Honeylocust pod gall midge

Honey locust pod gall midge (Dasineura gleditchiae) is a major pest of honey locust (Gleditsia triacanthos). Feeding by the midge larvae causes leaflets of new growth to form pod like galls in which the larvae pupate. After the adult midge emerges from the pod, the leaf tissue dies and drops prematurely. Much of the new growth can be affected, reducing the aesthetic quality of the trees in nurseries and landscapes. All cultivars of G. triacanthos grown commercially are susceptible in both nursery and landscape situations.

Damage 

Adult midges deposit eggs on new foliage along the rachis or on the edges of developing leaf buds. The eggs usually hatch in two days. The young larvae crawl along the leaf and begin feeding. Only one larva is required to initiate galling of the leaf. Leaf galls may be folded, partially podded, or the entire leaf may form a pod (Thompson, et al., 1998). The leaf gall dies and drops once the larvae pupate and emerge. Localized die-back is often associated with high infestation levels.

Midge Biology and Phenology

Research in California investigating overwintering and distribution of the pod gall midge indicates that the midge overwinters as late instar larvae or pupae in cocoons in the soil mostly in the upper two inches near the base of the tree trunks (generally within one foot of the trunk) (Thompson, et al.,1998). In the Northwest, study of midge phenology has shown discrete egg laying events occurring very early in the maturation of the leaf buds (before they leaf out) in Oregon (Rosetta and Bell, 1996). Soon thereafter the populations appear continuous with many life stages present. The first pod gall midge eggs generally are  found during the last week of March through the first week of April (Table 1). In 2000 the first evidence of oviposition occurred on April 7 and pod formation on April 13.

Year 1995 1996 1997 1998 1999 2000
eggs March 30 April 8 April 4 N/A April 19 April 7
podding April 27 April 15 April 21 N/A April 28 April 13

Table 1. Appearance of honey locust pod gall midge, Dasineura gleditchiae, egg deposition and pod formation at various Oregon sites from 1995 through 2000.

Monitoring

For more accurate application timing, monitor honey locust trees in nursery and landscape sites beginning in early spring and throughout the growing season to note appearance of eggs deposited on buds and new foliage by
over wintering and first generation adults. Clusters of the red midge eggs on honey locust buds can be observed with a hand lens.

Phenological indicator plants associated with HPGM activity include:

First oviposition-
Acer sp. (petal drop) Amelanchier ‘Forest Prince’, ‘Smoke cloud’ (blooming);Chaenomeles sp. (petal drop); Cornus americanus (blooming); Magnolia soulangiana (blooming); Pyrus ‘Aristocrat’ (petal drop); Pyrus ‘Autumn blaze’ (petal drop); Spirea sp. (petal drop); Viburnum sp. (beginning bloom); Weigela sp. (beginning bloom).

First appearance of pods-
Aesculus hippocastanum(beginning bloom); Cytisus scoparius ‘Moonlight’ (blooming); Cornus americanus (blooming);  Pyrus ‘Aristocrat’, ‘Autumn Blaze’; Weigela sp. (blooming); Wisteria sp. (blooming).

First appearance of pupal cases-
Aesculus hippocastanum(blooming); Cytisus scoparius ‘Moonlight’ (petal drop); Cornus florida (blooming);  Paulownia tomentosa (blooming); Sorbus sp. (blooming); Viburnum opulus ‘Roseum’ (blooming);Weigela sp. (blooming); Wisteria sp. (blooming).

Management

A critical window for enhanced control of the midge is targeting the first two egg depositions beginning in late March or early April with horticultural oil or oil/insecticide applications. These targeted sprays suppress midge populations, reducing the frequency and intensity of pesticide applications necessary to achieve acceptable control.

Our research has investigated the efficacy of soil drenches of the over wintering stages of the midge. These drenches are applied shortly before emergence of the adult midges in the spring. Our trials have shown a well-timed drench can greatly reduce the number of pods on honeylocust trees. Once midges have emerged in the spring, they no longer pupate in the soil but rather within the leaf galls.

Honeylocust pod gall midge is native to the east coast of North America where populations of the pest are generally maintained below an economic threshold by a complex of natural enemies. This may bode well for eventual suppression of the midge through biological control on the west coast.

For further information on management options, see the Nursery section of the PNW Insect Management Handbook.

References Cited:

Thompson, P.B. and M.P. Parrella.1998. Distribution and Density of Over wintering Dasineura Gleditchiae (Osten Sacken)(Diptera: Ceciomyiidae).Pan Pacific Entomologist. 74(2):85-98.

Rosetta, R.L., P. Thompson and N. Bell. 1998. IPM of Honey Locust Pod Gall Midge.The Digger. 42(3):34-36.

Original: 30 April 2013

Updated 17 July 2018.

Author: R.L. Rosetta, Extension Nursery Integrated Pest Management, Department of Horticulture, Oregon State University/NWREC.

Honeylocust pod gall midge on new bud

Honeylocust pod gall midge on new bud

Honeylocust pod gall midge on new bud

Honeylocust pod gall midge on new bud

Honeylocust pod gall midge eggs on new growth

Honeylocust pod gall midge eggs on new growth

Honeylocust pod gall midge adult

Honeylocust pod gall midge adult

Galls of honeylocust pod gall midge

Galls of honeylocust pod gall midge

Honeylocust pod gall midge eggs

Honeylocust pod gall midge eggs

Empty honeylocust pod gall midge pupal cases and newly emerged midge

Empty honeylocust pod gall midge pupal cases and newly emerged midge

Monitoring for honeylocust pod gall midge eggs

Monitoring for honeylocust pod gall midge eggs

Honeylocust pod gall midge galls

Honeylocust pod gall midge galls