According to Kline (Ramsey and Kollonitsch, 1977), Ortho was the largest manufacturer in this segment, with a 33% market share. Ortho's main active ingredients were captan, folpet, and sulfur. These active ingredients were used by other manufacturers as well.

Other active ingredients listed in Kline (Ramsey and Kollonitsch, 1977), and most likely used by both Ortho and other manufacturers, are chlorothalonil, maneb, zineb, thiram, andferbam.

Based on this information, we used judgment to derive the probabilities: