Agricultural entomology: Colorado potato beetle

Agricultural entomology: Colorado potato beetle

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Classification and host plants

Class: Insects
Order: Beetles
Suborder: Polyphages
Family: Chrysomelids
Genus: Leptinotarsa
Species: L. decemlineata Say

Bibliographic reference:
Phytopathology, agricultural entomology and applied biology” – M.Ferrari, E.Marcon, A.Menta; School edagricole - RCS Libri spa

Host plants: Potato, Tomato, other Solanaceae.

Identification and damage

The Colorado potato beetle is an insect originating in North America where it colonized some spontaneous Solanaceae, to pass on the cultivations of the potato as they spread in the range. It arrived in Europe, between the end of the 1800s and the beginning of the 1900s, on the French Atlantic coast from which it extended to the whole continent.
In Italy the first reports were made during the Second World War (1943) in Piedmont, since then it has spread throughout the Peninsula. The adults (about 8-12 mm long) are typical Coleoptera with yellow-white elytra, on which 10 evident black stripes are marked longitudinally (decemlineata); the prothorax is reddish-orange in color with a typical blackish staple open towards the head. They complete the livery of the scattered blackish punctuation. The larvae (about 10-15 mm long when ripe) are orange-reddish in color, with a typical double row of blackish tubercles placed on the sides of the body; they are oligopod larvae, campodeiform with a slightly curved body and the most expanded abdominal region, typical of the larvae of the Chrysomelids.
The eggs are elliptical-cylindrical, yellowish in color; they are laid in groups, glued on the leaf surface.
The damage occurs on the leaves and is determined by all the mobile forms that are defoliators. Infested plants are completely defoliated; the plants can succumb directly to the attack or react, producing lateral shoots and other leaves at the expense of the formation of the tubers which remain small and in few numbers.

Biological cycle

The Colorado beetle overcomes the winter in the adult stage, buried in the ground at a depth of about 20-30 cm. In spring, adults leave the ground when the temperature in the ground reaches about 14 ° C: they immediately begin their trophic activity on the vegetation. Subsequently they mate and lay under the leaves; the newborn larvae (1st generation) are very voracious and continue the trophic activity to the detriment of the vegetation, already started by the adults.
These, generally long-lived, continue to be present on the vegetation together with the larvae. The mature larvae (after about 3 weeks) descend into the ground (about 10-20 cm deep) and pupate to give rise to a 2nd summer generation. The adults of this generation can winter, in cold regions, or originate a second larval generation; in warm environments there may be a third generation of adults which is hardly completed. The Colorado beetle, therefore, performs from 1 (excluding wintering adults and considering only complete larva-adult generations) to 2-3 generations per year depending on the environmental conditions.

Colorado potato beetle adult (photo Adam Nuzban

Colorado potato beetle larva (photo Adam Nuzban


The fight against Colorado potato beetle is chemical and biological.

Chemical fight
The chemical struggle is carried out at the appearance of the first infestations, checking that the plant is not in bloom; if the plant is in bloom it is necessary to anticipate or postpone the interventions.
The treatments can be repeated, as needed, alternating the active ingredients to avoid desensitization phenomena.

Biological struggle
In 1980 an important Hymenoptera Eulophid was discovered in Colombia and Mexico: the Edovum puttleri, which is an active parasitoid of the Colorado beetle ovature.
Recently, this Hymenoptera was introduced in Italy by Prof. Bin, of the Institute of Entomology of the University of Perugia; its effects on the populations of Colorado beetles are currently being tested, in order to evaluate their possibility of use as a means of biological control. LEdovum puttleri is a small black Hymenoptera (about 1-1.5 mm long), with the dorsal part of the abdomen reddish, in the male, and greenish, in the female; the females lay, with their robust ovipositor, the eggs inside the eggs of the Colorado beetle or, sometimes, they feed on the inside of the egg, directly.