Effect of Triforine on Pollen Germination and Fruit Set in Highbush Blueberry. Peter R. Bristow, Assistant Plant Pathologist, Western Washington Research and Extension Center, Washington State University, Puyallup, WA 98371. Plant Dis. 65:350-353. Copyright 1981 American Phytopathological Society. DOI: 10.1094/PD-65-350.

Pollen of 13 highbush blueberry (Vaccinium corymbosum L.) cultivars germinated on 9% sucrose agar but was inhibited when the medium contained 10–50 µg (active ingredient) of the fungicide triforine per milliliter. Triforine applied directly to the stigma at 3,488 µg/ml (the concentration used in suspensions applied aerially to control the mummy berry disease) prevented pollen germination. Inhibition was greatest when triforine was applied to stigmas 2 hr before pollination and decreased as the interval between fungicide application and pollination lengthened. When sprayed on flower parts inside the corolla tube, triforine reduced germination of undehisced pollen; concentrations above 500 µg/ml caused stickiness and necrosis of the corolla tube and impaired the release of pollen. Blueberry bushes in the field sprayed during bloom to simulate aerial application of triforine did not develop blossom necrosis; pollen from sprayed flowers germinated readily on sucrose agar; and fruit set and berry development were not affected. Although it is toxic to blueberry pollen, triforine has no adverse effect when applied during bloom to control mummy berry.

Keyword(s): Funginex, Monilinia vaccinii-corymbosi.