• Introduction
• Damage
• Midge Biology and Phenology
• Monitoring
• Management
• Current Research
• References

Introduction

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. (back)

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. (back)

Midge Biology and Phenology

Research in California investigating over wintering and distribution of the pod gall midge indicates that the midge over winters 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.
 

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.(back)

Management

Our research indicates that most growers (87%) are missing a critical window for enhanced control of the midge by delaying applications until May or June. Oil or oil/insecticide applications targeting the first two egg depositions beginning in late March or early April should increase midge population suppression, possibly reducing the frequency and intensity of pesticide applications necessary to achieve acceptable control.

A 1996 survey of honey locust growers revealed that 75% of the nurseries used only one chemical or rotated within the same chemical class (organophosphate). This situation may lead to pod gall midge resistance to this chemical class, particularly where there are frequent applications and may explain why many growers (69%) were dissatisfied with the level of control that they achieved with insecticides.
 

The chemicals currently being used for control of the midge are as follows, at last check, these chemicals were registered in Oregon to control honey locust pod gall midge. Always check the label to be certain the formulation you select is registered for the plant and site that you plan to spray. Materials are not listed in order of preference or efficacy. This listing implies no endorsement on the part of Oregon State University Extension.

organophosphate: diazinon, oxydemeton-methyl (Metasystox-R), acephate (Orthene), chlorpyrifos (Dursban),  dimethoate (Cygon).

pyrethroid: bifenthrin (Talstar), tau-fluvalinate (Mavrik), cyfluthrin (Tempo 2), lambda-cyhalothrin (Scimitar, Topside O/S)

carbamate: fenoxycarb (Precision)

naturalyte: Spinosad *new registration (Conserve)
(back)

Current Research

We are investigating the efficacy of soil drenches of the over wintering stages of the midge. Initial results look promising.
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. Research investigating biological control of the midge is ongoing.

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.