Ba. Fulling et al., INTEGRATION OF HOST-RESISTANCE AND WEATHER-BASED FUNGICIDE SCHEDULINGFOR CONTROL OF ANTHRACNOSE OF TOMATO FRUIT, Plant disease, 79(3), 1995, pp. 228-233
The relationship between anthracnose resistance of tomato cultivars an
d disease incidence at various fungicide application intervals (determ
ined by a weather-based scheduling program) was evaluated in field stu
dies in 1992 and 1993. The resistance of tomato cultivars was indexed
relative to the disease response of a standard susceptible cultivar in
evaluations conducted in a disease nursery. Five different fungicide
application intervals, based on action threshold values determined by
the TOM-CAST program (12, 16, 20, 24, or 32 daily severity values), we
re tested on five tomato cultivars that represented a range of resista
nce currently available in commercial production. The relationship bet
ween application interval and disease incidence was determined by line
ar regression techniques for each cultivar. The slope of the regressio
n for each cultivar was designated as a TOM-CAST anthracnose coefficie
nt (TAC). TAC values were regressed on resistance indices to estimate
optimum fungicide spray intervals for cultivars with different degrees
of resistance. Results indicated that, with the TOM-CAST program, res
istant cultivars require three to four fewer fungicide applications pe
r year than susceptible cultivars to obtain adequate control of anthra
cnose. Optimum action threshold values may be increased from current r
ecommendations by at least two-fold for resistant cultivars currently
under development.