Apple Maggot

A4159 Apple Maggot

Annie Deutsch and Christelle Guédot pple maggot, Rhagoletis pomonella Apple maggot flies are differentiated from (Walsh) (Diptera: Tephritidae), is a many other fruit flies by the pattern of significant insect pest of apples. dark bands on their wings which form an AThe fly received its common name based “F” shape pointing towards the back of the on the immature (maggot) stage of body (figure 2). The wing pattern of the development; it is also commonly known blueberry maggot (R. mendax), however, is as railroad worm. Apple maggot is native almost identical, so it may not be possible to eastern North America, and its natural to visually distinguish between the two FIGURE 1. Apple maggot adult. host plant is hawthorn. When early settlers species. It is unlikely that blueberry introduced the domesticated apple in the maggots would be found on traps in 1600s, apple maggot flies took advantage apple orchards unless blueberry is grown of this new food source and began to lay on the farm. (For more information on eggs in apple fruit. Apple maggot was blueberry maggot, see fact sheet XHT1264 Predominantly a first reported as a pest of apples in the https://fyi.uwex.edu/hort/files/2018/02/ 1860s. Currently there are two races of Blueberry_Maggot.pdf.) pest of apples, apple apple maggot flies, one that preferentially Adult apple maggot females lay single feeds on hawthorn and a second that oval-shaped, white eggs that are preferentially feeds on apples. This approximately 0.04 inches (0.09 cm) long, maggot will also divergence has led to genetic evaluation of directly under the skin of fruit. Females live the species as a possible case of speciation, for around 30 days and can lay up to 300 infest pears, apricots, the separation of two new species from a eggs over the course of a lifespan. After single species. 3 to 10 days, the eggs hatch into cream- Although predominantly a pest of apples, colored, legless maggots (larvae) (figure 3). peaches, cherries, apple maggot will also infest pears, apricots, peaches, cherries, crabapples, crabapples, and wild and wild rose hips. Apple maggot is a significant pest in commercial and backyard orchards in most of the United rose hips. States and eastern Canada. In some western U.S. states, there are fruit-growing regions that do not have apple maggot. In some of these areas, counties where the pest is found have been quarantined to prevent further spread of the fly. Identification and FIGURE 3. Apple maggot larva inside a life cycle plum. Apple maggot flies are 0.16–0.24 inches (0.4–0.6 cm) long. The body is mostly The head of the maggot is identifiable by black, with a white triangular dot on the two dark, parallel, hook-shaped jaws, and end of the thorax and white stripes on the the posterior end has two tan-colored abdomen. The fly’s head is brown with spots (spiracles) for respiration. Larvae prominent, dark-red eyes (figure 1). Male proceed through three developmental flies tend to be smaller than females and stages within fruit before they drop to the have three white stripes on their abdomen ground to pupate approximately 20 to 30 FIGURE 2. Apple maggot distinguishing rather than the four stripes found on days after hatching. Full-grown larvae are features. females. 0.3–0.5 inches (0.7–1.2 cm) long. Pupae are APPLE MAGGOT typically found in the top 2 inches of soil, development throughout the growing Apple maggot damage can be and are about 0.2 inches (0.5 cm) long with season, even in areas with significantly differentiated from other apple fruit a yellow-brown color. Pupae overwinter different temperatures. (For more pests in that the brown tunnels are found and the adult flies emerge in early summer. information about calculating degree days, throughout the fruit flesh. Many other Adults are active for 8 to 10 days after see fact sheet XHT1086, https://fyi.uwex. internal feeders, such as codling moth, will emergence before egg-laying begins edu/hort/files/2014/11/Degree-Day- preferentially feed at the central core of the (pre-ovipositional period). Some apple Calculation.pdf.) apple. maggots will spend an additional year as Environmental factors including rain and pupae, remaining in the soil for the winter, soil moisture, as well as soil type and Control next summer, and following winter before topography, can affect the timing and Monitoring emerging as adult flies. may not be well represented in degree Trapping for apple maggot flies is crucial day estimates for apple maggot. Sufficient for controlling this pest. Traps allow for Degree days rainfall is especially important for adult information regarding when adult flies are Similar to other insects, the developmental emergence, and dry conditions may delay emerging from the soil and for estimating rate of apple maggot is dependent on adult hatch by 2 to 3 weeks. For this reason, the population size; both can vary year temperature: warmer temperatures degree day models should not be used in to year as well as at different sites within increase the speed of development, replacement of traps or other monitoring the same year. Additionally, because whereas cooler temperatures can slow tools, but rather to give additional flies are active before egg-laying begins, or inhibit development. Degree days are information regarding the timing for apple knowing when they first emerge allows for a method of using temperature rather maggot adult emergence and the growth a window of time to apply an insecticide, if than calendar date to approximate the stage of the new generation. time of different growth stages. For apple needed, before damage occurs. maggot, degree days are calculated using Traps for apple maggot include a yellow a base temperature of 50°F beginning Damage sticky card and a baited sticky red sphere accumulation at January 1 or March 1. In orchards, apple maggot damages trap. Yellow sticky cards are often baited There are a few models used for tracking only fruit, and if not controlled can cause with ammonium carbonate or ammonium apple maggot development. The Michigan extensive loss. Damaged fruit can become acetate (feeding attractants). A typical bait State University model predicts that distorted and lumpy from inhibited growth for the red sphere trap is a lure containing adult flies typically start emerging from at the site where the female fly laid an synthetically produced apple volatiles. overwintering pupae in the soil at 900 egg under the fruit skin. After the maggot In general, the yellow card trap is more degree days (approximately early July). hatches, it uses its pointed jaws to pierce effective early in the season as the flies The first eggs are laid around 1,100 degree cells in the fruit pulp and then consumes emerge from pupation, giving a better days, peak adult emergence is at 1,400 the juice. It tunnels its way through the estimate of the start of adult activity. The to 1,700 degree days, peak egg-laying is fruit flesh, leaving behind a brown and red sphere traps are much more effective around 1,750 degree days, and the end of rotting trail (hence the name railroad once egg-laying begins because the female adult emergence is around 2,800 degree worm). This damage is usually not apparent flies are seeking fruit on which to lay their days (Angus H. Howitt, Common Tree Fruit unless the fruit is cut open. If multiple eggs (figure 5). (For more information Pests (NCR063) [Michigan State University larvae are feeding inside a single fruit, the about trapping using attractants, see Extension, 1993] pg. 34). These values can damage can be great enough to cause UW-Extension publication Utilizing Insects’ be used to track apple maggot tissue collapse, which may be seen or felt Sense of Smell for Pest Management (A4135) on the outside of the fruit (figure 4). at https://learningstore.uwex.edu/Assets/ pdfs/A4135.pdf.) Adult flies emerge around early July, and traps should be placed outside in mid-June to ensure that the traps are out before the adults start emerging. Hang traps in tree canopies, especially near wooded or landscaped edges. Check traps at least once a week (ideally every day, especially at the beginning of the season), remove any insects, reapply sticky adhesive as needed, and change the lure according to the manufacturer’s recommendations.

FIGURE 4. Apple maggot damage to an apple. 2 UNIVERSITY OF WISCONSIN-EXTENSION Because apple maggot pupates in the Biological control soil, one possible control measure is to Apple maggot is native to the eastern prevent the larvae from reaching the United States, and thus there are native soil. This can be done by placing a tarp, predators present. Parasitoids are the landscape fabric, or thick mulch under most important natural enemies, and a tree to form a barrier. Picking up and researchers have discovered parasitoid destroying all dropped apples may wasps that attack both the egg and larval also reduce populations because many stage of apple maggot. In hawthorn, the damaged apples that contain maggots will fruit is small enough such that the female prematurely fall to the ground. Removing wasp can reach the developing maggot dropped fruit may help reduce populations with her egg-laying appendage, resulting of other insect pests including plum in some level of control. However, apple curculio (see UW-Extension publication fruit are too large, so many parasitoids Plum Curculio (A4160) at https:// cannot attack the maggot. For this learningstore.uwex.edu/Assets/pdfs/ reason, parasitoids have a minimal A4160.pdf). Placing a tarp under the trees effect controlling apple maggot in apple can also assist with collecting the dropped orchards. Other predators of apple maggot fruit. Fallen apples should be picked up include birds, spiders, carabid beetles, as frequently as possible. Composting and ants. These predators do not typically FIGURE 5. Red sticky sphere used for the fruit is not sufficient to kill any larvae reduce apple maggot populations to monitoring apple maggot (attractant inside. bait not shown). non-detrimental levels. While very labor intensive, in backyard Red sphere traps can be purchased, made orchard settings, bagging individual fruit Chemical control by hand from wood or plastic, or made by could also help reduce fruit damage. Insecticides are the main way to control hanging a store-bought apple covered in a Once fruit are ½ to ¾ inch in diameter, apple maggot. After confirming that an sticky substance (e.g., TangleFootTM). they should be thinned, if necessary, insecticide spray is needed (based on trap counts that have reached the action An insecticide application is warranted if and bagged. Plastic bags, for example threshold mentioned in the monitoring there have been a total of five flies caught sandwich baggies, can be tied or stapled section), it is important to determine the per red sphere trap baited with apple at the stem of the fruit, leaving ample best product to use. Factors to consider are volatiles, or one fly caught in an unbaited room inside the bag for the fruit to grow. the stage of fruit development, rotating red or yellow trap. This action threshold Cut two small holes at the lower corners different chemical classes to prevent should be used after each insecticide of the bag to allow condensation to drip insecticide resistance, the product’s application as well as to reevaluate if out. The bag can remain around the fruit residual activity, how effective it is on other another insecticide application is needed. until harvest. Fruit properly sealed in bags apple pests, if it could cause secondary Proper identification is critical because will be protected from apple maggot as pest outbreaks (especially mites) by killing there are other fly species that look well as other insect pests and will likely not beneficial insects, and the preharvest similar (e.g., blueberry maggot, black require additional insecticides. interval (the amount of time required cherry fruit fly, and cherry fruit fly) but In very small orchards or single trees, there between the last application and harvest). will not damage apple fruit. A 10X hand is potential for mass trapping to reduce Timing is also critical because once eggs lens may be necessary to see identifying apple maggot numbers. In this case, the are laid in the fruit, they are protected from characteristics, or the flies can be brought goal is to catch as many flies in the traps insecticides. Insecticide treatments need to a local Extension agent, crop consultant, as possible to reduce the population to target the adult flies before egg-laying. or diagnostic clinic for identification. enough to protect the fruit. Red baited sticky spheres described in the monitoring Insecticides should not be used when Mechanical and cultural controls section should be used for mass trapping, pollinators are present. The potential for controlling apple maggot as they are the most attractive traps for Some insecticides available for use in using mechanical or cultural controls apple maggot. For effective trapping, there commercial conventionally managed or varies depending on orchard size and would need to be a minimum of one trap organic orchards include: pest pressure. In all settings, removing per 50 to 100 fruit hung in the orchard. This • Diamides (e.g., Altacor, Exirel) abandoned apple or crabapple trees near is equivalent to approximately one trap per • Neonicotinoids (e.g., Admire Pro, Actara, the orchard and removing alternate host small tree, two to four for a medium-sized Assail, Belay) trees (ornamental or wild hawthorn) may tree, and six to eight for a large tree. Traps reduce fly numbers. should be in place before adult emergence • Organophosphates (e.g., Imidan) (mid-June) and remain hanging through early September. 3 APPLE MAGGOT

Pyrethroids (e.g., Asana, Baythroid, Danitol, There are a number of products that are Chemical registrations vary by year, state, Leverage, Mustang Maxx, Proaxis, and formulated for apple maggot control in a and crop. For products available for apple Warrior) and the carbamate Sevin are backyard orchard. Some examples are: maggot control, refer to the current year’s typically not recommended because they • Acetamiprid (e.g., Ortho Flower, Fruit, Midwest Fruit Pest Management Guide. can lead to secondary outbreaks of mites. and Vegetable) The publication can be purchased or downloaded for free at https://ag.purdue. An alternative option is kaolin clay • Carbaryl* (e.g., Sevin) (Surround), a fine-powdered mineral clay edu/hla/Hort/Pages/sfg_sprayguide.aspx. • Gamma-cyhalothrin (e.g., Spectracide that is mixed with water to form a physical Before using any insecticide, make sure Triazicide) barrier over the fruit. Surround is allowed to read the entire label as they are legally for use in organic production by the • Kaolin clay (Surround) (OMRI) binding documents. Insecticides are not Organic Materials Review Institute (OMRI) • Permethrin (e.g., Bonide Eight) labeled for use on every crop, and the and is rated to have excellent control regulations can change. The label will give • Pyrethrins (e.g., Ferti-lome Triple Action against apple maggot (Fruit Management directions for proper use, appropriate Plus, Pyganic) (OMRI) Guide [Michigan State University Extension, application rates, required personal 2018], https://shop.msu.edu/product_p/ • Spinosad (e.g., Bonide Captain Jack’s, protective equipment, and preharvest bulletin-e0154.htm). To be effective, the Ferti-lome Spinosad, Monterey Insect interval. Spray) (OMRI) material must be covering the fruit at all Although apple maggot can cause times, requiring frequent reapplications significant losses in an orchard, with proper after rain events or as the fruit grows. It is scouting, timing of treatments, and control also effective in protecting fruit from other measures, damage can be minimal. apple pests such as plum curculio.

*Carbaryl is an effective insecticide for controlling apple maggot, but it should References to pesticide products in this not be used within a month of bloom because it can cause healthy, developing fruit to fall off the tree and lead to secondary outbreaks of other pests. publication are for your convenience and are not an endorsement of one product over other similar products. You are responsible for using pesticides according to the manufacturer’s current label directions. Follow directions exactly to protect people, animals, and the environment from pesticide exposure. Failure to do so violates the law.

Copyright © 2018 by the Board of Regents of the University of Wisconsin System doing business as the division of Cooperative Extension of the University of Wisconsin-Extension. All rights reserved. Authors: Annie Deutsch is the UW-Extension Door County agriculture agent. Christelle Guédot is an assistant professor of entomology at the University of Wisconsin–Madison and a state specialist at UW-Extension. Cooperative Extension publications are subject to peer review. Photo credits: Fig. 1: Joseph Berger, Bugwood.org; fig. 2: drawing by Janet van Zoeren, UW-Extension and UW–Madison; fig. 3: Whitney Cranshaw, Colorado State University, Bugwood.org; fig. 4: H.J. Larsen, Bugwood.org; fig. 5: Dan Mahr, UW–Madison. University of Wisconsin-Extension, Cooperative Extension, in cooperation with the U.S. Department of Agriculture and Wisconsin counties, publishes this information to further the purpose of the May 8 and June 30, 1914, Acts of Congress. An EEO/AA employer, University of Wisconsin-Extension provides equal opportunities in employment and programming, including Title VI, Title IX, and the Americans with Disabilities Act (ADA) requirements. If you have a disability and require this information in an alternative format (Braille, large print, audiotape, etc.), please contact [email protected]. For communicative accommodations in languages other than English, please contact [email protected]. If you would like to submit a copyright request, please contact Cooperative Extension Publishing at 432 N. Lake St., Rm. 227, Madison, WI 53706; [email protected]; or (608) 263-2770 (711 for Relay). This publication is available from your county UW-Extension office (counties.uwex.edu) or from Cooperative Extension Publishing. To order, call toll-free 1-877-947-7827 or visit our website at learningstore.uwex.edu.

Apple Maggot (A4159) I-06-2018 4