Strychnine uptake by cereals and legumes grown in the glasshouse and field

Stryrhnine-coated wheat grain was used as bait in broad-acre agriculture in Australia to control severe mouse damage during 1993 to 1995. To establish whether plants could take up strychnine, glasshouse experiments were condu cted on wheat (Triticum aestivum L.), barley (Hordeum vulgare L), lupine (L upinus angustifolius L.), pea (Pisum sativum L.) and faba-bean (Vicia faba L.). Strychnine uptake was also determined by growing plants from germinate d baits. In the glasshouse experiments strychnine was detected in lupine gr ain (<80-2500 mu g kg(-1)) and in straw from wheat, barley, pea, faba-bean, and lupine (<40-390 mu g kg(-1)) when these plants were grown adjacent to 1 or 3 baits, equivalent to 36 to 107 times the recommended field rate, res pectively. Strychnine was also detected in straw from the germinated baits (<40-2233 mu g kg(-1)). Field experiments were then conducted to study stry chnine uptake by wheat, barley, lupine, chickpea (Cicer arietinum L), pea, and canola (Brassica napus var, napus) under more realistic renditions. In the field strychnine was detected in only 3 samples of pea straw (10, 24, a nd 58 mu g kg(-1)) where the bait was applied after flowering at eight time s the recommended rate. This is probably due to bait lodging in the pea str aw rather than from plant uptake of strychnine. The study has shown potenti al plant uptake of strychnine, but at the recommended rate of application u nder field conditions (3 baits m(-2)) it is unlikely that strychnine concen trations in the crops studied will exceed the detection limits (10-50 mu g kg(-1)). Nevertheless, the existing programs monitoring strychnine levels i n crops treated with baits should be maintained.