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Asparagus Beetle

Closer Look Of The Asparagus beetleThe most common asparagus beetle is about 1/4 inch long, slightly green legs and antennae, red thorax, metallic blue to black head, and wing covers with yellow to cream patches and red borders. A second type, the spotted asparagus beetle, is slightly larger and looks to be more destructive. The spotted adults are reddish-orange in color with black antennae, and each wing cover has six distinct black or dark spots. The first (common asparagus) beetle is the more significant pest of the two for home gardens.

Feeding on the spears by both species will normally cause scarring and browning, making them both un-sellable and not particularly appealing. And serious defoliation of the asparagus can impair the plant's ability to provide proper nutrients for a good crop for the next growing season. Both beetles can overwinter as adults and begin feeding first thing in spring. The asparagus beetle emerges somewhat earlier than the spotted beetle. Both insects are native to Europe but are now found throughout the USA.


Adult Asparagus BeetleAdults overwinter, in a pupa stage, in sheltered locations such as debris piles, loose tree bark or dead plant material, appearing just as the asparagus spears emerge in spring. There can be two or more generations per year, depending on climate and moisture conditions, and will ‘play dead’ when disturbed, rather than fly away. Adults can consume leaves and can scar the spears, making them look terrible, but cause little damage after late spring.


Asparagus Beetle EggsThe bullet-like eggs are about 1/25 inch long, oval in shape and olive to dark brown in color. They are deposited – cemented is a better word - either singly or in rows of three to eight, most commonly on the spear itself, and hatch in about a week. They are almost impossible to remove without damaging the spear, making the spears unmarketable.


Asparagus Beetle LarvaeThe larva are plump, humpbacked and sluggish, about 1/3 inch long, are olive-green to darkish gray, sometimes orange or cream colored, with a black head and legs, and feed for about two weeks or so, molting thru four instars, then falling to the soil to construct a silken cocoon to pupate. If weather conditions are right, adults emerge to start another generation in about a week or two.


Asparagus Beetle PupaPupa are protected by tough silken cocoons embedded with soil particles and are light yellow, and resembling the adults except for immature development of the wings. If temperatures and sunlight are good, they will mature into adults in one or two weeks, otherwise they will try to overwinter and emerge next spring. This last generation of beetles is usually smaller than the previous ones.

Vegetables That Asparagus Beetles Like To Eat



A small 1/8 inch green wasp will parasitize asparagus beetle eggs, as will lady beetle larvae (don’t confuse the lady beetles with the spotted asparagus beetles!). Trimming shoots just below ground level every two days during the cutting season will remove most eggs before the larvae can establish themselves in your garden. Handpicking can control most beetles and using a small broom to knock the larvae to the ground also is effective, as the larvae have difficulty climbing back on the plant.

The insecticides neem and most pyrethrums, as well as carbaryl are effective when the insects are young. A good spraying with insecticidal soap, especially one that knocks the insects to the ground is also effective in home gardens. Dusting with bone meal or rock phosphate is also said to be effective. Remember that most insecticides will also kill beneficial predators and parasites.

Floating Row Cover Over The Cabbage PlantsClean up the asparagus bed in fall of all debris, and try to till the soil somewhat to wake up the pupa and cause them to expire in the cold weather. Using floating row covers (see picture at left) in the early spring can help prevent new infestations. (See Bill's Projects for making your own row cover supports)

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