Is there "white pollution" in the insect world? At the end of the year, beware of the hungry "leaf-eating devil"!

The adult of the American white moth is inconspicuous in appearance, with the appearance of a common small white moth. The larvae have a black body with yellow stripes and are covered with very long fine hairs.

In December, Hebei, Shaanxi, Jiangsu and other places have been making every effort to promote forest pest control. Among them, only the gypsy moth can cause large-scale environmental damage, as well as great psychological impact and visual pollution.

Origin in North America

The gypsy moth is also known as the fall moth, and its larvae are called net-curtain caterpillars. As the name suggests, the larvae live in the net curtain formed by their own silk in the early stage to obtain protection. Every time the larvae shed their skin, they grow a little bigger and also grow one instar. After the fifth instar larvae, they will break through the net curtain and in a very short time, they can eat the lush plants "bare". Therefore, the gypsy moth is extremely destructive.

As an invasive species, the gypsy moth is native to North America. In the 1940s, it spread to Europe and Asia with the transportation of military supplies. In my country, the gypsy moth has not been invading for a long time. Around 1979, it spread from the Korean Peninsula to Dandong, Liaoning Province. In 1989, the gypsy moth broke through Shanhaiguan and entered North China. In 1998, the Beijing-Tianjin-Hebei region launched a national-level control project for the gypsy moth, which greatly slowed down its spread. However, after the 21st century, the presence of the gypsy moth in Beijing, Tianjin, Hebei and other places has been significantly strengthened.

More than one generation per year

The nymph caterpillars of the American white moth are not picky eaters. From walnut trees to sycamores, to quinquefolia, whether native or introduced, all are on their menu, whether woody or herbaceous, as long as the leaves are slightly wider, plants and crops, such as mulberry, ailanthus, poplar, elm, willow, locust, apple, soybean, corn, eggplant, cabbage, sweet potato, etc. For the American white moth, leaves seem to be only delicious or not, not edible or not.

Whether in the south or the north, the gypsy moth reproduces more than one generation a year. In Hebei, the gypsy moth reproduces three generations a year. The overwintering pupae emerge as adults and lay eggs from April to June of the following year. The first generation of larvae are born from May to July. After about 30 days of growth and development, the first generation of larvae become pupae, and then fully emerge as adults before the end of July. After that, the gypsy moth completes another round of reproduction in about 60 days, and after entering the third generation in autumn, it overwinters in the form of pupae. Because the gypsy moth has a strong reproductive capacity, a female can lay eight to nine hundred eggs, or even more than 1,000 eggs. Therefore, as long as there are a few gypsy moths at the beginning of the year, after two generations of reproduction, by the third generation, that is, in the autumn of that year, an explosive effect can be achieved. This is also the reason why the gypsy moth is more common in autumn.

The effect of the gnat wasp on controlling the gypsy moth is remarkable

Usually, the control of the gypsy moth is to kill it with drugs, which is effective, but this may cause the pests to develop drug resistance and also cause a devastating blow to natural enemy insects. In addition, the timing of drug use is sometimes inaccurate. Limited by insufficient monitoring power, it is often impossible to spray pesticides in time in the early stages of the pests. Action is only taken when the pests have erupted to a certain extent and caused losses. This not only increases the cost of prevention and control, but also makes it difficult to completely eliminate them.

Fortunately, unlike other invasive species, the gypsy moth is not without natural enemies in my country. Some predators and parasitic wasps can control its numbers. For example, Zhou's gnawing wasp is a good example. It is a native species in my country. From 1986 to 1988, the gypsy moth in Shaanxi was basically under control, which may be mainly due to this parasitic wasp.

According to the research conducted by Cao Banghua and other researchers from Shandong Agricultural University on more than 40,000 mu of experimental fields in Dongying, Shandong, the results showed that Zhou's gnawing wasp has formed a stable population and can control the number of plants with insects to less than 1%, creating a situation where the insects are not a disaster, and the control effect is significant. At present, Zhou's gnawing wasp has been put into use in many places in my country.

In addition, there are some other parasitic natural enemy insects that are also very potential, with more than 20 known species. In addition to using conventional drugs, we can also use their power to control the American white moth.

(The author Ran Hao is a member of the China Science Writers Association)