False yellowhead (Dittrichia viscosa) causes over infestation with the whitefly pest (Trialeurodes vaporariorum) in tomato crops.

*Corresponding author E-mail: Pia.Parolin@sophia.inra.fr Tel.: +33 492 38 64 36 Dittrichia viscosa is an entomophilous plant of the Mediterranean region known to enhance the presence of arthropods which feed on crop pests. The study tested D. viscosa in its function as potential banker plant in tomato crops using the predatory mirid bug Macrolophus pygmaeus to control whitefly pest Trialeurodes vaporariorum. In a greenhouse experiment in Southern France, the study assessed the population development of M. pygmaeus and T. vaporariorum on D. viscosa and on tomato. The question addressed was whether D. viscosa fulfils the function of banker plant while maintaining a predator population and reducing the presence of pests. The results showed that the predators did not only install on D. viscosa, but the combination of D. viscosa + tomato caused an increase of the population of the pest T. vaporariorum. On D. viscosa grown with tomato, 2246 individuals of T. vaporariorum (adults and larvae) were identified after eight weeks, in comparison to 241 on the treatment with only tomato plants and 34 with only D. viscosa. Although D. viscosa is efficient for other species combinations, it is not suitable for the protection of tomatoes against T. vaporariorum in greenhouse, and does not act as banker plant for M. pygmaeus.