Transition now to new pest controls
Summer codling moth and leafroller control.
Leafroller damage, left. Codling moth damage, right.
This is the fourth article in a series intended to help the apple industry transition insect pest management programs in apple to the use of new control technologies. This article focuses on control of pests, especially codling moth and leafrollers, in the second half of the growing season, roughly from early July through September.
An important goal of the apple pest management program lies in achieving good control of key pests, codling moth and leafrollers, in the first part of the growing season, from April through June. Achieving this goal provides opportunities to reduce pesticide inputs in mid- to late summer (July and August) and to choose products that are soft on natural enemies.
If summer leafroller control is necessary because a significant carryover population from the spring is expected, then treatments should be applied at the beginning of the egg-hatch period in order to minimize fruit injury. Because the life histories of leafrollers and codling moth do not match up well in the summer period, it is not possible to achieve excellent coincidental control of both pests with a single application of an insect growth regulator as it was in the spring. The insecticide products of choice for this time of year are Success, Proclaim, Bt, Rimon or Intrepid.
Esteem should not be used for summer leafroller control. Success and Proclaim are fast-acting products and, unless populations are unusually high, will control leafroller larvae with one application when well timed (see Summer Leafroller Control). The insect growth regulators Rimon or Intrepid can also provide good leafroller control at this time, but they act more slowly to kill larvae. If Bt products are used, repeat applications will most likely be needed, as residues last only about seven days in the summer.
New models will help in timing summer leafroller controls. Optimum timing for control of summer-generation leafroller larvae is during the egg-hatch period. [Consult the WSU Decision Aid System Web site (http:// das.wsu.edu/) to set up your own access to leafroller model predictions based on an AgWeatherNet location in your area.]
Codling moth starts its second life cycle at approximately 900 degree-days after biofix (first moth flight), when moths of the second generation emerge and begin laying eggs. If an insect growth regulator (Rimon or Intrepid) or oil is used to target codling moth eggs, it should be applied at 1200 degree-days (see Summer Codling Moth Control). The insect growth regulators applied at this time will provide additional control of leafroller larvae but should not be relied upon as the sole leafroller control, as significant fruit injury can have already occurred by this time. Significant hatch of codling moth eggs begins at 1250 degree-days, when larvicide applications should begin. Larvicides (Assail, Calypso, Intrepid, or granulovirus) from any insecticide class not used in the first generation could fit here. If, however, an insect growth regulator or oil was applied at 1200 degree-days, then growers can delay the first larvicide application until 1350 degree-days. If virus is used for codling moth control, repeat applications will be necessary every seven days during the peak egg-hatch period (1350 to1750 degree-days).
Washington growers now have a number of new products available for codling moth and leafroller control. The key to conserving the efficacy of these new products will be to avoid their overuse. The use of codling moth mating disruption has been, and will continue to be, a very important means of reducing the need for insecticide input and is therefore a valuable tool in a resistance management program.
In most orchards using codling moth mating disruption, insecticides will be necessary to supplement control. In choosing these supplemental controls, it is important for growers to conscientiously avoid using insecticides with the same mode of action against successive generations of a pest.
The neonicotinyls (Assail, Calypso, Clutch, and Provado) all have slightly different pest activity profiles. However, their mode of action is the same, and they should be used in such a way as to avoid exposing successive generations of any pest to their residues.
The insect growth regulators Esteem, Intrepid, and Rimon all target insect development, but their modes of action are different, making it possible to use these products in rotation with one another without selecting for insecticide resistance.
Other insecticides, like Success and Proclaim, fit into different classes with unique modes of action, and these can be rotated with neonicotinyls and insect growth regulators to develop a sound resistance management program.
In addition, the biological insecticides, oil, granulovirus, and Bt, are also unique in the way that they kill pests, and they make good options to use in a product rotation plan where pest pressures are low.
It can become a challenge to keep track of which insecticide class has already been used in the growing season and should therefore be avoided later in the growing season. One method that should help growers keep track of insecticide use is to adopt a resistance management checklist such as the one shown. Here, the growing season is divided into two parts, based primarily on the development cycles of codling moth and leafrollers. If a product is used in the first part of the season, it is marked "X." It is possible to use a product from the same class, or even the same product, more than one time in the first part of the season, because only one generation of a pest is exposed to the chemical class.
It becomes clear that the early-season choices limit what products can be used in the second part of the season if a sound resistance management program is being followed. Planning is therefore an important part of a resistance management program since the choice of pest-control products used at one time of the season will influence options available at a later part of the season. Advanced planning will lead to better management decisions in pest control and help to ensure that Washington growers will retain the use of new pest control products in their pest management programs.