Abstract:
Repeated foliar application of chlorothalonil significantly increased lentil (Lens culinaris) seed yield in field plots infested with anthracnose caused by Colletotrichum truncatum. Two to four fold increases over the yields of non-treated plots occurred when conditions for disease development were favourable. Propiconazole significantly increased seed yield at an irrigated test site at the University of Manitoba Campus Farm but did not significantly improve seed yield at other sites, probably due to dry conditions. Levels of infestation in harvested seed were generally low, ranging from 2.25% in seed from 16 commercial lentil fields, to below 1.42% from untreated plots and less than 0.25% from plots sprayed with chlorothalonil. No evidence of seed to seeding transmission was obtained when seed lots with 6.4%, 3.4% and 2.3% infected seed were sown in isolated plots at the Campus Farm. Propiconazole reduced disease severity on lentil when applied up to 48 hours after plants were inoculated with C. truncatum in the greenhouse. Chlorothalonil did not reduce disease severity when applied to plants 24 or 48 hours after inoculation. In growth cabinet studies, disease severity on inoculated lentil plants increased with increasing temperature and length of leaf wetness periods. Symptomless infection of lentil and faba bean was demonstrated in field and greenhouse studies. The ability of C. truncatum to overwinter on lentil stubble for up to two years in a commercial field was determined using a bioassay. In a three-year field study, lentil cultivars and breeding lines were ranked for disease severity from lowest to highest as follows; Indianhead, Laird, Laird-cross La x 17310-8, Eston, followed by the landraces French Green, Chilean and Spanish Brown. Greenhouse studies showed that lentil, faba bean (Vicia faba), field pea (Pisum sativum), flat pea (Lathyrus sp.) and vetch (Vicia sativa) were susceptible to C. truncatum from lentil. Several cultivars of soybean (Glycine max) and field bean (Phaseolus vulgaris) were resistant to C. truncatum from lentil.
