June 5, 2017

Sustained Flight of Codling Moth Established

As I mentioned in a previous post, of all the flying pests we encounter in the upper Midwest, codling moth is one of  the insect pests needing to be controlled the most.  Even though codling moth flight began several weeks ago, due to the cold nights and days in between, we had not been able to establish a sustained flight until this past weekend.   The first sustained flight of two days in a row with 5 or more moths in a trap, was on June 2, this past Saturday.   That first sustained flight date now becomes our biofix date.

Armed with a biofix of June 2, and by calculating the degree days from that biofix date, we can now begin our countdown for our first spray against the "proverbial worm in the apple"!  The degree days are a measure of temperature occurring during a day. They are useful for predicting activity of codling moth (and many other insects) because insects are cold-blooded and their development follows temperature.

Degree-days are determined by use of the average temperature for a day (maximum temperature + minimum temperature/2) and subtracting it from the base temperature  at which the insect does not develop. For the codling moth a base temperature of 50°F is used. (Temperatures above 88°F are upper thresholds for codling moth  activity  and  should  not  be  included in  degree  day accounting.)  As an  example, a day when the high temperature was 80°F and the low temperature was 60°F,  then 20 degree days would accumulate [(80 + 60/2)- 50]. 
Here is a Detailed Growing Degree Day Model for Codling Moth.  Following the model, we know that at 100 degree days after the biofix date codling moths begin to lay eggs and those eggs begin to hatch at 250 degree days after biofix.  It is this information that aids in the timing of necessary sprays for codling moth so they do not damage fruit.  Growers wishing to time sprays based on egg development and hatch should make an application of an insecticide at 250 DD (base 50 degrees F) after the first sustained capture of males in the sex pheromone traps.  If you have no way of monitoring these temperatures for degree days, I anticipate, given the projected forecast for the next week, that a spray date should be around June 13 or 14.  

 There  are only a very limited  number of spray products on the home garden/ consumer market that are available for managing codling moth in home orchards, as I have mentioned in previous posts. All of these require repeated application, timed for periods when eggs are being laid and are hatching, and thorough coverage of fruit.  Let's review these again.

Spinosad. Spinosad is a naturally derived material, produced by soil microbes (active ingredient, spinosyns). Several formulations are available, most of which are allowed to be used in Certified Organic production. Combination with horticultural oil is often useful in increasing control and fruit coverage. Applications should be made at 10-14 day intervals during periods when eggs are hatching. Effects of spinosad on natural enemies of fruit-infesting insects generally are minimal, although some are susceptible.

Acetamiprid.  Acetamiprid is a soft, conventional control and is available as  Ortho Flower, Fruit & Vegetable Insect Killer.  This is a ready to use product that contains .006% acetamiprid, a synthetic organic compound of the family of chemicals that acts as neonicotinoid insecticides. Acetamiprid is a contact, translaminar insecticide for sucking-type insects and can be applied as a foliar spray. Translaminar insecticides are absorbed by leaves and can move through the leaf to the opposite surface they contact, but are not truly systemic and do not move throughout the plant. Acetamiprid acts on a broad spectrum of insects, including aphids, thrips, plum curculio, apple maggot and Lepidoptera, especially codling moth.  When sprayed in the evening at sunset, it will not harm bees or other beneficial insects.

For additional information, see the following fact sheets which are available from local university extension services:

As with all spray products, be sure to follow all label directions on the bottle for proper application.  No endorsement of products mentioned is intended nor is criticism implied of products not mentioned.

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