Foliar damage, residue levels and tuber yield in potato treated with various concentrations of 2,4-D at three stages of growth

Abstract

A field trial with potato plants treated with 0, 0.1, 1 and 10 p.p.m. 2,4-D at the emergence, flowering and flower drop stages was conducted. Symptoms of foliar damage were noted a month after the treatments. The susceptibility of the plants to 2,4-D damage decreased in the order of emergence, flowering and flower drop of the plants, irrespective of the concentration of the herbicide. There may be economic loss for producers of seed potatotes owing to the foliar 2,4-D damage. Residues of 2,4-D in both foliage and tubers were determined. The limit of detection was 0.005 p.p.m. The average recovery of 2,4-D amine and acid from fortified foliage and tubers was 81 to 87 per cent. Residue levels of 0.110 p.p.m. 2,4-D were found in the slightly damaged foliage following application at flower drop, but only 0.010 p.p.m. was found in severely damaged foliage following application at emergence. Traces of 2,4-D residue were found in the tubers after the plants had reached maturity. In general, tuber yield (numbers, weight and specific gravity) was not affected by the various concentrations of 2,4-D applied at the three stages of growth. However, it appeared possible that the yield of No. 1 grade tubers might be slightly reduced when plants are treated at emergence, irrespective of the concentration of the herbicide.