It is the number one enemy of potatoes but also of eggplant and, to a lesser extent, of tomatoes and peppers. Tasty vegetables, widely used in Italian gastronomy for a great variety of recipes, which however are exposed to the attack of an insidious enemy, the Colorado potato beetle. The insect, native to North America, belongs to the order of beetles and has a devastating effect on nightshades. Farmers are engaged in a daily fight against plant infestations and from Colorado beetle is characterized by being particularly annoying. Even insecticides, which have become more and more powerful over time, have sometimes proved ineffective. Easily recognizable even by an inexperienced eye, due to the black stripes on the body, the Colorado beetles, after a period of winter inactivity, re-emerge from the earth in spring and, with enthusiasm, devote themselves to the search and attack of their favorite plants. The damages caused are generally considerable, also due to their prolificacy, a female lays from 300 to 500 eggs, and longevity, with two or three generations observable during the year depending on the climate. Generally the first and second generation overlap and you can easily observe adult insects and larvae all devoting themselves to the same identical goal: attacking the flowers and leaves of the Solanaceae until the entire plant often dies. When the attack is milder, the plants produce lateral shoots and new leaves but the tubers remain small. A real tornado for the vegetable garden and the countryside, most likely arrived in Europe in the second half of the nineteenth century, which spread rapidly throughout the continent, creating considerable damage to crops. Around the Second World War there was the peak of the invasion, so much so that the Nazi propaganda claimed that the insect had been launched by American planes to sabotage the crops. His arrival in Italy is to be placed around 1944 and since then every year, punctually, a real war has been unleashed against this greedy devourer of vegetables. Yet the techniques to annihilate it exist, just have patience and love for the land.
Manually removing eggs, larvae and adult Colorado beetles is a real undertaking that requires time and a lot of patience, also because the insect proves to be particularly tough and, especially if there are many plants, also a fair physical effort. So it is a partially applicable remedy. Then there is the mechanism of crop rotation, namely that of not planting solanaceae near areas where plants of the same type have been grown the previous year in order, essentially, to make the wintering adult insects lack nourishment. Mature organic fertilizers can then be used and antagonistic insects can be used Colorado beetle like the carabid beetles and the septempunctata ladybird: the biological fight seems to be, in fact, one of the most effective weapons in the fight against the parasites that infest the plants also because it does not involve the diffusion in the environment of chemical substances of any kind. The use of biological insecticides also goes in this direction, based, for example, on Bacillus thuringiensis, discovered at the beginning of the twentieth century in Japan and of which many strains are found on the market. For some time the use of a hymenoptera, the Edovum puttleri, has been affirmed in the context of biological struggle, the female of which lays its eggs inside the Colorado potato beetle egg, thus destroying several of them hundreds in a short time. Another natural remedy is turkey, used by farmers by virtue of their preference to feed on the annoying solanaceae eater. Then there is the so-called mulching, that is to say the use of an operation that consists in covering the soil with a heavy layer of organic material such as straw or pruning cuttings to lengthen the sleep of the insects that winter while maintaining the vitality of the soil. and thus preserving biological competition. Finally, a further remedy is to resort, where possible, to resistant cultivars such as, for example, the variety of eggplant known as "monstrous New York violet".
In case of particularly virulent infestation and on rather large extensions, the use of an insecticide can be considered, after technical evaluation by phytosanitary personnel and outside the flowering period. In addition to chemical pesticides that are not always recommended (such as Actara or Karate Xpress), there are substances of natural origin, such as pyrethrum or rotenone whose use is in any case subject to legislation as they are highly toxic substances for fish, reptiles and amphibians but also, moderately, for warm-blooded animals. They are also preparations without selectivity, therefore harmful to beneficial insects. Their use near water courses is forbidden and in any case a limited use over time is recommended.
Among all the phytophagous parasites, that is those that feed on vegetables, the Colorado beetle is the nightmare of anyone who has a vegetable garden or a land intended for the cultivation of solanaceae, namely potatoes, aubergines, tomatoes, peppers. Insects, which overwinter underground, re-emerge in spring and aggressively attack flowers and leaves until they destroy the entire plant or otherwise seriously damage it. Particularly useful is the biological fight, that is the use of bacteria and insects antagonists of the Colorado beetle but also operations such as mulching can prove to be effective in preserving these plants, the undisputed protagonists of the Italian tables.