Introduction
There are approximately 300 commercial apple growers in Illinois, with about 5,000 acres of orchards. Apple is among the most pesticide-intensive crops in Illinois, as well as worldwide. Several diseases are serious threats to apple production in Illinois of which the following can be mentioned: apple scab (Venturia inaequalis), powdery mildew (Podosphaera leucotricha), cedar apple rust (Gymnosporangium juneperi-virginianae), Quince rust (Gymnosporangium clavipes), American hawthorn rust (Gymnosporangium globosum), bitter rot (Colletotrichum gloeosporioides), black rot (Botryosphaeria obtusa), white rot (Botryosphaeria dothidea), sooty blotch (Pellaster fructicola, Geastrumia polystigmatis, Leprodontium elatius), flyspeck (Zygophiala jamaicensis), fire blight (Erwinia amylovora), and Phytophthora crown and root rot (Phytophthora spp.).