Raspberries are a wonderful midsummer fruit. They don’t take up a ton of space and are perfect for small gardens. But, there’s one issue that many gardeners encounter when they go to harvest fruit: Worms.
The small, white worms in raspberries are larvae of the spotted wing drosophila. The adults are small, yellowish brown files. You can get rid of the worms in raspberries by using organic pesticide, choosing an early-ripening variety, attracting beneficial insects, or using a trap.
I’ve written some details below on how you can identify such worms on your raspberries, how to prevent such worms, and how to get rid of them if they do infest your raspberry plants.
How to Get Rid of Raspberry Worms
If you want to have a bountiful harvest, you will need to address serious worm infestations. Here are a couple of methods to get rid of them.
1. Let Them Stay on the Plants
In some cases, getting rid of the tiny larvae is not necessary at all. You have to decide how much fruit you can tolerate losing.
Not all gardeners have to deal with a major infestation. In fact, there are some parts of the world where the Raspberry Beetle is relatively sparse. Populations can grow with time. However, smaller infestations aren’t a major cause for concern.
If the worm problem is minor, it may not be worth doing anything at all. You can let existing worms live on the plant. When you harvest, just toss out any affected fruits.
If the infestation is by the Spotted Wing Drosophila, it’s best to take care of the problem even if there are just a few larvae. They can grow relatively fast and damage the raspberries plants.
2. Pluck Them By Hand
Your second option is to physically remove the worms by hand. You can use a gentle hand or even some tweezers.
This method isn’t very practical if you have a large raspberry garden. But, it works well for single plants.
There are two schools of thought here. If you’re dealing with beetles, the first is to handpick and destroy them. We know that beetles emerge from the soil around April and May. Use this knowledge to be proactive and ready when they start feeding on your plant.
Raspberry Beetles can feed throughout the day. But, they are most active in the early evening. Just pick the beetles off and destroy them. Do this soon after they emerge from the soil and you can get rid of the population before they have a chance to lay eggs.
Another option is to remove the larvae after they hatch. This method may be a bit easier because it addresses both fly and beetle larvae. Adults from both pests always lay eggs in the same spot. Focus your attention on the flowers, buds, and fruit, and you can remove tons of worms before they start burrowing into the fruit.
3. Attract Beneficial Insects
Another great way to get rid of worms is to take advantage of the circle of life. Several beneficial insects eat larvae and other pests.
The Trichogramma Wasp, in particular, uses chemical stimuli to find eggs. Females then drill into existing eggs to deposit her eggs, which kills the original bug before it develops further.
You can attract these bugs, as well as other beneficial insects, with plants. Typically, herbs and umbrella-shaped flowers with pollen are good for attracting good insects.
Place a few plants near your raspberry plants and watch the worm population decline.
4. Till the Ground
As I mentioned earlier, worms continue to feed on fruits until they fall to the ground. After that, they move into the soil for further development. The soil plays an important role in the development of both Raspberry Beetles and Spotted Wing Drosophila flies.
You can disrupt the lifecycle by simply tilling the soil. It’s an old-school method that is surprisingly effective.
Till the soil in the late spring and early summer. This process moves the burrowed larvae up to the surface. There, the larvae are at the whims of birds and predatory insects.
5. Use Plant Odor Traps
A DIY odor trap can help to control small or moderate infestations. This method isn’t the most effective for large worm problems. But, it can help you monitor the issue.
All you need is vinegar or a mixture of sugar and yeast. Pour the vinegar or yeast mixture into a cup and put it near the base of your plant.
When you’re creating the trap, you’ll notice that it has a very strong odor. This is a good thing. The odor is stronger than the raspberries, which will help to attract the flies or beetles. When they go to investigate, they will fall in and drown.
Place traps when your raspberry plant starts to produce fruit. If you’re expecting a large infestation, you can even set it out about a month before the first flowers appear. A second setup at the end of the season can also reduce the worm population for next year.
6. Use Organic Pesticides
Organic pesticides are always a good option. Pesticides can kill off the beetles, flies, and larvae.
The best pesticide to use is Spinosad. Spinosad uses natural soil bacterium, so it’s safe. In fact, the EPA classifies it as a reduced-risk pesticide, which means that small amounts aren’t harmful to humans.
You can also use Pyrethrins or Neem Derivatives. These organic pesticides don’t last very long, so you may need to reapply frequently.
Generally, two applications are all you need. The first should occur when the flower buds are visible. The second should happen after the flower opens. This schedule can limit the adult population of flies and beetles while also taking care of any larvae that manage to survive.
Avoid spraying the pesticide early in the day. Aim for late evening applications so that you don’t accidentally kill bees or beneficial insects.
7. Destroy Infested Fruit
When you see infested berries, pick them off and dispose of them. You can often tell when a berry has worms because of its stunted development and poor overall quality.
Don’t toss the berries in your compost pile. The heat isn’t enough to kill the larvae, so they can still return. Instead, consider feeding them to chickens or bagging them up and tossing them out.
8. Choose Early-Ripening Varieties
There are several raspberry varieties. Most of them are ready to harvest around July. Unfortunately, this blooming timelines lines up to when flies and Raspberry Beetles emerge.
One way to diminish worm issues is to choose early-ripening varieties. By getting a plant that blooms early, you can harvest your crop before the insects are ready to invade.
Your options are pretty limited when it comes to raspberries. But, some cultivars are ready by June. One example is the Prelude Raspberry. You can also find ever-bearing plants or varieties that produce fruit well into the fall and winter season.
9. Refrigerate the Harvest
Here’s a method that you can use to stop larval development in its tracks. When you notice worms on your plant, pick the ripe berries as soon as you can.
Then, pop them in the refrigerator for a day or two. This will stop the development cycle. If you put them in the freezer, the cold temperatures will kill the eggs and larvae completely.
How to Prevent Raspberry Worms
Dealing with worms once you have a major infestation is no easy task. It’s better to be proactive so that you can start controlling the problem before it gets out of hand. Here are some tips to prevent worms from overtaking your raspberry plant.
1. Monitor your plants
The most important thing you can do is keep an eye out for these pests. if you’re not careful, an infestation could occur right under your nose.
Monitor your plants regularly and look out for signs of worm trouble. I’ll get into some common signs a bit later. But generally, monitoring is all about the close examination.
The insect larvae are small. But, they’re not invisible. You can easily see the worms and the parent bugs if you examine your plant regularly.
2. Harvest As Soon As Possible
Raspberries are usually ready to harvest in July. That said, not all of your berries are going to be harvestable at the exact same time. You must pick them when they’re brightly and consistently colored.
Pick off ripe fruits as soon as possible. This will decrease the chances of flies from laying their eggs in the fruit. Ideally, you should be picking off new fruits every day.
Be consistent and don’t let your fruits over-ripen on the vine.
3. Prune The Plants
Don’t let your plants get too dense. Prune them every spring to cut out bulk. Not only will this give your plant more access to sun exposure, but it will also ruin the bugs’ environment.
The larvae thrive in humid soil with a lot of shade. So, bulky plants that protect the soil from the sun is not good.
Regular pruning will keep your raspberry plant in good shape. Plus, it deprives the bugs of the environment they want.
When you prune, make sure to burn the trimmings. While it’s tempting to throw the cuttings in your compost, doing so will only spread the infestation.
4. Keep the Garden Clean
Another thing to avoid is letting your garden get overgrown in the off-season. We’re all guilty of it. Once the plant starts producing, many gardeners move on and stop maintaining the garden. This opens up the floodgates for weeds and bugs to flourish.
Weeds only provide more places for those larvae to hide during the winter. The goal is to prevent the bugs from coming back. So, continue to maintain your garden.
Till the soil. Loosen the dirt with a rake and consider applying some diatomaceous earth. Remove any weeds as they pop up and keep the area around your plant clean.
This continual maintenance can do a lot of things. First, it will expose the larvae to predatory insects or birds. Secondly, it exposes the pests to the elements and takes away the protection they need to come back next year.
5. Cover the Plants
Last, but not least, you can cover the plants. Use agricultural row covers for this technique.
This method will not address any beetles or flies that emerge from the soil. But, it can prevent new populations from moving in. You’re essentially creating a physical barrier to prevent the bugs from laying eggs on the plant.
Keep in mind that row covers can be detrimental to the health of your plant in some cases. The lack of air circulation and buildup of heat could cause some issues. Think long and hard before trying this method and make sure that it’s the best choice for your plant.
How to Check for Raspberry Worms
If you’re not sure if worms are affecting your plants, there are a few ways to check. In many cases, the signs are obvious. While small, the white larvae stand out very well against the rich color of the fruit.
But what if you want to see an infestation before the larvae emerge? Here are a few methods to check.
1. Check For Bud Holes
If you’re dealing with Raspberry Beetles, you can look at flower buds to check for problems. The beetles will chew through the sides of the bud to get inside. This leaves behind a small elliptical-sized hole.
2. Check For Leaf Damage
Beetles will feed on the foliage before they start mating. Look for linear damage or physical holes. Those are telltale signs that you have bugs.
3. Use Traps
Another good method to monitor infestations is to use a trap. You can utilize the odor traps I discussed earlier. Leave the trap at the base of the plant for a day or two. If you’re dealing with bug issues, you’ll likely see a few floating in the trap substance.
Sticky traps work well, too. Place them near the plant and monitor how many bugs it catches.
4. Catch Trays
Here’s an old-fashioned method gardeners use to check for bugs and worms.
Place a few parchment-lined trays at the base of the plant. Then, give the plant a gentle shake. If you’re using a trellis, anchor it down with one foot as you shake.
Bugs on the underside of leaves should fall down onto the tray where you can see them.
What Are Raspberry Worms?
Before you set out to get rid of these pesky worms, it’s a good idea to familiarize yourself with what they are.
Contrary to popular belief, raspberry worms are not technically worms. Instead, they are larvae. Two distinct insect species attack raspberries. These include the Raspberry Beetle and the Spotted Wing Drosophila.
In many cases, the worms you see are the larvae of the Raspberry Beetle (Byturus unicolor). The beetle is very small, measuring only a fifth of an inch in size. You may see them on the leaves or stalks of the plant.
They take on a reddish-brown color. If you’re able to get up close, you’ll also notice they have tiny hairs on the body.
Raspberry Beetles usually appear on plants sometime during the spring. Typically, gardeners will notice them around mid-April to mid-May.
When they invade a plant, the bugs will feed on the surface tissue of plants. With large infestations, you can see these beetles consuming entire leaves or bud clusters.
While it’s alarming at first, the damage isn’t a major problem. For the most part, the feeding cycle is nothing to worry about. The pests are so small and insignificant that the plant doesn’t suffer as much as you would think. However, the results of the mating process are another story.
Adult Raspberry Beetles gravitate towards flower buds and blooms. The insects will mate, leaving behind eggs on the developing fruit. By the time those tiny eggs hatch, the larvae find themselves on a flower or immature fruit.
Because they have nothing else to eat for further development, the larvae burrow into the fruit. They consume the fruit from the inside out. Usually, the larvae will stay inside the fruit as it grows and matures.
Spotted Wing Drosophila
The Spotted Wing Drosophila is an invasive species that attacks soft-skinned fruits. These flies are yellowish-brown in color and feature a black dot on each wing. They’re pretty easy to identify once you see them.
Like Raspberry Beetles, these flies will feed on your plant. But, they don’t eat the leaves. Instead, they consume the fruit directly. When they’re ready to lay eggs, the flies will deposit them into the fruit.
As the larvae emerge, they will continue to feed on the plant as they grow.
The Issue with Pest Larvae
A single worm here and there is no big deal. But problems start to creep up when you have a large infestation of larvae. As the wriggly creatures eat the raspberry, they’re depriving the fruit of the nutrients it needs. As a result, the fruit shrivels up, dies, and falls off. This can severely diminish your harvest.
Not only that, but it’s just setting up a world of trouble the next year. The larvae stay with the fruit even after it falls to the ground. When they’re ready, the larvae will move to the soil and wait to emerge as new Raspberry Beetles or flies the next growing season. It’s a never-ending cycle that can be detrimental to your plant’s fruit production capabilities.