dhr. dr. A.R.M. (Arne) Janssen

  • Faculteit der Natuurwetenschappen, Wiskunde en Informatica
  • POSTBUS  94240
    1090 GE  Amsterdam
    Kamernummer: C3.219
  • A.R.M.Janssen@uva.nl
    T:  0205257751

A spider mite that manipulates plant defence

When herbivores such as spider mites attack a plant, complex plant defence mechanisms are activated.In collaboration with colleagues from the Federal Universities of Viçosa and Tocantins, Brazil, we recently discovered that certain spider mites are able to disrupt these mechanisms, effectively disarming the plant.

Phytopathogens and herbivores induce plant defences. There is evidence that some pathogens suppress these defences by interfering with signaling pathways involved in the defence, but such evidence is scarce for herbivores. We found that the invasive spider mite Tetranychus evansi suppresses the induction of signaling routes involved in induced plant defences in tomato. As a result, the mites performed much better on previously attacked plants than on non-attacked plants. These findings provide a new perspective on plant-herbivore interactions, plant protection and plant resistance to invasive species.
Another mite species, the closely related T. urticae can also profit from the suppression of induction of defence by T. evansi . However, the latter protects leaf area with down-regulated plant defence by covering it with a dense web that is difficult to penetrate by T. urticae .



Adults, eggs and web of Tetranychus evansi on a tomato leaf. (photo: Jan van Arkel, IBED)





Parasitoid turns its host into a bodyguard

Parasites can induce dramatic changes of behaviour in their host species. This behaviour is thought to be detrimental to the host, but beneficial to the parasite. In a joint publication, researchers from the University of Amsterdam and University of Viçosa ( Brazil ) show evidence of spectacular behavioural changes induced by a parasitic wasp in the caterpillar of a moth species.

After the wasp ( Glyptapanteles sp.) has oviposited eggs in the body of a caterpillar ( Thyrinteina leucocerae ), these develop into larvae that live on the body fluids of the caterpillar. After the wasp larvae crawl out of the caterpillar to pupate, the caterpillar acts as a bodyguard to defend them from predator attacks. This results in a twofold reduction of predation of the wasp pupae in the field.

After several days, the adult wasps emerge from their pupae and the caterpillar dies.


A caterpillar standing guard near pupae of its parasitoids. (photo Jose Lino Neto, Federal University of Viçosa, Brazil)

For further information, see these links:









  • M.W. Sabelis, R. Hanna, A. Onzo, A. Pallini, I. Cakmak & A. Janssen (2009). Multiple predators, intraguild interactions and biological control of a single spider mite species. In E. Palevsky, P.G. Weintraub, U. Gerson & S. Simoni (Eds.), IOBC/WPRS working group „Integrated Control of Plant-Feeding Mites”: Proceedings of a meeting at Florence (Italy), 9–12 March, 2009 Vol. 50. IOBC/WPRS Bulletin (pp. 83-94). Montfavet: IOBC/WPRS.


  • M.W. Sabelis, A. Janssen, I. Lesna, N.S. Aratchige, M. Nomikou & P.C.J. van Rijn (2008). Developments in the use of predatory mites for biological pest control. In A. Enkegaard (Ed.), Working group "Integrated Control in Protected Crops, Temperate Climate": Proceedings of the meeting at Sint-Michielsgestel (the Netherlands), 21-25 April, 2008 Vol. 32. IOBC/WPRS Bulletin (pp. 187-199). Montfavet: IOBC/WPRS.
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