Sweet corn

Biological control of beetles that damage stocks by store chalcids

The store chalcids are naturally occurring antagonists of some beetle larvae that damage stocks. Especially their ability to find larvae living hidden in the grain makes the parasitic wasps very interesting for the biological control.

The beetle larva is stung through the grain and is paralyzed. The parasitic wasp bores its ovipositor into the grain and lays an egg on the beetle larva. During growth, the larva of the parasitic wasp feeds on the beetle larva. After the pupation, the adult animal gnaws a hole into the grain and leaves it looking for further pests. At about 26 °C (70% humidity) the development takes about 3 weeks, whereby the females live approximately for two weeks after hatching.

A female Lariophagus distinguendus is only 2-3 mm in size. These beneficial insects are black and shimmer slightly metallic.

The following beetle species are parasitized:

Australian spider beetle
Flour beetle
Pea beetle
Lesser grain borer
Bean beetle
Grain weevil
White-marked spider beetle
Golden spider beetle (see below for detailed description)
Shiny spider beetle (see below for detailed description)

Rice weevil
Tobacco beetle

Additionally to the use of Trichogramma, the store chalcids can also be used against the larvae of the angoumois grain moth (Sitotroga cerealella) that unlike other moth larvae develop inside the grain.

Application recommendation:

Preventively 40 parasitic wasps can be used for 25-100 qm grain (depending on the situation). For storage, beneficial insects are introduced 2-3 times at 14-day intervals.  In case of infestation or treatment of empty rooms the beneficial insects may be applied curatively and the dosage can be adjusted.
The application and the number of beneficial insects always depend on the infestation, the warehouse design, the climatic conditions.

Control the golden spider beetle and the shiny spider beetle in half-timbered houses with the store chalcid Lariophagus

Golden spider beetles and shiny spider beetles appear en masse especially in hot summers or after reconstruction works and unsettle the residents of old houses or half-timbered houses. The golden spider beetle and the shiny spider beetle belong to the family of the spider beetle. They have a spherical body and their appearance reminds of spiders.

The golden spider beetle (Niptus hololeucus)

The golden spider beetle (Niptus hololeucus) can grow up to 5 mm long and attracts attention due to the dense golden yellow hair. It infests any types of grain and cereal products. But it can also be found in feathers, plant cushioning material and alternative insulation materials. It often becomes a problem in older houses with hollow intermediate floors. If the infestation establishes itself, significant damage to the building structure may occur.

The female beetle lays up to 30 eggs on the underlay. If necessary, they also cover longer distances in order to find appropriate feeding conditions for the offspring. The larval stages and also the beetles feed on animal and plant substances, but cannot develop further on textiles. The pupation takes place in a cocoon. With a temperature of approximately 20°C (70% humidity) the development from the egg to the beetle takes about 7 months, if the temperature is 5° higher, the development accelerates to only 70 days.

The shiny spider beetle (Gibbium psylloides)

Unlike the golden spider beetle, the shiny spider beetle also infests dried spices and herbs. With a length of approximately 4 mm the shiny spider beetle (Gibbium psylloides) is slightly smaller than the golden spider beetle. The body is more ovate, hairless and shines like glass in brown-red. Only the antennae and legs are covered with fine golden yellow hair. The females lay their eggs individually on the nutritive medium, and these become covered by crumbs and dust. The beetle is a light sensitive fellow that appreciates a humid environment.

The development from the egg to the beetle takes about 3 months at 23°C (70% humidity). The beetles can survive hunger periods without food for up to 50 days. The shiny spider beetles can cover longer distances in a short time but are not able to climb up vertical walls. When touched, they play dead for several minutes!

The beneficial insects should be released in an infested house in places where the beetles come out of the brickwork. For this purpose, existing openings can be used. If there are no openings, then small holes should be drilled in inconspicuous places.
To attract or to catch the beetles, double-sided adhesive tape can be applied. A laid out damp cloth may also attract the beetles.

Application conditions for the beneficial insects:

The beneficial insects can be released all year round, but the temperature should be at a minimum of 16-20°C, this means in spring one can start the control at the end of April.

Of course, during and after the use of the chalcid wasps no chemical treatment may take place, this also includes agents like, for example, kieselguhr. Like all beneficial insects, parasitic wasps are also very sensitive to chemical plant protection products and die. However the beneficial insects may be spread before the chemical treatment to control the hidden insect life stages. The waiting time should be 6 weeks.

Additionally, the pests can also be controlled by measures like big heat (60-70°C), big cold (-25 °C) or biological compounds like Neem before using the beneficial insects. Caution should be exercised with heat and cold as this can result in a damage of the materials.

We are happy to answer your questions about the use.



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