Be on the lookout for sorghum midge

As sorghum throughout the Valley continues to flower, be on the lookout for sorghum midge, especially on later flowering fields.  These tiny flies can cause significant damage in a short window of time, thus it is important to scout for populations in a timely manner.  The female flies can be seen on flowering sorghum heads where each fly deposits up to 50 eggs.

Sorghum midge adults on blooming head

 Larvae will emerge in a couple of days and begin feeding on the ovary of the developing seed, preventing development.  A single larva will destroy a seed, but a seed may have more than one larva. Mature larvae pupate in the upper tip of the spikelet and when the adult emerges, leave a clear pupal skin at the tip of the spikelet.  Infested seeds have a ‘blasted’ appearance with hulls and bracts remaining but empty seeds that have been consumed by larvae.

 

Sorghum midge pupal skins (photo from Managing Insect and Mite Pests of Texas Sorghum)

An entire generation may be completed in as little as 14 – 16 days so there are many generations a year, with each generation more numerous than the last. As a result of these increasing populations, later planted sorghum is most at risk of damage.  For sorghum growing the Rio Grande Valley the last date (estimated) flowering sorghum stands a good chance of escaping significant sorghum midge damage is May 10^th.

Estimated latest sorghum flowering date most likely to escape significant damage by sorghum midge
 (From Managing Insect and Mite Pests of Texas Sorghum)

Scouting for these pests should be done daily during the vulnerable flowering stage.  Plants should be inspected earlier in the day when short-lived female flies are active.  Begin on field margins, especially those close to sorghum that has already flowered or Johnsongrass, an alternative host. If more than one fly/head is detected, the rest of the field needs to be inspected.  For more information on sampling for this pest, determining treatment thresholds, and treatment options, please see Managing Insect and Mite Pests of Texas Sorghum, TexasA&M AgriLife Extension.

Updated Handy Bt Trait Tables Available

The updated (2020) version of the Handy Bt Trait Table is now available.  This is a great two-page, quick reference guide that lists the Bt and herbicide packages available for U.S. corn.  Included is also information on what pests each controls along with those that have demonstrated developed resistance to various trait packages.

For the first time ever, there is now a Handy Bt Trait Table for sweet corn as well!

You can find both field and sweet corn Hand Br Trait Tables here:
https://www.texasinsects.org/bt-corn-trait-table.html

Reality Check From the Hemp Harvest

Interesting article that discusses a lot of the issues growers are facing in states where they are  (legally) growing hemp.

https://www.pewtrusts.org/en/research-and-analysis/blogs/stateline/2019/11/08/farmers-struggle-as-hemp-harvest-winds-down

Although not yet legal in Texas, there has been a lot of interest in this crop.  However, there is a lot of basic groundwork to be done regarding infrastructure as well as disease and pest management before we can consider this crop to be a reasonably safe gamble.

What's Infesting My Live Oaks?

Have been getting a lot of questions about several insects in oaks and what to do about them.  The first is a caterpillar that is feeding on leaves, often high up in the foliage where they go unnoticed until either frass (poop), or mature caterpillars start “raining” down out of trees.  These are most likely yellownecked caterpillars, Datana ministra (See photo).  Larvae are black with four yellow stripes running along the length of their bodies and one around their “neck” just behind the head capsule.  They are thinly covered in long white hairs and reach up to 2 inches long just before pupation.  The adults are small, rarely noticed reddish brown moths.  Females deposit large clusters of eggs (up to 100 or more) on the foliage of several woody plants, including oaks.  As caterpillars emerge, they congregate and begin feeding, skeletonizing leaves which may severely defoliate sections of trees,especially as caterpillars reach maturity.  Then, they use thin strands of silk to drop to the ground where they pupate within the soil.  Treatment is not typically recommended on large, well-established trees as it is costly and often difficult for homeowners to safely get insecticides up to where larvae are feeding.  In many cases, by the time the caterpillars are noticed they are nearly mature and will not be causing damage much longer.  We do not anticipate another generation this year and the defoliation will not cause long term damage to otherwise healthy trees.

Yellownecked Caterpillar
Photo by Drees

Caterpillar frass (poop) under oak tree where yellownecked caterpillars are feeding
Photo courtesy of  Cristina Villalobos 

Another concern is regarding the white to yellowish fuzzy balls and/or pea-sized hard, brown balls attached to the underside of oak leaves (see photo).  These are both types of galls caused by two different species of tiny cynipid wasps (the wool-bearing gall wasp, Andricus quercuslanigera, and probably Belonocnema sp., no common name).  Females deposit eggs singly on oak leaves and the insect’s activity causes a reaction in the tree so that it produces additional growth, or a gall, around the egg or larva.  This serves to protect the developing wasp. 

Oak Leaf Galls

In general, galls may be induced by many different species of tiny wasps, mites, fungi, and bacteria.  They often have complicated life cycles and are very specific to a single plant or tree species.  In many cases these gall-laden leaves will drop to the ground early, but there is no cause for alarm.  Although they might be unsightly, most galls will not negatively impact tree health.  For whatever reason, populations/pressure seem to fluctuate from year to year and they often do not re-infest the same tree the following year (please note this is not always the case).

RGV Bug Blog Kickoff!

Hello!  I am Holly Davis, the new Extension Specialist in Entomology located at the AgriLife Research and Extension Center in Weslaco,TX.  While my focus will be on agricultural entomology, I hope that this blog can be a place to post short, informational articles about arthropod pests impacting all residents of the LRGV.  This may include everything from important crop pest updates to occasional lawn, garden and even household pests. So, I am going to begin posting about insects that I am getting lots of questions about and we will see where it leads us!