THE IMPORTANCE OF OILS IN THE INTEGRATED MANAGEMENT OF THE PYRIFORM SCALE IN AVOCADO ORCHARDS IN ISRAEL. THE IMPORTANCE OF OILS IN THE INTEGRATED MANAGEMENT OF THE PYRIFORM SCALE IN AVOCADO ORCHARDS IN ISRAEL.

Abstract

The pyriform scale, Protopulvinaria pyriformis (Cockerell) (Hemiptera: Coccoidea: Coccidae) was discovered in Israel in 1980 and within a few years had spread to most of the avocado growing regions of the country. Several major avocado varieties (mainly Nabal) are highly susceptible to the pyriform scale. Other less susceptible avocado varieties, in the vicinity of the infected sites, can become damaged as well. The damage is caused by the secretion of large amounts of honeydew, resulting in a thick cover of sooty-mould on the leaves and on the fruit. Despite the large numbers of local natural enemies which accumulate in infested areas, as well as the establishment of the introduced encyrtid Metaphycus stanleyi Compere, which between them often cause high mortality of the scale, injury to susceptible avocado varieties has not been prevented. As a routine, application of synthetic insecticides in avocado orchards in Israel is avoided. Hence, to lower the pyriform scale populations with minimum negative consequences to the natural enemies, we studied the effect of several oils and a soap applications on the pyriform scale and the activity of the natural enemies. Several mineral oils (“mayonnaise-type” 1.75% (80% A.I.) and “stylet- oil” 1% (80% A.I.)) effectively controlled the scale nymphal stages. Therefore, oil application is conducted in the spring (February-April) and in the second half of the summer (July-October), when the population consists of mainly immature stages. Cotton oil and soap (potassium salt of fatty acids) were less effective. Application of the above mentioned compounds did not interfere with the activity of the natural enemies of the scale.