Identifying Leafrollers Including the Light Brown Apple Moth Production Guideline by Dr. Frank G. Zalom Issue 5.1 June 2010 The California Strawberry Commission Production Guidelines are produced in cooperation with scientists who conduct research related to strawberry production. These Guidelines are a tool for growers, providing critical scientific background information on diseases and pests common to strawberry production in California. For copies of this Guideline or others in the series, visit www.calstrawberry.com. Production Guideline by: Dr. Frank G. Zalom Department of Entomology University of California Davis, CA 95616 p. 530.752.3687 The light brown apple moth (LBAM), Epiphyas postvittana, was first reported in California in spring, 2007. It is a native of Australia and New Zealand, and is now established in Great Britain. It has a broad plant host range, encompassing over 50 plant families that include landscape trees, ornamental shrubs, fruit and certain vegetable crop hosts. The primary concern with LBAM is its regulatory status. A single LBAM larva in a fruit can result in the imposition of a quarantine. Quarantined fields must cease fruit shipment until treatment and inspection permit harvest to resume. In effect, there is no tolerance for LBAM infestation of fruit. The light brown apple moth will fly up to 328 feet (100 meters) to find suitable host material. The greatest abundance of LBAM appears to be in urban settings, where plant-feeding insects are not routinely managed. Therefore, fields near houses and other developed areas may be particularly susceptible to infestation by moths flying in. Since the larvae most commonly infest leaves, immature LBAM can move on foliage or green waste. An effective sex pheromone for attracting male light brown apple moths is available commercially. The LBAM pheromone lure placed into delta or wing-style traps can be used to detect the presence of the moth. Deploy pheromone traps to detect and monitor the male moths at one per 5 acres, with at least one in every field no matter how small. The presence of adult moths captured in traps is not an indication of fruit infestation, but it is a warning of LBAM presence that should not be ignored. The adult is about 0.4 inch (10mm) long, with a 0.75 inch (18mm) wingspan. The forewings of the male moth are light tan toward the body and darker brown towards the outer edges (Figure 1). 2010 California Strawberry Commission Figure 1. Light Brown Apple Moth adult
It usually stays sheltered in the foliage during the day, and flies after sunset and before daybreak. The eggs are pale white to light green and are laid slightly overlapping each other as an egg mass or a raft on the upper surface of the foliage. Newly hatched larvae are pale yellowgreen. Mature larvae are light green with a light brown (not dark brown or black) head. The larvae never have darkly colored or distinctly banded legs. The larvae also have an anal comb at the tip of the abdomen with 7 or 8 prongs. The newly hatched larvae are tiny and only about 0.06 inch (1.6mm) long, while mature larvae Figure 2. Light Brown Apple Moth larva range from 0.4-0.75 inch (10 to 20mm) in length (Figure 2). They wriggle vigorously when disturbed. After emerging, the larva builds a silken shelter by rolling a leaf lengthways and webbing its edges together. Leaves may also be webbed together or joined to fruit. The larvae feed within these shelters, and they may feed on fruit when it touches a leaf. A larva in a fruit is most likely to be found near the calyx or in the endocarp (fruit), near the seeds. The light brown apple moth does not have a diapause, and can overwinter in any life stage in mild coastal areas. A degree-day model used for predicting LBAM development indicates that there can be two to three generations a year in the central coast area. Our observation in the Monterey Bay area is that there are 2 major flight peaks each year (spring and fall). However, males can be captured in pheromone traps at any time of the year when temperatures are favorable for flight. A number of other leafrollers in the Lepidoptera family Tortricidae are common in California. These endemic leafrollers vary in importance with crop and region of the state. Leafrollers do not generally cause significant damage to strawberries, but they can be a problem when they feed on fruit and when there are high larval populations. The damage caused by larvae feeding is typically superficial and not deep within fruit. Because there is no tolerance for LBAM in fruit, the importance of detecting, identifying, and controlling leafrollers is critical, especially within quarantine areas, because it is very difficult to differentiate between endemic species and light brown apple moth. Common Leafrollers in Strawberry Production The presence of light brown apple moth in California makes it important to recognize the presence of egg masses or larvae of all leafrollers, and to understand their biology. Like the light brown apple moth, adults of all endemic leafrollers hold their wings over their abdomen when at rest, and all have protruding mouthparts that resemble a snout. Most moths of these species are about 0.4 to 0.5 inch (10-12mm) long. However, their color patterns differ. All lay their eggs in flat, tightly packed masses. Leafroller eggs are pale white to green, and cannot be distinguished from those of the light brown apple moth. Newly hatched larvae are less than 0.06 inch (1.5mm) long, and mature larvae of most species are about 0.60 to 0.75 inch (15-18mm) long and are not easily distinguished from one another. 2
The common leafrollers share life cycles and have feeding patterns similar to each other and to the light brown apple moth. The emerging larva builds a silken shelter in a rolled leaf, between leaves, or between leaves and fruit (Figure 3). Foliar injury is usually minor; the primary concern is their presence in fruit. Following are some comparison photos and descriptions of endemic leafrollers common to strawberry-growing areas. Figure 3. A leafroller larva and webbing in a curled leaf Garden tortrix, Ptycholoma peritana The forewings of garden tortrix are tan and marked with a dark brown diagonal stripe and a marginal spot producing a chevron pattern when at rest. The anterior edge of the brown stripe is bordered by a faint whitish line. This characteristic, and the overall lighter color, distinguishes adult garden tortrix from the adult orange tortrix. It is also somewhat smaller, about 0.25 inch (7mm) long (Figure 4). Figure 4. Garden tortrix adult Larvae have light brown-green bodies and light brown heads. The head has a small, distinct dark brown spot on each side. Mature larvae are about 0.5 inch (12mm) long (Figure 5). Figure 5. Garden tortrix larva 3
Apple pandemis: Pandemis pyrusana The forewings of apple pandemis are light brown to rust in color, and banded, with the center band on the forewings edged in white (Figure 6). Apple pandemis larvae are green with yellowish green or strawcolored head (Figure 7). Figure 6. Apple pandemis adult Figure 7. Apple pandemis larva Orange tortrix: Argyrotaenia citrana Orange tortrix moths have light brown to orange-brown forewings with a V-shaped marking at the center of each wing (Figure 8). Figure 8. Orange tortrix adults and egg mass 4
Orange tortrix larvae generally have straw-colored to pale green bodies with a yellowish-brown head and prothoracic shield which is adjacent to the head (Figure 9). They closely resemble LBAM larvae. This is often the most common leafroller found on berry crops in the central coast region. Figure 9. Orange tortrix larva Omnivorous leafroller: Platynoto sultana The omnivorous leafroller is not found in the cooler coastal areas, but rather in warmer parts of the inland valleys, the Central Valley and southern California. The forewings of omnivorous leafroller moths are dark, rusty brown on the upper half, and tan on the lower half. A darker colored band extends outward on the resting moth from the middle of the wings in a V-shaped pattern that separates dark and light areas (Figure 10). Figure 10. Omnivorous leafroller adult Omnivorous leafroller larvae resemble orange tortrix but have small, white tubercles with bristles arising along the back and sides of their body (Figure 11). Figure 11. Omnivorous leafroller larva Other Lepidoptera Larvae Other Lepidoptera larvae that might be confused with light brown apple moth include beet armyworm, tomato fruitworm, and cutworms. However, these members of the Lepidoptera family Noctuidae, have a much different adult, egg and larval appearance, and different feeding habits. These species are fruit feeding pests and are more common than 5
any of the leafrollers. Photographs and guidelines for management of these pests on strawberries can be found on the UC Statewide IPM Program website: http://www. ipm.ucdavis.edu/pmg/selectnewpest.strawberry.html and in the UCIPM manual IPM For Strawberries which is available at county UC Cooperative Extension offices. Monitoring and Control Since it is difficult to distinguish the larvae of light brown apple moth from endemic leafrollers, special care should be taken to keep all leafrollers from contaminating fruit, baskets or boxes, and keep any leaves or other materials that might harbor leafrollers out of the pack. Use of a LBAM pheromone trap as previously described can help detect the presence of adults in an area. We have found the greatest moth densities within quarantine areas to occur near urban areas where they infest ornamental and landscape plants that are seldom, if ever, treated with insecticides. Nearby fields are at greatest risk. Begin a monitoring program by examining leaves for leafroller egg masses and larvae, especially the characteristic webbing together of leaf surfaces. Younger, more supple leaves are most likely to be infested. Destroy any fruit with evidence of larval feeding. Several chemicals are registered for use for Lepidoptera control on strawberries which are also effective for LBAM. These include Bacillus thuringiensis kurstaki (various formulations of Bt), spinosad (Entrust and Success), spirotetramat (Radiant), methoxyfenozide (Intrepid), and bifenthrin (Brigade). Organic growers can use approved formulations of Bt and spinosad (Entrust). However, additional care may be needed to prevent infestations of the light brown apple moth in organic production fields since other insect pests are not being managed with conventional products that would incidentally control the light brown apple moth. Second year production fields should be closely monitored and plowed under if abandoned during the season to prevent them from becoming a potential source for light brown apple moth infestations. Established caneberry and blueberry plantings are also potential sources if they have not been recently treated for LBAM or other insects. Organically-approved LBAM pheromone products are now registered for mating disruption, but current products may be difficult to apply in strawberry plantings. Our research has shown that the application of 25 g or less per acre of the actual pheromone per acre will not completely prevent males from being captured in pheromone traps, so a greater rate should always be used. Mating disruption of moths is not recommended on fields less than 10 acres in size. Please consult your pest control adviser for further information and recommendations. Photo credits: Light brown apple moth adult: Provided by I.F. Smith Light brown apple moth larva and other leafrollers: Provided by UC Statewide IPM Program, Jack Kelly Clark, photographer. Copyright by the Regents, University of California California Strawberry Commission P.O. Box 269 Watsonville, CA 95077 p. 831.724.1301 f. 831.724.5973 www.calstrawberry.com 2010 California Strawberry Commission 6