If you are growing strawberries in your organic garden, eventually, there will pests that arrive to feed on them. While birds are a common annoyance for anyone growing berries, there are also several insect and gastropod pests that can be a problem. The most common strawberry pests are slugs, strawberry bud weevils, tarnished plant bugs, spittlebugs, and strawberry sap bugs. Let's look at organic, non-chemical methods for controlling each.
If you're seeing small, deep holes in the strawberry fruits, usually under the cap, chances are good that you're dealing with slugs. Slugs also leave tell-tale silvery slime trails that can often be seen on the foliage. Slugs generally cause damage at night and are more problematic during damp weather. Methods for controlling slugs include:
- Remove leaves and other plant debris from the area to eliminate hiding places and prevent slug damage.
- Water less frequently, but deeply. This will avoid the constantly wet soil that encourages slugs.
- Trap slugs with a board. During the night, slugs will crawl under the board and cling to it. Just be sure to check the trap each morning and remove any slugs you find, or they'll be right back to eating your strawberries again the next night.
- Use citrus rind traps. Place rinds of oranges, lemons, or limes around the base of your strawberry plants. Slugs are attracted to citrus, and you'll be able to gather up the slugs each morning to dispose of them.
- Lay a barrier of diatomaceous earth (DE), 1 inch wide and 3 inches away from the plant, around the base of plants. DE is a fine powder made of sharp particles of marine organisms. The material is an irritant to the skin of slugs, and they won't cross it. DE must stay dry, and you'll need to replace it after rains.
Strawberry Bud Weevils
Strawberry bud weevils are also sometimes called strawberry clippers. They are about 1/10 inch long and reddish brown in color with black patches on their backs. Like most weevils, they have a pronounced curved snout.
Strawberry bud weevils are a problem in early spring when the adults emerge from overwintering. They use their snouts to puncture the strawberry flower buds and feed on the pollen. Then the females lay a single egg in each bud and girdle the bud to prevent it from opening. This protects their larvae but also destroys any chance of that blossom becoming a berry. These blossoms will usually fall off or hang limply from the plants. The eggs hatch after a week and the adults emerge from the infested blossoms after three to four weeks.
Start checking for weevils as soon as strawberry plants form buds. To combat them:
- Remove any infested buds, as well as any that have fallen to the ground, to prevent the insects from wintering over to infest another year's crop.
- You can spray your plants with insecticidal soap if you see the weevils, but repeated applications may be required. There are no other organic insecticides that work well with bud weevils.
Tarnished Plant Bug
There are several species of tarnished plant bugs in the U.S., with the most common being Lygus lineolaris. Tarnished plant bugs are winged gray, greenish, or brown insects, oval in shape. They have a brassy or "tarnished" color. They are brown mottled with yellow, bronze, or reddish marks and each forewing has a black tip with a yellow triangle. These are very small insects, only about 1/4 inch in size.
The adult females emerge in spring as strawberry flower buds appear when they lay eggs. The nymphs hatch and feed on the blossoms and developing strawberry seeds, resulting in misshapen fruit. To control these pests organically:
- Remove weed and other plant debris near your berry patch to remove egg-laying environments.
- Place white sticky traps around the garden to trap bugs; check them daily to make sure you are not catching beneficial insects.
- Plant pollen-producing plants around the garden, which will attract natural predators of tarnished plant bugs, such as big-eyed bugs, damsel bugs, and pirate bugs.
- Try to keep the garden as weed-free as possible during the blooming and fruiting season. Weeds that tarnished plant bugs feed on include dandelion, chickweed, lamb’s quarters, smartweed, wild mustard, curly doc, and pigweed.
- Check plants at least twice each week before they start blooming for signs of tarnished plant bugs. Insecticidal soap can be used if you see the bugs on your plants.
- Use floating row covers over your strawberry plants. These are best installed right at planting time.
- Any fruit showing damage should also be removed; it will not grow properly.
- Garlic spray will deter insects from feeding and laying eggs.
Spittlebugs are very easy to identify: If you see a clear, bubbly foam at the base of your plants, you have spittlebugs. Spittlebugs are the nymph stage of insects in the Cercopoidea family, which will turn into adults commonly known as froghoppers. The nymphs are tan, brown, or black in color and are only about 1/4 inch in size. The foam is produced by the nymphs as a hiding place and shelter, and this is the symptom most often seen.
Spittlebugs do not often kill a plant, but severe infestations may stunt it. Spittlebugs puncture the stems and feed on the plant's juices. The damage occurs near ground level and results in small berries and weak or stunted plants. To control spittlebugs organically:
- Inspect the plants, and when you see the tell-tale spittle, use a strong stream of water to remove the pests.
- Get rid of old plant material around the plants at the end of the season. Spittlebug eggs overwinter in this garden material, and cleaning up will limit the number of eggs that can rewatch in the spring.
- Cover rows of strawberries with floating row covers in summer to prevent adult insects from laying eggs in your strawberries.
- Use a homemade spray made from garlic or hot pepper mixed with water to spray plants.
- Use neem oil or a citrus-based insecticidal oil to prevent infestations.
- Spray plants with insecticidal soap.
Strawberry Sap Beetles
Strawberry sap beetles are small oval insects, less than 1/8 inch long. They are dark colored, sometimes with yellow or orange spots. The damage to strawberries is caused by adult insects. As the berries begin to ripen in May and June, adult sap beetles attack ripe, nearly ripe, or decaying fruit by boring into the berry and eating a portion. Although the holes are sometimes very small, the injury often introduces rot into the fruit. To control sap beetles organically:
- Pick berries as soon as they are ripe. Sap beetles are drawn to fruit that is over-ripe.
- Clean up fallen fruit from the ground, as decaying berries will attract sap beetles.
- Bait sap beetles by placing containers of stale beer or other overripe fruit, such as banana or melon, in a location well away from the strawberry patch. Discard and replace the bait containers every three or four days.