Integrated Pest Management for Apples

Primary scab infection of foliage.

Apple Scab

Continue to monitor for scab infection periods as described in the dormant and pre-bloom section in order to make timely fungicide applications that stop primary infection. Make a note of any areas within the orchard where primary infection of foliage is apparent. If you see primary leaf infection, take a closer look at developing fruit to determine the degree of fruit infection. Apply sprays to control secondary scab if one or two primary scab lesions per tree are present.

Anthracnose

Scout the orchard in its entirety several times between mid-April and mid-June for newly developing and older cankers.

• Using a pocket knife, remove and destroy the bark within any older cankers to stop further spread of the disease.
• Where older cankers are detected, examine that tree and nearby trees closely for newly developing cankers.
• Flag trees that have developing cankers, map their location and return in August to remove these cankers before they begin producing spores.
• Consider removing infected trees entirely.

Obliquebanded Leafroller

If sampling at the pink stage (described in the previous section) indicated need for treatment then a second Bt. application would normally be made during bloom, 10 days to 2 weeks following the initial spray. This is the last opportunity to control over-wintering OBLR caterpillars. If sampling has not yet been conducted for this insect, do so now by examining a minimum of 100 developing fruit clusters for caterpillars and webbing within fruit clusters.

Surface damage to fruit caused by Syneta Beetle feeding.

Syneta Beetle

Use a beating tray as described in the previous section or direct observation during and immediately after bloom.

• Visit 3 to 5 sites within the orchard, focusing on borders adjacent to woodlots if present.
• Take a minimum of 10 tray samples at each site.
• Record the number of Syneta beetle detected at each site.
• Also record the number of lygus bugs and minute pirate bugs detected.

Due to the potential for direct damage to fruit from Syneta beetle feeding, the treatment threshold for this insect is quite low. Counts of 0.3 beetles/tray (3 per site) in mid-May at the end of bloom have been detected in area orchards with a history of damage from this insect. This density was felt to warrant treatment. This timing usually precedes optimum timing for White Apple Leafhopper.

Fifth instar White Apple Leafhopper nymphs.

Adult White Apple Leafhopper.

White Apple Leafhopper

The developing first generation nymph stages are the easiest for monitoring and decision-making. 1st instar nymphs are about 1mm long, pale white, wingless and with red eyes. 5th instar nymphs are almost 3mm long and are more yellowish in color. Counts, using the procedure described below, should be taken once or twice beginning in mid May.

• 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. ·
• Estimate the percentage of 4th to 5th instar (wing pads are evident) and presence of adults before moving to the next site.
• Repeat this procedure for the remaining sites.
• Total and compute the average number of WAL nymphs per leaf.
• In most situations, 3 nymphs per leaf is a suitable treatment threshold.
• Optimum control is achieved if timed when 10% of the population is in the 4th to 5th instar.
• This correlates to about 350DD(150DD after biofix) using the codling moth model as described on the following page.

Threshold levels are not precise for deciding whether or not to treat for this insect. Recent research suggests that previous levels (.5 per leaf) are too low and that 3 nymphs per leaf is probably more realistic. This threshold should be adjusted downward for young trees with limited foliar surface area, for trees in poor vigor, for trees suffering from moisture stress, or in orchards which have experienced consecutive years of attack. The important point is that the optimum timing to control this insect, with most insecticides, is during the first generation, just before the adult stage is present, as described above.

Codling Moth

• Monitoring and decision-making for this insect is based upon:
• Accurate knowledge of daily temperatures.
• Calculation of degree-days.
• Proper use of pheromone traps.
• Proper timing of cover sprays based on information from the previous three elements.

TEMPERATURE COLLECTION AND CALCULATING DEGREE-DAYS

Instruments to measure daily temperature and the calculation of degree-days are used to predict codling moth development. Only daily maximum and minimum temperatures are required for the model. The simplest and least expensive ($25) instrument for this purpose is a high quality maximum-minimum thermometer. It must be checked and reset daily, preferably at about 10 a.m. Though more expensive, some growers have found that it is more practical to use a recording thermograph, computer-compatible temperature data logger system (ie: Onset Computer Corp., priced at about $350), or a more permanent weather station (ie: Metos, several thousand dollars), which is designed primarily for insect and disease pest management modeling. The advantage of these systems compared to a simple max/min thermometer is that data is usually downloaded or recorded on a weekly rather than a daily basis, making it more practical for the farmer. Regardless of the temperature recording device used, it must be placed in some form of shelter, out of direct sunlight, preferably in the shade on the north side of a tree. Temperature collecting equipment should be in the orchard and operational by March 1, but no later than bloom (late April) which normally precedes first emergence and flight of adult CM. Continue collecting temperature information through harvest.

Degree-days must be calculated accurately and should be done once a week. This can be done manually by using the table in WSU Extension Bulletin 1072. Based on daily maximum and minimum temperatures, the degree-day total is recorded for each day using this table (shown on Page 5-6). By adding degree-days for each day, you will have a running accumulation of total degree-days for the entire season. WSU has also developed a computerized program (Excel spread sheet) which will compute daily degree-days and accumulated degree-days based on entry of your daily maximum and minimum temperatures1. A comparison of your accumulated degree-days to the CM development chart (EB 1072) provides specific information on codling moth development in your orchard. This chart correlates degree-day accumulation with percent egg hatch and percent adult emergence and highlights key timing for pesticide application. (Shown on page 5-7.)

1 Available through WSU Tree Fruit Research and Extension Center webpage: http://www.tfrec.wsu.edu

PHEROMONE TRAPS

Typical wing-type pheromone trap.

Adult Codling Moth. Wings have fine alternating gray and white bands and are tipped with a patch of bronze scales.

It is very important to monitor the initial activity of codling moth adults in the spring. This is accomplished by using wing-type pheromone traps, which should be in place after an accumulation of 150 degree-days but no later than first bloom. The first significant flight or trap catch is called BIOFIX and is used to initiate the codling moth model. Subsequent trap catch is used to determine the need for treatment.

• Place traps at mid-canopy height and away from the orchard border.
• Use 1 trap for each 2 ½ acres.
• Check daily or every other day from 150 degree-days until first catch of moths (BIOFIX). · Reset accumulated degree days to 200 at BIOFIX.
• After BIOFIX is established, check traps weekly and record the catch.
• Change pheromone lures regularly as recommended by the manufacturer.
• Replace trap bottoms as needed; usually when lures are replaced.

There are various methods for using this information to make decisions about the need for and timing of sprays. Below is the system used for managing the first generation CM by growers who cooperated in the Nooksack IPM Project in Whatcom County. It is based on guidelines described in "Orchard Pest Management", a manual published by GOOD FRUIT GROWER.

• Apply spray if 6 or more moths are trapped between 200(BIOFIX) and 450 degree-days.
• After this spray, begin recording trap catch again.
• If 6 or more moths are trapped over the next 21 days, apply a second spray.
• If not, then a second spray is not necessary to control first generation.

If less than 6 moths are trapped from 200(BIOFIX) until 450 degree-days, extend until 560 degree-days. If still less than 6 are trapped, do not control. If 6 or more moths are trapped, control at once.

It has been our experience that growers with moderate to high CM pressure make two applications to control the first generation, timed at 450 degree-days and again 21 days later. A single application, delayed until about 550 degree-days is effective in orchards with low CM populations based on trap catch results or little history of infestation. The combination of precise trap catch and degree-day accumulation using the thresholds described above should eliminate most of the guesswork.

Refer to chart on page 5-8 for further assistance with Codling Moth decision making and recordkeeping.