Biology

Glasshouse sciarids belong to the family of the Sciaridae. They are small (3-5 mm) dark flies with long, slender antennae and long legs. They are usually seen in warm and humid environment in the proximity of plants. That’s why they can occur the whole year round in the greenhouse.
After mating, the female fly lays 50-200 eggs, which hatch in 2-3 days. The emerging larvae develop through four instars over 2-3 weeks. By that time, they are about 5 mm long, translucent white in color with a distinctive black head. They then pupate in the compost and emerge as adult flies 3 days later. At temperatures in excess of 24°C, breeding is continuous and the life cycle takes 3-4 weeks.

Damage

The larvae of the glasshouse sciarids can cause a lot of damage. They not only feed on decaying organic matter in the compost, such as algae and mould, but also on living material such as root and stalk tissue. They pierce into the root and/or stalk of cuttings, seedlings or young plants. As a result of this, secondary plant diseases such as Pythium, Phytophthora, Botrytis, Fusarium and Verticilium can be spread.
The most common symptoms of such an attack are the wilting and the slowing down of the plant growth. In the worst case, this might even lead to the death of these plants.

The following crops frequently suffer severe sciarid attack:

seedlings, cuttings and young plants, especially if heated and under mist;

certain pot plants, e.g. ferns, Poinsettia, Azalea, Cyclamen, Kalanchoe, Exacum, Gerbera, Begonia, ...;

some long term rockwool grown crops;

mushrooms

Steinernema-System owes its consistent, effective control of sciarids to the way in which it works.
Applied to the compost, the nematodes actively seek out sciarid larvae. They enter each larva through natural body openings. Once inside of the larva, they move to the intestinal canal and drill through the intestinal wall of the larva. A specific bacterium which lives in symbiosis with the nematode is released and will eventually cause the death of the larva.
The nematodes reproduce inside the sciarid larva. As it decomposes, a new generation of nematodes moves off into the compost in search of further prey.

The key to success is applying routine, preventative treatments. That way, sciarid populations are not allowed to build up, and crop damage is prevented.
Compost should be treated as soon as possible after sowing seed or inserting cuttings. Many crops are susceptible to sciarid damage during the first six weeks, and a single Steinernema-System treatment is already sufficient. The dose that needs to be applied is always 1 million of nematodes/m². For very slow growing crops, it may be desirable to reapply Steinernema-System at six week intervals in order to maintain protection. If Steinernema-System treatment is delayed until sciarids are established in the crop, it will take 2-3 weeks before the numbers of adult flies are noticeably reduced.
Steinernema-System works best in moist, warm compost (15-20°C). If compost temperatures fall to less than 10°C or rise to 30°C or higher, the nematodes become inactive. Wet spots as well as the growth of algae are best to be prevented, as they could promote the number of glasshouse sciarids present.

Biology

Adult thrips are small, elongated insects with typical fringed wings. They measure about 1 mm, and have a greyish or yellow to brown colour. The female thrips deposits eggs in the leaf tissue. The eggs hatch within a few days into very mobile larvae which immediately start to feed. After the second instar they let themselves fall on the ground to pupate. The total development time from egg to adult takes from 20 days at 20°C (68°F) to 12 days at 30°C (86°F). At sufficiently high temperatures one female thrips can produce up to 100 descendants.

Damage

Thrips damage the crop by withdrawing the plant cell fluids. Empty cells are filled with air, causing a silvery appearance, on which dark spots (the excrements) are visible. Moreover, there exist many more damage symptoms depending on the crop. For instance, thrips can cause deformed fruits. In several ornamentals, flower damage through discoloration or deformation occurs. Only a few individual thrips are enough. Moreover, thrips are important vectors of several viruses (e.g. tomato spotted wilt virus or TSWV and impatiens necrotic spot virus ).

Steinernema-System can be used for all cultures control the thrips population, without having any negative influence on biological adversaries. If used in alternation to thrips pesticides, it reduces the resistance of thrips to chemical agents. No perceptible residue remains after the treatment. The use of Steinernema-system as part of a thrips control program seems obvious.

To control leafminer with these nematodes the timing of application is very important.
In case of synchronous population, one application is sufficient. When the population of leafminer grows asynchronously, it is necessary to repeat the treatment weekly. Doses and application techniques are the same as for thrips control.

Steinernema-System is delivered as a gelformulation. Depending on the pack size, they contain a minimum of 5, 50, 250 or 1250 (5 x 250) juvenile nematodes. During mixing with water, the nematodes form a suspension, which can be applied to the compost surface.

Advantages:

No re-entry time

No residue on the crop

Can be integrated in resistance management

Can be applied during bloom (e.g. strawberry)

Indifferent to most chemical crop protection means (tankmix)

Controls the problem before it appears

Practical and simple usage

Compatible with other biological or integrated systems

Absolutely safe to users, consumers and the environment

No disposal problems

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