April 12, AppleTalk Conference Call

AppleTalk Conference Call Summary
Tuesday, April 12, 2016, 8:00 – 9:00 AM
Presenter: John Aue, Threshold IPM
Moderator: Peter Werts, IPM Institute of North America; questions or comments, pwerts@ipminstitute.org

April 12th Call download: Click Here

Assessing cold damage from low temperatures
During the evening and early morning of April 8 and 9, low temperatures between 14 and 20 degrees were observed across the region. Cultivars that were at half-inch green may have sustained damage, from these temperatures. Damage will be difficult to assess at this time, since flower buds have not developed yet. Assessing injury from the freeze will be most effective at tight cluster or pink and can be assessed by dissecting flower buds. Damage is not expected to exceed 10% kill on these early varieties.

Expected near-term changes in tree phenology
The near-term forecast is showing day/night temperatures with highs 10-15°F above normal and lows 5-10°F above normal. These warm temperatures coupled with the precipitation we have had over the last few weeks will likely result in rapid development. This will be especially true for cultivars currently at green tip and expect there will be a short interval between green tip and bloom.

Copper application timing and rates
It is recommended to delay copper applications until 48 hours after a freeze to prevent damage to foliage and bark. Growers making applications this week should observe the short-term forecast (April 14-15, high winds, i.e., 10-20 mph) and make applications after dark or early morning to avoid spraying during the windiest part of the day. Note: Low relative-humidity, i.e., less than 65%, are important to preventing phytotoxicity issues when green tissue is showing. Applying copper when varieties are at silver-tip will likely prevent damage.

With minimal to no precipitation forecasted, copper applied now could remain on the trees by the time we reach petal fall and could cause fruit russeting. Ideally we should accumulate several inches of rain between the last copper application and petal fall. It is recommended to reduce the rate of copper and apply 1 lb. of actual metallic copper per acre to bearing trees, see examples below:

Copper table_041316

Apply 2 lb. of metallic copper to non-bearing trees, or trees where fruit russeting is not a concern.

Do not reduce the volume of water or concentration of oil with copper sprays.

If growing conditions, e.g., crop phenology, forecast (temperature and precipitation) are not conducive to making a copper application, consider on-farm history and regional history of fire blight and tree age when deciding to apply copper. Growers with old trees, blocks with a history of fire blight or young, newly planted trees should still consider applying copper. Organic producers should still apply copper due to the limited choices for fire blight control later in the season. Using a lower rate of copper, e.g., 0.5 lb. of metallic copper/acre, will work the same as a higher rate, e.g., 5 lb. of metallic copper/acre, as long as good distribution is achieved. Rates will only effect how long the copper lasts on the tree. Note: fire blight bacteria are not active at this time.

The effective life of a fungicide will be reduced as rapid-leaf development results in exposed and unprotected tissue. The small amount of fungicide, whether copper or an EBDC, will not redistribute well to keep new tissue protected. When we have rapid leaf expansion, exposed tissue can be present within 3-5 days after last application. During cool periods with minimal-leaf growth, applications should last seven days. Growers are not advised to follow a 10-14 extended spray schedule at this time. If warm temperatures prompt rapid leaf expansion, there will likely be exposed tissue, even three days after a fungicide application. Therefore, this first spray will not last very long as a protectant against scab.

If the rest of the month is dry, this will limit the number infection periods at tight cluster and pink. However, ascospores will continue to mature and when an infection occurs, with 20-50% spore maturity, it will likely be a severe. It is recommended to continue completing cultural practices, e.g., close mowing, sweeping, to reduce inoculum.

Horticultural oil timing and concentration for San Jose scale and mites
Recommendations on oil timing and concentration vary by region. Anecdotal evidence in our region shows effective control for San Jose scale (SJS) and spider mites is best achieved with multiple low-concentration applications of oil.
1. First application: Apply 1% concentration, e.g., 1 gallon of oil per 100 gallon of water
2. Second application: Apply four to eight days after first application at 2% concentration
3. Third application: Apply pre-pink at a 1-2% concentration. IPM guidelines from Cornell University, recommend to reduce the concentration of oil when close to pink.

Note: Oil also works as a spreader when applied with a fungicide. A 1% concentration will help break surface tension and promote the material to spread across the foliage.

Insect growth regulators for San Jose scale and early-season lepidoptera
In addition to oil, insect growth regulators, e.g., Esteem (pyriproxyfen), Centaur (buprofezin), can be applied pre-bloom to target SJS. If Esteem is applied closer to the end of pre-bloom period it will also control many early season lepidoptera, e.g., green fruitworm, redbanded and obliquebanded leafroller, spring cankerworm. Esteem works on larval stages of these lepidoptera, if applied too early it will not be around when the eggs are laid or larva are active.

What if I have not finished pruning or applying fertilizer?
It is still ok to complete last minute, small cuts when the forecast is dry. Finish pruning before temperatures get warm, 60-70°F during the day and above freezing at night as fire blight bacteria will begin to become active.

If foliar fertilizers are applied plan to begin applying by pink.

Useful IPM reminders
– Record McIntosh green tip. This date is important for tracking ascospore maturity for your orchard.
– Keep accurate application records throughout the season. If there is scab present in June it will be helpful to analyze scab management program to identify mistakes.
– Record keeping can be improved by using an electronic record-keeping spreadsheet, such as those offered by Penn State (http://extension.psu.edu/plants/tree-fruit/spreadsheets) or Cornell University’s, TracApple (http://store.ctl.cornell.edu/products/tracapple).
– Monitor accurate leaf wetness hours and temperature data, daily high/low, to accurately track scab infection periods.
– Rainfall: total amount per event and also each event’s intensity and duration)
– Document dates of cultural practices aimed at reducing disease inoculum. These may include: close mowing (destruction) of leaf litter, late brush chopping or pushing after tight cluster or application of nitrogen (urea), compost, lime or mulch.
– Record (for each tank) pertinent factors of all pesticide applications:
o Unexpected alterations in material amounts, changes in mixing sequence
o Visual evidence of insufficient mixing during application
o Changes in wind speed and direction, or location in block of possible wind effects (e.g. row ends)
o Tractor tire slippage when ground is wet (if not using Raven or equivalent)

Early season insect monitoring
Deploy pheromone traps for redbanded leafroller and spotted tentiform leafminer at this time. If green fruitworm or oriental fruit moth have been a problem in the past consider deploying a trap for this pest as well. Two traps per pest per orchard are sufficient to monitor the population dynamic and time visual scouting activities. Pheromone lures and traps are available from Great Lakes IPM, Gempler’s or CPS.

Codling moth, obliquebanded leafroller, lesser appleworm traps should be deployed by May 1st or bloom.

Phytophthora, collar, crown and root rot disease control
Symptoms of Phytophthora may be confused with winter injury or borer injury. Verify Phytophthora is an issue before proceeding with chemical control. Fungicide options include Ridomil (mefenoxam) and the phosphorus acid fungicides, e.g., Aliette (aluminum tris), Phostrol (ammonium phosphites). Resistance is a concern with Ridomil and the application window is limiting, see product label. The phosphorus acid fungicides work systemically through trees and are very effective and can be applied as a foliar. It is recommended to not plant in slow draining, wet soils to avoid Phytophthora. If planting in these soils cannot be avoided consider: adding organic matter to soil before planting, planting trees on berm to promote drainage or planting a larger rootstock which are more tolerant to wetter soils.