Options in the battle against forest pests

Public opposition to chemical insecticides is leading to experimentation with other protection strategies.

In the wake of public opposition to aerial forest spraying of chemical insecticides, Ontario's forest managers have to look at alternate forest protection strategies. "Natural", "biological" and "integrated pest management" options are gaining greater attention of foresters and the concerned public.

In Ontario, the forest policy for Crown Land is to use only B.t. (Bacillus thuringiensis), the bacterial insecticide, for aerial application. While this biological product has proven effective when used properly, foresters will attest that reliance on a single pest control agent is a weak position, given the diverse and complex nature of forest types and insect pests facing forestry operations.

A new biological insecticide shows promise as an option for forest insect control. With concern about limited management options for the protection of forests against damaging insects like the spruce and jack pine budworm, scientists have taken a closer look at biocontrol measures. A closer, almost microscopic, examination has focused on a tiny wasp, no larger than a fleck of pepper. Trichogramma minutum, as it has appropriately been named, can attack and kill the eggs of moths and butterflies, some of which are familiar pests like the budworm. These parasitic wasps (called parasitoids, because, unlike true parasites, they kill their host), locate spruce budworm egg masses and lay their eggs into these host eggs, killing would-be voracious larvae.

The genus Trichogramma includes many species, some of which have control various agricultural pests in the USA, Soviet Union, and China, among other countries. Use in forestry has been limited, but recent demand for biological pest control products has increased research activity into Trichogramma for forestry use.

This tiny insect is indeed a natural product - it is one of the organisms that lives in Canada's forests and contributes to the parasitism which naturally helps to keep insect populations in check. But the real threats to forest operations are the inevitable peaks of pest outbreaks. Naturally-occurring populations of the Trichogramma wasp scarcely put a dent in such epidemics.

Cooperative research by the Universities of Guelph and Toronto, the Ontario Ministry of Natural Resources, and Forestry Canada - Ontario Region, revealed the promising potential of Trichogramma minutum as a forest insect control option. The research lead to mass production capability in Canada, a technology for aerial release, and the conclusion that mass releases of the parasitoid could result in significant increases in parasitism of spruce budworm eggs and reductions in larval populations. The successful research program caught the attention of Ciba-Geigy Canada Ltd., the multinational with interest in a broad range of products including pesticides.

"Forestry involves so many environmental factors and non-target organisms," said Dr. Don Ridley, Vice-President of Research and Technology at Ciba-Geigy Canada Ltd. "A naturally-occurring biological organism that does not overwinter in large numbers is attractive because there is not a problem of undesirable side effects."

While the company is interested enough to contribute R&D dollars to Trichogramma minutum, Ridley is quick to caution that commercial application of the organism is "very speculative". "It's not easy to scale up from the laboratory stage to the operational," he said. "Much more research and development is required in the area of mass production."

"We have to take the principles developed in the production process at

Guelph, and streamline it to get rid of problems,"  Dr. Don  Wallace, entomologist

with Forestry Canada says. He sees the mass production of the parasitoid as a

major hurdle to clear before commercial success can be realized. "We need to

scale-up production and automate to reduce labor requirements and costs."

Dr. Sandy Smith, of the Facility of Forestry, University of Toronto, conducted much of the field research in collaboration with Wallace when she was a Post-Doctoral Research Fellow with Forestry Canada. While she agrees with the need for higher quantities of Trichogramma at a lower cost, she also points to problems with quality. As the crystal and spore combination in the bacteria Bacillus Thuringiensis is the active ingredient in the insecticide B.t., female wasps that can fly, locate their target and lay their eggs into the "host" budworm eggs, are the active ingredient in Trichogramma. Twelve million insects, therefore, are only as effective as the number of healthy females. Smith says that more research is needed to improve parasitoid quality through bioassays, the establishment of quality standards, and identification of superior strains of the species.

Despite the problems to face in the development of Trichogramma as a viable insecticide, Smith sees positive aspects as well. "The nice thing with Trichogramma is that it flies to its host. With B.t. the (budworm) larvae must find the insecticide and eat it." The tiny parasite "cues-in" to its target by detecting chemicals emitted from the budworm egg masses. Dwarfed even by budworm eggs, Trichogramma miraculously can fly from ground level to the far reaches of the upper canopy where it then parasitizes spruce budworm egg masses.

As a pest control product, it is released in the egg stage, either from a helicopter (equipped with a modified Brohm seeder) or from the ground. By regulating light and temperature during the rearing stage, researchers refined the art of timing parasitoid emergence from the eggs. With  careful planning  and  the

right field conditions, Trichogramma can be programmed  to emerge at the critical

point when host eggs are the most susceptible to attack.

The element of timing and the sensitivity to wind, temperature and

humidity, mean that special operational considerations are required for the

application of this product. "When you move away from chemical sprays you get more timing-sensitive," says Dr. Don Wallace. "Trichogramma is a living, moving organism; its life cycle must be in proper sync with the budworm to achieve a parasitic relationship." To be successful in an operational setting, this product would need to be accompanied by specific instructions for applicators.

Trichogramma appears to be most effective in combination with the insecticide B.t. Sandy Smith's research concluded that two parasitoid releases, combined with a spring application of B.t. to the larvae that survived the egg parasite, was the most effective strategy. Based on impact and costs, release rates greater than 12 to 16 million females per hectare were unnecessary.

Spruce budworm made an excellent test species for the evaluation of the parasitoid, as much is known about budworm biology and population dynamics. The same basic techniques of mass production and inundative release could be applied to other insect pests including the spruce bud moth, a particular problem in New Brunswick and the Gaspe region of Quebec.

Smith considers the cost of Trichogramma to be too high currently to justify commercial application on a broad scale, such as against the spruce budworm in boreal forest stands. She suggests the preferred strategy is to use the parasitoid for high value stands in sensitive areas such as public parks.

The driving force that determines the end-use of this technology may be public pressure. Ciba-Geigy Canada Ltd. recognizes that the use of chemicals in forestry is fairly restricted and sees the potential of a biological control alternative. Products currently on the laboratory table may become industry's main pest control  options in future (it took 25 to 30 years for B. t. technology to

progress from basic research to operational acceptance. Its  current popularity  in

Ontario is largely a result of public opposition to chemical sprays.

With the example of B.t. in mind, Dr. Sandy Smith continues her research

on Trichogramma minutum with an emphasis on improving  inundative  releases

through simulation modeling. "We've got to have people looking at alternatives so that there is something to fall back on," said Smith.

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3.Стала очевидной опасность истощения природных ресурсов, необратимого загрязнения и изменения окружающей природной среды и биосферы в целом.

4.Охраняемые природные территории предназначены для сохранения природных комплексов или объектов, имеющих хозяйственное, научное или культурно-просветительное значение.

5. Основные охраняемые природные территории в России – это заповедники, заказники, памятники природы, природные парки, курортные зоны и зеленые зоны вокруг городов.

6. За рубежом – это национальные парки, резерваты и др.

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8. Объектами экологии могут быть популяции организмов, виды, сообщества, экосистемы и биосфера в целом.

8. Переведите устно с подготовкой (рекомендуется для зрительно-устного и зрительно-письменного перевода):