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Massachusetts IPM Berry Blast
March 28, 2015
Winter Moth Basics for 2015
Sonia Schloemann, UMass Extension
Winter Moth ( Operophtera brumata): This is a new and important pest of blueberries, apples and other deciduous plants, especially in Southeastern New England. They can severely defoliate trees and bushes. Moths emerge from the soil usually in late November and may be active into January. The male moths are light brown to tan in color and all four wings are fringed with small elongate scales that give the hind margins a hairy or fringed appearance. The female is gray, almost wingless (brachypterous) and, therefore, cannot fly. Females are usually found at the base of trees or scurrying up tree trunks. Winter moth caterpillars are pale green caterpillars with a white longitudinal stripe running down both sides of the body. They are “loopers” or “inchworms” and have just 2 pairs of prolegs. At maturity, the caterpillars will be approximately one inch long, whereupon they drop to the soil for pupation. Pupation occurs from late May into early June. Winter moth caterpillars are often found in association with both the fall and spring cankerworms, which look and have similar feeding patterns to the winter moth caterpillar.
 
Life Cycle: After mating, the female deposits eggs loosely in bark crevices, under bark scales, under lichen, or elsewhere. The adult moths then die and the eggs over- winter. Eggs are dark-colored at first but turn orange within 3-4 weeks. In late-March or early-April, just prior to hatching, they turn red and eventually a deep, shiny blue. Eggs hatch when temperatures average around 55 ̊F. It is believed that egg hatch in Massachusetts occurs when approximately 177-239 GDD above a base of 40˚ F (starting Jan 1) have accumulated, which is historically during the second week in April but later if temperatures are atypically colder, depending. This means that egg hatch occurs just at or right before bud break of most of the host plants. After hatching, the larvae wriggle between bud scales of newly swelling buds of such hosts as: maples, oaks, ash, apples, crabapples, blueberry, cherries, etc. and begin feeding.
See http://www.yourweekendview.com/outlook/agriculture/growing-degree-days/ to calculate the Growing Degree Days for your location. Good bio-indicators are flowering red maples and green tip on Macintosh apples. See http://extension.umass.edu/fruitadvisor/2014-bud-stages for apple. This year, models suggest that we will reach egg hatch after April 15, 2014. Pinpointing a date is too risky now, but another alert will be sent out in a week to update the forecast.
 
Photo credit: Heather Faubert, URI from 2012
Damage: Caterpillars feed within both flower and foliar buds. Once a bud has been devoured from within, the caterpillar will migrate to other buds and repeat the process. Destruction of the flower buds leads to greatly diminished harvest on fruit crops. Older larvae feed in expanding leaf clusters and are capable of defoliating trees and other plants, when abundant.
Management: A dormant oil spray to the trunks and branches of bushes may be helpful to kill the overwintering eggs before they hatch. However, some eggs are under bark flaps and loose lichen and may be protected from oil sprays. Insecticides sprays timed to coincide with egg hatch are the most effective way of controlling this pest. The timing is important because if the newly hatched caterpillars are allowed to crawl inside the expanding buds, they are protected from any insecticide that might be applied. So, sprays should be applied within a day or two of egg hatch (approximately 220 GDD base 40˚F). Caterpillars may also invade host plants by ballooning onto them after treatment has been applied. Several insecticides are labeled for use against either Winter Moth or Spanworm or both and are outlined in the table below.
Additional information can also be found at: http://extension.umass.edu/landscape/fact-sheets/winter-moth-overview
Blueberry Bud Stage
Image and Description Source: Michigan State University Blueberry Facts website. |
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Dormant
Description: No visible swelling of the fruit buds. Bud scales tightly closed. No visible signs of growth. |
Bud Swell
Description: First sign of growth as plant growth begins in the spring. Visible swelling of the flower buds; outer bud scales begin to separate at the tip revealing paler interior bud scales. This bud stage can usually tolerate cold temperatures of 10 - 15⁰F. |
Budbreak-Green tip
Description: Flower buds open and the individual flowers can be seen between the bud scales. Can tolerate cold temperatures of about 20⁰F. |
Recommendation for Controlling Winter Moth or Spanworm |
Dormant oil, 2-2.5%
plus
Esteem 35WP, 5 oz/A or
Confirm 2F, 16 oz /A or
Asana XL, 4.8-9.6 oz/A |
Dormant oil, 2-2.5%
plus
Confirm 2F, 16 oz/A or
Delegate 3-7 oz/A or
Assail 70WP, 1.9-2.3 oz/A or
Asana XL, 4.8-9.6 oz/A or
Esteem 35WP, 5 oz/A |
NO OIL AFTER BUDSWELL
Confirm 2F, 16 oz or
Delegate 3-7 oz/A or
Asana XL, 4.8-9.6 oz or
Esteem 35WP, 5 oz |
Winter moth in Southern New England 2015
Heather Faubert, University of Rhode Island Cooperative Extension
We expect winter moth eggs to start hatching in Southern New England in early to mid April. The average date of egg hatch in RI is April 10. The hatching date depends on future Spring weather. Last November, I set up tree wraps at 5 locations: three in RI, one in Pawcatuck, CT and one in Acushnet, MA. The tree wraps encouraged female winter moths to lay eggs just below the tree wraps. Over the next week I'll remove all the tree wraps and look for eggs to monitor. I removed the tree wraps at URI last week and found hundreds of eggs to monitor. Winter moth eggs start out orange, but then turn blue a few days before hatching. Very handy for monitoring egg hatch!
For landscape trees it's not important to control winter moth just when hatching, but for apple and blueberry growers it's very important. Once eggs hatch, winter moth caterpillars wriggle into swollen buds and begin feeding. For apple trees and blueberry bushes, swollen buds are primarily flower buds and once caterpillars are inside buds they are protected from insecticide sprays until just before bloom. By this time many flowers may have been damaged or destroyed, destroying the crop. Landscape trees, on the other hand, can withstand early winter moth feeding damage. To save trees from being defoliated, insecticides can be applied after trees leaf-out, but before excessive feeding damage has occurred.
Dormant oil can be sprayed before eggs hatch, but this may not be very effective if there are unsprayed trees near where you are applying dormant oil. Winter moth caterpillars are pretty easy to kill, provided they are not inside closed buds.
Insecticide choices for newly hatched caterpillars for blueberry and apple growers include, but are not limited to, spinosad (Delegate), imidan, sevin, and synthetic pyrethroids such as Asana. Adding a dormant oil may be useful for the first spray. Once buds are open, B.t. kurstaki products (Bacillus thuringiensis kurstaki) such as DiPel and Biobit work well. For landscape trees, winter moth caterpillars can be controlled once trees leaf out with spinosad (Conserve), B.t. kurstaki (Dipel Pro, Javelin, and others), as well as synthetic pyrethroids such as bifenthrin.
Winter moth caterpillars continue to feed and grow until around the end of May. Once mature they drop to the ground, dig down a few inches, and pupate. Pupae will remain in the soil until November or December when winter moths emerge as adults. It's male moths that more and more Rhode Islanders are seeing at their porch lights and headlights, especially on warm evenings between Thanksgiving and Christmas. Females are rarely seen because they don't fly.
In collaboration with Joe Elkinton from UMass, we have released a parasitic fly that attacks only winter moth caterpillars. The fly, Cyzenis albicans, has successfully controlled winter moth outbreaks in Nova Scotia in the 1950's and the Pacific Northwest in the 1970's. Cyzenis albicans lay eggs on leaves of winter moth host plants. When eating leaves, winter moth caterpillars accidentally eat fly eggs too. A fly egg hatches and the larva develops inside a caterpillar body. When a parasitized caterpillar drops to pupate, it digs into the soil but instead of a winter moth caterpillar pupating, the fly pupates instead. The fly pupa remains in the soil until the following spring when it emerges as an adult fly at the same time winter moth eggs hatch.
Parasitic flies have been released in Massachusetts since 2006 and in Rhode Island since 2011. In Massachusetts, some of the early release sites are already seeing winter moth populations decline due to high rates of parasitism. In Rhode Island, we recovered flies for the first time in 2014 in Goddard Park. In a few years we hope to start seeing winter moth controlled by Cyzenis albicans. (March 16, 2015)
Archived IPM Berry Blasts are available at the UMass Extension Fruitadvisor website.
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