Erythrina Gall Wasp
The Erythrina Gall Wasp is an exotic pest of the Wiliwili tree. Common tree names include tigers claw, Indian coral tree and Wiliwili-haole.
It was first discovered in Hawaii in 2005. Populations of Wili-Wili or Erythrina occur in Hawaii, California and Florida. EGW completes its life cycle in as little as 21 days. It is a destructive, exotic pest that may kill trees in as little as two years. If trees are at risk of EGW infestation, inspect trees on a regular basis, especially the new foliage. Look for swelling (galls) in leaf tissue and in twigs. It is our recommendation to treat to protect trees in advance of an infestation or as soon as possible following EGW detection.
Erythrina Gall Wasp is an exotic leaf and twig galling wasp that attacks Wili-Wili trees. The developing EGW larvae induces galls in tender leaf and stem tissue. Unchecked infestations cause leaf deformation, reduction in growth, defoliation and tree death.
Research studies were conducted independently in Hawaii by the University of Hawaii and the USFS to evaluate the efficacy of Arborjet’s IMA-jet (5 % imidacloprid) systemic insecticide for treatment of Erythrina Gall Wasp. Trees that were systemically treated with IMA-jet effectively controlled EGW in both the ornamental landscape and in native, dry upland sites.
For optimum results, apply IMA-jet prior to infestation. Also apply when insects are infesting and feeding upon the tree. IMA-jet insecticide moves upward into the tree’s canopy from the application sites. Systemic activity occurs only after the active ingredient is translocated upward in the tree. This product must be applied below the bark into the sapwood (i.e., the vascular) tissues.
Uptake is dependent upon the tree’s transpiration. Transpiration is dependent on a number of abiotic and biotic factors, such as soil moisture, soil and ambient temperature, and time of day. For uptake, apply when soil is moist, soil temperatures are above 45 degrees F, ambient temperatures are between 40 degrees to 90 degrees F, and during the 24 hour period when transpiration is greatest, typically before 2:00 PM. Applications to drought or heat stressed trees may result in injury to tree tissue, poor treatment and subsequent control. Avoid treating trees that are moisture stressed or suffering from herbicide damage.
Dosages are designed for insect control and retreatment is generally not necessary during the year after initial treatment. Monitor insect activity to establish a damage threshold for retreatment. Repeat applications as necessary. Studies have demonstrated that label use rates of IMA-jet provided at least 13 months of control of EGW. Reduction of leaf and twigs galled were observed following systemic tree injection treatment. Treating with IMA-jet does not remove the existing galls (symptoms), but the active ingredient moves into the soft tissues where larvae feed to affect control.
Main photo and pupae inside gall taken by M. Tremblay, State of Hawaii Department of Agriculture “New Pest
Damage photos taken by Albert (Bud) Mayfield, Florida Department of Agriculture and Consumer Services, Bugwood.org