title: Mass Release of Trichogramma evanescens and T. cacoeciae Can Reduce Damage by the Apple Codling Moth Cydia pomonella in Organic Orchards under Pheromone Disruption.
abstract: Cydia pomonellais a major pest in apples in Denmark.Trichogrammaspp. are known biocontrol agents ofC. pomonellaeggs and two naturally occurring species in Denmark, which are also both commercially available, were chosen for mass-release trials.Trichogramma evanescens,T. cacoeciaeor a mix of the two species were evaluated for mass-release to controlC. pomonellain two commercial organic apple orchards, one in 2012 and one in 2013, using a complete randomized block design. Pheromone disruption was used in both orchards, making the study one of the first to evaluateTrichogrammarelease under a mating disruption regime.Trichogrammaactivity was assessed using bait cards withSitotroga cerealellaeggs. The percentC. pomonelladamaged fruit was recorded and the fruit yield was estimated. In 2012 cool and wet weather conditions resulted in lowTrichogrammaactivity (<16% bait cards parasitized) and onlyT. evanescenswas recovered from bait cards. The conditions in 2013 were warmer butT. evanescenswas still >10 times more frequently found in bait cards thanT. cacoeciae. There was a significant effect of the treatment and year (p= 0.009) and of the sampling period (p= 0.0008) onTrichogrammaactivity (proportion bait cards parasitized), with no significant difference between treatments in 2012. In 2013 the highest activity was found inT. evanescensand mixed treatments, in July reaching 69% and 47% bait cards parasitized, respectively. Fruit damage was highest in the control plots (7.1%) compared withTrichogrammatreatments (T. evanescens2.8%,T. cacoeciae3.8%, mixed 3.3%) (p= 0.028). Yield did not differ significantly between treatments. In conclusion,Trichogrammamass release is a promising biocontrol method for use in the Danish climate, but further studies are needed regarding the performance of the twoTrichogrammaspecies (and potential otherTrichogrammaspecies) towardsC. pomonellaeggs in the field to identify the best biocontrol candidate.
authors.affiliation: Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark. les@plen.ku.dk.
authors.forename: Lene
authors.initials: L
authors.lastname: Sigsgaard
authors.affiliation: Julius Kühn Institut, Heinrichstraße 243, Annette, D-64287 Darmstadt, Germany. Annette.Herz@julius-kuehn.de.
authors.forename: Annette
authors.initials: A
authors.lastname: Herz
authors.affiliation: Ecoadvice, Gefion, Fulbyvej 15, DK-4180 Sorø, Denmark. mak@ecoadvice.dk.
authors.forename: Maren
authors.initials: M
authors.lastname: Korsgaard
authors.affiliation: AMW Nützlinge GmbH, Ausserhalb 54, D-64319 Pfungstadt, Germany. wuehrer@amwnuetzlinge.de.
authors.forename: Bernd
authors.initials: B
authors.lastname: Wührer
keywords: Cydia pomonella; Trichogramma cacoeciae; Trichogramma evanescens; biological control; organic production