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Therodiplosis-System

A flying biological predator of red spider mite !

In contrast to the other spider mite predators Therodiplosis has a winged stage. Thanks to this, spider mite populations can be detected much faster and over larger areas.

Biology: Therodiplosis persicae

Therodiplosis persicae is a gall midge, just like the aphid predator Aphidoletes. The adult Therodiplosis lays yellow-coloured eggs of about 0.25 mm in red spider mite colonies. After about two days, a creamy brownish yellow larva hatches, which devours red spider mites.

After about one week, the larvae pupate. The fully-grown larvae are 1.7 to 1.8 mm long and have a diameter of 0.4 mm. The pupae of Therodiplosis look just like white fluff and are usually found near the veins of the leaf. They are from 1 to 1.5 mm long. The total life cycle varies with temperature, but generally takes about 2 to 4 weeks.

Therodiplosis is also found in nature, and can be often seen in crops towards the end of the summer.

Application

Therodiplosis has already proved its use in extensive practical experiments in cucumbers and tomatoes. In particular for tomatoes, where the biological control of red spider mite has so far been very difficult, Therodiplosis is a welcome improvement. At the moment Biobest is also conducting extensive research into the use of Therodiplosis in ornamental crops and in strawberries.

Advantages

Therodiplosis will become an important component of the biological control of red spider mite, particularly on account of the following advantages:

	In contrast to the predatory mite Phytoseiulus, Therodiplosis proves to be able to control effectively red spider mites in tomatoes. In case of heavy infestations of red spider mite, Therodiplosis can be used in combination with the special tomato-Phytoseiulus (Phytoseiulus-T-System).
	Therodiplosis also controls overwintered red spider mite, which may be important in spring and autumn.
	The "toxic" carmine spider mite (Tetranychus cinnabarinus), which can do great damage in crops, like carnations and tomatoes, can be effectively controlled with Therodiplosis.
	The adult Therodiplosis are capable, while flying, of tracking colonies of red spider mite. The great detective capacity of Therodiplosis is an important advantage in comparison with Phytoseiulus, which can only spread while walking. Especially, in ornamentals, where it is a very laborious business to scout for colonies, this means an important step ahead.
	Because of its excellent flying capacity, putting out Therodiplosis requires very little work.
	Therodiplosis larvae eat both eggs, nymphs and adults of red spider mites. Therodiplosis eats at least 5 times as many red spider mites per day as Phytoseiulus.
	Field tests show that Therodiplosis is also active in cold and dark weather in spring and autumn. This is another important advantage in strawberries and soft fruits.
	Therodiplosis can be found back in the crop easily. Both its larvae and its pupae are easily visible.

Side effects

At the moment, Biobest is conducting numerous tests to find out about the side effects of the major pesticides on Therodiplosis. Practical experiments have already shown that Thiovit (sulphur), Rubigan and Rovral are safe. Torque can influence the population build-up of Therodiplosis because red spider mite is killed off.

Therodiplosis-System

Therodiplosis is supplied as pupae on leaves in pots of 1 litre. One pot contains 250 pupae. These pots are very user-friendly. By piercing the paper disc in the cover, the adult gall midges can escape after hatching. The pots are simply placed in the shadow on the ground in the crop at the beginning of a row.

Biobest's advisory schedule

	In spring, when the red spider mites come out of their hibernation, introduce 2-3 pots per hectare weekly. It is best to place the pots in the vicinity of commencing red spider mite colonies.
	Heavy infestations across the entire greenhouse in spring are best controlled by putting out 10 pots (250 pupae) per hectare weekly, during 6 successive weeks. The purpose is to build up a Therodiplosis population across the entire crop as soon as possible.
	In summer, the number of introductions can be limited to 4, because the life cycle of Therodiplosis becomes shorter at increasing temperatures.

We recommend to apply Therodiplosis during the building-up period in combination with Phytoseiulus or Tomato-Phytoseiulus. In the beginning, Therodiplosis will be found back in particular in larger colonies of red spider mite. As the Therodiplosis population increases, Therodiplosis will also be found back in smaller colonies of red spider mite.

Advantages

	Also applicable in tomatoes.
	Applicable in crops where scouting is difficult, such as ornamentals.
	Also kills red spider mite and the toxic spider mite (Tetranychus cinnabarinus).
	Excellent detective capacity.
	Spreads while flying.
	User-friendly and labour saving.
	Can be used in cold and dark weather in spring and autumn.
	Provides long lasting protection.
	Can be seen easily in the crop