Late Summer/Early Fall Pest Alert: Fall Webworm

Fall is approaching and a common garden pest, the fall webworm (Hyphantria cunea) can become noticeable on trees, causing unsightly larval nests covering entire branches, resulting in stress to the tree and severe leaf damage. Fall webworm are caterpillars that weave loose webbing around the tree’s outer foliage while feeding on leaves, compared to tent caterpillars that appear in spring and build their more opaque nests within the inner crotch of the branches. The webworm caterpillar is approximately one inch in length with a light greenish-yellow body and black to reddish head. Adults emerge later on as white moths with dark spots on their wings.

Fall Webworm Caterpillar

The best way to eliminate fall webworm is to remove the infected branches immediately, before the larvae hatch and take over the tree. If the caterpillars have already left the nest, it is recommended to spray with an organophosphate insecticide such as Acephate (contained in Orthene or Sevin) or Malathion. Acephate is both a foliar and soil systemic which keeps on working 10–15 days after application. Malathion is a foliar insecticide which is also commonly used, but note that Malathion may leave a residue. The best proactive method of killing overwintering larvae is to apply a dormant oil in early spring while the tree is dormant. Dormant oil is a more natural solution and works by smothering and killing the overwintering eggs.

Fall Webworm Adult Moth (Source: Wikimedia Commons Author TampAGS, for AGS Media)

In the spring, adult moths emerge and deposit eggs, continuing the life cycle of the caterpillar. These caterpillars may go through as many as eleven growth stages before leaving the web.

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Author:  Lee@Landscape Design By Lee 2018. All Rights Reserved.

September Garden Maintenance-Virginia Creeper, Fall Webworm & Bagworm

September Garden Maintenance-Invasive Species & Pests

VIRGINIA CREEPER  (Parthenocissus quinquefolia) –“Five –Leaved Ivy”

It’s September and it is time to take a walk in the garden and look for late summer pests and damaging vines.  At this time of year Virginia Creeper, an aggressive native vine, will pop up in your garden and grow at a rapid rate.   Examine your perennial beds and around trees and shrubs that are especially located in a wooded area and try to get the root of this trailing vine.  This vine can grow to 50 feet long and will quickly wrap around your evergreens and deciduous trees choking them.

FALL WEBWORM: (Hyphantria cunea)

Examine your trees for signs of fungus and insect damage.  Fall web worm is ahead of schedule this year due to the heat wave and humidity we had during the month of July.  Fall webworm is a Long Island native pest of deciduous trees such as hickory, walnut, birch, cherry, and crabapple. It appears from late summer through early fall and constructs its nest over the ends of branches.   The large webs contain caterpillars, partially eaten foliage and fecal droppings. For immediate protection of your tree remove the damaged branch.  An insecticidal spray can be applied to the webs.  It is not necessary to spray the entire tree.  When in doubt ask a professional arborist.

BAGWORM:  (Thyridopteryx ephemeraeformis)

Bagworm has rapidly become a nuisance on Long Island over the past two years.  Bagworm defoliates evergreens such as arborvitae, pine, spruce and juniper along with select deciduous trees such as locust and sycamore.   Larvae are encased in tiny silk woven sacs on trees in early summer which are difficult to see.  As the sacs mature they appear as visible darker brown bags reaching 30-50 millimeters is size containing thousands of worms that hatch and move from tree to tree until each is completely destroyed.   For immediate protection of your tree remove the damaged branch containing the sac if possible then spray with the proper insecticide for this intruder.  When in doubt ask a professional arborist.

BAGWORM DAMAGE ON ARBORVITAE

These are damaged Arborvitae from Bagworm, which if left untreated can lead to the total eradication of the tree.  Be sure to frequently check your trees and shrubs for insect damage and try to be proactive by establishing a regular maintenance program.   Your landscape will benefit greatly and give you years of enjoyment.

Author: Lee@Landscape Design By Lee, 2013, All Rights Reserved