Wireworms attack germinating seeds and roots. However, their favorites are bulbs and tubers, especially potatoes. The yellow-brownish worms, about 1.5 inches (3.81 cm) long, penetrate the potatoes and leave holes as they feed.
Here is a guide on how to get rid of wireworms in potatoes.
- Thoroughly cultivate the top 6-8 inches of soil.
- Weed the area surrounding the garden.
- Avoid using coffee grounds in the potato garden.
- Set up bait balls in the fall and spring seasons.
- Spread diatomaceous earth.
- Plant potatoes in late spring.
- Treat potato seeds before planting.
- Hang bird feeders near the potato garden.
- Set up wireworm traps using cut potatoes or carrots.
- Crop rotation with non-host plants.
- Apply organic insect killers around the garden.
- Use beneficial nematodes when planting potatoes.
- Plant wireworm-resistant potato varieties.
- Spray soil drench insecticides.
- Predict planting period with lowest infestation levels.
- Use click beetle traps.
I’ll discuss the steps to follow in detail. Wireworms are not easy to eradicate, but you can take measures to control their population and the extent of damage to the potatoes. Some of the control measures are ideal before planting.
1. Thoroughly Cultivate the Top 6-8 Inches of Soil
When cultivating, you should make conditions unfavorable for wireworms. If the conditions are ideal, wireworms can survive for 2 – 6 years. The longest stage of its life cycle is the larva stage. However, all stages of the wireworms may be present during the potato growing season.
When cultivating the ground, ensure that you till the soil well, at least the top 6 – 8 inches (15.24 – 20.32 cm). This will expose wireworms to predators, like birds and rodents. Birds feed on exposed wireworms while rodents dig them out. However, they need to be close to the surface for the predators to get to them.
Wireworms are most active when the temperatures rise. They move to the soil’s surface in search of food, warmth, and moisture. However, when temperatures soar to over 80°F (27°C), they will go back deep into the soil, sometimes burrowing to depths of 24 inches (60 cm).
2. Weed the Area Surrounding the Garden
Click beetles (adult wireworms) often emerge from the soil during spring, and once mated, they lay eggs in the grassy areas close to the garden. The eggs hatch after 3 – 7 weeks.
Your potatoes are still at risk of a wireworm infestation if the surrounding environment is ideal for click beetles to lay eggs. Clearing the area around your garden will help control the wireworm population in your garden.
This video gives tips on how to naturally control wireworms.
3. Avoid Using Coffee Grounds in the Potato Garden
Coffee grounds are excellent organic fertilizer. Potatoes thrive in acidic soil, which makes coffee grounds a great addition.
You may be tempted to keep discarding them in the garden, especially if you are a heavy coffee drinker. Unfortunately, coffee granules attract worms, both beneficial and destructive.
If you have been disposing of coffee grounds in the garden, it is best to give them time to decompose. It takes about three months for coffee grounds to decompose. Ensure you look out for wireworm infestations before planting.
4. Set Up Bait Balls in the Fall and Spring Seasons
It isn’t easy to estimate the density of larvae in the soil. However, you can confirm their presence using bait balls. Wireworms will rise to the surface once they sense food is nearby.
You can make the bait balls using;
- 1 – 1.5 cups of wheat flour or oatmeal.
- 2 tablespoons of honey.
- ½ cup of water.
Mix the ingredients, make balls, and put them in mesh bags or cheesecloth. Bury the bait balls 4 – 6 inches (10.16 – 15.24cm) in the soil. It is best to set up the bait balls after cultivating the land or when the warm temperatures force the wireworms closer to the soil’s surface.
Place a mark where you place the balls for easy identification. Spread the bait balls evenly for a better assessment of how big of a wireworm problem you have before planting the potatoes. Ensure you cover each bait station with a plastic bag. Secure the edges with soil. This will restrict the movement of wireworms from the bait area.
Check the baits every 4 -5 days to see if it has attracted worms. If the worms are buried deep in the soil, it may take a while for them to get to the bait balls. If you do not see any wireworms after a week or more, you probably have nothing to worry about.
The ideal threshold is 0.5 – 1.0 live wireworm in every bait station. If too many wireworms are trapped in the balls, then you should consider taking measures to eradicate the wireworms.
Once you use soil drench insecticides or any other recommended wireworm treatment, you should set up a new set of baits at least 2-3 weeks before planting potatoes. This is the best way to tell how effective the treatment was because you can compare infestation levels before and after attempting to get rid of the wireworms.
5. Spread Diatomaceous Earth
Diatomaceous earth is made up of sharp sedimentary rocks that kill insects and pests, including wireworms. The sharp edges make it difficult for wireworms to move through the soil without their soft bodies being cut or penetrated by diatomaceous earth.
The diatomaceous earth will also absorb the oils and fat from the wireworms, causing them to dry out.
This Insecto Food Grade Diatomaceous Earth (available on Amazon.com) is premium quality 100% natural diatomaceous earth that is safe to use. It has no preservatives or fillers. It is an organic solution to a wireworm infestation problem that works quickly and effectively without harming your plants.
6. Plant Potatoes in Late Spring
One of the mistakes people make when planting potatoes is to plant them in early spring when the wireworms come close to the surface. As the weather starts to warm up after the winter season, wireworms start reproducing.
Potatoes are planted 6 – 8 inches (15.24 – 20.32 cm) in the ground. This is about the same depth as wireworms during the warm season. The wireworms will have easy access to the potatoes before they germinate, affecting the yield and quality of potatoes during harvest.
The soil will still be warm in late spring, so there is no harm in waiting. However, the surface soil may be getting too hot for wireworms, so they will go deeper into the ground, where it is cooler.
Their absence from the soil’s surfaces gives potatoes a chance to grow. They may attack tubers as they grow, but the damage may not be as extensive as the damage to potato seeds.
7. Treat Potato Seeds Before Planting
One way to keep wireworms away from your potatoes after planting is by treating the potato seeds before planting. Wireworms move towards germinating seeds because of the carbon dioxide they release.
They then dig tunnels through the potato tubers. Disease-causing organisms then get a chance to infiltrate the potatoes. Some common diseases include dickeya solani, pink eye, and ring rot. When you treat the potato seeds with beneficial nematodes, the wireworms will not be a problem, at least in the time it will take the potatoes to germinate.
Unfortunately, some seed treatments have been phased out over the years because of environmental and toxicological concerns. Beneficial nematodes can protect potato seeds from wireworms organically.
8. Hang Bird Feeders Near the Potato Garden
Once birds find wireworms in the potato garden, they’ll keep coming back for more. However, you can encourage them to camp around your garden using bird feeders. Instead of relying on a few birds which will discover the wireworms by chance, you can attract more birds.
As we’ve discussed earlier, birds are natural predators of wireworms, so they’ll eat any worms that they see on the surface.
9. Set Up Wireworm Traps Using Cut Potatoes or Carrots
You can also set up wireworm traps using potatoes. Since they burrow through tubers, they will do the same to potato baits. Cut potatoes in half and then run a stick in the middle. Bury the potato an inch (2.54 cm) with the cut side facing the ground and the rod standing vertically above the soil.
After a day or two, pull the potatoes out, and discard the worms. You can do this as often as you wish or until you see a reduction in the number of wireworms trapped in the potatoes.
You can also bury whole carrots 3 inches (8 cm) deep. Spread the carrots across the garden and check them after 2-3 days. Just like potatoes, wireworms will burrow into the carrots.
The burrowing activities will help you determine the level of damage to expect if you plant potatoes in your garden’s current state.
This video explains how to set up potato traps for wireworms.
10. Crop Rotation With Non-Host Plants
Alfalfa, onions, sunflower, and buckwheat do not host wireworms. Potatoes, on the other hand, attract wireworms. Planting potatoes season after season will only encourage more wireworms to turn your garden into their home.
Crop rotation will help manage the wireworms. Besides the plants known to repel wireworms, you can also consider planting sugar beets, tomatoes, and corn because these plants have insecticides specially made for insects that attack them.
To get rid of the worms you can use Monterey Garden Insect Spray (available on Amazon.com) which is a fast-acting and odorless insect killer that targets borers, like wireworms, in tomatoes. Other insects targeted include caterpillars, leafminers, and fire ants. It is organic, safe, and easy to use.
Practice crop rotation for at least four years before planting potatoes. By this time, wireworm infestation is expected to be as low as 10%. Avoid rotating potatoes with carrots, grains, pasture, and grasses because wireworms target them.
11. Apply Organic Insect Killers Around the Garden
Organic insect killers will control wireworm infestation in your garden and, at the same time, protect your plants and the soil from long-term damage. The insecticides will target wireworms in the larva and adult stages. It will also discourage adult click beetles from laying eggs.
The MGK PyGanic Pyrethrin Insecticide (available on Amazon.com) targets more than 200 garden pests, including beetles, larva, mites, and ants. Use it on multiple plants, such as potatoes, tomatoes, and peppers. Pyrethrin is a mixture of at least six naturally occurring toxic insecticides.
12. Use Beneficial Nematodes When Planting Potatoes
Beneficial nematodes have become quite popular because they effectively fight pests in the soil. Nematodes will not only feed on wireworms but other insects that may attack the potatoes. The nematodes infiltrate the wireworms and start killing them from within. They are safe for the environment, pets, and plants.
13. Plant Wireworm Tolerant Potato Varieties
No potato variety is entirely resistant to wireworms. However, some are more tolerant, with only a tiny percentage infected.
Here are potato varieties and the level of wireworm infestation in them.
| Potato variety | Wireworm Infestation level |
| Jacqueline Lee | 30% |
| Sagre | 27% |
| Nicola | 24% |
| Mountain Rose | 20% |
| Satina | 20% |
| Red LaSoda | 17% |
| Colorado Rose | 16% |
| Ozette | 13% |
| Cherry Red | 3% |
| VC1009 | 1% |
| AC9531 | 1% |
Potato varieties and wireworm resistance levels
14. Spray Soil Drench Insecticide
You can also control wireworms using a soil drench insecticide. Wireworms love moisture. You can draw them to the soil’s surface by watering your garden deeply. You can then apply a soil drench insecticide. The worms will be eliminated when they come into contact with the insecticide.
You may choose to do this before or during planting season. These insecticides repel wireworms, so you will minimize the damage to the plant when the potatoes start germinating.
15. Predict Planting Period With Lowest Infestation Levels
Another way of controlling wireworms in potatoes is by timing the planting season with a period when the wireworm infestation is low. You can assess the risk of crop damage using soil samples.
The best time to collect soil samples is when the temperatures are at least 50 – 60°F (10°C – 15°C). Wireworms are closer to the soil’s surface at this temperature, so you will have a clear picture of the infestation levels.
Collect the soil samples from different areas of the garden for a more accurate analysis. If you intend to plant potatoes during spring, take soil samples in early spring so that you can tell the risk level. If the soil sample indicates a large concentration of wireworms, the damage to potatoes may be extensive.
A large infestation of wireworms will;
- Penetrate the potato seeds, resulting in a low yield.
- Damage the root system.
- Leave shallow and deep holes in the potatoes.
When you test the soil samples early, you have the chance to take measures to reduce the wireworm infestation. This way, by the time you plant the potatoes, you would have suppressed the wireworm population enough to give the potatoes a chance of a high yield.
Ensure you collect soil samples at least 6 inches (15 cm) deep. Sift the soil with a ¼ inch (6.35 mm) hardware cloth to confirm the number of earthworms per sample.
16. Use Click Beetle Traps
Besides the larva stage (wireworms), the click beetle can also be a challenge for potato gardens. Adult click beetles are not as damaging as the wireworms. They feed on nectar, flowers, pollen, and aphids.
Unfortunately, you have reason to be concerned because the male and female click beetles mate and lay eggs, increasing the likelihood of wireworms in your potato garden. The wireworms remain in the larva stage for years before changing to click beetles.
Click beetles are attracted to lights. You can set up click beetle traps close to the lights near the potato garden.
The Bonide Beetle Bagger (available on Amazon.com) is a dual-action system that uses floral and pheromones to lure click beetles. The disposal bags have an hourglass shape that holds the click beetles once they are trapped. The traps can last an entire season. You can get replacement lures and collection bags as well.
Conclusion
Wireworms are challenging to control because they have a long lifespan. They spend years in the larva stage, which is the most destructive phase. You should use multiple methods simultaneously to control an infestation.
If possible, stop the click beetles from mating and laying eggs. You should also try to get rid of the wireworms or reduce their population significantly before planting potatoes.