Fluazinam is a nonregistered new product for control of apple scab. Benlate and Topsin have not been used for several years because resistance has developed by the fungus, and thus they were not included in this trial. The experiments tested the efficacy of currently available organic chemicals in comparison to several conventional fungicides. Four different orchards were selected, each with a history of severe apple scab infection. After two years of experiments and several years of observations, we have come to a number of conclusions about organic materials for control of apple scab.
Lime sulfur is difficult to work with, especially out of large drums.
It cntrols scab moderately well in the early part of the season but not as well as Thiolux or fixed coppers. It can be used to eradicate or give kickback control of infections within 36 to 72 hours of the infection period. Orthorix is very similar to lime sulfur but somewhat easier to work with. It is used at a much lower rate since it is formulated with a surfactant. It has the same tendency to russet fruit.