How to Fight Asparagus Beetles

by Saffyre Falkenberg

If you’re growing asparagus in your home garden, the asparagus beetle is a pest you will be all too familiar. This annoying insect is about half a centimeter long and is a metallic bluish-black color with white or yellow spots on its back. Its back also has a red border. The larvae are fat, grayish-green grubs with black heads. The eggs of the asparagus beetle are small, brown ovals and will usually be present in abundance.

There is also another species of asparagus beetle known as the spotted asparagus beetle. The spotted asparagus beetle’s body is similar to that of a ladybug’s, but it has a large, red head. The spotted asparagus beetle is still a pest to your asparagus plants, but it only feeds on the asparagus berries, making this type of beetle less of a threat to the plant.

Both the adult and larvae asparagus beetles will eat the leaves off of the asparagus fronds. This behavior will slowly kill the plant, as the asparagus is deprived of its ability to absorb and process sunlight as nutrients. Asparagus beetles will also chew on the stems of the asparagus and lay eggs on them, which will make the asparagus inedible. The larvae will feed on the plants for a few weeks before they falling to the ground and pupate.

Just one year of asparagus crops will oftentimes see two or three generations of the beetles. The adult beetles go into a dormant state underground or in leafy areas during the winter months.

An asparagus beetle infestation can ruin an asparagus crop, which can be very frustrating for gardeners who put so much time and effort into growing their plants. There are many ways a gardener can fight the asparagus beetle at home, using both natural and artificial methods.

1. Physical Removal of Asparagus Beetles

One of the easiest ways to deal with minor asparagus beetle infestations is to physically remove the bugs from the plant. Pick off adult beetles or larvae by hand, and toss them into a bucket filled with soapy water in order to easily kill them.

During this process, make sure to scrape off any of the brown eggs you see on the asparagus spears. This extra step will help break the life cycle. The adults are able to fly, so make sure to check your garden daily.

2. Brushing to Get Rid of Asparagus Beetles

If you don’t want to pick off the insects by hand, you can use a broom or another brush with stiff bristles. Brush over the asparagus plants with this tool, and the stiff bristles will knock adult beetles and larvae to the ground.

Have a bucket of soapy water available to drown the adults. The larvae, once on the ground, will usually not be able to make it back onto a plant.

3. Early Harvest to Control Asparagus Beetles

Another way to break the life cycle of the asparagus beetle is to harvest the spears of asparagus early. Make sure to check the harvested spears for adults, larvae, and eggs, then rinse them down the sink.

On asparagus plants with foliage, there will most likely be adult beetles. Continued early harvesting will discourage the asparagus beetles.

4. Other Insects as Predators of Asparagus Beetles

There are many insects that are natural predators of the asparagus beetle. Ladybugs and lacewings will eat the eggs and small larvae.

There is also a species of small, black wasp that will destroy the asparagus beetle eggs. The wasps lay their own eggs within the eggs of the asparagus beetle during the warm summer months. Earlier in the year, the wasps will also eat the adult beetles. These wasps are not available commercially, but they are naturally attracted to asparagus.

5. Animals to Control Asparagus Beetles

Wild birds and backyard chickens will readily eat the larvae and the adult beetles, both directly off the plant and from the ground. Allowing chickens to forage in the garden over the summer months will easily rid a garden of asparagus beetles without damaging the asparagus plants.

6. Neem Oil to Treat Asparagus Beetles

For extreme infestations of asparagus beetles, neem oil may be your last resort as far as natural options go. Liberally slather the spears in neem oil when it becomes clear that harvesting is not possible. Make sure to apply the neem oil each week to any new spears. Do not use neem oil if the small, black wasps are present.

7. Insecticides for Asparagus Beetles

Only use commercial insecticides as a last resort. Gardeners can spray chemicals, such as pyrethrins, malathion, and permethrin, in order to destroy large infestations of asparagus beetles. These pesticides should not have any long-term effects on your garden. Do not use any pesticides that contain carbaryl, as carbaryl will kill bees and other helpful pollinators. Be very careful with using and storing pesticides; follow the directions on the containers exactly.

8. Clean Garden Area to Prevent Asparagus Beetles

One way to prevent the propagation of the asparagus beetle is to make sure that the garden beds are clean and clear. By doing this, you will be able to prevent the adult beetles from finding places to hibernate during the winter months. Taking preventive action will make sure you’ll have fewer pests around during the new season.

Asparagus beetles can be a huge problem for anyone growing asparagus in their home gardens. The larvae and the adults can both be very damaging to the leaves and the stems of the asparagus plant and can even make harvesting difficult. Many of the methods for getting rid of the asparagus beetle involve physically removing them or relying on other insects and animals to eat the beetles. In the event of a really bad infestation, neem oil or pesticides may be the only way to get the problem under control. Try to catch the problem early, and you’ll be enjoying a bountiful harvest of asparagus from your garden.

Want to learn more about how to prevent and control Asparagus Beetles?

University of Minnesota Extension explores Asparagus Beetles in Home Gardens
Planet Natural covers Asparagus Beetle Control
Gardening Know How explores Controlling Asparagus Beetles
Pennsylvania State University covers Asparagus Beetles
Mother Earth News covers Pest Control: Asparagus Beetles Organic Control