One day, you’re happily growing gooseberries or currants, dreaming of munching into those tart treats, visions of preserves, pies, smoothies, or sun-warmed fruits in your mind. Then you take a bite and you meet with an unpleasant surprise inside.
What happened?
One culprit could be the currant fruit fly and its ravenous offspring. Currant fruit flies lay eggs that hatch into larvae, and these larvae eat the flesh of currants and gooseberries. Learn how to identify and address these pests.
What Are Currant Fruit Flies?
Currant fruit flies (Epochra canadensis syn. Euphranta canadensis) are small flying insects in the family Tephritidae. Native to North America, these flies are primarily found in regions where currants, gooseberries, and other Ribes species are grown.
There are numerous species of fruit flies that attack most types of fruit. But currant fruit flies stick to Ribes fruits. They prefer red, black, or white currants, but gooseberries are an acceptable second choice.
These fruit flies cause endless problems, both in the home garden and commercial orchards.
The issues arise from the adult’s feeding habits and where the females lay the eggs. Left unchecked, fruit crops can be completely devastated.
Characteristics and Habitat
Currant fruit flies measure about a third of an inch long and are typically yellow to brown in color. They have very dramatic red bulbous eyes and black bars in otherwise translucent wings.
Once mature, they can reproduce rapidly. They’re extremely agile movers, able to spread easily from plant to plant.
Currant fruit flies favor warm and humid weather of temperatures between 60-80 °F. They also prefer areas with abundant vegetation and shelter. This, combined with ripe and soft fruit, is this pest’s idea of heaven.
The larvae’s feeding inside the flesh reduces the quality and usability of the crop. Most people don’t want to bite into a fruit that has wriggling maggots inside.
Lifecycle
The lifecycle of currant fruit flies is influenced by environmental factors. In warmer climates, the lifecycle may be shorter, with more generations occurring in a single growing season. Colder climates will have fewer generations.
It all starts with the adult female laying eggs on currants or gooseberries.
The female inserts eggs into the body of the fruit just under the skin’s surface. She looks for breaks or splits in the skin or overripe fruit. Typically, she will lay one or two eggs per fruit to maximize the success of the next generation of the larvae.
One mature female currant fruit fly may lay up to 200 eggs. In perfect conditions, eggs will hatch within days of being laid. When they hatch, a larva emerges, eating the berry’s pulp and demolishing it from the inside out.
These larvae are small, white to yellowish maggots with hook-like mouthparts that they use to feed. Each larva must transform through two instar stages and be developed enough to become a pupa via a third form of instar.
Typically, the currant fruit fly egg to larvae to pupae process only takes eight days.
Once the larvae are mature and ready for that third instar change, they will drop down onto the soil and burrow in. If conditions in the soil are not suitable, they will crawl to a drier location.
To become an adult, the maggot larvae sheds its head, mouth, cuticle, spiracles, and hooks to pupate. This is a non-feeding stage.
Currant fruit flies pupate using a chemical reaction in which the larvae skin darkens and hardens, forming its cocoon shell. The larvae stay in their protective casing for six to ten days, during which time they completely metamorphose into their last-stage form.
If a generation reaches the pupae stage late in the season, it may enter a period of dormancy to await the new spring and better conditions.
When adults emerge, they aren’t automatically able to reproduce. It takes two days to fully mature. Once ready, the adult females may mate with several males and store a range of their sperm for use later.
A day after mating, the female will begin laying her eggs, and the lifecycle of the next generation of currant fruit flies will begin.
Signs of a Fruit Fly Infestation
Currant fruit flies are at their peak numbers during the summer months, starting in June or July, but can stay longer if the climate allows for a longer breeding season. You want to catch the flies before they lay eggs. Once they do, it’s too late.
Look for the following signs:
1. Fruit Damage
One of the most obvious signs of currant fruit flies is damage to the fruit itself. Infested fruits may show puncture marks or small oval-shaped entry holes where the females have laid eggs.
The fruit may become discolored, misshapen, and appear to be rotting on the plant. This rotting is a clear sign that the eggs have hatched and larvae are developing.
2. Larvae Presence
Of course, the presence of larvae is a certain sign that you’re facing currant fruit flies. On close inspection when cutting open the fruit, you might see tiny white maggots wriggling inside.
In extreme cases of an infestation, most of the ripening fruit can be affected so the visual indication that there is a problem will be obvious. This is especially so once you’ve picked the fruit and found maggots inside.
3. Premature Fruit Drop
Early fruit drop is another common sign of the presence of currant fruit flies. As the larvae feed, the berry becomes damaged, and the bush aborts the fruit. The fruit can be young, mature, or over-ripe and rotten. It all depends on the plant.
4. Adult Fly Activity
Keep an eye out for adult currant fruit flies hovering around your plants, especially in those warmer months when the berries are forming.
If the plant is disturbed, a cloud of tiny flies will hover around the plant. It might be a ton of flies or just a few, but if you see them at all, it’s a sign to act.
5. Diseased Fruits
Damage to the skin, which is the protective layer of the fruit, leaves it open to disease problems. Fungal growth, discoloration, or rotting could be a sign that there are currant fruit flies lurking.
As the infested fruit decays, it may become a breeding ground for mold and fungal growth.
Control and Management of Fruit Flies
In your arsenal of weapons against this miniature nightmare, you may want to consider a combination of tactics.
1. Monitoring
Monitoring for populations of currant fruit flies is essential. You can’t avoid an attack if you don’t know the adults have arrived. Once they do, you need to be able to assess the level of infestation and determine the best management strategies.
Check your plants regularly to look for adults. You can also hang yellow sticky traps. The adults will stick to these, and you can be certain they’re present. Then, you can create a targeted approach to stop further damage.
2. Timing
Understanding the life cycle of the currant fruit fly is important in determining the optimal timing for control measures.
Control measures should be implemented before the flies lay their eggs on the fruits. Once they do, it’s too late to save your fruit. You might be able to get rid of some of the adults and save some of the fruits, but once the eggs are laid, the fruit is ruined.
Your local extension office will usually be able to tell you when the adults will emerge in your area, or you can simply take note one year and be prepared for the next.
3. Garden Hygiene
Maintaining good garden hygiene needs to be at the heart of the prevention plan where the currant fruit flies are concerned.
These pests can hide in weeds and like areas that are overgrown with lots of shelter. If you keep weeds far away and maintain proper pruning of your plants, currant fruit flies will be less likely to make a home in your garden.
You should also remove fallen fruits and plant debris, as this can help interrupt their lifecycle by disrupting the burrowing larvae or existing pupae.
4. Traps
Positioning traps around susceptible plants is a good method for reducing their numbers and also as a monitoring device. You won’t be able to stop an infestation with traps alone, but it lets you know how many adults are around and reduces numbers slightly.
Yellow sticky traps, gnat traps, or fruit fly traps can all work. You can even make your own fruit fly traps at home. Grab a wide necked glass canning jar, some aluminum foil, apple cider vinegar, and liquid dish soap. Then:
- Pour a half cup of the vinegar into the jar.
- Add 2-3 drops of liquid soap. This makes it so the insects can’t float on the surface.
- Cut two pieces of foil big enough to cover the jar neck.
- Place the foil pieces on top of each other
- Secure the foil pieces onto the jar neck with twine or rubber band.
- Using a toothpick or small skewer, pierce a few holes in the foil.
- Place the trap in the garden next to or under your bushes.
This trap entices the currant fruit flies into it, but the foil lid prevents their escape.
5. Floating Row Covers
Floating row covers are your secret weapon in the battle against currant fruit flies. If you prevent the adults from being able to access the plants in the first place, you don’t have to worry about the larvae in the fruits.
Don’t use these covers if an infestation has already begun. You’ll just trap all those hungry flies in with your crops while protecting them from predators. Definitely not the right solution.
You should also be sure that there aren’t any larvae hiding out in the soil when you place the row covers. You don’t want them emerging and making a nice home in there with your plants.
6. Biological Control
Encouraging natural predators to live in your garden and putting your poultry to work is always smart. Birds like swallows, warblers, swifts, cedar waxwings, spiders, frogs, dragonflies, and other insect lovers will make quick work of the adults, eggs, and larvae.
If you’re raising chickens, ducks, guinea fowl, peafowl, or other poultry, let them wander through your plants. Just keep netting around the berries as they ripen, or you might find your birds nibbling in the fruits, and not just the flies.
7. Treatments
Should an infestation be so severe that you can’t seem to reduce the population of currant fruit flies, you might need to use pesticide treatments.
Always try more natural remedies and sprays first, as chemicals can harm beneficial insects and upset the balance of your garden environment.
Start with pyrethrin-based sprays, spinosad, or neem oil. Use these once a week as long as you see the adults present. If that doesn’t work, you can try products containing zeta-cypermethrin, bifenthrin, carbaryl, or fenpropathrin.
Any chemical treatments need to be applied in the evening and when there is no wind to avoid harming beneficial insects.
