It’s that time of year – Yellownecked Caterpillars Are Back

It’s that time of year, yellownecked caterpillars, Datana ministra, are once again active in oak trees.  This generation is nearing maturity and, although the frass (or poop) “raining” out of trees, unsightly defoliation, and caterpillars falling and crawling out of oaks can be annoying, it is too late to gain much by eliminating this generation. For the most part they have completed feeding and are moving out of the trees where they will pupate in the soil.  Killing mature caterpillars to prevent them from pupating and thus re-infesting an area has not been shown to be effective. This includes the use of systemic insecticides (soil drenches) or treating the soil for pupating caterpillars. The exception being, if you can see branch tips where a large group of these caterpillars are feeding, you can trim these areas and destroy larvae.  However, this does not guarantee that your oak won’t be infested again later in the season. 

 

In most parts of the U.S. there is only 1 generation a year.  However, based on last years’ experience, we have another 1-2 generations ahead of us here in the LRGV. Last year, our second generation became active in early September.  While it can be distressing and unsightly, the defoliation caused by yellownecked caterpillar feeding will not cause long-term damage to healthy, well-established trees.  If you would like to control the next generation, it will be important to keep a close eye on oak trees and take action as soon as caterpillars begin feeding.  Chemical options include Bacillus thuringiensis var. kurstaki (biorational) and most home landscape insecticides labelled for caterpillars (conventional).  Successful control depends on good coverage of the caterpillars (these are all contact insecticides), and application timing (when larvae are small). 

For more information on the biology and management of yellownecked caterpillars, please click here and here.

Armyworms on the March!

Have received reports of significant populations of fall armyworms (FAW) feeding on foliage in corn and sorghum and consuming pasture grasses throughout the RGV. Egg and larval survival are favored by cooler temperatures and wet conditions so our recent conditions have been perfect. Like all caterpillars, they are eating machines and will actively feed for several weeks, reaching a length of 1^1/2 inches before pupating in the soil.  While small larvae do not cause much damage and may be hard to detect, more mature larvae can consume significant amounts of foliage and cause considerable defoliation.  As their name suggests, they feed in large groups, moving like an army and consuming foliage as they go.  They are most active at night, or on cloudy days thus sampling will be most successful early morning, at dusk, or during the cloudy periods we have had plenty of lately.  Infestations often begin in grassy pastures, weedy roadsides and along fence rows and move into small grains, corn and sorghum.  

 

In young corn and sorghum, the smaller the plant, the less defoliation can be tolerated, but sorghum in the RGV is largely past seedling/whorl stage damage.  As a general recommendation - insecticide applications may be considered if feeding reduces leaf area by 30% or more and you are finding 1-2 larvae per plant. Foliar feeding at later stages has been pretty impressive (see photo) but unfortunately, we do not have established thresholds for these later stages of corn and sorghum.

A major concern is if/when fall armyworms move into sorghum heads where they may cause significant damage. Thus, sorghum should be scouted for in a timely manner from flowering through soft dough.  

In general, 1-2 fall armyworm and/or corn earworm per sorghum head may warrant control. For a more detailed management decision calculator, please click here. For more information on control options for armyworms in sorghum, please click here (page 37).  Note that pyrethroids are not recommended for corn earworms and FAW larger than 1/4 inch (2nd instar). 
 
In pasture thresholds very with crop stage and value but 2-3 armyworms per square foot may justify control. For more information on FAW and insect management in pasture, please click here.

Fall Armyworm Feeding in Corn and Sorghum

We are starting to see fall armyworm (FAW) activity in corn and sorghum.  Larvae feed down in the whorl of plants and, as these chewed leaves unfurl, plants can take on a ragged look.  This defoliation is typically not of economic importance and thus treatments are not recommended.  However, insecticide applications may be considered if feeding reduces leaf area by 30% or more and you are finding 1-2 larvae per plant, especially in drought-stressed fields.  Later planted fields may suffer more damage when small plants are attacked.  If you do decide to spray, keep in mind it is difficult to reach larvae, protected down in the whorl of the plant, with contact insecticides. By the time damage is noted larval feeding may be complete or nearly complete.  Once mature, larvae crawl out of plants and pupate in the soil where treatments will not impact them.

We will have multiple generations of FAW and they may be of economic concern later in the season if they infest sorghum heads.  At this stage, “headworms” (FAW and corn earworms) may cause approximately 5% yield loss per worm, per head.  So, an average of one larva per head may lead to a 5% yield loss, two worms per head a 10% yield loss, and so on. 

 

For more information on fall armyworms and other sorghum arthropod pests, please see:  Managing Insect and Mite Pests of Texas Sorghum.

South Texas Audio IPM Updates

As a new row crop season gears up we have kicked off a weekly audio update for South Texas IPM in row crops.  This is new for our area this year and each week we will provide a 5-7 minute update on what is going on in the LRGV and Costal Bend.  It is a great way to get a heads up on what pests you may need to be on the lookout for in your area and other issues that may be of concern to you.  We hope that you will follow this link and sign up:

https://www.texasinsects.org/south-texas.html

 

You will receive text when a new update is available and can listen to it right there in your truck, tractor, or wherever you may be.

 

Signing up is easy:

 

Click on this link, https://www.texasinsects.org/south-texas.html 

On the top of the page select:

>> Signup to get a text message when a new post is made.<<  

 

Next, Signup for South Texas IPM Updates, by entering your cell number and input if you are a PRODUCER, CONSULTANT, AG INDUSTRY, AGRILIFE OR OTHER. 

 

And that’s it!

 

 

Happy Planting!

Did the cold kill the insects?

 

I think a lot of us are looking for a silver lining in this disastrous historical cold spell. I have been getting a lot of questions to the theme of - will this cold weather kill all the insects?  The short answer is no.  As one of the most successful groups of animals on the planet, arthropods have developed mechanisms to avoid succumbing to cold temperatures, even if they don’t often have to endure them here in the Valley.  Different species go about it in different ways.  Some more mobile life stages will seek shelter in leaf litter, other debris, outbuildings or even our homes.  Other insects can actually produce cryoprotectants like glycerol and sugar that work like antifreeze, allowing the insects to survive freezing temps without actually freezing.  This time of year, many of our important row-crop insects are overwintering while their host plants are unavailable.  Most overwintering, or off-season, life stages are already in protected stages (eggs or pupae) and/or safe locations (in the soil, under residue, etc.) and most will probably emerge as usual.  

Where we will likely see some impact of the cold temperatures is in our more tropical species such as the sugarcane aphid and with insects that were actively infesting vegetable crops.  For example, most exposed whitefly adults were probably killed as it only takes 3 hours at 21° F to kill 90% of adults.  However, whitefly eggs and nymphs must be exposed to that same temperature for 57 or more hours to get the same mortality.  Keep in mind, if the host plant dies, so do the whitefly eggs and nymphs.  

Bottom line, the insect world is diverse, and each species was impacted by the cold to a different degree.  And, while low temperatures dramatically reduced some pest populations, they will eventually make a comeback. We may not see some of our early season pests in as large of numbers as we typically do, however, their ability to produce large numbers of offspring in a relatively short time will allow them to rebound. One thing for sure, time will tell us more.  

NEW! Texas A&M Research Reports 2020

Texas A&M AgriLife is launching a new statewide effort from Extension Agents - IPM and Extension Entomologists to share our 2020 field research findings.  Last week, we released a short audio discussion on sesame leafroller control based on efficacy trials and research conducted this summer.  

You can click here to listen and don't forget to sign up so you will be notified of new posts.

Yellownecked caterpillars are in full swing

Have had multiple calls, and my own experience, with significant defoliation in oak trees this past week.  And, almost as distressing for some is the frass, or poop, “raining” down out of these trees onto patios, sidewalks, pools, etc.  Both problems are caused by yellownecked caterpillars, Datana ministra.  These caterpillars, or worms, are mostly black, with white to yellow stripes running down their bodies.  They are sparsely covered in long white hairs and usually have a yellow or orange band just behind their black heads, and reddish-orange fleshy legs, called prolegs.  

 

Eggs are laid in masses in trees and caterpillars remain grouped, feeding on foliage until they reach a length of about 2 inches.  They then crawl or drop from trees and burrow just under the surface of the soil to pupate. According to most sources, there is only one generation a year.  However, we have had reports of two generations here in the RGV, one in September to October and another in the spring, around May.  For more information on their biology please click here.

Mature Yellownecked Caterpillar. Notice the way they  raise both ends of their body when disturbed. 

Generally, yellownecked caterpillars are a nuisance and aesthetic pest, but do not cause damage to otherwise healthy trees.  As with any pest, the earlier they are detected and treated, the better the control.  As they are often way up in the tree canopy, their presence is often not noticed until defoliation is significant and/or worms begin falling or crawling out of trees to pupate in the soil. Additionally, because worms are so high it is challenging to get treatments (contact insecticides) to them safely and effectively.  The use of systemic insecticides(soil drenches) or treating the soil for pupating caterpillars has not been shown to be effective.  Chemical options include Bacillus thuringiensis var. kurstaki (biorational) and most home landscape insecticides (conventional).  Again, successful control depends of good coverage of the caterpillars and application timing (when larvae are small).  Killing mature caterpillars in order to prevent them from reinfesting the area has not been reported to be effective, although I have been told by a few that it makes them feel a little better.