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Sorghum Midge

CROPS IMPACTED: Grain sorghum

sorghum-midge-1

Family: Cecidomyiidae

sorghum-midge-2. sorghum-midge-3

About Sorghum Midge

Reproduction and Life Cycle

The sorghum midge overwinters as larvae in a cocoon that can be found inside the sorghum spikelets. They will emerge sometime in the spring, depending on cultural practices and temperature. The females only live for about 24 hours, and in that time, can lay up to 120 eggs. The eggs are placed singly in the plants glume. A large portion of the eggs are laid 4 days after the emergence of plant heads. The entire life cycle of the sorghum midge will take between 14 and 18 days. Male adults live a short few hours. The eggs are connected to the plants spikelet and typically take 42-60 hours to hatch, varying with temperature changes. When the larvae hatch, they will take about 9-11 days to complete their instars and then enter their pupae. This stage is completed between 2 and 3 days, when the midge will emerge fully developed. You can tell the pupae are about to emerge when their whitish skin is seen sticking out of the glume tip.

Sorghum Midge Identification and Habitat

Identification

An adult sorghum midge is a small fly (about 1.3mm long) that has wings fringed along the edges, is orange in colour and is often challenging to spot. The eggs are cylindrical and white, usually 0.6mm long and 0.3mm wide. Larvae have no colour and feed on sorghum seed. They will turn more orange in colour as they mature, becoming slightly flattened and having the shape of a spindle with a pointed head. Fully mature larvae are anywhere from 1.5 to 2mm in length. Pupae will also be orange, later changing to black (other than the abdomen, which will keep its original orange colour).

Habitat

The sorghum midge is most destructive to grain sorghum; however, they are also a pest to johnsongrass. They are difficult to find in a field so sometimes identifying an infestation can be challenging until the damage is already done. This midge is most common in fields where sorghum was grown consecutively for a few years, and if johnsongrass is close by. Sorghum is only vulnerable to damage caused by the sorghum midge when the plant is in bloom. This pest can be located worldwide, and is mainly attracted to the sorghum flower. They will damage the blooms within the first 4 to 9 days. The female places her eggs in between the floret glumes. When the larvae hatch, they eat the spikelets, damaging the seed. A plant that has been badly damaged will result with a head that has gaps and appears compressed. The adults will tend to be the most active from midmorning until early afternoon. This pest can have up to 9 generations annually if conditions are favorable.

Sorghum Midge Management and Control Methods

Cultural Control

Make sure to plant all of your sorghum seed consistently on the same day and at the exact same depth at the appropriate time of year, as suited for that variety. The sorghum midge tends to be much more prominent when you stagger your planting over several days. Also, make sure to keep johnsongrass away from your fields, especially when it heads. All crop debris should be removed from your fields to avoid this pest from using the residue to overwinter in. There are also varieties of sorghum that are resistant to the sorghum midge. It is important to note that having satisfactory control is often dependent on using an integrated management system that includes the use of both cultural and chemical methods.

Chemical Control

Insecticide should only be applied when the pest has reached the economic threshold (20 to 30 percent of sorghum heads are in bloom with one adult sorghum midge on each head). Spray pesticides should be aimed towards females while they are laying their eggs, typically when the heads of the sorghum plants emerge since the larvae are guarded by the spikelets. Insecticides recommended for the midge in sorghum fields are carbaryl, lambda-cyhalothrin, and zeta-cypermethrin. Be sure to carefully read the label for cautions and proper application. It is extremely important to never spray on days that are windy.

Latin / Alternative Sorghum Midge Names

  • - Contarinia sorghicola

Sources

http://msucares.com/pubs/infosheets/is1331.pdf

http://ipm.ncsu.edu/AG271/corn_sorghum/sorghum_midge.html

http://bugguide.net/node/view/358516