On Crops: Asparagus (vegetable only – not ornamental asparagus)
All areas where asparagus is grown
Slender, elongated beetles, black in colour with six white or yellow spots on their wing cases and a distinctive dark red thorax. These small beetles are around 6-8mm in length. Their larvae are greyish-green and soft-bodied, resembling miniature slugs.
These beetles (adults and larvae) emerge and chew notches in asparagus spears, causing them to become crooked. As the season progresses, larvae feed on asparagus foliage.
Remove old fronds and weeds from the asparagus patch in early winter and compost in an active compost pile. Asparagus beetles can overwinter in dead asparagus foliage.
There are two generations of asparagus beetle between May and September. Both adults and larvae can also be removed by hand and dropped into a bucket of water. Other creatures such as beneficial wasps and poultry can also help keep these insects under control. Organic insecticides containing pyrethrum can be used where it is not feasible to remove beetles by hand, but avoid spraying when plants are in flower so as not to harm beneficial insects.
Removing debris from autumn through winter forces the beetles to hibernate in the soil, where they are often eaten by other predators and thus will not threaten your crop in the spring. Attentive harvesting and cleaning of early spears will keep many asparagus beetle eggs from hatching.