The "king of acting" in the animal world: the destructive tree-boring pest that "dies" with just one touch - the Yanggan elephant

Among the many types of wood in the world, the most widely distributed and adaptable tree species is poplar. Poplars have a wide range of uses. In addition to being used as basic wood, poplars also have strong wind and sand prevention effects, and are also very helpful for water and soil conservation. However, during the growth of poplars, they are often attacked by poplar weevils. The poplar weevils are a worldwide borer pest and have become one of the important quarantine pests that are extremely destructive to forestry development and urgently need to be controlled.

Biological characteristics of Elephanthus yangganensis

The Yanggan weevil belongs to the order Coleoptera, the family Curculionidae, the subfamily Cryptorhininae. It is also known as the Yanggan weevil, the white-tailed weevil and the Yanggan white-tailed weevil. It is a national forestry quarantine pest. The development of the Yanggan weevil can be divided into four stages: egg, larva, pupa and adult, which belongs to the complete metamorphosis. The Yanggan weevil eggs are oval and milky white; the larvae are 9mm long, milky white, with sparse short yellow hairs; the pupa is 8-9mm long, milky white, with several spines on the pronotum, and many small spines scattered on the back of the abdomen; the adult is 8-10mm long, oblong, and dark brown. The eggs, larvae, and pupae of the insect live in the hidden trunks of trees. The adults have the ability to fly, but rarely fly, and the natural spread range is limited. It has strong reproductive capacity and stress resistance, and has a strong ability to spread with the host plant seedlings and saplings. In addition, the adults have the property of suspended animation, and they shrink and fall to the ground when disturbed.

Yang Ganxiang (picture from the Internet)

Distribution and harm of Loxodon yangganensis

The distribution range of the poplar stem weevil is wide in China, mainly concentrated in parts of the three northeastern provinces, Inner Mongolia, Gansu, and Ningxia Hui Autonomous Region. It was listed as a Chinese forest plant quarantine object in 1984, 1996, and 2004. Abroad, the poplar stem weevil is mainly distributed in countries and regions such as Japan, Hungary, Germany, the United Kingdom, Poland, France, and the Netherlands. The poplar stem weevil mainly harms Canadian poplar, small-leaved poplar, small green poplar, Beijing poplar, and Salix matsudana plants of the Salicaceae family, and is a destructive pest of poplars.

The reason why the poplar weevil is so harmful is that each stage of its larvae will cause serious damage to the host tree: the first-instar larvae drill into the bark; the second-instar larvae drill holes around the trunk to form channels, destroying the phloem and cambium; the third-instar larvae drill into the xylem to feed. Throughout the life cycle of the poplar weevil larvae, they can completely cut through the plant's drainage tissue, causing the tree to die due to lack of nutrients and water. This also leads to broken branches and stems, pathogen invasion and reduced wood quality, which directly affects the economic benefits of forest farmers.

The harm of the Yanggan elephant to plants (picture from the Internet)

How to prevent and control the Yanggan elephant?

Since the larvae of the weevil bore into tree trunks and live in seclusion, it is difficult to control the weevil, so the control of the weevil has become a global problem. At present, the main research methods for the control of the weevil focus on silvicultural control, chemical control and biological control.

Afforestation and prevention: When designing afforestation, try to choose native tree species and resistant tree species to create mixed forests to reduce the chance of being attacked by trunk-boring pests.

In forestry production, most of the prevention and control measures for poplar weevils are based on traditional chemical prevention and control. Traditional chemical pesticide prevention and control mainly include the following methods: crown spraying method: use 50% chlorpyrifos emulsifiable concentrate and 2.5% diazinon emulsifiable concentrate to spray on the tree crown; trunk spraying method: use 40% oxydemeton-methyl emulsifiable concentrate and 50% fenitrothion emulsifiable concentrate diluted 800 times to spray on the tree trunk; plugging method: plug the entry holes with 56% aluminum phosphide granules, and then seal the holes with clay or foam glue; ring coating method: use 40% oxydemeton-methyl and water in a ratio of 1:3 to make a solution, use a brush to apply 10 cm wide ring 1~2 circles on the tree trunk 1.5~2m from the ground.

Biological control: Natural enemies of the weevil, such as woodpeckers, toads and scleroderma, have a control effect on the weevil. In addition, spraying of some microorganisms, such as Beauveria bassiana and broccoli, has a significant effect on controlling the larvae of the weevil.

The natural enemy of Yanggan elephant, the Swelling-legged Wasp (picture from the Internet)

Author: Luo Mingdan (graduate student of School of Life Sciences, Hubei University)

Scientific review: Xu Letian (Professor and doctoral supervisor at Hubei University)

Planning: Zhao Qingjian, Wu Yuetong