This article is not about pheromones but I will start with these because apple, peach and pear growers in Australia know a fair bit about these for controlling codling and Oriental fruit moths.
Pheromones are a special kind of perfume. The most well known are those produced by female moths to attract males.
Pheromones can work well as control agents against small moths where mated females don’t fly too far.
They are useless as control agents for large moths like Heliothis and armyworms that fly hundreds of kilometres in a night and mate outside any area treated with a pheromone disruption agent.
This is a tale of how certain floral perfumes have been developed for these long–distance fliers, some of which are important pests.
GM is one solution
Repeated sprays for Heliothis: cotton bollworm, corn earworm, tomato fruitworm (Helicoverpa armigera), has led to multiple insecticide resistance.
The same applies for Oriental leafworm Spodoptera litura and beet armyworm Spodoptera exigua in China and elsewhere.
GM (genetically modified plants) can solve the problem of Heliothis in cotton—providing the technology keeps ahead of resistance—but for food crops, this is not a favoured option.
The attraction of flowers
For years, entomologists have known that many moths, particularly large strong flying moths, are attracted to flowers.
The female moths need energy to develop their ovaries and increase their fecundity, and have a strong drive to find sugar.
The males use the flowers as a convenient place to meet females and don’t mind a nectar feed as well.
The flowers can be weeds or wildflowers, hundreds of metres or even kilometres away from the crop where the females lay eggs. To locate flowers that produce nectar, moths follow perfume trails.
Perfume trails
A strategy was developed to use the strong flying ability of these moths as a means for their control.
A sprayable bait that could attract and kill young female moths could be highly effective.
In the late 1990s, USDA research workers analysed perfumes of some highly attractive flowers that release their perfumes at night. These included Gaura longifolia (a relative of the butterfly bush, Gaura lindheimeri—a common garden plant in Australia), and Japanese honeysuckle Lonicera japonica, a fragrant and sometimes weedy garden plant.
This work revealed more than 40 compounds that made up the fragrances and a smaller number which were found to be particularly attractive to Corn Earworm Helicoverpa zea.
Work on Australian flowering plants including Eucalyptus was done at the University of Armidale and revealed a similar group of compounds which proved to be attractive for Australian Helicoverpa species.
Commercialisation
Attractive perfumes are not much use to farmers until they are turned into products that are effective, practical and easy to use.
(cont next issue)
See this article in Tree Fruit Jan 2019
