In the business of apple production, knowing when i.e being able to predict when to make timely applications for disease and insect pests is not optional as we move further into the age of narrowing insecticidal specificity. The loss of broad spectrum insecticides and development of newer ‘family specific’ materials requires a greater need for scouting, an understanding historical emergence of the insect complex throughout the season on your farm so as to optimize timing for management applications.
Plum Curculio: Accumulated degree days (base 50°F) from 95% McIntosh Petal Fall through 3 June has reached 338DD. This model prediction signals that we have turned the corner on 308DD (June 1st) indicating the end of plum curculio (PC) migration by the 2nd of June. Effective insecticide residual for PC beyond this date will have provided adequate control of the remaining beetle immigrants.
However, in some of the Hudson Valley’s colder sites, freeze injury has left very few apples if any to support the ‘wild’ population of PC that typically utilize abandoned and naturalized apple trees. In Michigan these populations have been found to migrate into orchards in search of egg laying sites in years of few wild apple. These sites may require longer insecticide residual as these beetles prolong the migration period.
We also see continuing PC activity in organic blocks where Surround WP, Entrust and Pyganic provide little in the way of PC mortality. Only by protecting fruit from oviposition through maintaining effective coverage and residual will PC egg laying be controlled.
Scouting: We are now seeing adult moth emergence in the field, signaling the beginning of a sequence of events leading to egg hatch, larval feeding and fruit injury if left unmanaged.
Don’t confuse the damage from European apple sawfly (EAS) with internal lepidopteran (OFM and CM). The codling moth frass tend to be dry in very small pellets that exude from the calex end OR from a red ‘bulls-eye’ hole in the shoulder of the fruit. EAS produces a ‘runny’, very wet frass that oozes from the large hole at the calex end.
Predictive Modeling: The two pome fruit insects of concern at this point in time are the codling moth (CM) and the obliquebanded leafroller (OBLR). Effective materials should be maintained for codling moth management this coming week. OBLR emergence is predicted to begin the 6th of June, with management timed for first hatch.
The use of pheromone traps to determine presence of these insects should be placed in each block of concern, hung in the upper tree canopy at 6-8′ trees (Gemplers, Sentry, Great Lakes IPM. Sustained pheromone trap captures of adult males of both species were captured last week. We are averaging over 10 CM per day and 1.2 OBLR per day.
Models we use to calculate the timing of pest management are based on the the lowest temperature at which an insect egg and larva develop, called developmental base temperature, unique for each insect species. For codling moth, a base 50F is used. Two timings should be considered when applying insecticides. At 50 Degree Days (DD) the insecticide Rimon, an insect growth regulator, would be applied prior to egg laying. Having the insecticide beneath the egg provides greatest efficacy for this material. First hatch begins at 220DD at which point . CM first eggs are laid at about 50 DD and the first eggs usually hatch after about 220 DD (Wednesday June 3rd of this week).
For obliquebanded leafroller, base 43F is used. At this lower temperature at which the insect develops it will accumulate degree days more quickly. The first timing for management should begin at first hatch in blocks with historical injury from the pest. The second timing should be made 14 days after the first to cover the remaining hatch.
If materials such as Dipel (containing Bacillus thuringiensis or Bt) are used in organic apple production, management will not be effective against the remaining codling moth population. In this case Entrust (spinosad) should be used against both leafroller and the internal worm complex.
Management: A comprehensive guide to CM and OFM management, developed by Debbie Breth and Art Agnello provides details to CM management.
Resistance Management: CM, and OBLR have 2-3 generations per year while the OFM will have 3-4 generations. As the newly hatching larvae of CM, OFM, and OBLR are the target life stage for control, maintaining an understanding of emergence throughout the season is important for optimum management timing. When adult pests are present signals degree day accumulations and modeling predictions of larval hatch.
OBLR and CM have both shown development of either resistance, or reduced susceptibility to insecticide classes. Thus the use of rotational programs for each generation will likely prolong the efficacy of newer insecticide tools such as Delegate and Altacor. A single generation of each insect should be treated with a single insecticide class. So, if you plan to treat OBLR in two applications of the 1st summer generation, then 2 applications of Delegate (Spinetoram IRAC Class 5) should be made at 14 day intervals. In August when the 2nd generation of OBLR appears and needs management, a second class of chemistry, such as Altacor (Chlorantraniliprole, in IRAC Class 28) can be used to reduce the overwinter generation