Integrated Pest Management for Apples

AUGUST AND SEPTEMBER (Late-Summer)

Adult Codling Moth.

Codling Moth

Management of the second generation is still based upon pheromone trap catch and degree day accumulation. As mentioned above, pheromone lures should be replaced in mid-July in anticipation of 2nd generation codling moth flight which begins at around 1000 degree days (800 DD after BIOFIX). Egg hatch from this second generation usually begins at around 1250 degree days (1050 DD after BIOFIX). Second generation codling moth is usually successfully controlled in western Washington with a single insecticide application timed at 1660 degree days (1460 DD after BIOFIX). In some cases, trap catch does not exceed the treatment threshold, and a spray is not required. Under heavy pressure, two sprays may be required to control the second generation. Below is the spray decision making system used successfully by apple growers who cooperated in the Nooksack IPM Project in Whatcom County.

• Check pheromone traps weekly beginning in mid-July or at 1200 degree days (1000 DD after BIOFIX).
• Record weekly trap catch.
• Apply spray if 5 or more moths per trap are caught between 1200 and 1450 degree days (1250 DD after BIOFIX).
• If less than 5 moths are caught over this period, do not spray, but start accumulating moth catch from zero again.
• In either event, accumulate moth catch for the next 21 days after 1450 degree days and treat only if 5 or more moths are caught during this period.

4th - 5th Nymph stage of White Apple Leafhopper.

White Apple Leafhopper

Beginning in late July to early August, repeat the leafhopper sampling procedure described in the post-bloom section to evaluate threat from second generation leafhoppers. This timing usually corresponds with the appearance of most of the second generation nymphs in late July and early August. Although it is more difficult due to overlapping stages which occur in the second generation, sprays when necessary should target leafhoppers when most of the population is in this nymph stage of development.

• Visit 3 to 5 sites within the orchard.
• At each site, collect 5 older leaves from each of five trees (25 leaves per site).
• Count the number of nymphs found at each tree and record the total for the site.
• Repeat this procedure for the remaining sites.
• Total and compute the average number of WAL nymphs per leaf.

Threshold levels are less precise for the second generation. The decision to treat should be based on some consideration of several factors including:

• General vigor of the planting and size of the canopy.
• Crop load - more foliar damage can be tolerated if the crop is light.
• Degree of foliar damage from other pests; spider mites and rust mites.
• Concerns regarding picker annoyance during harvest.

If a spray seems necessary, treatment for the second generation should be applied before adult populations begin to increase rapidly, which usually occurs in mid to late August.

Adult European Red Mite.

Spider Mites and Predatory Mites

If a detailed field count or mite brushing has not been conducted, early August is now an appropriate time to do so. Two or three surveys taken during August through early September will provide the information needed to make an informed decision.

• Collect a minimum of 25 leaves per site from 4 to 5 sites within each block.
• Select moderate aged leaves representing different areas within the canopy.
• Examine them closely in the field using a 10X hand lens.
• Record the total number of spider mites and predatory mites found on the underside of the leaves at each site.
• If European red mites are present, the upper leaf surface must be checked as well.
• It is not necessary to count spider mite eggs in the field, but make a note of their relative density.
• If a mite brushing machine is available, it is usually more efficient and accurate to return samples to the lab for brushing, rather than count them in the field.
• A rough treatment threshold is 30 spider mites per leaf.
• A ratio of one predatory mite to 10 spider mites usually indicates good potential for biological control.
• Sample weekly when near threshold to better determine population trends and need for treatment.
• Note the degree of leaf bronzing and relate to population density and intuition regarding need for treatment.

Experience with the Nooksack IPM scouting program illustrated that most orchards do not require late season use of miticides to control spider mites. They usually do not exceed the treatment threshold due to numerous factors including a complex of predatory mites, which regulate them

The Dock Sawfly larva excavates a neat chamber in the flesh of the fruit.

Dock Sawfly

This insect is usually kept under control due to sprays targeting other insect pests such as codling moth. Damage is usually more likely to occur in orchards with reduced insecticide programs and in orchards where weeds (primarily in the buckwheat family) within the row are not well controlled. However, damage to fruit has been observed in western Washington under conditions that should not favor survival of this insect. The following monitoring ideas are suggested:

• Examine weed hosts in the tree row for presence of larvae in mid-September.
• Examine fruit (100 apples per site) in 4 to 5 sites within the orchard to document injury and to determine the percentage of damaged fruit.
• Look for a shallow entry hole which is about 1/12 inch in diameter, often surrounded by a reddish ring.
• Weed control (particularly buckwheat family, which includes dock, sorrel, knotweed, bindweed, and wild buckwheat) within the tree row should reduce likelihood for dock sawfly buildup and the potential to damage fruit.

Main stem and side branches on this tree are severly infected with Anthracnose canker.

Closeup of mature, spore producing Anthracnose canker.

Anthracnose

In early August, return to areas in the orchard where anthracnose was previously identified and flagged in the spring. Look carefully for cankers in these areas, which should now be fully-grown and preparing to release spores, which cause further spread of the disease.

• Remove the dead bark inside of the canker using a pocket knife.
• Place it in a bag and remove it from the orchard.
• It is important to get all the canker bark. Perhaps brushing with a stiff wire brush is beneficial, even if a small amount of injury to callus occurs.
• Small cankered branches, where it is difficult to cut out the old bark, should be removed entirely and destroyed.
• Do not wait until the winter season to remove cankers because infection will have already occurred.
• Partial control may be achieved with specific fungicides applied before and during the fall rainy period, but sanitation (canker removal) is a critical component of an integrated program.