The Monmouth County Shade Tree Commission began spraying for gypsy moth caterpillars on May 10, weather permitting, according to a press release from the county.
A total of 641 acres are targeted for spraying this year, down from the 6,891 acres that were sprayed last year. Public Works and Engineering Director John W. Tobia, who oversees the Shade Tree Commission staff, said the infestation is cyclical and is now waning.
“Monmouth County has been spraying for gypsy moth caterpillars since 2006 when they reappeared in large numbers and began damaging county parks and open spaces,” Freeholder Director Lillian G. Burry said. “The county has been vigilant in its attempt to control them, and at one point even pressed two county helicopters into service for the spraying. Because of that vigilance, the county has been successful in interrupting their cycle and slowed them down considerably.”
Spraying this year will take place in Colts Neck (Hominy Hill Golf Course, 100 acres); Freehold Township (127 acres); Howell (168 acres); Millstone Township (120 acres); Tinton Falls (32 acres); and Wall Township (84 acres). Exact spray days and times are dependent upon weather conditions.
Spraying will last 21 days and will target the larvae as the caterpillars hatch. The Shade Tree Commission is spraying a naturally occurring, soil-dwelling bacterium called Bacillus thuringiensis, or “Bt” for short. Neither Bt bacteria nor the protein toxins it produces have any effect on people or pets, according to the press release.
The gypsy moth caterpillar population is cyclical. The county began making preparations to combat the gypsy moth caterpillars in 2005, when they were spotted in concentrated pockets in Wall, Howell and Freehold Township. Spraying for this population cycle began in spring 2006.
“Even though we spray, we cannot expect to control all of the larvae,” Tobia said. “Due to our efforts, the county has curtailed their proliferation. The food source, the environment and the weather are all factors that affect the numbers of gypsy moth caterpillars in a given year.”
The caterpillar first began defoliating New Jersey forests in 1966, and three major population cycles have occurred: one in 1972 when 256,000 acres were defoliated, another in 1981 when 798,000 acres were defoliated, and another in 1990 when 431,000 acres were defoliated.
Caterpillars hatch in April and early May and climb into tree canopies to begin feeding. If their first tree is not to their liking, they will produce a silken thread that carries them on wind currents to other trees. The caterpillars continue feeding throughout the spring, undergoing five to six molts.
The first three caterpillar instars have black heads and generally black bodies. By mid June, the caterpillars are about 1 inch long, have brown heads, bodies covered with black and brown hairs, and a series of five pairs of blue spots followed by five pairs of red spots on the tops of the bodies.
In wooded suburban areas, during infestation when trees are visibly defoliated, gypsy moth larvae can be seen crawling up and down walls, across roads, over outdoor furniture, and even inside homes. During periods of feeding, they leave behind a mixture of pieces of leaves and excrement.
According to the press release, the greatest damage is done by older caterpillars during the last two weeks of June, sometimes making it appear as if trees are stripped of leaves overnight. After they have completed feeding in early July, caterpillars enter the pupal stage from which adult moths emerge after 10 to 14 days.
The Monmouth County Shade Tree Commission had visited areas where the caterpillars have been reported by residents, and mobilizes each September to conduct egg mass counts. The egg masses are described as a velvet mass attached to the trunks of trees, rocks, benches or wood piles. These counts help the county focus its aerial spray program the following spring.
Gypsy moth larvae prefer hardwoods, but may feed on several hundred different species of trees and shrubs. In the East, the gypsy moth prefers oaks, apple, sweetgum, speckled alder, basswood, gray and white birch, poplar, willow and hawthorn, although other species are also affected.
When gypsy moth populations are dense, the caterpillar feeds on almost all vegetation, but has avoided ash, yellow poplar, sycamore, butternut, black walnut, catalpa, flowering dogwood, balsam fir, red cedar, American holly, and shrubs such as mountain laurel, rhododendron, and arborvitae.
Homeowners who find egg masses are urged to contact the Shade Tree Commission at 732-431-7903 to report their location and obtain information on how to destroy them.