Fight vine weevils with nematodes

Fighting the black weevil (Otiorhynchus) is comparatively easy with nematodes, as long as the right circumstances are observed during application. Here's how it works.

Signs of black weevil

The adult beetles feed primarily, but not exclusively, on the leaves of ornamental plants. For example:

• Cyclamen
• Berry
• Chrysanthemums
• ivy
• yew
• Fuchsias
• Geraniums
• pagan
• Hydrangeas
• Cherry laurel
• Tree of life
• Medlars
• Primroses
• rhododendron
• Roses
• Grapevines

Other plants can also be affected. The feeding marks of the adult specimens can be seen on the leaves. The larvae, on the other hand, live in the ground and feed on the roots and tubers. Therefore you should fight the black weevil as soon as possible. The beetles occur more frequently between May and September. Typical signs are:

• inexplicable death of the plants
• irregular feeding marks on the leaves
• withered leaves despite good care conditions and correct location

Larvae

The larvae are up to an inch long. The body is white and appears almost transparent. The head is brown. This makes them comparatively difficult to distinguish from other larvae.

They initially feed on root hairs, but later also go to woody sections, tubers and onions. The latter can be completely hollowed out by the animals. This damage mainly occurs at the end of summer and early autumn. Therefore, an exact assignment is often difficult.

Nematodes

These beneficial insects are roundworms. They are placed in the soil and feed on larvae by invading them and killing them from within. They help fight the black weevil. They also have other advantages. These include:

• simple application
• low price
• Life span six weeks even without a host
• die on their own without food
• act against several pests

Application

Spreading is very easy. All you have to do is follow the steps below:

1. Observe the correct temperature: The beneficial insects may only be brought out when the soil temperature is above 12 degrees Celsius. Otherwise the roundworms will not be sufficiently active to fight the black weevil.

2. Loosen the soil: So that the animals can penetrate the ground as quickly and deeply as possible, you should carefully loosen the soil in advance with a rake. Be careful not to damage the roots of the plant.

3. Avoid the sun: Full sun can have a negative effect on beneficial insects if they are directly exposed to it. You need a few hours to protect yourself from UV radiation underground. Therefore, choose an overcast day or the evening hours for spreading.

4. Best time: Depending on the activity of the larvae, it should be used between April and May and between August and September.

5. Keep the soil moist: Otherwise the animals will dry out very quickly and will not be able to take action against the pests.

Tip: Repeat the application every six to eight weeks to effectively control all developmental stages of the larvae. Because of its low cost, the pests are safely removed without putting too much of a strain on the budget.

combination

If you want to control black weevils, you should target both the adult beetles and the larvae. Collect the beetles from the plants and crush or smother them. This will reduce the chance of oviposition again. Bring in the roundworms at the same time to kill any larvae that are already there.

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