Changes to the types of pesticides available for use in fruit production, and the progress of research into biological control of major insect pests, is providing fruit growers with safer, cost-effective and environmentally friendly options to incorporate into their pest management systems.
Codling moth is the most serious pest of pome fruit worldwide and the most damaging pest of commercial apple, pear, quince and nashi orchards in Australia.
It is widely distributed in all Australian states except Western Australia and Northern Territory.
In the past, codling moth was controlled by multiple applications of organophosphate insecticides until the pest developed resistance to those pesticides.
Newer pesticides with lower human toxicity are more specific and more expensive than the organophosphate pesticides they replaced, but also require more attention to timing of spray applications and adherence to resistance management strategies.
Life cycle
Codling moth overwinters on pome fruit trees as hibernating mature caterpillars in cocoons in sheltered areas such as under bark scales on the trunk.
In spring, as day length and temperature increase, the caterpillars emerge from hibernation, enter pupation and eventually emerge as adult moths ready to mate and lay eggs.
Mating disruption
Mating disruption is designed to reduce or delay mating so that fewer eggs are laid.
Although application of sex pheromone mediated mating disruption (MD) can be an effective alternative to the use of pesticides for control of low to moderate population levels of codling moth, control of moderate to high population densities is more problematic.
Several consecutive seasons of area-wide MD treatments are needed to control higher pest population levels. The aim of MD is to prevent, or at least significantly reduce, mating between the moths. However, if there are enough female moths present then mating can still occur.
It is therefore important that fruit growers have access to a number of tools that can help reduce the number of female moths in their orchards.
A new biocontrol agent
A wasp called Mastrus ridens targets codling moth. It has been introduced into Australia.
The wasps were confined in quarantine until approval was granted to release them into orchards (after five years of host-specificity testing).
The first release was into an organic orchard in the Goulburn Valley in 2014 to establish a nursery site and to provide a field site in which establishment issues such as dispersal, predation and hyper-parasitism could be studied.
Since then the research team has been releasing Mastrus into sites in Queensland, New South Wales, South Australia, Tasmania and Southern Victoria.
The team has also been investigating the effects on wasp survival of commonly used orchard pesticides.
Mastrus ridens seeks out hibernating codling moth caterpillars and lays eggs in the cocoon. When the wasp eggs hatch, the wasp larvae feed on the codling moth caterpillars.
(cont next issue)
See this article in Tree Fruit Jan 2019
