NC State Extension

Focus on Treatment Windows – Shoot Elongation

SHOOT ELONGATION: MID-MAY THROUGH JUNE

Shoot Elongation

Shoot Elongation

Stages of pests. Pests continue to be very active through the spring.

  • RBM — Mites move out of the old rosette buds as vegetative buds break and are blown to newly breaking buds. Mites feed at the growing tip of the shoot and start to develop new rosette buds.
  • EHS — All stages present. Crawlers most common. Scales move onto new growth
  • BWA — Adults laying eggs. All stages including eggs, crawlers, nymphs and adults present.
  • BTA — Twig aphids very active. Adults and immatures present. Different life stages found including winged adults and the production of males. The overwintering egg are starting to be produced.
  • Cinara aphids — Cinara aphids may be very active.
  • SSM — All stages present including eggs, immatures, and adults.
  • HRM — Rust mites activity continues until temperatures get hot.
  • Predators — Most predators are active and commonly found.

Advantages to applications during shoot elongation. From bud break through shoot elongation is the traditional treatment window for rosette bud mites but other pests are also readily controlled during this time. Twig aphids are killed before they can lay the overwintering eggs. Scales are very active with peak crawler production and are most vulnerable to pesticide applications. Miticides that control eggs work well as eggs are newly produced and will hatch soon.

Disadvantages to applications during shoot elongation. One of the disadvantages to treating for pests during shoot elongation is that the foliage is tender. High pressure can break off shoots, and spraying with multiple products mixed together on hot days may cause foliage burn. Predators and pollinators are both very active and can be impacted by pesticide applications. Also if trees are to be harvested they will have to be retreated for Cinara aphid control again in the fall.

Materials That Can Be Used During Shoot Elongation
Pesticides RBM EHS BWA BTA* Cinara** SSM HRM
Bifenthrin products (Talstar, Sniper) None May be some suppression but not long lasting control. Excellent Excellent Excellent if aphids are active. Excellent None
Asana None May be some suppression but not long lasting control. Excellent Excellent Excellent None None
Dimethoate Excellent May be some suppression but not long lasting control Poor Excellent Excellent but will need to treat again in fall. Excellent control of active mites but eggs not controlled. Population may rebound. Excellent control of active mites. Warm temperatures should reduce rust mite activity. Therefore mites typically do not rebound.
Asana + Dimethoate Excellent Excellent Excellent Excellent Excellent Excellent control of active mites but eggs not controlled. Population may rebound. Excellent control of active mites. Warm temperatures should reduce rust mite activity. Therefore mites typically do not rebound.
Safari None Excellent Excellent None Good if aphids are active. None None
Talus None Excellent Not known None None None None

*BTA control is for the following spring.

**Cinara aphid control is for that spring. If trees will be harvested in the fall, trees will have to be retreated at that time.

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Written By

Photo of Dr. Jill SidebottomDr. Jill SidebottomExtension Specialist (Mountain Conifer IPM) (828) 684-3562 jill_sidebottom@ncsu.eduForestry & Environmental Resources - NC State University
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