Insects and mites update
Apple looper – update on investigation to assess pheromones
As mentioned in the last edition of the WIN, the project to assess whether pheromone traps can be used to monitor moths of apple looper commenced in September.
Four to five replications of traps baited with each of seven different blends of pheromones were deployed at three sites – two organic apple orchards, in the Perth Hills and Manjimup, and one vineyard in the Carbanup area.
The traps were checked weekly for apple looper moths and foliage and flower clusters/fruitlets checked on the same day for the larvae.
Very few moths were caught in the pheromone traps. To some extent, this reflected the low abundance of looper larvae from the observations in the foliage of grapevines and apple trees where traps were located. However, nearby trees and vines were infested with looper larvae at levels considered high enough to warrant use of insecticide.
The conclusion from the study was that the pheromones used were not sufficiently attractive for the detection of looper moths.
If pheromones are to be used to warn of impending damage to grape and apple crops by apple looper larvae, consideration needs to be given to identifying the chemistry of the natural pheromone so that a synthetic compound can be produced.
A full report on this project will be available in early 2016.
Six-spotted mite – the experience with predatory mites in avocado orchards in 2015
This season, six avocado orchards in the Pemberton area were monitored to prevent a re-occurrence of defoliation experienced in spring – early summer 2014 by six-spotted mite. Being deciduous, grapevines typically don't experience premature defoliation early in the season, therefore the experience of applying miticide and introducing predatory mites in avocado orchards may have some relevance to managing six-spotted mite in vineyards.
It was found that early monitoring across orchards was critical in recognising infestations early enough to take action with a miticide application to prevent significant levels of defoliation. Unlike the reasonably obvious mite feeding symptoms present on leaves of grapevines, infestations on avocadoes require monitoring for the mites themselves because leaf feeding symptoms are much more subtle.
Release of two species of predatory mites on a small number of infested avocado trees in January 2015 were checked for predatory mite survival and effect on the pest mite. While populations of six-spotted mite increased to levels higher than nearby trees that were sprayed, the predatory mites survived in the release trees and seemed to keep pest mite numbers below levels that prevented the trees from dropping leaves.
Severe defoliation of avocado trees occurred in areas where the pest mites were not detected early enough or were detected but a spray was not applied early enough. This latter situation is a reflection of the inexperience we have with infestations of this pest mite in avocados.
If vignerons experiencing consistent problems with six-spotted mite and wish to experiment with predatory mites, the species used were Metaseiulus occidentalis and Neoseiulus californicus. These are available from suppliers listed on the Australian Biological Control website.
More information on six-spotted mite can be found on the DAFWA website or by contacting Stewart Learmonth or Helen Collie.