Treesearch

Aerial spray trials with a variety of viruses have been conducted between 1971 and 1983 with 2656 ha (65 plots) treated to control spruce budworm in Ontario and Quebec and 424 ha (6 plots) treated to control western spruce budworm in British Columbia. Generally, results have been inconsistent and less than satisfactory, but research continues in an effort to develop a viral insecticide for spruce budworm population regulation.

Improvements in Bt performance and cost, coupled with public concerns over human health risks have elevated Bt to a viable alternative to chemical insecticides. Operational use of Bt in recent years has demonstrated that while foliage protection can generally be achieved in most situations, gypsy moth population reduction cannot. Efforts are needed to improve Bt performance in healthy, building gypsy moth populations.

The CANUSA working group on the use of B.t. against the spruce budworm has prepared a document entitled "Guidelines for the operational use of Bacillus thuringiensis (B.t.) against the spruce budworm" following six years of extensive cooperative field trials in Canada and the U.S.A. (Morris et al 1984). The document summarized below (Table 1) describes the current state of the art and is based on the concensus of a committee of scientists actively involved in the management of this insect pest in the two countries.

Efforts to improve the effective use of B. thuringiensis and reduce its application costs has stimulated the development of higher potency formulation. Recent field studies have shown that a single application at 30 BIU/ha (12 BIU/acre) is as effective as the split double application of 20 BIU/ha (8 BIU/acre) formerly recommended. Also results of using volumetric application rates of less than 9.6 L/ha (gallon/acre) are discussed.

The entomopahtogenic fungus Erynia radicans, has been under investigation for several years as a possible alternative to chemical control of the eastern spruce budworm. A commercial production method has been developed which allows the formulation of this pathogen as a mycoinsecticide. A standardized bioassay method was used to select strain RS141 as the most potent isolate. The SD50 was found to be 11 conidia/mm2 with a slope o f 2.21 against 6th instar larvae and a ST50 at 20 C of 3.5 days. When the mycoinsecticide is applied in the field, conidia were produced for up to 5 days during...

In food consumption and utilization studies, observations were confined to a period of 5 days after which mortality of Erynia radicans larvae began to occur. Mortality due to the fungus was 76 and 83% in male and female larvae, respectively. In control larvae the pupation rate was over 95%. Control larvae of both sexes consumed significantly (P = 0.05) more food than fungus treated larvae on day 4 and 5. Treated as well as control larvae showed a continuous gain in body weight up to day 3, following which treated larvae of both sexes gained significantly (P = 0.05) less weight than the...

Thank you, Dave (Grimble). Let me begin by saying that it is particularly fitting that this group meet at this point in time. First, it a fair guess that in the 1984 field season more forest acreage will be treated with microbial insecticides than in any previous year. Second, the research effort devoted to all phases of microbial insecticide formulation and application appear to have arrived at a unique stage when recent R&D is finding ready application -- I am thinking of B.t. -- current R&D, particularly on viruses, fungi, and parasites, is well along in development, and the possibility...

Bacillus thuringiensis (B. t.) has been used operationally in the eastern U. S. since 1978 with most applications occurring in Maine. Changes in B. t. dosage rates, volume, cost, spray aircraft, and use patterns will be discussed. Evaluation of B. t. dosage in the east has consisted of variable results with 8 B.I.U. treatments in 1978 through 1980, to consistently good results with 12 B.I.U.'s for 1981 t o 1983. Application technology has changed from high volumes in 1979 to undiluted or neat applications in 1983. Spray delivery systems have changed from boom and nozzle equipped small...

I want, during this presentation, to give you a spray program coordinator point of view on Bt and try to explain why things are always different in Quebec. Not always better but always different, even in the application of Bacillus thuringiensis where 4 engine aircrafts were used to control the spruce budworm, Choristoneura funiferana (Clem.), infestation. First, a background of the situation is required: background of the Quebec forest and background of our perception of Bt. In order to progress in our approach to use Bt , some KEY FACTORS and GOALS have been established. This brought us...

The principal purpose of this Symposium is to take advantage of the CANUSA experience, which has engaged so many of us recently, to share and place in the context of our total experience, the current situation regarding microbial insecticides and their use. The exercise will be useful not only for information exchange ? the traditional purpose of symposia -- but also to sharpen and hone future research program planning for microbial insecticide research.