Moth is a rare, but big, problem
A single leopard moth larva can kill a 3-inch-diameter branch.
New Jersey grower John Hickerson trapped up to 66 male leopard moths per night in traps.
Organic grower John Hickerson of New Jersey has a big pest problem. It's called the leopard moth.
has a 137-acre farm at Newton in Sussex County with nine acres of organic apples. About two years ago, he began noticing that some of the shoots in the trees would die out in late August. From a distance, it looked like fireblight, but on closer inspection, he found that an insect had been boring into the branches. He sent an infested branch to Rutgers University scientists, who identified the culprit as the leopard moth (Zeuzera pyrina).
The leopard moth, which is white with black spots and about 1.5 inches long, evidently has been around for a long time. According to information supplied by Rutgers, it was introduced to North America from Europe and North Africa and was first seen in New Jersey in 1887. The moth may appear throughout the growing season from May to September. Female moths usually lay eggs in clusters in bark crevices, and a single female may lay as many as 800 eggs. After hatching, the larvae often crawl some distance before entering the shoot tips and boring into the wood. Larvae can measure up to two inches long, and a single larva can kill a limb three inches in diameter.
Bill Tietjen with Rutgers Cooperative Extension said the pest only occasionally appears in sprayed orchards, but is probably a bigger problem in Hickerson's orchard because of the lack of conventional sprays.
Hickerson said organic orchards are not common in New Jersey and until last year, his was the only certified apple orchard there. His ranch is in an area with many deciduous trees and neglected wood lots and fence rows.
The leopard moth larva feeds on more than 125 species of deciduous trees, including maple, elm, beech, ash, oak, walnut, chestnut, poplar, willow, and lilac, as well as pome fruits and stone fruits. Hickerson said he's seen willow trees in the neighborhood that he thinks were killed by the moth. Woodpeckers and other birds are its major predators.
He has tried to target the young larvae with Bt (Bacillus thuringiensis) before they bore into branches, but Bt has a short residual effect, and it is difficult to maintain good coverage of the foliage at that time of year, when the trees are growing vigorously, he said.
He has also tried mass trapping, using Scentry wing traps with a lure containing the female pheromone of the leopard moth. He places traps on poles above the canopy. One trap caught 217 moths over a ten-day period in June this year. One night, one of his traps was filled with 66 moths. Because of the size of the moths, he had to change the traps daily. The adult flight is brief, however. This year, trap catch in his orchard began on June 9 and had ended by June 18.
Hickerson buys his traps from Great Lakes IPM, Inc., of Vestaburg, Michigan. Business owner Jim Hansen said Hickerson was the first person he'd heard of in the United States who had a big problem with the leopard moth, although some growers in Pennsylvania are buying traps for monitoring. However, Hansen sells a lot of leopard moth pheromone lures overseas. "Some of these pests are becoming international pests and not so localized any more," he said.
Hansen noted that the pheromone attracts only males, so is not ideal for mass trapping, because it won't prevent mated females coming into the orchard and laying eggs.
Hickerson has not lost any trees to the pest yet, but said it is something he has to manage carefully at certain times of year. "In August, I have to go around and take a look at each tree to see if there's any infestation and remove any visible sign."
Codling moth, tufted apple bud moth, and the obliquebanded leafroller are other major pests he has to deal with besides the leopard moth. Other challenges he faces are pressures from residential development, a lack of local suppliers for pest control tools, and off-target shots by hunters. Since lead is not permitted in food production, he has to pay to have his apples tested to certify that they contain no lead shot.
Hickerson said that because of such difficulties it's a challenge for him to make the orchard economically productive, but he will persevere because he likes agriculture, and his farm has good terrain for apples, with hills and slopes. His oldest trees are in their fifth leaf. The farm, which is mainly planted to hay, was part of William Penn's first tract of land in New Jersey in the late 1700s and was expanded in the early 1800s.
"There's not too much agriculture in the area," he said. "There are a lot of problems caused by abandoned and neglected land. Agriculture's very difficult. You have to be dedicated. I'm learning about these problems so I can have better success here with production."