With petal fall sprays now being applied, or near completion in lower elevation orchards, this week will focus on management options for key pests to target at First Cover – codling moth and San Jose scale.

Traditionally, the first cover spray is applied about 10 to 14 days after petal fall, but optimum timing should be based on the codling moth degree-day model.

Biofix (i.e., when degree-day accumulation begins) is set when pheromone traps capture the first moth of the year. In Henderson County this date was April 11. While we do not have traps in other locations, the first capture in Wilkes County is usually similar to that of Henderson, and in Cleveland County it is generally about one week before Henderson County.

The degree-day model predicts percentage emergence of moths from the pupal stage and cumulative hatch of eggs for each of the two to three generations per year. The timing and number of applications is dependent on the intensity of populations, because in orchards with low populations insecticide sprays can be delayed, resulting in only one or two total sprays against the first generation. Initial egg hatch begins at about 250 DD after biofix, and under high populations sprays can be necessary up to 1000 DD, resulting in 3 or 4 sprays against the first generation alone.

While pheromone traps are not an exact measure of codling moth population abundance, they are the best tool to gauge population intensity. Based on my experience, the following can be used as a guideline for timing insecticide sprays. Note that if pheromone traps are not being used, it would be wise to assume that a high population exists in an orchard, unless experience tells you otherwise.

For at least 15 years the apple industry has successfully relied on the use of the diamides (MOA group 28, including Altacor, Exeril, Verdepryn) and the spinosyns (MOA group 5, Delegate) for control of codling moth. Rotation of these two groups (diamides or spinosyn) against the first and second generation has worked well as a resistance management tool. However, in 2025 a population resistant to the diamides was detected in one orchard in Henderson County. This resistance was documented by Dr. Greg Krawczyk at Penn State, who has conducted resistance monitoring in Pennsylvania for the past several years and to whom we sent larvae last year. The extent of diamide resistance in North Carolina is not known, but similar to Pennsylvania, it is not believed to be widespread. Unless you have experienced codling moth damage in recent years, it is probably not necessary to eliminate the diamides from your rotation.

If you suspect you have experienced control failures with the diamides, the new insecticide Zivalgo is an excellent alternative for codling moth (as well as for oriental fruit moth (OFM) and leafrollers). It is registered for use at 1.6 to 2.5 fl oz per acre. Considering that codling moth populations have not been exposed to this new chemistry (isoxazolines, MOA group 30), rates at the lower end (1.6 to 2.0 oz) should work well. Zivalgo has at least 14-day residual activity and is one of the few insecticides that have activity against adults as well as larvae. In addition, it also has excellent activity against European red mite (ERM), and with translaminar activity provides preventive control of ERM when applied for first generation codling moth.

In those orchards where an insecticide effective against SJS was not applied before bloom, targeting the crawler stage at first cover (or between petal fall and first cover) is the last opportunity for effective preventive control. There are several very effective insecticides for SJS at this time, including Esteem, Centaur, and Movento. While Assail is generally rated a notch below these products, it still provides good control, especially at higher rates (8 oz/A). Additional benefits associated with these insecticides when applied for crawlers include:

• Esteem (MOA group 17): Has translaminar activity and provides good residual activity, and also has ovicidal activity against codling moth.
• Centaur (MOA group 16): Is primarily a scale material. While it does control white apple leafhopper, this is a very sporadic pest of apples in NC.
• Movento (MOA group 23): Has systemic activity and moves in both directions in the tree; i.e., moves via the phloem to the roots and xylem to foliage. This timing will also provide preventive control of aphids, including woolly apple aphids.
• Assail (MOA group 4): Has translaminar activity and gives good SJS control. It also serves as an effective first cover spray for codling moth under low to moderate pressure, particularly when applied at the higher rate of 8 oz/acre.

SJS is a permanent resident of the orchard and a sessile pest, two attributes that are highly conducive to resistance development. Hence, it is strongly recommended that insecticides with different modes of action (MOA) be rotated annually. Fortunately, the four insecticides mentioned above all belong to different MOA groups.

Learn more about southeastern apple insect pests at the Apple Insect Management page.

About degree-day models