RESIDUES OF 2,4-D, DICHLORPROP AND PICLORAM IN WILD BERRIES FROM TREATED RIGHTS-OF-WAY AND CONIFER RELEASE SITES IN ONTARIO, 1979–1981

Abstract

Between 1979 and 1981 fruit of the wild red raspberry (Rubus strigosus, Michx.), blueberry (Vaccinium myrtilloides, Michx. and V. angustifolium, Ait.), wild strawberry (Fragaria virginiana, Duchesne) and pin cherry (Prunus pensylvanica, L.f.) were analyzed for herbicide residues from 24 sites across Northeastern Ontario. Seven sites were along rights-of-way, one was on a farm and 16 others were conifer site preparation or release sprayblocks. 2,4-D was applied at all sites, picloram at five and dichlorprop at two. Application rates varied from 0.8 to 6.0 kg/ha total acid equivalent between June and September to plants in flowering to ripe fruit stages. Spraying red raspberries in the flowering stage resulted in negligible residues on ripe fruit. Spraying immature fruit with 2,4-D resulted in only 0.2 mg/kg on ripe raspberry fruit; however, when ripe fruit was treated, initial residues ranged from 2.6 to 31 mg/kg. These levels declined to 0.1 and 3.3 mg/kg over a 2- to 5-wk period. Similar exponential declines in residues occurred with picloram. Fruit harvested in the year after treatment appeared normal and had no detectable residues of 2,4-D. No decline in the residues were observed on blueberries from eight sites and on pin cherries at one site where treatment was made to immature and/or mature fruit. At only one of nine sites did residues of 2,4-D decline in blueberries. With wild strawberries, herbicide residues declined rapidly at two sites and slowly at one site. Of the approximately one million hectares of raspberries and blueberries growing wild in the Province of Ontario, about 0.3% is treated annually with herbicide. With the timing of applications ranging from flowering to fruiting only 50% of fruit from the treated areas would have residues above 0.5 mg/kg.Key words: 2,4-D, dichlorprop, picloram, wild berries, rights-of-way, forest