Control weevils, Curculionidae in the house and garden

The majority of the weevil species specialize in certain plants and differ significantly, especially in terms of color and size. Common to all species is the characteristic of the trunk as an extension of the mouth area. Since the motto for combating weevils is ‘Recognized danger is averted danger’, the most important species of the genus are briefly presented below:

Furrowed vine weevil

• 10 mm in size
• Black grained top
• prefers herbaceous plants and trees
• crepuscular and nocturnal

Large brown weevil – spruce weevil

• up to 14 mm long
• gray-brown tank
• Wings with yellow spots and horizontal stripes
• Above all, it damages young trees and conifers

Common gray weevil – gray pine needle weevil

• 7 to 10 mm elongated body
• colored black or black-brown
• copper-colored to light gray scales
• red-brown antennae
• specializes in pine

Strawberry blossom cutter

• 2 to 4 mm long
• shiny black metallic
• striped wings with dots
• specializes in strawberries, raspberries, blackberries
• less often on roses and carnations

Apple blossom cutter

• 3 to 4 mm long
• black-brown basic color
• brown and white scales
• damages apple and pear trees

Another member of the genus is the bark beetle, of which more than 150 species cause great damage to all woody plants in Germany alone. Sometimes they appear in huge swarms with several thousand specimens. In addition to the bark beetle, the black weevil does the greatest damage in the garden with its broad spectrum of plants that it attacks. While various chemical control agents are permitted in commercial forestry and agriculture, their use is problematic for the hobby gardener. Therefore, the following approaches will mainly focus on biological agents.

Nematodes against weevil larvae

When we talk about nematodes, we mean tiny, colorless or white roundworms that cannot be seen with the naked eye. Among the more than 20,000 species, various specialists have proven to be an effective biological control against weevils in the garden. While the experts initially assumed that the roundworms would only start looking for the weevil larvae in the soil at temperatures above 12 ° Celsius, other nematode species have since been discovered that are also active at temperatures above 5 ° Celsius are. Depending on the time of year, gardening enthusiasts can use a watering can to dissolve the appropriate nematodes in water:

• February / March and October / November: SK nematodes (Steinernema kraussei)
• April / May and August / September: HM nematodes (Heterorhabditis bacteriophore)
• May to September: SC nematodes (Steinernema carpocapsae)

The nematodes are supplied in a powder that puts them into a kind of hibernation. As soon as they come into contact with the water, they become active and can be sprayed with a watering can in the hobby garden up to an area of ​​200 m². If a crop protection sprayer is used on a larger area, the sieve must first be removed from the nozzle. Used correctly, the weevil larvae die within 24 to 48 hours of being attacked by the nematodes. The rule of thumb for the dosage is that 500,000 nematodes per m² work with an effectiveness of up to 90%. The following factors must be taken into account:

• the species of weevil is well defined;
• the type of nematode appropriate to the season is used;
• the delivered quantity was kept for no more than 2 days;
• treatment with nematodes replaces normal irrigation;
• the dosage is adhered to according to the instructions;
• there is no blazing sun;
• the treatment is repeated several times;
• the soil is kept moist for the next 14 days;
• do not lime during and after treatment;
• no simultaneous use of neem-containing products.

It is also important to note that the garden soil is not completely in the water, because nematodes are non-swimmers and can then not hunt for the larvae of the weevil. Therefore it is preferable to re-water again later if necessary. This can be the case especially when used in greenhouses. Since the pests do not spare potted and flower box plants either, gardening enthusiasts can use nematodes in the form of liquid suspensions in this case. They are inserted into the substrate like fertilizer sticks, whereby 10 million nematodes per m³ are usually sufficient.

Nematode trap against adult weevils
While the useful roundworms could previously only be used against the larvae of the weevil, the scientists have now developed an effective bait trap that also kills adult pests, especially the black weevil. The ingenious construction consists of a small wooden board in which several grooves have been milled. These grooves are filled with a nematode gel that also contains an attractant for the weevils. With this side down, the bait trap is laid out in the garden. The soil must be slightly damp so that it can take effect. One trap per 10 m² is sufficient for a period of 6 weeks. It is sufficient if the lured weevils only come into contact with the gel for a short time.

Wood wool trap
The weevils are mostly up to mischief in the garden at dusk and at night. During the day they look for a hiding place. Anyone who fills flower pots with wood wool in his garden and hangs them up or puts them upside down lures the nuisances into them and can get rid of them.

Neem press cake for weevils not very appetizing
The seeds of the neem tree not only provide the plants with additional nutrients, but also contain a certain amount of neem oil, which is poisonous for weevils. If the neem press cakes are worked into the soil around the endangered plants, the neem oil gets into the cycle of the plants and permanently spoils the appetite of the weevils and their larvae. Already 40 to 50 grams per m² are enough to keep pests away from the lovingly grown plants. It must be reapplied every 8 to 10 weeks. Neem press cake and nematodes must never be used at the same time, because the neem oil is also poisonous for the roundworms.

Attract predators of the weevil

Those who make their garden inviting for the natural enemies of the numerous species of the weevil receive effective support in the fight against the pests. The following useful garden dwellers like the weevils to eat:

• Birds
• be crazy
• centipede
• Hedgehog
• Spitzmäuse
• Lizards
• Common toads

Dense hedges offer birds, spiders and ground beetles attractive, cozy retreats. Feeding places and water troughs ensure the physical well-being of the feathered beneficial insects, which the weevils do not disdain either. Piles of leaves, dry stone walls, piles of wood and piles of brushwood invite hedgehogs, lizards and shrews to linger. Incidentally, free-range chickens also like to peck at the weevils, their eggs and larvae.

Insecticides approved for the home garden

If all biological and mechanical means of control do not help to get rid of the weevil, the only thing left is chemical means. For the hobby garden, the list of permitted insecticides and pesticides is quite manageable:

• Spinosad
• Thiacloprid
• Deltamitrin
• Calyps
• Acetamiprid

The list of funds allowed for private ornamental and kitchen gardens can change daily. It is therefore advisable to find out exactly whether the approval is still valid immediately before buying. The simultaneous use of nematodes and chemical insecticides has not yet been adequately investigated. The experts at the chemical company Bayer advise against parallel application as long as there is no sound knowledge of possible interactions.

Fight weevils indoors

The weevils usually get into the four walls of your home through newly purchased plants or via the terrace and balcony. As a preventive measure, houseplants that have just been bought should therefore be repotted in fresh substrate that has previously been heated in the oven for 15 minutes at 200 ° and then cooled. In addition, the root balls, leaves and branches are examined for the pests. Plants in the house that have a strong immune system are more resistant to attack by diseases and pests such as the weevil. Therefore, the right location and good care are always an effective method of not giving the voracious larvae and beetles a chance.

Go hunting with a torch
The nocturnal weevils go in search of food in the dark. They can be spotted quickly with the help of a flashlight. If you feel caught, play ‘Dead Beetle’, fall on your back and can simply be collected.

Nematodes for use
indoors HM nematodes can be used indoors all year round. They do not harm the plants, humans or pets. In this case, it makes little sense to spread the nematodes with a watering can. A special nematode syringe, which is offered inexpensively in specialist shops, is more suitable.

Wood wool trap also works in the home
Since the weevils are always looking for a place to hide during the day, the wood wool trap can also be used in your own four walls. It doesn’t necessarily have to be a conspicuous flower pot that is filled with wood wool or straw, as in the garden. An inconspicuous nursery pot also functions as a beetle trap.

Chemical insecticides in the house as the last solution
The chemical-based pesticides that are permitted for the hobby garden could theoretically also be used in the home. When the weevil plague gets out of hand and biological agents don’t work, environmentally conscious gardeners also turn to bug spray. It is important to carefully follow the instructions for use, not to inhale the spray mist and to ventilate thoroughly after the exposure time. In addition, the following products are offered especially for indoor use:

• Bambule Insect Powder
• Bambule insect spray
• KWS 500 insect foam for cavities
• Anti Insekt RTU
• Killgerm Universal Aerosol
• Pistal instant insecticide

Only recently was the devastating effect of fossil plankton on insects such as the weevil discovered. It is applied as a powder, is odorless and non-toxic.

Conclusion
You move out at night, destroy entire forests and transform an idyllic garden into a construction site. The weevils, which owe their name to the tool on the head, do not stop at any plant, wood or tree. Except for orchids and cardiac plants, the beetles and their larvae destroy everything that gets under their proboscis and drive many gardening enthusiasts to despair. The power struggle is not entirely hopeless, however, because resourceful researchers and scientists have developed many effective means of control.