Asparagus Beetles are a significant pest of asparagus (*Asparagus officinalis*), primarily attacking both the spears (the harvested portion) and the mature ferns (which are essential for future growth). There are two main species: the **Common Asparagus Beetle** (*Crioceris asparagi*) and the **Spotted Asparagus Beetle** (*Crioceris duodecimpunctata*). Both beetles are native to Europe but have been introduced and established in North America, where they cause widespread damage in commercial and home asparagus patches.
Taxonomy and Classification
Asparagus Beetles belong to the family Chrysomelidae (leaf beetles) in the order Coleoptera. They are phytophagous (plant-feeding) insects. Both the common and spotted species are classified under the genus *Crioceris*. They undergo complete metamorphosis and are specifically adapted to feed exclusively on asparagus plants and related plants in the *Asparagus* genus.
Physical Description
The **Common Asparagus Beetle** is about 6–8 millimeters long, possessing a glossy, dark bluish-black body. Its most distinctive markings are three large, square, yellowish-white spots or blocks on each wing cover (elytron), and a reddish-orange border. The head is also reddish-orange.
The **Spotted Asparagus Beetle** is similar in size but is reddish-orange overall, with six distinct black spots on each wing cover (totaling 12 spots). The larvae of the common beetle are gray-green and slug-like, while the larvae of the spotted beetle are yellowish-orange. Both larvae have black heads and three pairs of legs near the head.
Distribution and Habitat
These beetles are found throughout most regions where commercial asparagus is grown in Europe, North America, and parts of Asia. Their habitat is strictly the asparagus patch. They overwinter as adults in the crowns of the asparagus plants, in hollow stalks, or in plant debris near the crowns, emerging in the spring as the spears begin to emerge.
Behavior and Life Cycle
Asparagus beetles typically have two to five generations per year, depending on the climate. Adults emerge in spring to feed on the tender spears and mate. Females lay dark, slender eggs either individually (spotted beetle) or in rows of 2–8 eggs (common beetle) on the spears or ferns.
The larvae hatch, feed externally on the plant tissue for several weeks, and then drop to the soil to pupate in earthen cells. The Common Asparagus Beetle larvae feed on the ferns and spears, while the Spotted Asparagus Beetle larvae burrow into and feed on the seeds inside the asparagus berries, making the spotted species a particular problem for seed production.
Feeding and Damage
Damage occurs at three stages: **Adult feeding** on young spears causes cosmetic damage (scars, browned tips) that makes the spears unmarketable. **Larval feeding** on the mature ferns later in the season defoliates the plant, stripping the needles (cladophylls). Since the ferns are vital for photosynthesis, this defoliation severely reduces the energy stored in the crown, leading to lower yields the following spring.
Additionally, the common beetle lays black eggs glued to the spears, which, even if cleaned, reduce the marketability of the crop. The spotted beetle’s larvae damage the seed crop by feeding inside the berries.
Management and Prevention
Management involves a combination of cultural and chemical controls. In the spring, **frequent harvesting** (every 2-3 days) removes eggs laid on the spears. After the harvest season ends, when the ferns grow, **scouting for eggs and larvae** is essential. Physical control can be used in small patches by hand-picking adults and washing off larvae with a strong stream of water.
Chemical control (using approved insecticides) is generally targeted at the *post-harvest* fern stage, protecting the plant when it is storing energy for the next year’s crop. Cleaning up old plant debris and volunteer asparagus in the fall also reduces overwintering sites.
Conservation and Research
Asparagus Beetles are common agricultural pests. Research focuses on developing systemic insecticides that protect the ferns without interfering with the edible spears, and on utilizing natural enemies, particularly tiny **parasitic wasps** (*Tetrastichus asparagi*) that attack the larval and egg stages of the common asparagus beetle.