The spotted asparagus beetle (Crioceris duodecimpunctata) is a reddish-orange beetle with twelve black spots on its wing covers, found exclusively on asparagus plants. Unlike its close relative the common asparagus beetle, which feeds heavily on spears and ferns, the spotted asparagus beetle targets asparagus berries. It’s generally the less destructive of the two species, but it still weakens plants and can reduce yields over time if left unchecked.
How to Identify Spotted Asparagus Beetles
Spotted asparagus beetles are about a quarter inch long with a distinctive reddish-orange body and six black spots on each wing cover, totaling twelve. Their appearance is quite different from the common asparagus beetle, which has a dark, metallic blue-black body with cream-colored or yellowish spots and red borders on its wing covers. If the beetle on your asparagus is orange with black dots, it’s the spotted species. If it looks dark and shiny with light-colored markings, that’s the common asparagus beetle.
The larvae also look different between the two species. Common asparagus beetle larvae are dark, slug-like grubs found on ferns and stems. Spotted asparagus beetle larvae are orange to yellowish and typically found inside asparagus berries rather than on the plant’s surface, making them easy to miss entirely.
What Spotted Asparagus Beetles Feed On
Adults feed on asparagus foliage, but the real damage from this species comes from the larvae. Spotted asparagus beetle larvae appear just before or during berry formation, bore into developing berries, and eat the pulp and seeds inside. A single larva can destroy three to four berries before dropping to the soil to pupate. This makes the spotted species most active and damaging later in the growing season, well after the spring harvest period when the common asparagus beetle causes its worst problems.
Because spotted asparagus beetles focus on berries rather than spears, they rarely affect the edible harvest directly. The concern is cumulative plant health. Heavy feeding on ferns and berries weakens plants over the season, and that weakness shows up as poor yields the following spring. Damaged plants also become more susceptible to disease. For home gardeners harvesting spears, the spotted asparagus beetle is the less urgent pest, but ignoring it year after year takes a toll on your asparagus bed’s productivity.
Life Cycle and Seasonal Timing
Adult spotted asparagus beetles overwinter in garden debris, especially old asparagus ferns left standing through the winter. They emerge in spring as temperatures warm and are most active during afternoon hours when sunlight and temperatures peak. After mating, females lay eggs on asparagus foliage. Those eggs hatch in 3 to 8 days, and the larvae feed for several weeks before dropping to the ground and pupating just below the soil surface.
New adults emerge in 1 to 2 weeks after pupation, and the cycle repeats. In warm climates, there can be up to five generations per year, meaning populations build through the growing season. By late summer, when berries are forming, spotted asparagus beetle numbers are often at their highest. This aligns perfectly with when their preferred food source, the berries, becomes available.
Cultural Controls That Actually Work
The single most effective thing you can do is clean up your asparagus patch in fall. Remove ferns once they’ve turned completely brown, and take them out of the growing area entirely. This eliminates the sheltered overwintering sites beetles depend on. If snow arrives before your ferns die back, get them removed as early as possible the following spring. This one habit disrupts the beetle’s life cycle at its most vulnerable point, when overwintering adults have no alternative shelter.
Floating row covers placed over asparagus beds in early spring keep emerging beetles off the spears. Remove the covers after harvest is complete. For spotted asparagus beetles specifically, removing berry-producing female asparagus plants (asparagus is dioecious, meaning plants are either male or female) eliminates the larvae’s primary food source. Many modern asparagus varieties are all-male for this reason, which has the added benefit of making your patch less attractive to spotted asparagus beetles.
In small gardens, handpicking works well. Drop adults and larvae into a pail of soapy water. Check your plants regularly, since new adults can fly in from neighboring areas. Remove any dark brown eggs you spot standing on end on the spears or foliage.
Natural Enemies
A tiny parasitic wasp called Tetrastichus asparagi is the most important natural predator of asparagus beetles. These wasps attack beetle eggs in two ways: they feed directly on the eggs, killing them, and they also lay their own eggs inside surviving beetle eggs. The immature wasps then grow inside the beetle larvae and kill them when they pupate. Studies have found that over 50% of beetle eggs are killed by wasp feeding alone, with half the surviving larvae also parasitized.
You can encourage these beneficial wasps by planting umbrella-shaped flowers (like dill, fennel, or Queen Anne’s lace) near your asparagus beds, which provide nectar the wasps need. Another strategy is to clean up the asparagus patch in fall but leave field edges and borders undisturbed. This forces overwintering beetles out to the margins where ground-dwelling predators are more likely to find them.
Spotted vs. Common: Which One to Worry About
If you’re growing asparagus for eating, the common asparagus beetle is the bigger threat. It feeds directly on spears during harvest season, causing browning, scarring, and distorted growth. Its larvae chew on stems and ferns and can defoliate plants. The black fluid (insect feces) it leaves on spears makes them unappetizing even when the physical damage is minor.
The spotted asparagus beetle is more of a long-term problem. Its berry-focused feeding doesn’t ruin your current harvest, but it degrades plant vigor over successive seasons. In practice, both species often show up together in the same asparagus patch, and the same control strategies, fall cleanup, handpicking, row covers, and encouraging parasitic wasps, work against both. If you’re managing one, you’re managing the other.