Potato Beetle

  • Symptoms

  • Trigger

  • Biological Control

  • Chemical Control

  • Preventive Measures

Potato Beetle

Leptinotarsa decemlineata

Insect


In a Nutshell

  • Adult and larvae feed on potato leaves.
  • At high population densities plants can be completely defoliated.
  • Reddish larvae with a beetle-like aspect and two rows of black spots on their sides.
  • Beetles with ten black stripes on their white-brown back wing cover.

Hosts

Potato

Symptoms

Adults and larvae of the colorado potato beetle feed on the edge of leaves and can eventually defoliate the stems. Black excrements can sometimes be observed. Potato tubers exposed to the elements are also eaten occasionally. The adults are yellowish-orange and oval in shape. Their most characteristic feature is the presence of ten black stripes on their white-brown back. The head has a triangular black spot and the thorax has irregular dark markings. The larvae in turn are characterized by their beetle-like aspect, their reddish “skin” and the two rows of black spots that flank their sides.

Trigger

The adult potato beetles overwinter deep in the soil, protected from the sun. They emerge during the spring from the pupae and start to feed on young plants. Females lay orange, elongated oval eggs in groups of 20 to 60 on the underside of the leave. At hatching, the larvae feed almost continuously on leaves. At the end of their development, they drop from the leaves and burrow into the soil where they construct a spherical cell and transform into yellowish pupae.

Biological Control

Apply treatments based on the bacterial insecticide Spinosad. The bacterium Bacillus thuringiensis is also effective against some larval stages. The stink bug Perillus bioculatus and the nematode Pristionchus uniformis also feed on the beetle. The parasitoid wasp Edovum puttleri and the parasitoid fly Myiopharus doryphorae can also help to control of the colorado potato beetle. A number of alternative biological treatments are possible.

Chemical Control

Always consider an integrated approach with preventive measures together with biological treatments if available. Insecticides are commonly used against the potato beetle but resistance can develop rapidly due to the life cycle of the insect. Imidacloprid and neonicotinoids have been used to control populations.

Preventive Measures

Use resilient varieties if available. Plant early to avoid peak populations of the larvae. Use yellow sticky traps to monitor or mass-catch the beetle. Use trenches with 45% slope or plastic/organic mulches. Monitor and pick the beetles by hand or shake them off the plants. Employ companion planting to repel or deter the potato beetle from foraging on potatoes. Stimulate populations of beneficial insects like ladybugs, lacewing and spined soldier. Rotate with non-host plants. After harvest plow and remove plant residues from the field.