Coddling Moth

Coddling Moth trap is lowered from tree on cord to check for moths. Then it is raised to about 20 feet to catch moths.

Insects are a big concern for walnut farmers at this time of year. The Coddling Moth is one of them.
They usually have three generations each growing season. The first overwinters from the previous year, surviving between cracks in tree bark or debris on the ground. They come out as moths in early to mid April, mate and lay their eggs on or near the developing walnuts. The larva hatch out and eat their way into a nearby walnut.
The second comes out in early to mid June, mate and lays their eggs on what are now mostly full-sized nuts. The larvas again move to a nut and eat their way in. The third comes out in late July or August, and because of the shorter days and cooler weather in September and October, usually remains as a larva until spring. Some warmer growing areas can have a fourth generation, but that is rare in Red Bluff.
If left uncontrolled, Coddling Moth can cause extensive economic damage to the crop, even to the point of making it unmarketable. Fortunately a lot of scientific research has been done resulting in various control strategies to help keep damage to a minimum.
Most moth control is done by spraying an insecticide on the trees. The idea is not to kill off the flying moths, although any that are around will be goners. The real strategy is to coat the outside of the walnut husks with the insecticide. This will kill the moth larva when they eat into the nuts.
One problem with this method is the insecticides only last 10 to 15 days before they become ineffective. That means timing is critical. If sprayed too early or too late some larva will be missed.
Through research it has been determined that it takes a specific number of day degrees for a Coddling Moth generation to be completed. If the spray is applied at a certain point in that day degree cycle, the generation can be suppressed.
It takes a fair amount of monitoring and attention to get an accurate total of day degrees. Here in Red Bluff the Davis University of California extension office monitors this for farmers.
One of the newest control measures is called mating disruption. The idea is that if we can prevent the moths from mating, then there will be no eggs, thus no damage.
When mating, the moths find each other through a pheromone scent given off by the female. The disruption occurs from a number of “puffers” or aerosol cans located throughout the orchard that emits Coddling Moth pheromone. These automatically dispense a puff of pheromone at predetermined intervals through the night during moth mating time. With the orchard saturated in pheromone, the moths cannot find each other to mate. This method is new but it shows great promise.
The cost is currently why most farmers are not using them. They are waiting for mass production to kick in and the price to come down to an affordable level.