English names: Colorado beetle
Nordic names: Coloradobille (DK)
Estonian name: Kartulimardikas
Major host plants
L. decemlineata attacks potatoes and various other solanaceous plants. Potatoes, tomatoes and aubergine are at risk throughout Europe. Wild solanaceous species can act as a reservoir for infestation.
Both adults and larvae eat the foliage, eventually stripping all leaves from the haulm. Exceptionally, the tubers are also eaten. Characteristic, black and rather sticky excrements are left on the stem and leaves by all stages.
The Colorado beetle was first found in North America and has spread to Europe and Asia.
A map can be downloaded from EPPO’s website. See instructions here.
The beetles overwinter as adults in the ground and walk or make a short flight to the nearest potato field in spring or early summer. After feeding, they mate, and after a day or two, oviposition takes place. The eggs are laid in rows on the lower leaf surface, 10-30 at a time. Egg-laying usually continues over a period of several weeks until midsummer with each female laying about 2000 eggs. The number of generations is largely dependant on temperature, varying from 4 in the hottest areas of its habitat (cycle completed in 30 days) to one full and one partial generation near the colder extremes. Sunny weather and a mean daily air temperature of 17-20o C result in mass spread and development. However, if the temperature does not exceed 11-14o C and humidity is high, mass spread and development is inhibited and the population may actually decrease.
Natural spread of the beetle over large areas happens mainly by wind-borne migration, particularly of the spring generation. Adults can also be carried over long distances in sea water.
Adults and larvae can be easily transported on potato plants and tubers, and in all forms of packaging and transport. Fresh vegetables grown on land harbouring overwintered beetles are common means of transport in international trade.
Detection and inspection
Eggs: Yellow or light orange, about 1.2 mm long, found in rows on the underside of potato leaves.
Larva: Characterised by a large abdomen and an arched body. First instar is cherry-red with black head and feet. Later instars become progressively carrot-red, then pale-orange, with a line of several small black dots on each side of the body.
Adult: A stout, oval, strongly convex and hard-backed beetle, about 1 x 0.6 cm. It is yellowish-brown except for 5 narrow black stripes on each of the two creamy-yellow wing covers. It has small black spots on the top of the head and thorax. Because of their size and distinctive coloration, adults and larvae are not difficult to observe by visual inspection. Beetles easily drop from foliage when disturbed.
Pest status and importance
L. decemlineata is one of the most destructive insect pests of potato. Both adults and larvae feed on this host and often cause complete defoliation of the potato plants attacked, resulting in considerable yield losses, - especially in organic production where pesticide use is banned.
Source of information
See further information here:
Author: Göran Kroeker
Editor: Dorthe Vestergaard