June 12, 2014

Pine Sawflies

Notice needle damage on pine trees?  Look close.  It may be caused by conifer-feeding sawflies.

Sawflies feeding on Scotch pine

Sawflies feeding on Scotch pine

Sawflies? As larvae they look caterpillars which might develop into moths, their name implies they’ll be flies, but they actually become non-stinging wasps as adults. And the saw? As adult wasps the females cut slits in pine needles with saw-like structures on the tip of their abdomens and lay eggs into these openings.

Checkout the synchronized movement they make to deter predators!

Although there are several species of sawflies that can be seen on conifers the gray-green European Pine Sawfly (Neodiprion sertifer) is represented in this post. 

European pine sawfly group

European pine sawfly group

Sawfly Management

  • Monitor to detect infestations before they reach a size that can cause significant needle loss.
  • Know that sawfly larvae are attractive as food to parasites and predators and are usually kept in check by these natural enemies.
  • If a small outbreak occurs they can often be handpicked, or pruned out and destroyed.
  • For rare situations where the population of sawflies are high insecticides labeled for their control can be used.
individual pine sawfly

Pine sawfly larvae

July 8, 2013

White Pine Weevil

Dieback due to white pine weevil larva feeding.

Noticing a wilted leader on pines or spruces?  White pine weevil is likely the culprit. Although it’s almost officially summer when the symptoms are first noticed it all started back in the early spring when, on a warm day in March- April, the female weevil lays her tiny eggs a few inches below the terminal bud. Those eggs soon hatch and the young larvae start to consume the stem’s vascular tissue.    With the loss of this vascular pipework the tree’s terminal leader wilts and brown dieback soon becomes visible.

With the bark peeled back, a white pine weevil larva is visible inside spruce leader.

In late July and August adult weevils emerge through small holes they carved at the base of the dead terminal.  After the adult weevils emerge they enter leaf liter and are not seen until March of the following year.  If you prune out and destroy the affected leaders before the holes appear and the adults emerge (Late June to mid-July for most of New York) you can reduce numbers of adults that will lay next year’s eggs.

Exit holes of at base of area damaged by White Pine Weevils. Prune and destroy before these are visible.

A blue spruce disfigured due to a missing leader caused by White Pine Weevil damage.

White pine weevil is one of the earliest pests we treat for in the spring.  Knowing when to treat can be tricky.  Using growing degree days in the spring can be helpful to prevent damage.  

See the Insect Section of Pest Management Guide for Commercial Production and Maintenance of Trees and Shrubs for growing degree day target window for treatment  and other control information.

June 7, 2013

Allies in the Trees

Do you recognize this one? I saw this insect at a couple of tree farms during the last week of May and first week of June. This is an immature ladybug a.k.a. Ladybird beetle. The ladybug larvae, like the adult beetles they become, are voracious eaters of aphids and other insects.

Ladybug larva. Click on image for larger view.

ladybug pupa

The larva becomes a pupa before morphing into an adult beetle.

ladybug adults

An adult ladybug may consume 5000 insects in its lifespan. The ladybug on the right is on its way to a meal of balsam twig aphids.

ladybug eggs

This is a good sign. Bright yellow ladybug eggs hanging from a fir needle means more of these “eating machines” will be hatching soon.

There are many other beneficial creatures, which feed on pests in tree farms and often go unnoticed.  These include “good” mites, various predatory and parasitic insects, spiders and even birds.  By keeping pesticide applications to a minimum the populations of the beneficial partners are maintained and nature can do its good work without us even knowing it.