- Spot Bugs That Look Like Blueberries
- The Viral Bug Video
- Identifying the Bugs That Look Like Blueberries
- Finding Blueberry Pests
- 3 Tips on How to Find Infestation Areas
- Don’t mistake Indianmeal moths for maggots
- Recognizing Insect Larval Types
- I Accidentally Ate Maggots. Now What?
- What Are Blueberry Maggots: Learn About Maggots In Blueberries
- What are Blueberry Maggots?
- Monitoring for Blueberry Maggot Identification
- Managing Blueberry Maggots
- Cooperative Extension: Maine Wild Blueberries
- 201-Monitoring for the Blueberry Maggot (Rhagoletis mendax Curran)
- Blueberry Maggot
Spot Bugs That Look Like Blueberries
Have you ever seen a bug that resembled something entirely different? It’s easy to identify the common small creatures in your garden — there are the ladybird beetles and the bumblebees. But what about the bugs that look like blueberries?
The Viral Bug Video
Back in August 2017, the Internet became temporarily fixated on several bugs located on the side of a house in Houston, Texas. The Houston Chronicle noted that the owner was Mandy Trichell, who had three kids.
One of her children, a 17-year-old girl named Faye, spotted six peculiar bugs in their property during the last week of July. Faye called her mom to check out the bugs as well, and Mandy was intrigued.
She was interested in how they moved. The bugs seemed to have a formation and knew when to stop moving at the same time. Eager to find out what exactly the bugs were, Mandy recorded a video and posted it on Facebook.
You can check out her video right here:
Her friends convinced her to publicize the video, which made it gain more than a million views. Still, all this attention didn’t help identify the bugs until Mandy looked for an expert.
Identifying the Bugs That Look Like Blueberries
Eventually, Mandy decided to seek the assistance of Texas Invasives, a partnership dedicated to handling invasive plants and pests in the state. According to them, the bugs she recorded were called Homaemus proteus — a kind of shield-backed bug.
Specifically, those blueberry-looking bugs were still in the nymph stage. This meant that they were quite young and they would still undergo metamorphosis. Upon becoming adults, the bugs will no longer be mistaken for blueberries that can crawl.
The bugs are part of the Scuttelleridae family. Species in this group are also known as jewel bugs because of their colorful appearance. In the case of the Homaemus proteus, its once dark appearance will become a mix of brown and yellow after the metamorphosis.
Finding Blueberry Pests
Speaking of bugs that look like blueberries, what about the actual small creatures that like to linger around your blueberry plants?
Blueberry Bud Mites
These creatures not only eat blueberries but they also live in them. They are typically located in the eastern region of North America and are so small that you have to use a microscope to see them — but you won’t always need such equipment to know that they’re around.
A severe infestation of blueberry bud mites is characterized by red blisters on the blueberry buds. The scales along with the leaf and floral section are all targets of these tiny insects. If nothing is done, entire buds can get killed in just two weeks.
As its name implies, this caterpillar mainly fees on feeds on the azalea flowering shrubs. However, it’s also found on red oak, apples, and blueberries.
Thus, it’s important to note that not all caterpillars in your garden will become highly beneficial butterflies. This one is black with broken yellowish stripes and has reddish legs — and it can destroy the leaves of your blueberry plants.
But while you’d need to apply pesticide on a big population of Azalea caterpillars, you can simply get rid of them by hand if they are few in number.
In the end, it matters to pay attention to the creatures in your garden. Identifying bugs and insects help you understand whether they are beneficial or harmful to your plants. Plus, there’s nothing wrong with learning a new bug species that looks like a blueberry.
If you have any questions or suggestions, feel free to send us a comment.
Blueberry is a crown forming, woody, perennial shrub in the family Ericaceae grown for its fruits, or berries, of the same name. The blueberry plant possesses oval or elliptical leaves which grow alternately on the stems. The stems, or twigs, are yellow/green in color and turn reddish in winter. Flowers are bell shaped and can be either white or pink, occurring in clusters of 8 to 10 flowers. Berries are blue to black in color and 0.6–1.3 cm (0.25–0.5 in) in size. Lowbush blueberry plants (including Vaccinium angustifolium) are smaller in stature, reaching heights of 35 to 60 cm (13.8–23.6 in) and with proper management can produce fruit for between 40 and 50 years. Lowbush blueberries are also sometimes referred to as Maine, New Hampshire or wild blueberry and are native to eastern/central Canada and northeastern United States. Highbush blueberries (including Vaccinium corymbosum) are generally 2–3 m (6.6–9.8 ft) in height but can reach up to 5 m (16.4 ft) and may also be referred to as huckleberry or swamp blueberry. Highbush blueberry accounts for most of the commercial production of blueberry fruit and is also native only to North America.
Blueberry fruit on bush
Flooded blueberry bog
Blueberry blossoms ‹ ×
Blueberries can be eaten fresh or can be dried or baked for further processing. Frozen or pureed berries are commonly used to make jams and preserves and baked goods. Lowbush blueberry is commonly used to make wine.
Lowbush blueberry grows best in well-drained, acidic soils with a pH between 4.5 and 4.8 and should be planted in early Spring as purchased plants or as “plugs” (a small cutting, including root, from an established bush). The newly planted blueberry should be covered in a couple of inches of mulch to conserve moisture in the soil. Any flowers produced by the plants should be removed for at least one year after planting to promote vigor and new growth. Plants should be pruned by cutting close to the ground and a pruned plant will not produce any fruit in the first year, but in the second year subsequent to pruning their should be a good yield. Growth can be stimulated by field-burning, as these plants are very fire-tolerant. Highbush blueberry can be propagated from seeds, cuttings from an established plant or bare root and should be planted in late Fall. Blueberry plants grow best in well drained, highly acidic soils with a pH between 4.5 and 5.8. The plants have a shallow root system and should be planted in a hole at least twice as large as the existing root system and mulched with a 7-10 cm (3-4 in) layer of organic mulch. The first year of blossom should be removed to encourage new growth and it is also recommended to do the same in the second year. Plants should be pruned annually, particularly after the first two years, to promote plant vigour and remove diseased or broken canes. Irrigation is recommended due to the shallow root system and greatly promotes the fruit yield this practice is highly recommended if growing commercially.
CABI Crop Protection Compendium. (2008). Vaccinium datasheet. Available at: http://www.cabi.org/cpc/datasheet/55994. . Paid subscription required. Caruso, F. L. & Ramsdell, D. C. (1995). Compendium of Blueberry and Cranberry Diseases. American Phytopathological Society Press. Available at: http://www.apsnet.org/apsstore/shopapspress/Pages/41736.aspx. Available for purchase from APS Press. Lord, W. (2001). Growing Highbush Blueberries. University of New Hampshire Cooperative Extension. Available at: http://extension.unh.edu/resources/files/Resource000578_Rep600.pdf. / Free to access. Lord, W. (2013). Wild New Hampshire Blueberries. University of New Hampshire Cooperative Extension. Available at: http://extension.unh.edu/resources/files/resource001686_rep2265.pdf. / Free to access. Nelson, G. & Davis, K. (2002). Highbush Blueberry Vaccinium corymbosum L.. United States Department of Agriculture & Natural Resources Conservation Service Plant Fact Sheet. Available at: http://plants.usda.gov/factsheet/pdf/fs_vaco.pdf. / Free to access.
White Worms Crawling Up the Walls!
By Chris Williams on November 21, 2012.
For the last few days, I have been finding white worms crawling around my kitchen. They’re about ½ inch long. I’ve probably found about 20 of them and they’re starting to freak me out. Can you tell me what they are and what they’re doing?
If the “worms” are limited to your kitchen and are crawling up walls and along ceilings, it’s a good bet that they are Indianmeal moth larvae. The other white worms (in that size range) that can be found in kitchens are fly maggots, but those do not have legs. Maggots wiggle along; they can’t crawl. Indianmeal moth larvae have a brown head while fly larvae have no noticeable head. Indianmeal moth larvae have the typical caterpillar shape, but they are small (about ½ inch long, as you said) and almost hairless. You should have a pest control company confirm the identification though.
The reason the larvae are crawling around your kitchen is that they are fully grown and are looking for protected places to pupate so they can turn into adult moths. They have the habit of leaving the food in which they have been feeding (probably on your kitchen shelves or in the pantry) when ready to pupate. They usually crawl upward, often ending up in a wall/ceiling corner or a crack, where they spin a silken cocoon. Sometimes they will pupate at the top of the same cabinet where they have been feeding, or even in the food material itself.
The tricky part, once you have confirmed that they are Indianmeal moth larvae, is finding out where they came from. You’ll probably need a pest control expert’s help here, too, since Indianmeal moth larvae can feed on many different things and you may have multiple infested sites.
3 Tips on How to Find Infestation Areas
Here are a few tips on how to find the moth larvae infestation sites:
- Check “old” foods first, those boxes and bags that are rarely used, have been on the back of the shelf for a long time, or are past their use-by date. Keep in mind that Indianmeal moths can be found infesting even unopened packages.
- The most common infestation site for Indianmeal moth larvae in homes is dry pet food, which may or may not be stored in the kitchen. Other most likely food sources are coarse-milled grain products like cornmeal (Indian meal), wheat or graham four, or cereals.
- Infested foods will be covered with irregular silken webbing spun by the feeding larvae. You may also find larvae, shed skins, droppings, even adult moths in the food package. If you think about it, you might realize that you have been seeing some small moths fluttering around near your kitchen.
Even after you find and discard the infested foods, there’s the chance that adult moths may have laid eggs in other food products. So any susceptible foods should be thrown out or at least stored in airtight containers. Your pest control technician can treat shelves and other areas to kill any new larvae that may hatch, and can advise you on how to “moth-proof” your kitchen and pantry.
If you have any of the above problems, contact Colonial Pest for a free quote, or call us at 1-800-525-8084 right now!
Don’t mistake Indianmeal moths for maggots
By: Dr. William H. Robinson
As an online “Dear Abby” for homeowners and their pest problems, I have come across a couple letters that go like this:
Dear Dr. Robinson,
This morning, I found little, white larvae-like, crawly things all over my kitchen floor. I thought they might be maggots because I had chicken bones in the garbage…
Dear Dr. Robinson,
I have small moths about three-eighths of an inch long, and arrow-shaped when they are resting; and I have little white worms with a dark head in my cabinets, and crawling on the ceiling…
Both of these customers have Indianmeal moths. This is the one of the most common insects in stored food in households, and yet one of the most unrecognized of all pests. They are found throughout the country — and the world — in residential and commercial food stores. There are several generations a year, but they seem to be noticed more often in the fall and winter months.
The habits of the caterpillars and moths annoy homeowners. The full-grown caterpillars migrate a short distance (during the day) away from the infestation site before forming the pupa, and the moths fly (but not very well) in early evening. So, infestations are usually evident day and night by the presence of moths and caterpillars. There may be noticeable peaks in abundance, but generally, there are a few caterpillars or moths out all year.
However, the descriptions provided by homeowners are often a mix of useful and misleading information. For example, the caterpillars are often thought to be maggots (as in fly maggots), and at times Indianmeal moth caterpillars may be in kitchen locations that would otherwise have fly maggots. The link to the Indianmeal moth is the “dark head” on the caterpillar, and the fact that the critters are crawling on walls and the ceiling (something not done by maggots).
Moths do not always fly near the infestation, just as caterpillars move off the site. Moths may be fluttering in rooms away from the food source and, once separated from kitchens and pantry, they are often suspected as clothes moths. The link to an Indianmeal moth is the “arrow shape” and coloration that is half gray and half dark brown. Clothes moths are uniform gray and slender moths that don’t fly far or well from their infestation site.
Dear Dr. Robinson,
The pest management technician who came to spray said that the Indianmeal moths probably had built a nest somewhere. We cleaned out all our cabinets and pantry, but don’t see any type of nest…
This letter is a good example of how the wrong information can mislead and misdirect people and treatment efforts! The idea that all insects make “nests” is common—ants do it, so cockroaches must (wrong!); wasps do it, so flies must also (wrong!); and Indianmeal moths don’t do it! Large numbers of caterpillars may be on infested food, but it is not a nest. Also, by looking for an obvious nest site, infested food material may be overlooked. Technicians should be trained to be careful of what they say about an infestation. The wrong information can lead to continued frustration.
What is the best treatment strategy? Like most household pests, finding the source is the key to success. For most residential and commercial sites, the source will be easily found—dry pet food, bird seed, cake mix, chocolate, dried fruit or a few forgotten pieces of Halloween or holiday candy. Sometimes, though, the food source is in the back of the cabinet (or clothes closet) in a box of cereal that shows no outward sign of being infested.
Keep in mind, it is not enough to find and remove the source. The site should be vacuumed to remove food debris and any stray caterpillars.
Even after all this, there may be some continued problems unless you explain some features of the life cycle. Moths live for about three weeks, and during that time they may fly about the house. They are usually active a few hours after sundown, and can be seen flying from wall to wall, and resting on walls and ceilings—generally making a pest of themselves, and making your service look bad! The infestation source and the caterpillars may be removed, but moths will remain. One or two pheromone-based sticky traps can help. Yes, they only attract males, but they can help to reduce the few moths that may linger after the clean-up.
Recognizing Insect Larval Types
ENTFACT-017: Recognizing Insect Larval Types | Download PDF
by Lee Townsend, Extension Entomologist
University of Kentucky College of Agriculture
Insects develop from egg to adult in a process called metamorphosis which may be generally classified as either gradual or complete. Gradual metamorphosis has three stages – egg, nymph, and adult. Nymphs generally look much like their adult stage except for being smaller and lacking wings, if the species has winged adults. Common examples include stink bugs, grasshoppers, and cockroaches.
About 75% of all insect species go through the four stages of complete metamorphosis – egg, larva, pupa, and adult. The larva is a specialized feeding stage that looks very different from the adult. Fortunately, there are just a few basic larval types and they are relatively easy to recognize. Often, insect identification must be based on the larval stage because no adults are present. Being able to recognize larval types can tell you a lot about the insect, For example, is it a plant feeder, predator, or a scavenger? Are any management or control practices necessary? This publication is designed to help you to follow a series of choices in a process to recognize the basic type of the insect that you have.
Insect Metamorphosis: Gradual (left) and Complete (right)
- Head – usually a dark, often hard capsule at front of body. It may be partly covered by the thorax. In some larvae, a hard or distinct head may be absent or completely hidden.
- Thorax – three segments immediately behind the head. A pair of segmented legs usually is attached to each. These segments may be fused together rather than being separate and distinct.
- Abdomen – eight to 10 body segments immediately following the thorax.
- Segmented thoracic legs – three pairs of segmented or
jointed legs that are found on the body segments immediately behind the head.
- Fleshy legs- usually short, often paired, unsegmented extensions from the underside of the abdomen that are used for movement.
This key is like a path with a series of forks along the way. A choice is made at each fork that will send you toward an answer. The end point will be a drawing of one of the common larval types that should resemble your specimen.
Start- The first decision along the identification path is whether or not the larva has segmented thoracic legs. If it does, you stay on the first section of the key. If it does not, then go to the second page.
SECTION 1: Larvae with segmented thoracic legs and fleshy prolegs
Look at the abdomen for relatively distinct pairs of fleshy legs. Caterpillars (Order Lepidoptera) are immature stages of butterflies and moths; they have 5 or fewer pairs (Box 1). These plant feeders have chewing mouthparts. Often, caterpillars have “hairs”, spines, or distinct coloring. Those with 4 or fewer pairs of these legs are called “loopers” or “inchworms” because of the distinctive way that they crawl.
Larvae with pairs of fleshy legs on all abdominal segments (Box 2) are called sawflies (Order Hymenoptera). They often occur in groups on deciduous trees or evergreens.
Larvae with segmented thoracic legs but no fleshy prolegs
Larval types with segmented thoracic legs but no fleshy abdominal legs are shown in Boxes 3 and 4. These types are found in many species of beetles (Coleoptera) and some lacewings (Neuroptera) The decision at this point is more subjective. Larvae with relatively long thoracic legs and a relatively streamlined, often pointed bodies are shown in Box 3. These predators are active crawlers that hunt prey. Usually, they have a relatively flat heads and prominent forward-pointing jaws. Examples are a) lacewing, b) lady beetle, and c) ground beetle.
Larvae in Box 4 have shorter, thicker thoracic legs, a more box-shaped head, and wider abdomen. They can crawl but tend to be slow and deliberate. Soft, white bodied forms, like the white grub and rootworm, live in protected places while leaf feeders and scavengers tend to have harder, more protected bodies. White grubs (a) often occur in soil, decaying organic matter, rotting logs, etc. Wireworms (b) have hard, cylindrical, bodies. Many species live in soil feeding on seeds or roots or in decaying wood. Rootworm larvae (c) live in the soil and feed on plant roots. Leaf beetle larvae (d), like that of the Colorado potato beetle, resemble caterpillars without fleshy abdominal legs. They feed exposed on foliage. Hairy carpet beetle larva (e) are scavengers that feed on plant and animal products. They may be found in stored products or natural fibers, such as cotton or wool.
Picture Key to Larval Insect Types: Section 1 (click for larger picture)
SECTION 2: Larvae with no segmented thoracic legs
These are highly specialized larvae; most live in water, soil, wood, or in decaying organic matter. Some species have distinct, usually dark heads while others do not.
Legless larvae with distinct heads
Most of these larvae are beetles or flies (Diptera). Each of the pictures represents a larval type.
5 – Weevil grubs can be found in plants, plant tips, seeds, nuts, or with plant roots in the soil. The underside usually is flat while the upper side is rounded, giving them a humpbacked appearance.
6- Midge larvae occur in water or moist organic litter. There is a single fleshy leg at the front and back of the body. They are the immature stages of varies species of gnats.
7- Mosquito larvae (wiggler) are very distinctive. The thorax is wider than the abdomen and many species have a distinct air tube at the end of the abdomen. These larvae live in still water.
8 – Drain fly larva have narrow, strap-like plates across the upper surface. They live in standing,
stagnant water, and especially seldom used drains.
9 – Fungus gnat larvae resemble midge larvae but do not have fleshy legs. They live in moist, decaying
organic matter, especially accumulations of fallen leaves or dead grass.
10 – Soldier fly larva has a flat, gray, palm-shaped body with a distinct tapered head the protrudes from
the front. They are common in compost piles and decaying organic matter.
Head mostly hidden or no distinct head
These larvae either do not have distinct visible heads or the head is withdrawn almost completely into the thorax. They are fly larvae that with one exception live in wet or moist areas.
11 – Crane fly larvae often have fleshy lobes at end of their abdomens. The distinct head is completely hidden within the thorax. These dingy gray larvae live in decaying organic matter.
12 – Rat-tailed maggots have long distinct tails that are extensible breathing tubes which allow them to live in very stagnant water.
13 – Flatheaded wood borers have a distinct wide area behind their heads and a long white, soft body. The dark head is withdrawn into the thorax but part of it usually is visible. These borers live in tree limbs, branches, and stems.
14 – Roundheaded wood borers are similar to flatheaded borers but do not have the wide area behind the head.
15 – Fly maggots have no head and a cream to white body that is distinctly tapered at head and blunt at the rear. Many flies have this larval type including blow flies, house flies, and fruit flies.
16 – Aphid predator maggots are headless, they tend to have green tinged bodies and are found wandering on leaf surfaces where they feed on aphids. They are good crawlers and resemble small caterpillars but lack a distinct head and legs of any sort.
Picture Key to Larval Insect Types: Section 2 (click for larger picture)
There are thousands of variations of these basic forms but it is usually possible recognize its basic features and to place the specimen in one of the main groups. Help with larval identification is available thru your local Cooperative Extension office.
Life cycle drawings are from:
Virginia Tech – Department of Entomology
University of New Mexico – Entomology
CAUTION! Pesticide recommendations in this publication are registered for use in Kentucky, USA ONLY! The use of some products may not be legal in your state or country. Please check with your local county agent or regulatory official before using any pesticide mentioned in this publication.
Of course, ALWAYS READ AND FOLLOW LABEL DIRECTIONS FOR SAFE USE OF ANY PESTICIDE!
Images: University of Kentucky Entomology, except where indicated
I Accidentally Ate Maggots. Now What?
It may be safe to consume maggots themselves, but you may be susceptible to whatever they’ve eaten or been exposed to, such as feces or rotting flesh. Fruit infested with maggots is likely to be rotting and ridden with bacteria. Other risks include the following:
Myiasis is an infection that occurs when maggots infest and feed on the living tissue of animals or humans. It’s most common in tropical and subtropical counties. People who have difficulty maintaining good oral hygiene are particularly at risk. Larvae can settle in areas of the mouth where hygiene is poor.
Eating maggots is also thought to leave the internal organs and tissue susceptible to the larvae, although myiasis is more commonly something that occurs under the skin. The maggots that cause myiasis can live in the stomach and intestines as well as the mouth. This can cause serious tissue damage and requires medical attention.
Myiasis is not contagious. Symptoms of myiasis in your gastrointestinal tract include stomach upset, vomiting, and diarrhea. In the mouth, the larvae are typically visible.
Eating maggots or maggot-infested food can cause bacterial poisoning. Most foods that have maggots aren’t safe to eat, especially if the larvae have been in contact with feces. Some houseflies use animal and human feces as breeding sites. They also breed on garbage or rotting organic material.
It’s possible for maggots to become contaminated with Salmonella enteritidis and Escherichia coli bacteria. Symptoms of an E. coli infection include fever, diarrhea, nausea or vomiting, and cramping. Symptoms of salmonella are similar. Both conditions can also cause bloody stool and fatigue.
Some people may be allergic to maggots. Certain types of larvae have been shown to cause respiratory and asthmatic symptoms in people who handled the larvae to use as live fishing bait or who are occupationally exposed. Contact dermatitis has also been reported.
It’s been suggested that you may have an allergic reaction if you eat larvae that have been exposed to or consumed foods you’re allergic to. Scientific research is needed to clarify this view.
What Are Blueberry Maggots: Learn About Maggots In Blueberries
Blueberry maggots are pests that often go undetected in the landscape until after blueberries are harvested. Tiny, white worms may appear in affected fruits and can spread quickly, ruining your entire year’s harvest. Let’s learn more about blueberry maggot control.
What are Blueberry Maggots?
Blueberry maggots are the larval stage of a 3/16 inch long, black fly marked with black, horizontal bands across its wings. Maggots in blueberries are found across the eastern United States, as well as the Canadian provinces of New Brunswick, Nova Scotia, Ontario and Prince Edward Island. Careful monitoring of your blueberry bushes for adults can aid in swift blueberry maggot identification.
Adult flies appear in the summer, feeding for up to two weeks before they begin searching for mates. Over the next 30 days, females may lay as many as 100 eggs, each in an individual berry. Since eggs can hatch in as few as three days, it’s vital to begin blueberry maggot control as soon as you notice the adult flies lingering on your plants.
Monitoring for Blueberry Maggot Identification
Although maggots in blueberries won’t damage your plants, they will contaminate your harvest, making your fruits suspect for home use and completely unsellable at the Farmers’ Market.
A gardener with a good eye may notice plenty of adult flies buzzing around the blueberries, but experienced gardeners hang yellow sticky cards laced with a hydrolysate- or ammonium acetate-based protein bait around their plants. When the flies land on these cards, they stick permanently, making positive identification simple.
You should always make positive blueberry maggot identification before spraying pesticides of any kind in your garden in order to protect beneficial insect species that may be hunting or foraging nearby.
Managing Blueberry Maggots
Organically-managed blueberries can be protected from infestation of blueberry maggots by coating the berries with kaolin clay or applying spinosad-based sprays liberally to the leaves of blueberries where flowers are just starting to swell into fruit. These safer insecticides leave parasitic wasps, one of the blueberry maggot’s primary enemies, untouched and able to naturally kill many blueberry pests. Spinosad and kaolin must be reapplied weekly throughout the fruiting season, since they break down quickly.
Imidacloprid, a systemic insecticide, can be applied to blueberries early in the season for long-term treatment in many areas. Use this pesticide with great caution, however, and only when your blueberries are overwhelmed year after year with blueberry maggots, since it can poison pollinating bees.
Another strategy for managing blueberry maggots in aging blueberry bushes is to replace your bushes with varieties that have shown that they can resist egg-laying attempts by blueberry maggot adults.
Blueberry varieties “Bluetta,” “Earliblue,” “Herbert” and “Northland” are excellent choices if your blueberry patch is constantly bothered by blueberry maggots. Using these more resistant varieties can reduce the work it takes to harvest useful blueberries and save you money on pest control.
Cooperative Extension: Maine Wild Blueberries
201-Monitoring for the Blueberry Maggot (Rhagoletis mendax Curran)
Fact Sheet No. 201, UMaine Extension No. 5030
Prepared by James Dill, Frank Drummond, and David Yarborough, The University of Maine, Orono, ME 04469. All photographs taken by James Dill. Original prepared by J. Dill, H. W. Forsythe and A. A. Ismail in 1982 as Cooperative Extension Service Fact Sheet No. 201. Revised February 2001.
The blueberry maggot, or blueberry fruit fly, is the major insect pest of blueberries in Maine. The first flies (Figure 1) begin to emerge from the soil in late June or early July. The date of initial fly emergence is dependent upon soil temperature. Emergence will begin to take place in mid-June if spring temperatures have been very hot, but not until mid-July if spring temperatures have been unusually cool. Growers can estimate emergence if daily soil temperatures are measured (see Prediction of Emergence section in this fact sheet for more information).
Flies continue to emerge until early August. After emerging, the flies, which live for about 30 days, and spend one to two weeks feeding on dew, insect honeydew, and secretions on foliage. During this nourishment period, adult females become sexually mature. It is believed that once flies are sexually mature they leave feeding sites and search for fruit. It is at this point that the flies colonize blueberry fields from the outside margins. Mating occurs on the fruit after which mated females seek out ripe blueberries in which to lay eggs. The females only lay a single egg in each fruit and each female can lay up to 100 eggs (infesting up to 100 fruit) in a period of 15 to 25 days.
The female fly punctures the skin of the blueberry with a long pointed structure called an ovipositor which can be withdrawn into the insect’s abdomen. Once the ovipositor is in the berry, a single white elongate egg is deposited. The fly then drags the ovipositor over the surface of the berry leaving behind a chemical called an ovipositing deterring pheromone. This chemical deters other flies from laying an egg in the same berry for a few days.
In seven to ten days the egg hatches and the larva (maggot) begins feeding. The first maggots appear in berries about mid-July. The full-grown larva is whitish in color, is about 7.75 mm (5/16 in.) long, round and pointed at one end and blunt at the other. As the larva feeds and grows, the berry begins to shrivel (Figure 2). After two or three weeks of feeding, the larva becomes full-grown (Figure 3), and the berry is almost completely destroyed. An infestation, if present, increases rapidly to a peak by approximately the second week of August. At this time, many of the larvae begin exiting the berries and dropping onto the soil.
The larvae burrow into the soil to a depth of one to two inches to pupate. The insect spends the fall, winter, and following spring in the soil in this resting stage encased in a tough, brown outer skin called a puparium from which the adult emerges in early summer. In the first year after pupation, approximately 85 percent of the adult insects emerge. In the second year, roughly 10 percent emerged. In the third and fourth years, the remaining 5 percent of the flies emerge. This ensures the survival of the species. If a calamity should befall the population in any given year, some of the pupae would still be in the soil to emerge later.
Figure 1. The first blueberry fruit flies begin to emerge from the soil in late June or early July.Figure 2. The full-grown larva is whitish in color, is about 7.75 mm (5/16 in.) long, round and pointed at one end and blunt at the other.
Figure 3. After two or three weeks of feeding, the larva becomes full-grown and the berry is almost completely destroyed.Figure 4. The female has four white cross-bands. The male has only three white cross-bands.
The female fly is about 4.75 mm (3/16 in.) in length with a wingspan of approximately 8 mm (1/3 in.). The female abdomen is pointed and black with four white cross-bands. The thorax is basically black with a small, backward-pointing, white projection. The two large compound eyes are reddish. The male fly is somewhat smaller than the female and has a rounded abdomen with only three white cross-bands (Figure 4). The wings of both sexes are clear and are marked with characteristic black bands (Figure 5).
Figure 5. There are three other species of fruit flies, including the black cherry fruit fly, the cherry fruit fly, and the Northern walnut husk fly that are found near the edges of blueberry fields in Maine (Figure 5) and that can end up on the traps used to monitor for blueberry maggot flies. Because these three species do not infest blueberries but are attracted to the blueberry maggot fly monitoring traps, it is very important to be able to distinguish blueberry maggot flies from these other species. These flies are distinguished by their wing patterns. The blueberry maggot has a continuous dark wing pattern. The black cherry fruit fly has a small, oval, clear spot in the wing and the cherry fruit fly’s dark wing pattern is not continuous. The Northern walnut husk fly’s wing pattern closely resembles that of the blueberry maggot fly. However, on close inspection, it can be seen that the walnut husk fly’s wing pattern is not continuous, but the outer edge of the wing is black. The Northern walnut husk fly is the least common in Maine, since its host, the black walnut, is uncommon.
The blueberry maggot fly attacks both wild blueberries and cultivated blueberries. This insect has also been reared from huckleberry (Gaylussacia baccata), which may serve as an alternate host.
Type of Trap
Yellow rectangles coated with sticky material and an attractive bait are used for monitoring the blueberry fruit fly. These rectangles can be made and painted by oneself or purchased pre-coated and baited. The pre-coated and baited traps are easier to use and are available from commercial suppliers. If you are interested in purchasing the traps, please see Great Lakes IPM catalog-Ready to Use Kits, Source for Pherocon AM Baited Trap. Tel: 989.268.5693, 989.268.5911, or 800.235.0285.
It is thought that the flies perceive these yellow traps as extra large and attractive foliage covered with insect honeydew, plant sap, or bird excretions, and thus the traps mimic a feeding area for the flies. Also, an ammonium-based bait on the commercial traps aids in luring the flies to traps. Traps without the bait are not as attractive and will not be as effective in monitoring flies invading your field. If you are making your own traps be sure to purchase the ammonium bait to mix in with the sticky coating. Once the flies are attracted to the traps, they are caught in the sticky material (Figure 8).
The traps should be suspended from stakes with the underside 4 to 6 inches above the tips of fruiting blueberry plants. To be most effective and consistent with the action thresholds indicated below, the yellow, rectangular traps should be placed in a position, with the yellow sticky surface directed downward (Figure 6 and Figure 7).
Traps should be placed about 25 feet from the perimeter of the blueberry field, especially facing unmanaged blueberry areas. Put at least one trap into the interior of the field since some flies may emerge within the bearing field. The flies prefer protected areas; therefore, traps should be located one to two feet from bushes or thick patches of weeds. Weedy areas, with sweet fern or barrenberry, are good locations for trap placement.
Use one trap per acre in fields under ten acres. In larger fields, a trap should be placed every few hundred feet along the border. This may figure out to be one trap every two or three acres, depending on the size of the field. There is no strict guideline as to the number of traps per field, but the more traps you set out in a field the less chance there is of missing a major infestation. Do not leave any large portions of your field edge without traps, especially those field edges adjacent to woodlands or pruned fields.
The traps should be replaced every two to three weeks. The trapping surface will degrade as it gets covered with many insects or when the sticky surface becomes weathered. During trapping periods with abundant hard rains or extremely hot days, traps may have to be replaced more frequently (10-14 days). Therefore, three traps will be needed at each trap site to monitor the field throughout the season.
Prediction of Emergence
Fly physiological development in the soil is determined by temperature, therefore, the expected date of initial, middle, and end of fly emergence can be predicted for a given area or field by measuring the daily average soil temperature starting on April 1st. The soil temperature has to be measured one inch below the soil surface. Temperature measuring devices, such as soil thermometers or automated soil temperature thermocouples wired to a waterproof data logger are available commercially. Please contact The University of Maine Cooperative Extension for sources. A computer program is available from Cooperative Extension that will make all the calculations given that you have collected daily soil temperatures and predict when expected emergence should occur. The program only runs on a computer with Windows 95 or higher operating system.
On a calculator, you can easily predict the date for the middle of fly population emergence if you have measured the daily soil temperatures starting on April 1st. The method for calculating this date is based upon the degree-day requirement for emergence. In the laboratory at The University of Maine it has been found that on average, a fly will emerge after having been exposed to enough days of certain temperatures that they have accumulated enough degree-days (ºF). A degree-day is the average daily temperature above a base temperature at which physiological development occurs. The base temperature for blueberry maggot fly physiological development is 43º F. To calculate the number of degree-days that a fly experiences in a day, one must determine the average daily soil temperature and subtract the base temperature. For example, if the soil temperature on May 5 was 73º F then the number of degree-days accumulated on May 5 are:
73º – 43º = 30 degree-days
The degree-days are calculated for each day starting April 1 and added to one another to arrive at the number of accumulated degree days since April 1. If the average temperature is less than the base (43º F) then the number of degree-days is 0 for that day. One keeps doing this until the number of degree-days totaled equals 971. The date when 971 degree-days are reached is when the middle of the fly population emergence is expected to occur.
It is useful to be able to predict this date since you should have put your traps out at this point. The computer program will give you the date when the first fly is expected to emerge, this provides a better date for making sure that your traps will be out just before the flies begin to colonize fruit-bearing fields.
The traps should be placed at the selected sites seven to ten days before anticipated fly emergence. Once the first fly is captured, the traps should be checked every three to four days. After checking a trap, record their numbers and then remove all blueberry fruit flies. If an average of six or more blueberry flies are found on all the traps in a field in a single visit or if an average of the cumulative total of ten flies or more are captured on all the traps in more than one visit, then a decision should be made to treat the field with an insecticide (see Wild Blueberry Fact Sheet No. 209). Remember that flies only lay eggs in ripe fruit. If thresholds are exceeded, but no fruit has ripened in the field, there is no immediate danger of fruit infestation.
Monitoring blueberry fruit flies in individual fields can reveal the approximate time of their emergence. Monitoring information will also show the relative abundance of flies throughout the season. This information can help the grower avoid using insecticides unnecessarily and to properly time any insecticide applications which are used.
In addition, setting out a grid of traps in a field will allow spot insecticide treatment or a field edge perimeter insecticide treatment to be a management option for the blueberry maggot fly (Figure 9). Research at The University of Maine has shown that an entire field does not have to be treated with an insecticide if it is known where the majority of the fly population resides. In small fields of a few acres or less, setting out a grid of traps throughout the field, one trap about every 50 feet (for a 4 by 4 or 16 trap grid) will allow one to manage the field as 16 sub-units (in this example). When the threshold is exceeded for a particular trap, or on a few traps, only the area 25 feet from the trap or traps that have exceeded the threshold need to be treated with a backpack sprayer. This strategy will only work for small fields since a high density of traps is necessary and frequent (every 2 to 3 days) monitoring of the traps needs to be practiced.
A field perimeter treatment can be practiced for larger blueberry fields (Figure 9). As flies colonize a field with ripe berries they travel limited distances (about 10 yards per day) and tend to stay near field edges or weedy portions of fields. Typically, the majority of the fly population remains within 50 feet of the field edge. Therefore, if one sets out a series of trap lines perpendicular to the perimeter of the field (traps at 25, 50, 75, and 150 feet from the field edge), an airblast sprayer can be used for control when thresholds levels of fly captures on the traps are exceeded on the traps 25 feet from the edge. The reason that additional traps are deployed at 50, 75, and 150 feet into the field is to verify that the vast majority of the flies are within the 75 to 80-foot strip that the airblast sprayer will protect.
Information in this publication is provided purely for educational purposes. No responsibility is assumed for any problems associated with the use of products or services mentioned. No endorsement of products or companies is intended, nor is criticism of unnamed products or companies implied.
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Authors: Christelle Guédot and Janet van Zoeren, UW-Madison Entomology
Last Revised: 01/29/2018
Blueberry maggot was first detected in Wisconsin in the summer of 2016 in Adams and Sauk Counties. This pest feeds inside blueberry fruit and caused damage in commercial blueberry production in the eastern and southern United States, as well as in eastern Canada. This insect is expected to eventually have a significant impact on blueberry production in Wisconsin.Appearance: The adult blueberry maggot is a fly that is approximately 3/16 inch long and resembles a small housefly, but with dark bands on its wings. Larvae (or maggots) are legless and can grow up to 5/16 inch in length. Each larva has a single hook-like tooth at its mouth end. Blueberry maggots are very similar in appearance to the closely related apple maggot, with adults of both being virtually identical in size and appearance (including wing patterns). However, apple maggot does not feed on blueberries.
Host Range: Blueberry (Vaccinium corymbosum) is the only commercially-grown fruit crop affected by blueberry maggot. Wild hosts include plant species in the genera Vaccinium and Gaylussacia including wild blueberries, lingonberry, dangleberry, deerberry and huckleberry.
Symptoms and Effects: A single larva feeds inside each fruit causing the berry to become soft as it develops. Damage may go unnoticed until after harvest, when maggots crawl out of fruit and become visible among fresh fruit or in processed blueberry products (e.g., jams, preserves, pie fillings).
Life Cycle: Adult blueberry maggots begin to fly in June or July, and continue to fly through August. Females feed and mate for at least one week before they move to blueberry plants to begin laying eggs. Females lay a single egg under the skin of a nearly ripe blueberry fruit and can lay up to 100 eggs during their approximately one month-long life span. Eggs hatch within one week and damage from larvae generally first appears in mid-July, continuing until blueberries have been harvested. Each maggot feeds in a single blueberry during its two- to three-week development. After completing their development, larvae drop to the ground and overwinter as pupae in the upper few inches of soil. A distinctive characteristic of the blueberry maggot is that, although most pupae develop to form adults by the following spring (completing one generation of the insect in a year), some pupae remain underground and do not mature for two or three years.
Monitoring: Monitor for blueberry maggot adults several weeks before blueberries begin to ripen (usually in early June) using yellow sticky cards impregnated with a feeding attractant (ammonium acetate or ammonium carbonate). You can buy cards that are pretreated with the attractant, or buy the cards and attractant separately and apply the attractant yourself. Fold the sticky cards in a V-shape with the yellow side facing down and put up two traps for every five acres. Because blueberry maggot is currently not widespread in Wisconsin, you can check cards weekly until you find the first adult. After this initial find, check cards every few days. Once you find an average of greater than one adult per trap for several days in a row, begin chemical treatments (see below). Note that the feeding attractant is not specific for blueberry maggot, so you may find other types of flies on the cards – use a hand-lens or magnifying glass to positively identify any blueberry maggot adults. Remember that blueberry maggot and apple maggot look very similar, but that apple maggot does not feed on blueberries, so flies trapped in blueberry fields/patches are most likely to be blueberry maggot.
Once you have detected adults, you can also test fruit for the presence of larvae. Collect 100 berries from throughout your planting. Then break the skins of the berries and mix the berries with a salt-water solution (1 part salt to 4 parts water). Larvae will float to the surface. The number of larvae you find represents the percentage of fruit infested.
Control: Cultural control methods can be useful in preventing blueberry maggot infestations. Remove weeds to eliminate habitat for blueberry maggot. Remove wild blueberry and huckleberry plants as these can serve as alternate hosts for the insect. Harvest fruits thoroughly and heat (to at least 120°F) or freeze any damaged or unusable fruits to kill blueberry maggot larvae. This is particularly important if you compost fruit, because blueberry maggot pupae can readily survive in compost and serve as a source of an infestation in future years. Clean soil thoroughly from equipment or beehives that might be moved between blueberry patches. Blueberry maggot pupae can easily be moved in soil. As noted above, start chemical control once you find an average of greater than one adult blueberry maggot per trap for several days in a row. Alternatively, if you have had a serious problem in the past, you may want to start sprays one week after you trap your first blueberry maggot fly. Continue sprays every seven to 10 days through harvest. Some reduced risk active ingredients, such as novaluron, spinetoram, and spinosad are most effective when used as soon as flies are found in traps. In addition, consider choosing a product that also provides control of spotted wing drosophila, another serious blueberry pest (see University of Wisconsin Garden Facts XHT1237 for details). Spinosyn, spinetoram, diamide, carbamate, pyrethroid, and organophosphate-containing insecticides are effective against both insects. Be sure to rotate use of at least two active ingredients with different modes of action to help delay development of insecticide resistance (see http://www.irac-online.org/modes-of-action/ for details), and be sure consider the effects of sprays on non-target (e.g., beneficial insects). Finally, because you will be spraying ripe berries, pay particular attention to the pre-harvest interval when choosing insecticides. Check the most recent Midwest Fruit Pest Management Guide (see https://learningstore.uwex.edu/Midwest-Fruit-Pest-Management-Guide-2017-P1785.aspx) for complete product recommendations.
For more information on or help diagnosing blueberry maggot: Contact your county Extension agent.
- Blueberry_Maggot PDF
Tags: insects Categories: Fruit Problems, Fruits