SYMPOSIA PAPER Published: 01 January 1993
STP25136S

Rain-Fastness of Deposits on Conifer Foliage

Source

Eight oil-based and four aqueous experimental formulations of Bacillus thuringiensis var. kurstaki, were sprayed in a laboratory chamber over potted seedlings of white spruce and balsam fir. Foliar deposits were assessed before and after 3 mm rain with a rainfall intensity of 5 mm/h, using a force-feeding bioassay (FFB) method of foliar extracts on the spruce budworm larvae. In addition, a total protein assay (TPA) method was used to compare the two sets of results.

The FFB method showed that formulations that provided high deposits (IU/cm2) on foliage, showed some residual activity after the rainfall, whereas formulations that provided low deposits showed no activity after the rain. This trend was observed regardless of the formulation type, oil-based or aqueous. The TPA method was more sensitive than the FFB method because with all formulations, some protein deposits (ng/cm2) remained on foliage after the rain. In general, the oil-based formulations showed greater rainfastness than the aqueous formulations, a finding that was not as evident in the FFB method. The differences in the two sets of data were due to the fact that the FFB method depended on the biological response of an insect, thus resulting in high variability in deposits, whereas the TPA method provided a direct estimation of protein deposits that were less variable.

Author Information

Sundaram, A
Forestry Canada, Forest Pest Management Institute, Sault Ste. Marie, Ont., Canada
Leung, JW
Forest Pest Management Institute, Sault Ste. Marie, Ontario, Canada
Devisetty, BN
Formulations Research and Development, Abbott Laboratories, Agricultural Research Center, Long Grove, IL, USA
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Details
Developed by Committee: E35
Pages: 227–241
DOI: 10.1520/STP25136S
ISBN-EB: 978-0-8031-5238-0
ISBN-13: 978-0-8031-1888-1