Echinothrips escapes integrated control

Problems with Echinothrips in ornamental plant cultivation are increasing. This pest insect may show an explosive development as result of the increasing application of integrated control. Reports of damage by Echinothrips in particular in rose, gerbera, bouvardia and pot plants are increasing. In the summer of 2009 Wageningen UR Greenhouse Horticulture started an investigation into new control methods.

Since its appearance in Europe in the early 1990’s Echinothrips has established itself in many greenhouse crops. The presence of this pest insect often remains unnoticed for a long time. This is because the adults are hardly flying, which means that these insects have already been able to develop considerably in the crop before they are found on the traps. This means that there is a good chance that no timely action is taken as a result of which the plants are turning completely grey.
Existing control methods of this thrips by spraying Vertimec or Conserve cannot be combined with the use of natural enemies. A new approach is required for the further development of integrated control in ornamental plant cultivation. Last summer Wageningen UR Greenhouse Horticulture started testing various chemical and biological products. A number of natural enemies (predatory mites, predatory thrips and predatory bugs) are tested as well for their possibilities for use against Echinothrips. The first part of the study has meanwhile been completed and demonstration on commercial holdings will follow in the course of this year.

Identification
Echinothrips americanus can easily be confused with other leaf-dwelling thrips species. The black body with the white shoulders (wing basis) and legs are characteristic of this thrips species. The prepupae and pupae are found on the crop, not in the soil or the substrate. Pupae and larvae are white. The larvae are easily identified by their wing construction. Spreading from plant to plant and from greenhouse to greenhouse is slow in comparison with Californian thrips.
 
Results
The first part of the study has been completed. This showed the following results:

• Good control of Echinothrips can be achieved with Vertimec Gold, Conserve, Match and Actara. These products cannot be integrated into biological control methods.
• Spraying of Botanigard, a product on the basis of the insect-pathogenic fungus Beauveria bassiana, on plants reduced the population of Echinothrips but the pest insect was not eradicated.
• The predatory mites Amblyseius swirskii and Euseius ovalis were found to reproduce better on Echinothrips than Amblyseius cucumeris, but were still insufficiently effective.
• In the laboratory several stages of thrips were treated with the nematode Steinernema feltiae. No nematodes were found in Echinothrips larvae, pupae or adults. In a greenhouse experiment a nematode solution yielded insufficient control. It did reduce the number of Echinothrips in comparison with water but had no better effect than water plus the surface active agent Motto. In particular the surface active agent was found to have an insecticidal effect on Echinothrips.

Follow-up research
Follow-up research focuses on new natural enemies. A number of promising results have meanwhile been booked. Demonstrations in practice will follow in the course of this season.