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Gypsy Moth Q & A |
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- What is the Gypsy Moth?
- The European Gypsy Moth 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.
- How much damage can the Gypsy Moth cause to trees?
- 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.
- What kinds of trees are most affected by the Gypsy Moth caterpillar?
- 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.
- What is the lifecycle of the Gypsy Moth?
- 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 other 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.
- Are there any natural enemies (control factors) to the Gypsy Moth?
- 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.
- How severe will the infestation be?
- Inspections in 'hot spot' areas saw trees covered with hundreds of egg masses. In some cases, trees had as many as 800 egg masses, with each egg mass yielding up to 1000 caterpillars. When the egg masses hatch in these areas, a single tree will be infested with hundreds of thousands of caterpillars.
- How many trees are expected to die in the most heavily affected areas?
- Many trees in Toronto are already stressed or weakened and will not survive repeated defoliation by the Gypsy Moth caterpillars. If no action is taken, the result may be the loss of hundreds of trees (which does not include the trees on private property.)
- What are the proposed spray zones?
There are 7 aerial spray zones located throughout the City of Toronto:
- Moore Park and Mt. Pleasant Cemetery
- Sunnybrook Park
- Cranleigh Ct.
- Royal York/Kingsway
- Bayview Avenue/Lawrence Avenue East/Mildenhall Road
- Don Valley Golf Course
- Humber Valley Golf Course
There are also trees to be treated with ground spray applicators rather than by helicopter. These trees are located in Wards 4,7,12,24,25
Specific locations are identified on the attached maps. - Do I still need to be concerned if I don't live in one of those areas?
- There are other areas in Toronto that will experience an increased Gypsy Moth population. Mechanical methods of pest control (egg mass removal and banding for control of caterpillars) have proven effective to keep lower population levels of Gypsy Moth in check.
- What measures can I use to help keep the Gypsy Moth population in check on my property?
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 behavior 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. Such traps are used for monitoring increases or decreases in population levels. In a population outbreak, they are quickly filled and become ineffective. - Should I use a commercial insecticide to help control the population?
- 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 Toronto pesticide by-law, other chemical pesticides are regulated and may cause significant environmental harm if applied. You should also be 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.
- Is Toronto planning to aerial spray?
- Yes, if approved by Council. Based on the recommendations by staff and independent consultant BioForest Technologies, City Council may endorse both aerial spraying and ground spraying of Bacillus thuringiensis subspecies kurstaki (Btk) as the only effective way to deal with egg masses located high in tree canopies within 'hot spot' areas.
- What is Bacillus thuringiensis subspecies kurstaki (Btk)?
- It is a rod-shaped bacterium that occurs naturally on dead or decaying matter in the soil. It is grown from soil bacteria that occur naturally worldwide. When Btk is ingested by a susceptible caterpillar, the highly alkaline environment of the caterpillar's gut triggers the Btk bacterium to release a crystalline protein called an "endotoxin" that poison's the insect's digestive system. The caterpillars must ingest the Btk bacterium to be affected.
- When should Btk be used?
- The best time to apply Btk is late April or early 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.
- Will there be City-wide spraying of Btk?
- No. The total area estimated to be sprayed equals approximately 239 hectares, located in seven blocks where the Gypsy moth population level is high and surveys have shown that individual trees have a high number of egg masses on them.
- What are the environmental impacts of Btk use?
- 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 organisms 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 been raised.
- What are the human health risks associated with Btk?
- 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.
- How can I reduce my exposure to Btk?
- If you live in an area that is being sprayed, you can avoid exposure to Btk by remaining indoors during and immediately after the spraying. You can also cover patio furniture or outdoor playing areas prior to the spraying or hose them off afterward.
- What management program was implemented in last years to control Gypsy moth in the City?
- City staff and residents in affected areas have been working cooperatively for some time implementing various Integrated Pest Management (IPM) measures and monitoring population levels of Gypsy Moth. Unfortunately, the populations have continued to increase and natural controls while building in some areas have not yet been effective in controlling the populations. Mechanical methods of control are only effective in the early stages of infestation, and only on certain types and sizes of trees. When the gypsy moth egg masses are deposited in large number on the upper part of the canopy, mechanical methods of control may become ineffective.
- Where can I get more information or provide comments?
- See the full report on Toronto's proposal for control of gypsy moth. A Gypsy moth fact sheet can be found here.
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