P. Amirault, G. Cormier, D.C Davies, S.E. Holmes and E.G. Kettela

SERG Project # 1998/01 (2001)


Executive Summary

The pine false webworm (Acantholyda erythrocephala L.), an introduced insect, has become established in south-central Ontario and is a major defoliator of both red pine (Pinus resinosa Ait.) and white pine (P. strobus L.). These trees are valuable for the lumber and poles produced and for their aesthetic values. The pine false webworm was initially considered to be a pest only of small plantation trees; in recent years, however, it has become established in mature plantations and in wild stands of red and white pine. Tree mortality and growth increment loss has occurred in many stands, which is of paramount concern to county forest managers. Pest management products that are environmentally acceptable and meet social values are needed by land owners for use against this forest pest. One such product is Neemix® 4.5 (Certis USA). This product has a temporary registration but needed to be evaluated in a demonstration operational pest management program.

Accordingly, demonstration spray trials covering a total of 701.7 ha were negotiated with Simcoe and Bruce counties in Ontario. In Simcoe County, 513 ha of red and white pine plantation were treated at a dosage of 45 g/ha of azadirachtin in 6 L/ha of formulated product. An additional 30 ha received a dosage of 10 g/ha in 6 L/ha so that the efficacy of a lower dosage could be explored. In Bruce County, 158.7 ha of semimature white pine heavily infested with pine false webworm were treated at a dosage of 30 g/ha of azadirachtin in 6 L/ha. A Cessna 188 supplied by Forest Protection Limited and equipped with four Micronair® AU 4000 atomizers set to rotate at 6000 rpm was used to apply the insecticide.

Efficacy monitoring was conducted at both treatment zones and in suitable unsprayed areas. Included in the sampling array were prespray sampling for eggs, larvae per branch, and defoliation; periodic postspray sampling weekly until early July; the establishment of frass collectors and a twice weekly measurement of frass deposit; and periodic determinations of insect development and egg hatch to aid in spray application.

In the Simcoe County blocks, Neemix 4.5 had a profound impact on feeding by the pine false webworm as shown by a postspray reduction in frass and the low level of damage caused by the insect compared to the controls.

In Bruce County, the impact of the webworm on the treated white pine resulted in only light defoliation with moderate defoliation occurring at the edges of the blocks, compared to very severe defoliation in the untreated stands. Measurements of frass show a clear impact of Neemix 4.5 on feeding inhibition.

Although Neemix 4.5 performed up to its expectations, problems associated with its odour and deleterious impact on rubber seals in the Cessna 188 spray system were documented. Solutions to cope with this are suggested.