Are longhorn beetles beneficial insects or pests, and are their bites poisonous?

The longhorn beetle is an insect we often caught to play with as children, with long antennae and a black outer shell marked with white spots. There are many species of longhorn beetles, and they are widely distributed in our country. Most longhorn beetles are large or medium-sized and like to be active on trees. So are longhorn beetles beneficial insects or pests? Are their bites poisonous?

1. Are longhorn beetles beneficial insects or pests?

Longhorn beetles are major pests in forestry production, crop cultivation and construction timber. Longhorn beetles are mainly pests of woody plants, boring into trunks, branches and roots during the larval stage. Some harm herbaceous plants, with the larvae living inside the stems or roots, such as the chrysanthemum longhorn beetle and the melon vine longhorn beetle. A few species, such as the cotton boll longhorn beetle, harm cotton bolls. There are also a small number of species whose larvae do not live inside plant tissues but instead feed on roots in the soil, such as the large-toothed and curved-toothed sawyer beetles, grass longhorn beetles and so on.

2. Are longhorn beetle bites poisonous?

Longhorn beetles are not poisonous, so you can rest assured. So what should we do if we are bitten by a longhorn beetle? The first step after being bitten by a longhorn beetle is definitely to find a way to make it let go. The specific method is to relax your hand and wait for it to release its grip on its own; do not pull forcefully, otherwise it may cause abrasions. Once the longhorn beetle lets go, you can observe the wound. If the skin has not been scraped open or bleeding, then you only need to apply a little ice to relieve the pain.

3. What harm do longhorn beetles cause? How can they be prevented and controlled?

The larvae of longhorn beetles bore into and feed on trunks and branches, affecting the growth and development of trees, weakening tree vigor, leading to invasion by pathogens, and making trees easily broken by wind. When the damage is severe, the entire plant dies, and the wood is bored through, losing its craft value. Longhorn beetles bore into trunks, branches and roots during the larval stage. Some harm herbaceous plants, with the larvae living inside the stems or roots, such as the chrysanthemum longhorn beetle and the melon vine longhorn beetle; a few species, such as the cotton boll longhorn beetle, harm cotton bolls; there are also a small number of species whose larvae do not live inside plant tissues but instead feed on roots in the soil, such as the large-toothed and curved-toothed sawyer beetles, grass longhorn beetles and so on.

The larvae and adults of longhorn beetles mostly prefer to be active on trees, such as mulberry, willow and poplar, citrus, and pine, all of which have multiple longhorn beetle species reproducing on them.

(1) Physical control

1. Capture and kill adults:

For longhorn beetles that have a death-feigning habit or rest at the base of the trunk, manual shaking to knock them down for capture or direct capture can be used.

2. Eliminate larvae:

Manually crush eggs with a hammer and peel back bark to hook out and kill larvae.

3. Whitewashing tree trunks:

Whitewash tree trunks from 1.5-2 m above the ground to prevent longhorn beetles from laying eggs. If there are pruning cuts or saw cuts on fruit trees, protective agents (such as varnish) should also be applied promptly to prevent longhorn beetles from laying eggs.

4. Attractant trapping:

Some longhorn beetle adults (such as the peach red-necked longhorn beetle) are attracted to sugar and vinegar, so a sugar-vinegar-alcohol liquid can be prepared manually (sugar:vinegar:alcohol at 1:0.5:1.5) and an insecticide (such as trichlorfon) added for trapping and killing.

(2) Biological control

Longhorn beetles have many predatory and parasitic natural enemies, and the sclerodermus wasp is one of them. The sclerodermus wasp can find longhorn beetle larvae and pupae along the bore tunnels and lay eggs inside the bodies of the longhorn beetle larvae or pupae. After the sclerodermus wasp eggs hatch, they absorb the nutrients of the longhorn beetle larvae and pupae, causing their death and achieving control. Besides the sclerodermus wasp, there are also flower velvet beetles, Beauveria bassiana and parasitic nematodes, all of which are now commercialized and can be applied.

(3) Chemical control

1. Adult control

During the peak period of larval emergence (the peak period of adults emerging from holes is June-July), use pyrethroids, chlorpyrifos, imidacloprid and other agents for control, spraying the orchard once every 5-7 days, mainly on branches and trunks, spraying thoroughly each time so that the liquid runs down the trunk to the roots; or use the above agents to coat the trunks.

2. Control of eggs and young larvae

Longhorn beetle eggs and young larvae are active under the bark of fruit trees and have not yet damaged the xylem, so at this time care should be taken to let the larvae or eggs under the bark come into contact with the agent to kill the eggs and young larvae.

During the peak period of longhorn beetle egg-laying and larval hatching (the egg-laying peak is generally in June-July), look for egg-laying notches and larval damage sites (check wounds on the tree surface and bore holes), and use three methods for control: applying agent, wrapping with poisoned cotton, and sticking with poisoned soil.

3. Applying agent

Use pyrethroid, organophosphorus and other insecticides mixed with diesel for application;

4. Wrapping with poisoned cotton

Soak the liquid into cotton and wrap it around the branches (first scrape off the old bark), then wrap the outside with plastic film;

5. Sticking with poisoned soil

Mix the liquid with an appropriate amount of clay to make poisoned soil, and stick it onto egg-laying and larval damage sites.

6. Control of larvae inside bore tunnels

Older larvae enter the xylem to cause damage, making control more difficult at this time. First find the bore holes with fresh frass (after heavy rain, the frass on the trunk and under the tree has been washed away, making fresh frass holes easy to identify). If there are multiple frass holes, choose the last hole, first dig out the frass debris, insert or inject the agent into the bore tunnel (you can choose camphor balls, gasoline, cotton dipped in agent, etc.), then seal the hole opening tightly with wet clay or wet yellow mud, and check the effect after 7-10 days. If there are holes with new frass discharged, treat them again.