Today’s post is written by Tom Harper, “orchard-meister” of the B H Ranch.
Do you have worms in your apples or pears from your orchard? Then you have codling moths! If you live in the Foothills and you want to get rid of them, now is the time to start doing something.
Codling Moth Life Cycle in 200 words or less (whew):
A codling moth begins its life as a very very tiny egg, laid on a leaf or the base of a fruit blossom. It will hatch into a tiny caterpillar, and in very short order will chew its way into your fruit, tunneling towards the core. Safely inside the fruit, it will feast until it’s time to pupate. Then it will chew its way back out, pupate, and later emerge as a moth, to begin the next generation. We usually expect three or four generations per season, from April through September. The codling moth spends the winter in the pupa stage, hiding typically in the rough bark of pear trees. When Winter turns to Spring, and sunset temperatures approach the low 60s, the over-wintered moths emerge and begin to fly and mate with other moths, and the cycle repeats. The codling moth is most vulnerable in the very short time between when it hatches, and when it enters the fruit. Once it’s in the fruit, it is safe from the outside world.
The hatching of the first generation is dependent on temperature in two ways:
- Warmer sunset temperatures will cause last year’s overwintered moths to begin flying, mating, and laying eggs. The date this begins is called the biofix.
- How long the eggs then take to hatch depends on how warm the subsequent days are. If temperatures are warmer, the moths will hatch sooner. In a cool year, it will take longer. We use degree-days to calculate when the eggs hatch.
We start our codling moth management program in early April, before the trees are blooming. We begin by setting out pheromone traps, usually three spread throughout our two acres of pears. We check the traps daily, and record the number of moths caught in them. Tracking how many moths are caught every night and maintaining daily trap counts lets us know when the moths begin flying, and we can determine the dates of maximum moth activity. The first date we begin to catch moths consistently is called the biofix. That date is the starting point for our spray-timing calculation.
We also need a measurement of how warm the weather has been to predict when the eggs will hatch. This is provided by tracking degree-days. Degree-days are accumulated based on the maximum and minimum temperatures for every day. We used to track these with our own maximum-minimum thermometer, but have since discovered we are located near a state-run station that provides this information over the Internet: http://wwwcimis.water.ca.gov/cimis/welcome.jsp (that’s the California Irrigation Management Information System, hosted by the Department of Water Resources; they also provide temperature information to help us irrigate — your tax dollars helping farmers to feed you). The University of California Davis (more tax dollars at work) provides a codling moth degree-day calculator that we use with these temperatures to predict when the eggs will hatch, and when we need to spray. When 250 to 300 degree-days have accumulated, it’s time to spray.
Organic, microbial control of codling moth
The spray we use is a microbial virus that targets only the codling moth. The virus attacks the moth’s digestive system. No other insects are impacted. That’s good because beneficial insects like bees or ladybugs or lacewings are free to go about their business of eating the aphids and leafhoppers and caterpillars that can cause damage. We spray this granuovirus six times throughout the three generations of codling moth. Altogether, we use one quart of spray, about six ounces per 150 gallons. Because it a biological — not synthetic — control, it’s organic.
Let us do the spray-timing calculations for you! We’ll post on our Facebook page when we are spraying, in case you live near us (at the 1,200 foot level, in Auburn). Usually we start in mid-May.
In a home orchard, you can use an organic spray, such as spinosad, to control the codling moth. Follow label directions, and be careful not to spray on any blooming plants, because it can kill honey bees and other beneficials.
UC Davis provides additional recommendations for codling moth control in home orchards. These include organic methods like trapping, using parasitic wasps, and fruit bagging, if you don’t want to or can’t spray. www.ipm.ucdavis.edu