Southeastern Apple ProductionENTOMOLOGY |
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James F. Walgenbach
Extension Entomologist
Mid-May through mid-June is a critical time for assessing first generation codling moth populations to determine their potential for causing damage, and to make decisions on the need for and timing of insecticide applications to prevent damage. The choice of insecticides to use against codling moth should be limited to only a few chemicals, while the number and timing of applications will depend on the intensity of moth pressure in specific orchards. The only reliable method of measuring the intensity on a preventive basis is by using pheromone traps to monitor moth activity, although history of damage in an orchard is also useful in assessing population density.
A widely accepted insecticide resistance management (IRM) practice for the codling moth is to NOT expose successive generations against the same insecticide or insecticide(s) with the same modes of action. The most effective insecticides available for codling moth control belong to two chemical groups, 1) the spinosyns that include spinetoram, the active ingredient in Delegate, and 2) the anthranillic diamides that include chlorantraniliprole (active ingredient in Altacor) and flubendiamide (active ingredient in Belt). Chlorantraniliprole is also sold as a premix with thiamethoxam (Voliam Flexi). As shown in Fig. 1, first generation codling moth flight occurs in May and June, and second generation in late July and August. Hence, if Delegate is used against the first generation, it should not be used later in the season when second generation flight occurs. Instead Altacor (or Belt or Voliam Flexi) should be used against the second generation. Alternatively, if Altacor or Belt is used against the first generation, Delegate should be used against the second generation.
Large
plot field trials in North Carolina during the past
two years have demonstrated that the same excellent
level of codling moth control can be expected regardless
of whether Delegate or Altacor is used during the
first or second generations. The most important thing
to remember is that whatever insecticide is used
in May and June against the first generation, it
should NOT be used in July or August against the
second generation. The most compelling argument for
using one product early or late is that Altacor has
longer residual activity than Delegate, and therefore
is a good choice late in the season when both second
generation codling moth and tufted apple bud moth
are potential threats for several weeks after harvest
has begun.
Pheromone traps to monitor codling moths are useful tools to help determine the timing and frequency of insecticide applications necessary to reduce the potential for damage. Pheromone traps for codling moth consist of bottom liners (coated with a sticky substance) covered by a top, and a lure containing the sex pheromone of the codling moth is placed inside the trap. Both Delta and Wing style traps will work for codling moth, but in our experience Delta style traps are easier to maintain, capture more moths, and can be reused for several years. Pheromone lures do not last the entire season and must be replaced at regular intervals. Several companies make different types of lures, some that will last for several months and others that will last for only a month. During our recent RAMP project we used Trece L2 lures that emit pheromone for 12 weeks, so they need to be replaced only once during the season. Finally, because the upper apple canopy is where codling moths fly and mate, it is recommended that traps be placed in the upper one-third of the canopy, which can be accomplished with a bamboo pole (see the figure below).
It is also important to recognize that codling moth
populations are not evenly dispersed throughout an
orchard, and there are “hot” spots that
may or may not be predictable. Also, a pheromone trap
will only attract and capture moths that are in close
proximity to a trap (possibly as close as 100 ft),
so it is necessary to have multiple traps in an orchard.
The number of traps required to accurately assess a
population within an orchard needs to be a compromise
between what is actually needed and what is practical.
While the exact number is debatable, it is generally
agreed among tree fruit entomologists that traps should
be deployed at a density of 1 trap for every 3 to 5
acres. But, too few traps are better than no traps
at all! Traps should be checked once per week
and the number of moths captured in each trap recorded
and a permanent record maintained.
Decisions on the timing and frequency of insecticide sprays targeting codling moth should be based on the intensity of a codling moth population, because an orchard with a high population will obviously require more frequent insecticide use than one with a low population. Advantages to reducing the number of sprays to the minimum needed include a cost savings and reduced potential for codling moth to develop resistance to new insecticides.
Classifying the size of a codling moth population is somewhat subjective, but knowledge of the history of damage in an orchard and the number of moths captured in pheromone traps are the best tools to determine the need for insecticide use. Below are some guidelines on determining the need for insecticide use in orchards managed with and without mating disruption.
In mating disruption orchards it should be recognized that this passive management tool will control low populations of codling moths, so there are greater opportunities to eliminate insecticide use compared to non-disrupted orchards.
In orchards where mating disruption is not used, there is a higher level of risk associated with eliminating insecticide used compared to disrupted orchards, because there is no “backup” control program to account for potential errors in the interpretation of trap captures.
Recommendations for the use of agricultural chemicals are included in this publication as a convenience to the reader. The use of brand names and any mention or listing of commercial products or services in this publication does not imply endorsement by North Carolina Cooperative Extension nor discrimination against similar products or services not mentioned. Individuals who use agricultural chemicals are responsible for ensuring that the intended use complies with current regulations and conforms to the product label. Be sure to obtain current information about usage regulations and examine a current product label before applying any chemical. For assistance, contact your county Cooperative Extension agent.
Southeastern Apple Production
Mountain
Horticultural Crops Research & Extension
Center
455 Research Drive
Mills River, NC 28759
Phone: 828.684.3562 ~ Fax: 828.684.8715
Email: jim_walgenbach@ncsu.edu
Web Crafters: Anne S. Napier and
Steve Schoof
Email:
steve_schoof@ncsu.edu
Posted May 19, 2010