MOTH A New Invasive Pest of Crops

Amy Ivy, Horticulture Educator, Cornell Cooperative Extension Anthony Shelton, Ph.D, Professor of Entomology, Cornell University Dan Olmstead, Research Support Specialist, Cornell University

h"p://web.entomology.cornell.edu/shelton/leek-moth

The is surrounded with a cocoon Diagram Courtesy of OMAFRA having a net-like structure and is often found attached to outer plant surfaces that may be healthy or necrotic. The eggs are tiny and translucent. They are Amy Ivy laid on the undersides of leaves and are Figure 1. Adult and larval life stages of leek moth. Mao Chen very difficult to see.

Introduction There are two to three generations per

Leek moth (LM) is a pest of plants in the year in , CA. LM overwinters as Allium family which includes , a pupa. In spring, adults emerge, mate, , , and . The and lay eggs when temperatures reach larvae feed on crop foliage, stunting plant 10°C (Figure 3). A female will lay about 100 eggs, singly, on the underside of Figure 3. Diagram of leek moth developmental progress through growth and compromising the storage life a typical growing season. of the crop. LM is native to and is host plant leaves over a 3-4 week now common in , Japan, and period. Eggs hatch in about a week. Management Larvae burrow into the leaves and grow Algeria. It was discovered in North In July 2010 the NYS Department of in size over the next two weeks, and America in 1993 in Ontario, and Environmental Conservation granted then pupate. Adults emerge about 10 the first confirmed occurrence of leek special insecticide registrations for: days later. moth in the continental was Warrior II (pyrethroid), Radiant SC in Plattsburgh, NY (Clinton County) during (spinetoram), Lannate LV (carbamate), Damage Symptoms the summer of 2009. In 2010 and 2011, it Entrust (spinosad), and DiPel DF reappeared in the same sites as well as The first generation (May-June) feeds (Bacillus thuringiensis). DiPel DF and additional sites north of Plattsburgh on Allium leaves, causing some Entrust can be used in organic

(Figure 2). It was also confirmed in the damage. The second generation (July- production. Canton/Ogdensburg area of northern NY August) causes more severe damage Insecticide applications made 7-10 days (St. Lawrence County) those same years. due to higher numbers and better following a peak flight of LM can greatly There is speculation from growers there growing conditions as LM larvae move reduce LM populations. Applications of that it may have been present for a towards the bulb. Feeding damage organic insecticides must be precisely number of years, but this cannot be stunts plant growth, introduces rots and applied to have an effect. Thorough confirmed. shortens the storage life of onions and coverage of a plant is essential to garlic. On crops with hollow leaves control young larvae, especially with (onions, shallots and chives), larvae DiPel. feed inside the leaf causing ‘windowpane’ damage to the leaves. Row covers can be effective for control Look for LM larvae by splitting open of LM on a farm and rotation to non- damaged leaves and looking for frass host plants can be effective for area- (excrement) and debris (Figure 4). Even wide management. after the larvae have left the plant to pupate, the telltale debris remains Parasitic hymenopteran wasps, visible. On garlic and leeks, larvae feed Diadromus pulchellus (Ichneumonidae) on the leaf surfaces and sometimes and Conura albifrons (Chalcididae), and tunnel through the leaves. They are generalist predators may be helpful in often found between leaves or in the suppressing LM populations.

Figure 2. Distribution of confirmed leek moth populations in the protection of folded leaves. northeastern United States as of 2011.

Biology

The moth is speckled brown, white and black with a distinctive white spot halfway down its outer pair of wings (Figure 1). It is about 3/8” long and is nocturnal so it will rarely be seen unless trapped. The is a creamy yellow, A Amy Ivy B Amy Ivy C Amy Ivy slender caterpillar, less than a half inch Figure 4. Examples of leek moth larval damage in Allium crops including (A) window pane damage in , (B) a split onion leaf showing interior damage, and (C) leek plant damage. long when fully grown (Figure 1).