OVERWINTERING AND EFFECTS OF AUTUMN HABITAT MANIPULATION AND CARBOFURAN ON NEOSEIULUS-FALLACIS AND TETRANYCHUS-URTICAE IN PEPPERMINT

The percentages of Neoseiulus fallacis (Carman) in four subhabitats of peppermint fields in November were 37% on dead leaves, 45% in debris below dead leaves, 3% in hollow stems and 15% on live foliage. in Dece mber, the percentages were 36, 39, 7 and 18%, respectively, for these same sites. The values were 40, 37, 18 and 5% and 6, 80, 14 and 0% for January and February, respectively. By April, 95% of all predators we re on new foliage feeding on Tetranychus urticae Koch, while the rest were still in debris. Augmenting plots with debris increased overwinte ring survival of N. fallacis compared to the natural condition while r emoval of debris decreased it. An autumn carbofuran (Furadan 4F) treat ment completely eliminated overwintering N. fallacis, thus leading to outbreaks of T. urticae the following spring. The results of these ove rwintering studies are discussed in relation to improved biological co ntrol and spider mite management.