Insects: Colorado potato beetle (Leptinotarsa decemlineata)
The Colorado potato beetle looks striking with its yellow-colored elytra with black stripes. This insect is mainly found on potato fields and is native to the United States. The beetle was first found in Europe in 1877. The larvae of this beetle can cause a lot of damage to potato plants in a short time. They sometimes emerge en masse at the end of April and eggs are laid on the underside of the leaves of the potato plant in June. Reproduction and growth are highly dependent on temperature.
Insect expert Thomas Say discovered the beetle in 1824 during an expedition in the United States in the state of Colorado. This is what gives the insect its name. Originally, the Colorado potato beetle does not come from America, but from Mexico. There the beetle of the plant lived the “spiny nightshade”. This plant is related to the potato plant. The beetle has spread rapidly across North America. In 1854 this leaf beetle got its final Latin name: Leptinotarsa decemlineata. It belongs to the leaf beetle family. The name refers to the stripes on its gold-colored elytra.
The Colorado potato beetle was first seen in Europe in 1877. Due to a control program, the beetle did not spread that quickly. But the world wars of the last century gave him the opportunity to spread considerably. He was first seen in Belgium in 1935 and in the Netherlands in 1937. Due to the lack of natural enemies, the beetle was able to multiply considerably everywhere. A female produces a total of 500 to 2500 eggs per year and they can produce 1 to 2 generations per year. In Europe, the beetle is mainly seen on potato fields. A striking feature of the Colorado potato beetle is the dark longitudinal stripes on its yellow-colored elytra. There are 5 stripes on each elytra. There are black spots on its head shield. An adult beetle is about 10 millimeters long and 7 millimeters wide.
A female lays between 500 and 800 eggs at a time on the underside of a potato leaf. Depending on the weather, larvae hatch after 5 to 21 days. Both the beetle and the larva live on the potato leaf. At first a larva is grayish in color. After 2 to 4 weeks and after molting 3 times, they have grown to a length of 1.5 centimeters. After the last molt, the larvae are red with black spots. They can occur en masse and eat entire potato fields bare. When they have eaten enough, they fall to the ground and crawl underground to pupate. After 2 weeks, an adult beetle will emerge from the ground. Several generations can develop in a year. Both adult beetles and larvae try to survive the winter. If the beetle has laid eggs after hibernation, it will die.
The beetle is active until about mid-October, after which it will hibernate. The beetle overwinters in the soil to a depth of 20 to 50 centimeters and can withstand temperatures of up to ?? Survive 7 degrees. Larvae can survive harsh winters if they are deep enough underground. When the temperature rises in the spring, the larvae hatch from the eggs. Usually, the Colorado potato beetles will reappear in late April to early May and will fledge. Eggs are laid until June.
The beetle is mainly active during the day and its survival is largely dependent on temperature and weather. If it rains a lot, many eggs and larvae will wash off the leaves and will not survive. The females only lay eggs from 17 degrees. In a cold spring, hardly any eggs will be laid. In a warm summer, the development of an egg takes about 35 days, while in a cold summer it can take up to 80 days. If there is an early autumn, the beetles will already crawl into the ground in August. If the temperature is below ?? 7 degrees, the adult beetles will die.
It is mainly the larvae that are voracious and can cause great damage to the potato plants. They start to eat at the leaf margin and eat so many leaves. With a large number of larvae, plants are eaten bare down to the petioles. In a short time they can eat the entire potato field bare. If you discover that there are a large number of beetles or larvae during a potato crop check, action must be taken quickly to save the crop. Different products exist under different brand names.