VEGETABLE OIL APPLICATIONS CONTROL SCALE INSECTS ON DORMANT APPLE AND PEACH TREES.

Abstract

Twigs from peach trees heavily infested with terrapin scale (Lecanium nigrofasciatum) and from apple trees heavily infested with San Jose scale (Quadraspidiotus perniciosus) were collected in January 1993. The twigs (10 replications) received no treatment (control) or dips for 1 second in 2.5 or 5.0% petroleum (dormant) oil (PO), 2.5, 5.0, or 7.5% soybean oil (SO), 5.0% corn oil (CO), 5.0% canola oil (CAO), or 0.6% Latron AG44M emulsifier. All vegetable oil treatments contained 0.6% Latron AG44M. After 2 weeks, mortalities of San Jose scale on apple (“blackcap” stage, 10 per twig) and terrapin scale on peach (mean of 36 scale insects per twig) were visually determined. Approximately 2% of the terrapin scale and 6% of San Jose scale on control twigs were dead at time of evaluation. Twigs treated with 2.5 or 5.0% PO had 76 or 97% mortality of terrapin scale on peach, respectively. Twigs dipped in 5% SO, CO, or CAO had 89%, 88%, and 96% mortality of terrapin scale. On apple, twigs dipped in 5% SO, CO, or CAO had 98, 100, and 100% mortality of San Jose scale, respectively, compared to 94% mortality for the 5.0% PO treatment.