ANTIBIOTIC XG AS A SEED TREATMENT FOR THE CONTROL OF LEAF AND POD SPOT OF PEAS CAUSED BY ASCOCHYTA PISI

Abstract

Antibiotic XG has been studied for its possible application as a pea seed treatment in the control of Ascochyta leaf and pod spot. Fungistatic properties of Antibiotic XG against Ascochyta Pisi at various concentrations in relation to pH and temperature in vitro were studied. At antibiotic concentrations up to 1 p.p.m. no fungistatic effect was observed at pH values from 3.5 to 6.5, but, at concentrations above 1 p.p.m., complete inhibition of growth was found at all pH values tested. In the temperature range of 22 °C. to 30 °C. antibiotic concentrations of 1 p.p.m. had no effect on growth. Fungicidal activity to spores of A. Pisi has also been tested. A spore suspension of 10,000 spores per ml. required an exposure of 12 hr. with an antibiotic concentration of 100 p.p.m. for complete lethal dosage. The soaking of diseased pea seed samples in Antibiotic XG at a concentration of 25 p.p.m. for a period of 18 hr. effectively controls A. Pisi infection as determined by laboratory test and does not seriously impair germination. This treatment is compatible with Spergon applied after the seed has been air-dried. Storage of treated seed for a period of three months did not affect the degree of control but reduced the germinative capacity in laboratory plate tests.