Written by Louis Nottingham and Robert Orpet, WSU TFREC, Entomology
Using Surround (kaolin) is a very effective method for repelling pear psylla. This white clay powder covers the bark of trees, preventing psylla from laying eggs. It works best when used before the psylla invade the orchard in the spring, so March or April are optimal spray times. However, many orchard blocks are difficult to drive through with sprayers that early in the spring due to lingering snow and moisture. For those blocks we recommend spraying Surround WP the previous fall. Right now is the perfect time because the leaves are dropping and it is still dry enough in many areas to spray. Surround WP is formulated with a spreader-sticker, helping it to remain on the tree through winter snow and rain (Figure 1). Our research has shown that fall Surround sprays provide surprisingly good psylla control the following spring (Figure 2). You can improve this method by increasing the Surround rate to 100 lb/a of kaolin and using an additional spreader-sticker, such as NuFilm.
IMPORTANT: We are not recommending fall Surround sprays as a replacement for spring Surround sprays. This is an “insurance policy” for certain blocks that are notoriously difficult to access in the early spring. Even if you sprayed Surround in the fall, we still recommend spraying it again with Surround (or another particle film like diatomaceous earth) in the Spring to gain optimal control of pear psylla.
Research Assistant Professor
WSU TFREC Wenatchee
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