Another teeny tinny insect is here to cause unprecedented and huge damage to our trees and plants. The gall wasps, also called gallflies, are a family (Cynipidae). Their common name comes from the galls they induce on plants for larval development. About 1300 species of this generally very small creature (1-8 mm) are known worldwide, with about 360 species of 36 different genera in Europe and some 800 species in North America.
The larvae of most gall wasps develop in characteristic plant galls they induce themselves, but many species are also inquilines of other gall wasps. The plant galls mostly develop directly after the female insect lays the eggs. The inducement for the gall formation is largely unknown; discussion speculates as to chemical, mechanical, and viral triggers. The hatching larvae nourish themselves with the nutritive tissue of the galls, in which they are otherwise well-protected from external environmental effects. The host plants and the size and shape of the galls are specific to the majority of gall wasps, whereas about 70% of the known species live in various types of oak trees. One can find galls on nearly all parts of such trees, some on the leaves, the buds, the branches, and the roots. Other species of gall wasps live in eucalyptus trees, rose bushes or maple trees, as well as many herbs. Frequently, the determination of the species is much easier through observation of the galls produced rather than the insect itself.
A gall provides the developing gall wasp with a safe refuge for the most vulnerable stage of its life cycle, but many other wasps have found a way to penetrate this defense and parasitize the larvae within. Some of these parasitoids use their long, hardened egg-laying tube (ovipositor) to bore into the gall and lay an egg on the helpless gall maker.
The galls cause the upper surface of the leaf to lighten in color and form a kind of blister that is often ringed with a yellow halo. Severe infestations will cause the leaf tips to turn brown. Heavily damaged leaves may curl and fall from the tree and the entire crown of the tree may be affected. Each gall contains a single wasp larva that feeds on the inner lining of the gall. The galls drop to the ground when they have matured. The activity of the larva inside the gall actually makes the gall jump around on the ground after they have fallen from the tree. The insect overwinters inside the gall. In the spring, the females emerge and lay their eggs in newly opened leaf buds. The galls form in response to chemicals in the larva’s saliva.
Gall makers must attack the plant at a very precise time if normal plant tissue is to be successfully stimulated to form a gall. It has been shown that trees whose buds open earlier than nearby trees have larger numbers of these galls than trees whose buds opened later.
Let us look at the below news article demonstrating the effects of gall wasps damage;
Tiny insect menace chokes trees across Cape Cod
20 Oct, 2013
DENNIS, Mass. — A minuscule menace is buried in the gnarled, deformed limbs of black oak trees across Cape Cod, slowly choking them to death.
Its common name — the crypt gall wasp — is like something out of a horror movie, but for property owners, the evil it wreaks is all too real.
Hordes of the tiny wasps deposit their eggs in the trees’ new spring growth. The larvae grow inside the wood and form swelled chambers known as galls.
A year later, the adult wasps — measuring only 5 millimeters — emerge through pinprick holes in the wood and repeat the cycle over again, cutting off the system that distributes nutrients throughout the tree.
Starved of food, twig growth slows, leaves turn brown and eventually, if the infestation continues unabated, the tree may die.
Even though much is known about the tree-killing culprit, much is still a mystery, including whether it is a native or wash-ashore.
“So little is known about the life cycle,” Russ Norton, educator in horticulture at the Cape Cod Cooperative Extension, said.
Norton, who is monitoring a research site in Nickerson State Park in Brewster, and other researchers are working to fill in those gaps.
Recently, workers with Arborjet, a Woburn company that tests and sells tree injection systems and insecticides, took a stand against the crypt gall wasp in Dennis Village Cemetery, a setting seemingly made for the fight against the pernicious pest with the deathly name.
Arborjet is working with University of Massachusetts-Amherst professor of entomology Joseph Elkinton and one of his graduate students to study the best ways to deliver insecticide that will stop the wasps in their tracks.
Researchers are not even convinced the species has been correctly identified, Elkinton and Arborjet officials said.
“We’re starting from square one with this insect,” Elkinton said.
Widespread damage from the wasp became apparent on Martha’s Vineyard a couple of years ago, he said.
But, while a similar infestation on Long Island crashed after only three years, the outbreak on the Vineyard has lasted longer.
On Cape Cod, property owners and arborists started seeing widespread damage in 2012.
“You probably don’t even see the symptoms for two years,” Peter Wild, CEO and founder of Arborjet, said.
At the Dennis Village Cemetery, Arborjet’s Don Grosman demonstrated how the injection systems use the tree’s vascular system to transport chemicals to fight the wasps, Grosman said.
A small black plug called an arborplug is inserted into holes drilled into the trunk, he said.
A needle attached to a pressurized reservoir is then connected to the plug, forcing the chemicals into the tree’s active tissue.
The company is testing two solutions: TREE-age, which relies on emamectin benzoate, a pesticide that causes insect paralysis, and IMA-jet, based on imidacloprid, a pesticide derived from synthetic nicotine, according to the National Pesticide Information Center, a collaboration of the University of Oregon and the U.S. Environmental Protection Agency.
Unlike spraying or other methods, injecting the chemicals keeps them contained within the tree and out of the surrounding environment, Grosman said.
“We pride ourself in that we put everything into the tree,” he said.
Even so, only a small amount of each product is required, he said.
For a tree with a 20-inch diameter, only 8 grams of the solution is used, Grosman said.
Although work in Hawaii on a similar infestation in banyan trees has shown that the method works, the exact effects on the crypt gall wasps are not yet clear, Grosman said.
About 50 trees in Barnstable, West Harwich and Dennis were injected with the two chemicals. An additional 20 trees are being monitored as controls.
The effect on different levels of infestation is being studied, Grosman said.
The trees will be checked over several years to see how long the chemicals keep the wasps at bay.
So far, there are pockets of the infestation in black oaks across the Cape, he said.
“It’s widespread but at the same time it’s somewhat sporadic,” he said.
This could be because of changes in the weather such as drought or it could be because of other factors, such as disease or the amount of salt used on nearby roadways, Grosman said.
At the cemetery, digging for graves could even be a factor, he said.
Natural conditions could lead to a collapse in the wasp population, such as what happened in Long Island, he said.
Infestations of exotic species are the cost of climate change and global trade, Wild said.
Still, like so much else with the crypt gall wasp, there is much more to be learned, both men said.
Education is the first step, Wild said. “Usually by the time you call the arborist, it’s time to cut the tree down,” he said.
Once a gall begins to develop, it is almost impossible to stop or reverse its development. Unless registered insecticides can be applied when gall wasps are flying, they offer little or no effective measure of control. Lack of serious plant damage from leaf galls and the difficulty in proper timing of insecticide applications pose a strong argument against the use of insecticides to reduce galls on oak.
Moreover chemical control is seldom suggested for management of leaf galls on oak. Cultural methods of control may be effective in reducing the impact of these insects. Some fallen leaves may harbor various life stages of gall-producing pests. Therefore, it may be useful to collect and destroy all infested leaves. Some of these pests overwinter in twigs and branches of oak. Where such woody galls are detected, prune and destroy the infested plant material when the galls are small and have just started to develop. But this isn’t a 100 percent effective treatment and more treatment options need to be explored.
C Tech Corporation can offer a solution in the form of their non-toxic, non-hazardous product Termirepel™. Termirepel™ is an eco-friendly insect aversive. It is available in the form of polymer masterbatches as well as lacquer form which can be coated on the trees or diluted and sprayed on them.