Suppression of wheat seedling establishment by maneb

Abstract

Seed of eight wheat cultivars dusted at 2 g kg-1 with the new bunticide maneb (75 per cent) was compared for possible phytotoxicity with seed dusted with phenyl mercuric acetate (1.5 per cent Hg), previously used for bunt control, and with untreated seed. Maneb and PMA did not affect field establishment when the seed was sown two months after treatment. Field establishment of all cultivars was reduced when dusted seed was stored for more than one year. The reduction was greater with maneb-treated seed than with PMA-treated seed except for the cultivar Summit, which was more susceptible to PMA. Cultivars varied in their susceptibility to maneb: Eagle was most affected, giving less than 50 per cent establishment compared with untreated seed. Grain yields, 1000-grain weights, and hectolitre weights, however, were not reduced. It is concluded that prolonged storage of seed treated with maneb should be avoided and that prospective commercial wheat cultivars should be tested for tolerance to current bunticides.