adequate soil moisture should now be safe from thrips damage. However, fields with less than 4-5 true leaves/plant should be continued to scout for thrips. Normally, once we are past thrips season, I shift my attention towards cotton fleahopper. This year, however, grasshoppers can come into play early in the season. Last year we experienced grasshopper outbreaks in spots causing severe stand reduction and defoliation on larger plants. With the extended spell of hot and dry conditions on the Southern High Plains, my antennae are already wiggling for grasshoppers.

Grasshopper populations can increase dramatically under low rainfall and dry weather condition and be very destructive to young cotton. Grasshoppers have a high reproductive capacity. The female can lay up to 400 eggs in variety of crops as well as non-crop areas including ditches, fence rows, grassy fields, along roadsides and in pasture areas. Both the nymphs (immatures) and adults feed voraciously on plant foliage. When wild grasses and other plants become dry, the grasshoppers migrate to crop plants. Margins of fields are usually impacted first. Typically, grasshoppers feed on cotton foliage without causing significant crop injury. However, during the outbreak periods, they can become very destructive. Large numbers of grasshoppers are capable of completely destroying stands of seedling cotton, especially around field edges.

Fields with a known history of grasshopper outbreaks can be protected using mechanical and cultural methods (tillage and weed control) that target eliminating egg-laying sites and weedy hosts around the crop field. Producers need to watch out for grasshoppers and begin control measures if needed while they are in the immature stages as adults sometime can be hard to kill with insecticide applications.

Results from 2016 grasshopper insecticide performance trial can be found at: 

http://lubbock.tamu.edu/files/2017/02/2016-Cotton-Insecticide-Performance-Trials.pdf

Heat Damage to Cotton Mimics Thrips Damage

Kerry Siders, IPM Agent in Hockley, Cochran and Lamb counties, has posted a special edition newsletter that describes heat damage to cotton that may be mistaken for thrips damage. The reprint is below.

Special Edition West Plains IPM Update - Not Thrips Damage

So I have received a few calls about seeing what was thought to be thrips damage to cotton, even on 4-7 true leaf cotton. See damage referenced in pictures below. So the scouts and I are finding a few thrips but in most all cases well below threshold. The damage you are seeing below and I suspect in many if not most all fields is this cupped, puckered, damaged cotton leaves. Looks like thrips, but if you look on the underside you do not see the feeding damage from thrips rasping on the leaf causing rupture of tssue and leaking of plant fluids. This then results in a scared silver tissue. The damage we are seeing now is on the uppermost new tender leaves. This is caused by the hot desiccating winds. So it may be 102 degrees out there, but that bare soil surface could reach well over 120 degrees. Combine that with the constant wind, that will pucker anything up. So what happens is the tender leaf margins become desiccated or injured to a point where they cannot develop normally. Meanwhile the leaf continues to develop around the center portion of the leaf causing this cupped appearance. This is not thrips, not herbicide damage, no disease, no genetic failure, just plain HOT! And until this weather breaks with a more moderate temp of less than 97 degrees, decreased wind speed, higher humidity, needed rainfall - these symptoms will continue to be seen in cotton as well as other crops. I am seeing the same thing in peanuts today. 

Soldier Beetles, Not Blister Beetles

A Lubbock County grower came to my office this morning with a bottle that held 20 or so beetles he collected from the edge of a field. His concern was that they were blister beetles, and I was pleased to be able to say that they were soldier beetles. However, given the high numbers he described in the field, soldier beetles must be very abundant this year.

Photo credits: Ed Bynum and Pat Porter

There is some resemblance, but these beetles are different enough to be separated on sight. One problem though is that he showed me a web page that incorrectly identified soldier beetles as blister beetles; the internet strikes again. Texas growers can always send us a photo of an insect if they want an identification.

Soldier beetles, insect Family Cantharidae, are predacious on other insects as both adults and larvae. Blister beetle larvae, insect Family Meloidae, are predacious on grasshopper eggs and the larvae of wild bees. When disturbed, blister beetles exude hemolymph (the insect version of blood) that contains cantharadin, a potent blistering agent. The University of Florida has a good publication on blister beetles, and there is a section near the end that covers the medical aspects.

Texas South Plains Cotton: Thrips Numbers on the Rise in Spots

Cotton ranges from seed just placed in soil to four true leaf stage in South Plains region. In most areas thrips pressure remains low, however, we are seeing some hotspots in counties north of Lubbock where thrips numbers are well beyond economically damaging levels. As the wheat is drying down and becoming an unfavorable host for thrips, adults are taking flight on breezes and winds to young cotton plants. Thrips feed on the lower surface of cotyledons first or any exposed true leaves before moving to the very tender terminal bud or growing point of developing seedlings. With their piercing-sucking mount parts, they stab and rasp away at plant surfaces causing severe scaring and then suck up the plant juices.

 

Young cotton leaves damaged by thrips

Controlling thrips at an early stage is very important as we try to protect these young and rapidly developing plants from damage. Excessive amounts of damage to these first leaves or growing point can have a huge impact on how the plant develops later and ultimately performs. Preventive insecticidal seed treatments provide control up to 3 weeks after planting. However, this can vary with growing conditions and the weather.

Once the plant reaches the 3 to 4 true leaf stage, with a healthy growing point and true leaves, growth accelerates rapidly and the risk of thrips damage usually starts to decrease. However, the plants will need to reach pinhead square stage before they are truly past economic thrips damage.

During the plant’s early growth stages, growers should apply foliar insecticide at a threshold level of 1 thrips per true leaf. When scouting for thrips, there is truly no substitute for whole plant inspections from a representative sample from across the whole field. More information on thrips management can be found at: http://lubbock.tamu.edu/files/2017/05/ENTO-069_fn.pdf

Check out our video to know how to scout for thrips: https://www.youtube.com/watch?v=uD2dIDQmRb0

Suhas Vyavhare, Texas A&M AgriLife Extension Service