Honeylocust pod gall midge, Dasineura gleditchiae
Order: Diptera
Family: Cecidomyiidae
Description
Dasineura gleditchiae, commonly referred to as the “honey locust pod gall midge”, is an important pest of honeylocust in North America. Adults are small flies that measure 1.6 mm (1/8 inch) in length. Females are black with a red abdomen, while males are completely black. Although rarely observed, the larvae of D. gleditchiae are pink to white maggots that measure about 2.5 mm (1/10 inch) long, while the oblong pupae are orange or white and about the same size as larvae. Eggs are yellow to red, kidney shaped and very small.
Quick Facts
- Dasineura gleditchiae is a native species to North America.
- Immature stages of D. gleditchiae develop within galls, which act as protective structures that make chemical control challenging.
- Signs of an infestation include the presence of green, brown, or red galls on leaflets and plants with a thin appearance.
- Management options for D. gleditchiae include planting resistant honeylocust varieties and applications of insecticides during the egg-laying period.
An opened gall containing larvae of D. gleditchiae. Both larvae and pupae develop within galls. Image credit: Whitney Cranshaw, Colorado State University, Bugwood.org
Pod galls on honeylocust created by larvae of D. gleditchiae. Galls produced by D. gleditchiae can be green, red, or brown. Image credit: Whitney Cranshaw, Colorado State University, Bugwood.org
Galls formed by D. gleditchiae. Note the red appearance. Image credit: Gyorgy Csoka, Hungary Forest Research Institute, Bugwood.org
Life history
This species overwinters as pupae or adults in the top 2.5 cm (1 inch) of soil near honeylocust trees. Adults emerge the following spring during budbreak. This pest tends to be most active from the time of first shoot growth through summer and only develops on honeylocust. Eggs are laid singly or in small groups on leaflets, and newly hatched larvae begin feeding on the succulent young leaves which produce galls. Larvae feed and develop within galls and remain in galls to pupate, and adults often pull pupal skins from galls when emerging. Multiple generations are produced each year and populations typically begin declining in early July. However, in highly fertile, irrigated sites such as nurseries where sprout growth is produced for extended periods, there may be additional generations of D. gleditchiae.
Injury
Feeding of D. gleditchiae larvae causes the formation of brown, green, or red galls on leaves, which can diminish the aesthetic value of trees. Heavy infestations can lead to browning of foliage, premature leaf drop, and dieback of leaflets and twigs. After adults emerge, the vacated gall often darkens, becomes dried, and eventually falls from the tree. All new growth can be destroyed by infestations of D. gleditchiae, leaving entire portions of branches defoliated which gives the host tree a thin appearance. Although unsightly, these injuries do not typically threaten the health of the plant. However, additional stressors can cause twig dieback, and under heavy infestations of D. gleditchiae, newly forming buds may be killed, producing club-like swellings on twigs.
Monitoring
In the spring, a hand lens can be used to inspect new shoot growth and honeylocust buds for the presence of D. gleditchiae eggs. The presence of pupal skins protruding from galls is another indicator of a D. gleditchiae infestation. Adults can be captured on yellow sticky traps deployed on the lower outer branches of honeylocust. The use of a 10x hand lens can be used to help identify adults on traps.
Management
Cultural control
It is recommended to avoid planting Sunburst honeylocust in areas where D. gleditchiae is present, as this honeylocust variety will rapidly defoliate in response to D. gleditchiae feeding and environmental fluctuations. The Shademaster cultivar is less susceptible to D. gleditchiae.
Chemical control
Chemical management is not usually needed for this pest, but moderate control can be achieved on small trees by applying carbamate, horticultural oil, pyrethroids, or spinosyns to young leaves when eggs or adults are observed in the early spring. Effectively timing the application to coincide with egg laying will improve the efficacy of the insecticide application, and the insecticide may need to be reapplied at three-to-four-week intervals to reduce the density of subsequent generations. To protect pollinators, insecticide applications should be made after bloom.
CSU Extension Fact Sheet
Download or view the CSU Extension’s PDF fact sheet for your reference.
References
Cranshaw, W. 2010. Honeylocust Podgall Midge. BugwoodWiki. Available here.
Rosetta, R. 2019. Honeylocust pod gall midge. Oregon State University – Extension. Available here.
UCIPM. (n.d.). Honeylocust pod gall midge – Dasineura gleditchiae. University of California – Agriculture and Natural Resources. Available here.