Photo courtesy Wikipedia.
Male Gypsy Moth
Remember the defoliation last summer resulting from a particularly aggressive gypsy moth infestation? Experts advise that the month of April is a good time to take some preventative measures to avoid a repeat of last year’s experience.
First, the terminology has changed. The common name “gypsy moth” has been officially replaced with the name “spongy moth” by the Entomological Society of America to avoid offense to the Romani people. The new name stems from the sponge-like egg masses the creature leaves behind. The scientific name for the pest is Lymantria dispar.
Photo courtesy Wikipedia.
Female Gypsy Moth
As snow melts, homeowners can inspect their trees and shrubs for these egg masses to eliminate them. According to the University of Wisconsin Division of Extension website, eggs can be killed by soaking them in soapy water for two days before discarding them in the garbage. Experts warn not to just scrape the egg masses on the ground or crush them with a shoe, as these eggs are tough and survivors will hatch later in the spring. The same goes for egg masses that remain on trees: surviving eggs lurk beneath. Don’t leave any part of the egg mass attached, and pick up any that have fallen to the ground. These creatures are persistent!
Once the temperature climbs above 4C, egg masses can be sprayed with a horticultural oil labelled for use on Lymantria dispar, which are available at Canadian Tire and many large home improvement retailers. Motor oils, mineral oils and non-horticultural oils are not a substitute. The oil will suffocate the eggs so they won’t hatch. If you have a large area to cover, experts suggest adding food colouring to the spray oil so you can easily identify the areas that have been treated.
Later in the season when the eggs have hatched into caterpillars, placing sticky barrier bands around trees can prevent their movement. Travelling on silk threads, many of them fall out of trees, and these man-made barriers prevent their return. It is important to avoid putting sticky material directly on the trees and to ensure that trees with deep bark furrows have effective barriers that don’t allow caterpillars to sneak up underneath the barrier band. Trees with bands should be monitored daily and caterpillars swept into buckets of soapy water for disposal.
There are insecticides that can control the pest at the caterpillar stage. These products contain Bacillus thuringiensis kurstaki (Btk), which is a selective biological insecticide. Crystals of this ingredient release a toxic protein when dissolved in the alkaline digestive system of the insect. The caterpillar stops feeding soon after, and dies within five days.
There have been reports that this year’s winter weather conditions have killed off many of the eggs that remain on local trees and shrubs. If not, this can be our plan B. KG
