Small predatory mites against small mites

Some pest species are extremely small and hardly visible for the naked eye. Examples are mites of the family Eriophyidae and Tarsonemidae, which are not larger than 0.2 mm. The mites are easily overlooked because of their small size. Moreover, they typically hide deep into plant parts, which can be problematic for biological control with predatory mites when they are too big to enter these microhabitats. Crop protection experts from Wageningen University & Research has selected a number of small species of predatory mites that are better adapted to enter the hiding places of the small plant feeding mites. The new predators will be further tested in tulip bulbs, black berries, amaryllis and bromelia. The work is part of the recently started project with public private funding. Results of the first laboratory trials look promising.

The dry bulb mite on tulip

Small phytophagous mites of the family Eriophyidae and Tarsonemidae are increasingly causing serious crop damage in various ornamental and fruit crops in the Netherlands. The most problematic small mite is currently the tomato russet mite, Aculops lycopersici. Other mites of this family that cause damage are the dry bulb mite, Aceria tulipae, during storage of tulip bulbs and the redberry mite, Acalitus essigi, which causes fruit damage in blackberries. Tarsonemid mites give serious problems in various ornamental greenhouse crops. A major pest in amaryllis is the bulb scale mite Steneotarsonemus laticeps. Similar to the dry bulb mite, this mite hides deep into the bulbs and is thereby very hard to control with pesticides or biological control agents. Bromeliaceae are mainly attacked by the tarsonemid Stenotarsonemus ananas, whereas the most abundant tarsonemids in gerbera are Tarsonemus violae and the broad mite Polyphagotarsonemus latus. These mites live deep in flower microhabitats and cause flower deformation.

The bulb scale mite hide deep into amaryllis bulbs

Although these various crops all require a specific approach for pest control, they all have in common that the phytophagous mites in these crops are extremely small and difficult to reach. Previous research showed that predatory mites that are commercially available are often too big to enter the microhabitats of the small phytophagous mites. However, several species of predatory mites that occur in nature seem to be adapted to these microhabitats. Studies with the coconut mite Aceria guerreronis in palm trees show that some species of predatory mites associated with the coconut mite are typically small sized and have flat bodies which enables them to enter the hiding places of coconut mites. Wageningen University & Research has selected a number of these small sized predatory mites for further research. The first laboratory trials look promising: they all accepted the dry bulb mite, redberry mite and the bulb scale mite are prey. Further research will focus on the control of phytophagous mites in the different cropping systems of flower bulbs, Bromeliaceae and blackberry. The first trials in tulip bulbs are currently running. The project will furthermore develop methods to enhance predatory mite establishment and increase our knowledge about the migration behaviour of tarsonemid and eriophyid mites to better target releases of predatory mites.

This work is part of the public private funded project 'Biological control of plant feeding mites' within the Topsector Horticulture & Starting Materials and runs from 2017 till 2020. The project is funded by the ministry of economic affairs and the private partners Anthos/iBulb, Biobest, KAVB, LTO Glaskracht Nederland, NFO, Amaryllis growers and the cooperatives Bromelia and Cucumber.

Source: Wageningen University & Research