Asparagus Beetle Overview
There are 3 adults beetles that are destructive to Asparagus:
Currently, there is 1 larva that is also destructive:
The C. asparagi larvae burrows into the top portion of the shoot and causes it to die, making the Asparagus unusable.
The adult C. asparagi is a medium-sized body ranging in color from light gray to chestnut brown. It has 13 black dots on its wing covers.
The adult C. saccharalis is a small body with black-tipped antennae and chestnut brown wings that are dotted with 20 black dots.
The adult C. laspidis is a medium-sized body with black-tipped antennae and speckles of black on the body.
The C. laspidis adult is brown and speckled. The speckles on the body can be white, chestnut brown or black, depending on the specimen.
C. saccharalis adults are not harmful.
Types of Asparagus Beetle
Different species of asparagus beetles feed on different hosts, and they will only eat asparagus if they can't find another plant to munch on. Some species are attracted to the color white, so they can settle on eggplants, green beans and their relatives. They eat away at the leaves while the interior of the plant stays unharmed. Other beetles will settle for brussels sprouts, cabbage, broccoli and kale.
Damage usually happens on the underside of the leaves because that's where the white-colored beetles want to feed.
Some adult beetles are attracted to the color yellow, so be sure to plant dill in your vegetable garden. Asparagus beetles aren't good flyers, so they eventually will abandon your crops to fly off for a different source of food. Once they find another food source they tend to leave your asparagus alone. But asparagus beetles are persistent, so you will have to use pest control methods to get rid of the insects and their larvae.
Asparagus Beetle Life Cycle
Asparagus beetles have an interesting life cycle with specific colors signaling each stage.
Asparagus beetles overwinter in the soil in the form of a grub. They emerge in spring and feed on the succulent stems of the asparagus plant. As they feed, they lay eggs in the stems. The eggs hatch and the larvae eat, grow, and continue to lay more eggs in the stems. As summer arrives, the larvae emerge from the stems and pupate. After about two weeks or so, new adults emerge from the pupae and the cycle begins again.
If you are concerned about an asparagus beetle infestation, a thorough visual inspection of your plants in late spring and early summer is the best way to determine if you need to take action.
One way to inspect your asparagus plants is to use a kneewalk or bench walk around the plants. Another way is to use a garden hose to wash the plants off and perform the inspection. Infested stems have diagonal stripes running from the soil to the tip of the shoots. The best time to inspect your asparagus is when it's new shoots are approximately 6 to 8 inches tall.
Common Habitats For Asparagus Beetles
The Asparagus beetle is a ferocious looking beetle. It looks a bit like a roach, and it has six legs. The best defense against asparagus beetles is to know what attracts them.
Thick asparagus stalks are their preferred meals. But they also like to dine on the berries that grow on asparagus plants. If you have a thick seedling bed, they may also try the seeds.
The beetles are fond of more than just asparagus beans and stalks. The beetles also like to eat the entire plant early on in its growth. This can hurt or destroy the growing cycle of many asparagus plants.
Asparagus beetles aggressively chomp their way through the leaves of the asparagus plant, leaving them a mess. The beetles lay their white eggs on leaves and plants.
These eggs will hatch into the larvae you see munching on the plants and producing masses of a white material. This material is their excrement. Your plants won’t last long with these pests munching away at them, and you can find that their excrement is covering your plants, as well.
What Do Asparagus Beetles Eat?
There are many different species of this beetle, and they can cause a great deal of damage to your garden. The larvae that these pests produce are always harmful to your plants.
Asparagus beetles often make their homes in garden borders and beds. They hide in the soil throughout the coldest winter months and often start feasting in March. Asparagus beetles damage the root systems of your plants by feeding on their roots. This can cause fairly significant damage to the underground part of your plants. Asparagus beetles are especially prevalent in the northern states.
Asparagus beetles have wings, and have a characteristic bronze-like hue. They vary in length from one-quarter to three quarters of an inch. The female beetle feeds primarily on asparagus plants, but both male and female beetles are attracted to the plants that they are going to feed on. The beetle will feed on ferns, ground covers, strawberries, and numerous other plants.
How To Get Rid Of Asparagus Beetles
When a gardener tells you he has an asparagus beetle problem, it is likely to be quite a small irritation in the grand scheme of things. When I say “small irritation” that is probably the wrong way to describe the problem.
While asparagus beetles are not a serious pest in warm climates, they can still do a lot of damage. If you decide that you want to grow asparagus, you may have to protect it. There are two main species, the European and the common asparagus beetle. Gardeners in the United States have to deal with the latter, which also lives in Europe, North Africa, and the Middle East.
Asparagus beetle larvae chew up the foliage of the asparagus plant. The grubs eat the plant from the inside out because beetle larvae also feed on plant stems. They prefer the tender growing points of the plant. This weakens the plant, and it slows growth. The adults feed on the leaves, the flowers, and the shoots of the asparagus plant.
The beetles prefer some varieties to others. They feed on all asparagus, but prefer the white variety. The yellow variety is usually not bothered by the beetles.
Organic Asparagus Beetle Control
Before we go into organic control options, it would be wise if we get to know more about bean beetles.
Asparagus beetles belong to the genus Crioceris. These insects are tiny (3 mm is the largest) but they can cause severe damage to asparagus plants. Asparagus beetles come in both black and green colors. Asparagus beetle eggs are laid inside the stems of asparagus plants. Asparagus beetle larvae are grayish-green with 13 segments, a dark head and a prominent white spot on the tail end. When they are ready to go to pupation stage, larvae withdraw into their burrows and turn black. Larvae pupate in these burrows and moths emerge in 30 days.
The adult asparagus beetle's life cycle is influenced by temperature. In the end of May or beginning of June, asparagus beetle population is the highest. They are most active during the day and during hot sunny days.
Environmental Asparagus Beetle Control
The Asparagus beetle is a flying insect with wings that has red coloring on the under side of their legs. Across the tops of the wings, you can notice thin, yellow-colored stripes that separate the wings. The beetles are about a quarter of an inch long and have three-quarter inch antennae.
The adult beetles are as large as the larvae and come in two colors, red and black. Some of the female asparagus beetles have black heads and are able to lay between 270 and 510 eggs in their lifetime. The larvae are what causes the actual damage to the plant.
The eggs are light yellow and once they hatch, the larvae begin to feed on the adult plants. In order for the larvae to develop, they have to feed on the leaves, the flower buds, and even the stems. If the leaves are damaged by the larvae, then the asparagus won’t grow properly and it can attract other insects to the plant.
Preventing Asparagus Beetles
The best way to deal with an infestation of asparagus beetles, is to prevent it. Here are a few steps you can take to make sure your crop is safe:
The best way to prevent an infestation is to plant different varieties of plants alongside the asparagus. This will confuse the beetles as to which is the asparagus and they won’t be able to lay eggs.
You can also plant marigolds, garlic, purslane, and nasturtiums. They are allelopathic, which means that they release a chemical which prevents the growth of other plants.
You can also place pheromone traps around your asparagus bed. These traps attract the beetles. Once they’ve been caught in the trap, they can’t emerge to lay their eggs on your asparagus. The best time to release the beetle traps is when the leaves on the asparagus plants begin to unfurl. This is one of the best times for the beetles to lay their eggs.
Frequently Asked Questions
1 “Asparagus beetles are expensive little buggers who attack the plants I have in my backyard. I have heard they are also very destructive to the rows of asparagus in the ground and therefore I should monitor my vegetable patch regularly. Are they really that dangerous and pricey?”
2 “How can I stop buying asparagus in the stores when I can grow it myself?”
3 “What is Asparagus Beetle control? Is there a way to mitigate the situation?”
4 “What is the life cycle of the asparagus beetle? I want to control their growth at the nymph stage.”
5 “Can I make Asparagus beetle traps to catch them when they first hatch?”
6 “Asparagus beetles are yellow in color. Will their color affect my cooking in any way? Asparagus is healthy, correct?”
Q: I am having problems catching adult beetles. Help!
A: Asparagus beetles are flying adult insects similar to both the common cabbage butterfly and the imported cabbage worm. The adult beetle is somewhat smaller than either of these enemies (picture a brassica head, slice off the top third and you will have about the right scale) and generally light green with orange wings. They feed on asparagus plants, laying eggs 1-3 days after emerging from the ground.
What can you do? The best time for beetle control is during the egg laying period, which is about 3 weeks after emergence in warmer climates. However, it is not too late, even if you don't catch them laying eggs. You can usually catch a few if you go out at dusk and turn off all the lights at night. The beetles don't like the dark and will try to find lights to fly to.
The females are also attracted to fluorescent lights, especially under black light (something to try if you need to take action in the day time). Hand-picking and burying beetles is effective, but if you have large infestations, you may need to use predators such as a beetle eater (lacewing) or a soldier bug. Once the eggs hatch, these predators are of limited use, so if your problem is larvae, you must get them before they grow into adults.
Q: Are there companion plants that repel asparagus beetles?
A: There are many plants that repel asparagus beetles. If you plant them near the affected plants, they will attract beneficials to help fight off the asparagus beetle population. Some good attractants are garlic and mustard seed. To be effective, you must plant these within a couple of weeks of the first asparagus beetle sighting.
Some good repellents are plants such as nasturtiums, marigolds, tansy, and borage. If you plant these plants near the asparagus plants, it will help repel the adult beetles.
Wear a pair of diatomaceous earth shoes if you are worried about the beetles invading.