Q What is the Gypsy Moth?
A The European Gypsy Moth ( Lymantria dispar) is an introduced defoliating insect that is considered to be a major pest in North America. The caterpillar, or larva stage of the insect, eats the leaves of trees making them more susceptible to disease and damage from other insects. The Gypsy Moth can severely weaken or kill trees. Caterpillars hatch from overwintering eggs in mid-spring. They feed on tree leaves at night for about 7 weeks. In mid-summer the caterpillars pupate in sheltered areas. Adult moths merge about two weeks later in early August. Soon after mating, females lay oval shaped egg masses on tree limbs, rocks, building, vehicles, and other sheltered areas.
Q What do Gypsy Moths look like?
A There are four stages in the gypsy moths’ life cycle, all which appear very different. In order to control these pests, it is important to be able to recognize each life stage.
Egg Mass – The gypsy moth egg mass contains thousands of tiny eggs. Egg masses are usually the size of an oblong one-dollar coin and appear to be the colour and texture of a car chamois.
Larvae (caterpillars) – When eggs hatch in the spring, very tiny (and very hungry) larvae, or caterpillars, exit the egg mass and being to travel to their food source, the leaves of trees. The gypsy moth caterpillar grows to be about 6 cm long , consists of eleven segments, and is partly covered with course black hairs. Each segment has a pair of coloured dots: the first five segments have blue dots and the last six have red spots.
Pupae - Once the invasive feeding stage is over, the mature caterpillar will commonly seek a protected area on a tree or other structure, such as a crevice in tree bark or a crack in a rock, to enter their “cocoon” stage and become a moth. The cocoon, or pupae, is about 3 cm long and dark brown in colour. It has a hard and somewhat shiny appearance. This stage last about 10 days in female and 13 days in male gypsy moths.
Adult – The adult, or moth stage of the life cycle, produces very different looking males and females. The adult female is white with a few dark-coloured stripes across its wings and has a prominient white fuzzy head. Despite having fully-functional wings, the female does not fly, but relies on the release of pheromones (chemical attractants) to lure males to the site where she will lay her eggs. The adult male is a mottled dark beige to brown colour with feathery brown antennae. During this week-long stage, the adult moths do not feed and focus all of their energy on reproducing.
Q How much damage can the Gypsy Moth cause to trees?
A Tree damage depends on the degree of infestation, past defoliations, the trees vulnerability and the environment, and can range from light to almost complete defoliation. If the tree has been weakened or stressed by other conditions, and attacked repeatedly in recent years, the defoliation can result in the death of the tree. Caterpillars chew small holes on the upper surface of the leaves. Older larvae may eat entire leaves, except the major veins. Caterpillars disperse on silk threads to be carried by the wind to other trees. Most deciduous trees can withstand only two or three consecutive years of defoliation. Repeated leaf loss stresses trees and can lead to their death. During outbreaks the caterpillars are an extreme nuisance; trees lose their foliage, caterpillars crawl everywhere, and their droppings rain from trees.
Q Why should I worry about Gypsy Moth?
A Loss of Leaves – Leaf or foliage loss robs the area of shade, affecting the temperature of the area, as well as the health of lawns and any shade-tolerant plants. This also weakens a tree, as it no longer has a means to produce its own energy. Deciduous trees usually refoliate a second set of leaves in mid to late July.
Tree Mortality – After repeated defoliations, trees can become weakened and may die. Healthy, vigorous trees in a well-managed forest can usually withstand several defoliations with few lasting effects and recover quickly from the short term impacts.
Spread of Infestation – If a local infestation is not treated or controlled, it can easily spread to other unaffected areas, broadening the problem. This cannot only create problems in neighbouring yards, but also in large parks and forests.
Caterpillar frass – With their ability to consume so much leaf matter in such a short period of time, the amount of fecal matter or “frass”, produced by caterpillars can become a concern. Frass can quickly cover driveways, patios, picnic tables, and other areas and can become a nuisance to clean up and to endure during outdoor activties.
Q What kinds of trees are most affected by the Gypsy Moth caterpillar?
A It prefers the leaves of deciduous hardwood trees like maple, elm and particularly oak. It will also feed on apple, alder, birch, poplar and willow trees. As the caterpillar matures it will also begin to attack evergreens such as pine and spruce. They don’t appear to like ashes, sycamores, butternuts, black walnuts and dogwoods.
Q What is the lifecycle of the Gypsy Moth?
A The moths are seen only in mid-summer. They exist only to mate and after the female lays its eggs, moths of both sexes die. They lay their egg masses on the limbs and trunks of trees, on rocks, buildings, vehicles or in ther sheltered areas. The masses remain in place all winter and will hatch the following spring from late April to mid-May. Once hatched the caterpillars begin to feed and continue for approximately seven weeks.
Q Are there any natural enemies (control factors) to the Gypsy Moth?
A Yes. Predators include other insects like wasps, flies, beetles, ants and spiders as well as birds such as
chickadees, blue jays, robins and nuthatches. Animals such as chipmunks, squirrels and raccoons will also prey on the caterpillar. Diseases caused by bacteria, fungi or viruses contribute the most to keeping levels within a normal range. Gypsy Moth diseases include a fungus native to Japan called Entomophaga maimaiga. This fungus was deliberately released in the United States around 1910-1911 to help control gypsy moths. Although the exact means by which this fungus made it to Canada are not known, its presence in our forest has become quite evident as it has been responsible for bringing past gypsy moth infestations under control. The amount of wet weather experienced in the spring months is directly related to the success of this fungus, with wetter springs showing greater declines in gypsy moth caterpillars than in drier springs. Caterpillars killed by this fungus appear shrivelled and elongated, hanging in a vertical position.
A virus known as the “nuclear polyhedrosis virus”, or NPV, was also released in the United States in the 1960’s
as an alternative to DDT and other chemical pesticides. While most caterpillar mortality can be attributed to
the fungus, it has been shown that NPV controls caterpillars effectively, and has been responsible for mass die-offs. The advantage of this disease is that it is directly specific to gypsy moth caterpillars, and does not affect any other species. Caterpillars killed by this fungus hang downwards in a “V” shape and ooze a dark fluid.
Q How severe will the infestation be?
A Inspections in “hot spot” areas saw trees covered with hundreds of egg masses. In some cases, there were over 37,000 egg masses per ha with each egg mass yielding from fewer than 100 to more than 1000 eggs. When the egg masses hatch in these areas, a single tree mayl be infested with hundreds of thousands of caterpillars.
Q What measures can I use to help keep the Gypsy Moth population in check on my property?
A One way to reduce the population is through the manual removal and destruction of egg masses. You can scrape egg masses into a cup and place them in soapy water for 2 days. Alternatively, you can use a vacuum to remove egg masses, followed by disposal of the vacuum bags.
Burlap banding or sticky band barriers can be used to control caterpillars. In May, young caterpillars climbing from the surrounding area to the tree canopy can be trapped by a sticky band placed around the tree stem. Later in June, caterpillars will leave the canopy of trees during the day looking for a shelter to hide from the heat. They return to the canopy each evening to feed at night. You can take advantage of this behaviour to reduce the number of caterpillars by putting up single-folded burlap bands. Caterpillars find the burlap band an attractive hiding spot and will congregate there. It is important to collect the caterpillars from under the bands each afternoon, scraping them into a cup of soapy water or just mechanically destroy them.
Moths can be captured by hanging traps containing pheromone scents. These traps act as decoys and prevent male moths from mating with female moths.
Attract to your yard birds and other beneficial organisms by planting appropriate plants (herbs, flowers,
and shrubs). Birds eat caterpillars and moths.
Q What are Phermone traps?
A These traps come in a variety of shapes and sizes and can be baited with a powerful chemical attractant called a “pheromone”. Traps can be deployed in mid to late summer in infested areas when male moths are seeking their pheromone-releasing mate. These traps attract male moths and prevent them from reproducing with the females.
Q Should I use a commercial insecticide to help control the population?
A During severe infestation when the life of a tree may be in jeopardy an insecticide may be considered a viable option. While the cost and complexity of implementing an aerial application of bacterial insecticide will almost certainly limit your ability to use this technique on your property, it may be possible to hire a contractor to apply pesticide from ground spray applicators. Timing of the application and the treatment of the entire canopy is essential to the success of control using a commercial insecticide to control gypsy moth.
The bacterial insecticide Bacillus thuringiensis subspecies kurstaki (Btk) is recommended if it is determined that a spray is warranted. Be aware that while Btk is not controlled by the Hamilton pesticide by-law, other chemical pesticides are regulated and may cause significant environmental harm if applied. You should be also aware that pesticide applications do not produce an instant defense and will not completely eradicate the problem. Spraying is not an effective preventive measure and is only effective for a short time. It will not stop the moths from entering your property.
Q Is Hamilton planning to aerial spray
A Yes, if approved by Council. Based on recommendations by staff and independent consultant BioForest Technologies, City Council may endorse both aerial spraying and ground spraying of Bacilus thuringiensis subspecies kurstaki (Btk) as the only effective way to deal with egg masses located high in tree canopies within “hot spot” areas.
Q What is Bacillus thuringiensis subspecies kurstaki (Btk)?
A Bacilus thuringiensis subspecies kurstaki, commonly referred to as Btk, is a rod-shaped bacterium that occurs naturally on dead or decaying matter in soil. It occurs naturally worldwide and is cultured specifically for pesticide use using high quality controls.
Q How Does Btk Work?
A Btk is only toxic to specific lepidopteran insects in the caterpillar stage of their life cycles. When Btk is ingested by the susceptible caterpillar, the highly alkaline environment of the caterpillar’s gut triggers the Btk bacterium to release a crystalline protein called an “endotoxin” that is toxic to the insect’s digestive system. The caterpillar must ingest the Btk bacterium in order for it to be effective. Btk does not affect adult moths and butterflies. Btk does not affect other insects, honeybees, fish, birds or mammals. There is also no impact on animals that may eat a Gypsy Moth caterpillar that has ingested Btk. Once applied, the Btk biodegrades quickly into the environment through exposure to sunlight and micro-organisms. There are no groundwater contamination concerns, as Btk does not percolate through the soil beyond 25 cm.
Q Is Btk Safe?
A The safety and heath of residents and the preservation of the environment are top priorities for the City of Hamilton. Btk is a naturally occurring bacterium that is approved for use on organically grown produce and one which most of us have already had contact with. Btk has been extensively studied by the United State Environmental Protection Agency (EPA), Health Canada Pesticide Management Regulatory Agency (PMRA) and the United Nations Environmental Programme in conjunction with the World Health Organization (WHO). These agencies conclude that Btk poses minimal risk to human health when used as directed. Research and studies of Btk show low potential for adverse public health impacts – including impacts on children, pregnant women and the elderly. In addition, the aerial spray program is not expected to have adverse affects on children with asthma or people with weakened immune systems. The weight of evidence from studies demonstrates that Btk is not infective or pathogenic. The City believes that a co- ordinated spray program is preferable to an individualized approach in which toxic chemical pesticides may be used.
Q When should Btk be used?
A The best time to apply Btk is dependent on the emergence of the caterpillars; however, it is generally mid to late May when the caterpillars are small. Btk is less effective in older more mature caterpillars and highly ineffective during the Gypsy Moth’s non-feeding life stages – eggs, pupa and adult moths.
Q What are the environmental impacts of Btk use?
A According to Health Canada, Btk is only toxic in the caterpillar stage of the Gypsy Moth life cycle. It does not affect adult moths and butterflies, other insects, honeybees, fish, birds or mammals. It biodegrades quickly and there are no groundwater contamination concerns.
The United States Environmental Protection Agency categorizes the risks posed to non-target organisims as “minimal to non-existent”. The World Health Organization (WHO) and Pest Management Regulatory Agency (PMRA) feel it is a safe substance to use in pest management.
Even with many years of widespread use of Btk in forestry, agriculture and urban settings, no significant environmental concerns have been raised.
Q What are the human health risks associated with BtK?
A According to Health Canada, Btk poses little threat to human health through either handling products directly or being exposed to them indirectly such as during a spray program. Some reports indicate Btk may temporarily cause mild irritation to eyes, skin and nose in some people.
Q How can I prepare and follow up?
A It is not expected that resident will see a lot of Btk residue on items such as siding, children’s play equipment, etc. It is recommended however, that where possible residents bring in children’s play toys (e.g. bicycles, wagons, play houses, small slides, balls, bats, hockey nets, etc.) cover sand boxes and other larger equipment, park cars inside the garage and either cover or bring in patio furniture and barbecues. These are simply precautionary measures. For a short time following a spray, residents may notice an organic smell in the air as a result of the bacteria.
Following a spray, increased attention to good personal and food hygiene is recommended (e.g. hand washing after outdoor activities, especially gardening and yard work; washing all fruit and vegetables before cooking and eating). Btk is formulated to stick to foliage when it dries. To remove dried Btk from any surface, wet the surface with water and then sponge or wipe with a soft cloth for some items, such as car windshields, soap or a cleaning product may be needed. As for backyard swimming pools, normal maintenance procedures are all that’s required.
Q Where can I get more information or provide comments?
A Resources - Canadian Forest Services - www.glfc.cfs.nrcan.gc.ca
Health Canada - www.pmra-arla.gc.ca
Hamilton Conservation Authority – www.conservationhamilton.ca