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.