By AMY ADAMS
Illustrations by AUDRA LOYAL
Male coddling moths have a lot to worry about in this world, what with
having to find apple, pear or walnut trees to infest, avoid farmers'
pesticides, and finally find a mate. Their job got a little harder six
years ago, when a UC Santa Cruz entomologist named Sean Swezey encouraged
apple farmers to decorate their trees with alluring decoys. The devices
confuse male moths, and prevent them from mating with females. No sex
means no larvae, and no larvae means no little brown worms to surprise
unsuspecting apple eaters.
This technique relies on the fact that male moths "smell" females with
their antennae. Lusty male moths leave females waiting in the branches
while they court a grey or red twist tie or shiny flap of aluminum covered
in the sex scent
females exude to attract males - called a pheromone. With 100 to 400
dispensers per acre, males are too overwhelmed by the scent of these sexy
gadgets to find females and mate. They are adrift in an aromatic fog,
searching in vain for expectant females. Imagine being in perfume factory
trying to smell an individual person, and you may understand the plight of
today's male moth.
In the ever-escalating battle between moths and men, or pests and farmers,
this latest weapon of the farmer is called "mating disruption". Also
called "male confusion", this technique has reduced damage from pests in a
smorgasbord of fruits and vegetables including artichokes, strawberries,
cherries, and almonds, and has successfully battled the coddling moth.
It's easier than spraying, it's non-toxic, and it doesn't kill off
beneficial insects - a big problem with chemical pesticides. Some "good"
insects help pollinate or may be natural predators of coddling moths and
Coddling moth larvae are the most
serious economic threat to apple orchards across the country. Their
voracious tunneling leaves a tell-tale hole on the apple's surface,
ruining an apple for future sale and costing farmers a percentage of their
profit. The exact amount of profit loss varies wildly by geographic
location and age of the orchard. Sean Swezey, head of UCSC's cooperative
extension program, has a USDA grant to stop these larvae before they ever
get started - by preventing mature moths from mating.
Mating disruption has kept damage from coddling moth larvae under control
in orchards across the state. Steve Loyal, an apple farmer and agriculture
biologist in Santa Ynez, CA, has two percent damage to his apples using
mating disruption, and says, "The cost of losing that percentage is less
than the cost of spraying." Loyal could acheive this level of control
using chemicals, but on his farm mating disruption is both less costly and
allows Loyal to sell his apples as "unsprayed"- a competitive advantage in
the apple market.
Jim Rider, who farms organic apples in Watsonville, CA, has had a similar
experience. "Mating disruption is now the best organic control available,
both in terms of effectiveness and cost," Rider said. However, he can't
estimate damage from coddling moths. "Every year and every block is
different," he says. Mating disruption varies in efficiency by location
and apple type, so it is impossible to predict exactly how effective it
Mating disruption works best in densely planted orchards. The dense canopy
traps pheromones near trees, and therefore near male moths. By the edges
of orchards, or in windy, hilly, or "gappy" orchards, where pheromones may
escape or be blown away, male moths may sniff out females amidst the
thinner haze of pheromone. It is also more successful on early developing
apples such as Gala, Jonagold, Gravenstien, or Red Delicious, which spend
less time on the tree, and therefore have a smaller chance of feeding a
hungry coddling moth larvae. But the technique isn't perfect. Even in
closely planted orchards, males and females may bump into each other by
Mating disruption costs slightly more than conventional sprays. Farmers
pay 75 to 100 dollars per acre per application with one to three
applications a year. But Swezey says mating disruption could save in
convenience what it loses in cost. For every application of every toxic
spray, farmers are required to fill out forms reporting the chemical's
use. Using non-toxic pheromones saves on paperwork and on labor, balancing
out the cost increase.
"We hope to get the cost down
to more encouraging levels," said Swezey. Then, he hopes, more
farmers will be hindering amorous intentions of moths on their farms.
For more information on mating disruption call Sean Swezey at (408)