June 28, AppleTalk Conference Call

AppleTalk Conference Call Summary
Tuesday, June 28, 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

June 28th call download: Click Here

Current degree-day (base 50°F) accumulations for codling moth biofix dates, May 23 – 27
• La Crescent, MN: 728-646 DD
• Lake City, MN: 708-631 DD
• Gays Mills, WI: 706-624 DD
• Woodstock, IL: 751-673 DD

Trapping and monitoring notes:
• Long-life (L2) codling moth lures hung in late April or early May should be replaced during the first week of July.
• Continue to replace monthly lures for codling moth, obliquebanded and redbanded leafrollers, oriental fruit moth, lesser appleworm and dogwood borer.

Summary of 2015 fruit rot discussion with Dr. Patty McManus, University of Wisconsin Madison:
• Any fruit left on the tree from last year, e.g., hail-damaged fruit, will be a source of fungal inoculum for this year. If bitter rot is present in the orchard, it can overwinter on the orchard floor, or in trees on mummies. If rotten fruit is found, inspect the lesion and fruiting bodies. If it is not sporulating place in sealed Tupperware with wet paper towels to induce sporulation. Note: fungi do not typically produce spores if weather is hot and dry.
• Characteristics of bitter rot, fruit:
o Generally takes several weeks following infection before symptoms develop, may become visible before other rots.
o Symptoms first appear as small, light-brown, circular spots. Many spots per fruit may be found.
o Under high temperatures initial lesions may rapidly enlarge and change to dark brown in color.
o 1/8 to 1/4 inch in diameter lesions are distinctly sunken or saucer shaped.
o When lesions reach 1/2 inch in diameter, small, black fruiting bodies appear in the sunken lesion. Fruit bodies may be arranged in concentric rings.
o Fruiting bodies will begin to ooze a gelatinous, salmon-pink mass of spores, which is washed by rains onto other fruit.
o Beneath the surface of the spot, the flesh is light brown and watery in a cone or V-shaped area, with the small end of the cone toward the fruit center.
o Cankers can form on vegetative tissue, but are rare.
• Characteristics of black rot, fruit:
o Black rot infections on fruit usually appears at the calyx end and can originate at any wound that penetrates the epidermis, e.g., insect or hail injury.
o Usually only one spot occurs per fruit, a characteristic that distinguishes black rot from bitter rot.
o Initial infection becomes brown and stays brown or turns black as it increases in size.
o A series of concentric rings often forms as the rotten area increases in size. Lesions are usually amorphous. The flesh of the decayed area remains firm and leathery. Fruiting bodies will appear on the surface of the rotted tissue.
• Fungicides that will offer protection against fruit rots include captan, strobilurins, e.g., Pristine (boscalid, pyraclostrobin) and Flint (trifloxystrobin), and Topsin (thiophanate-methyl). Do not apply strobilurins if scab lesions are present. A high rate of captan may provide adequate protection. Note: to reduce resistance concerns always tank-mix single-site fungicides with a protectant.

Sooty blotch and flyspeck management with fungicides
• Beginning around petal fall, the first influx of sooty blotch and flyspeck (SBFS) spores are released from wild brambles, e.g., raspberries. This typically occurs during first cover when scab fungicides are still be applied. After about 175 hours of leaf wetness, sporulation will occur and result in the second spore release. This can happen between three and 11 weeks post-bloom, with an average of seven weeks post-bloom. It is important to apply a fungicide for summer disease at this time. Follow the first application with a protectant program. The reapplication interval following the first application is dependent on rainfall and weathering of the material. A 2-3 lb. rate of captan is greatly reduced after two inches of rain or 14 days, higher rates may offer added protection.
• Dr. McManus’ has recently developed a new summer disease model for the upper Midwest. Relative humidity (RH) was used rather than leaf wetness hours (LWH) to predict infection periods. It was found that 192 hours of RH above 97% was a better predictor than 175 hours of leaf wetness for our region. During the summer, dew usually contributes to more wetting hours than rainfall. Within the tree canopy, RH is more stable. Regardless of this research, Dr. McManus recommends using LWH because the instruments are more precise. It is important to place the leaf wetness plates within the canopy to accurately record LWH.
• Fungicide performance was greatly improved when appropriate coverage was achieved. Increasing the amount of water applied per acre can greatly improve coverage. Large semi-dwarfs or standard trees may require up to 100 gallons of water per acre if canopies are dense and air circulation is poor. Using a higher rate of fungicide will also improve protection.
• Do not apply strobilurin or DMI fungicides if scab is present. It is recommended to apply high rate of captan or captan + Topsin.

2016 summer disease management
• If you received hail in 2015, you may likely have more black and bitter rot inoculum in the orchard.
• Trees with a lots of vegetative growth may produce higher humidity within the canopy and could increase problems for summer diseases.
• Remember, strobilurins, DMIs and Topsin will eradicate the SBFS pathogen before symptoms are produced, whereas captan is only a protectant.
• Go with the 175 LWH for any event over four hours and start counting one week after petal fall or one week after your last fungicide that is labeled for SBFS control.

Summer management of shoot blight (fire blight)
• If terminals are set, the risk for additional fire blight greatly decreases. If there are still new vegetative shoots, there could still be risk of fire blight.
• Where shoot blight is present, snap off infected branches rather than pruning. Bacteria dies in a few days if it does not have living tissue to thrive on.
• Do not apply strep, unless there is a severe weather event, e.g., hail or wind, which causes open wounds in the trees.

Apple maggot
It is advised to hang yellow boards or red spheres by July 1. Yellow boards can provide an early warning system by attracting apple maggot (AM) during their feeding period. If bait is used in addition to visual traps replace volatile lures according to the manufacturer’s directions, e.g., seven to ten days. A minimum of three traps per ten acres should be deployed at the beginning of July; trap density should gradually increase to one trap every 200-300 feet along the orchard perimeter, as the season progresses. Locate traps along perimeter where wild hosts are present and near early ripening cultivars. Hang traps at eye level, and make sure they are visible. Traps can be placed in early-season varieties that exist on the interior of block, since the trees can harbor resident populations that may not affect neighboring varieties. Always apply more Tangle-Trap then you think is necessary, insects should be easily caught in the adhesive film. If a spray-on formulation is used, it should begin to drip. If you do not apply enough Tangle-Trap it can lose its tackiness and wear off in the rain.

Thresholds vary from one fly on unbaited traps to five flies with apple-volatile bait. Treatment practices for AM can include spot spraying perimeters and early-ripening varieties, and alternate-row-middle applications. Consider applying traps to differentiate pressure between spray tanks: 20 (total acres) / 5 (acres per spray tank) = 4 monitoring blocks. A block of attractive varieties, e.g., Redfree or Yellow Transparent, in the middle of a large block may require every row to be sprayed. In majority of situations a full cover application is not necessary for effective control.

If apple maggot management overlaps with first generation codling moth, a neonicotinoid may be tank mixed with a codling moth material to target hotspots or perimeters. An orchard-wide application of a neonicotinoid targeting AM is usually not necessary unless woolly apple aphid or San Jose scale are a concern.

Apple rust mites (ARM) are a common secondary pest that require high populations to cause damage; current threshold is 200 mites per leaf. Damage can be observed as an olive drab color on the underside of leaves. Populations will continue to grow once the terminals have set. Not much of a concern on large established trees, yet can be harmful on young trees. While scouting, turn over growing shoots and look for discoloration and scan leaf surface with hand lens to see if mites are present (requires 10x or greater magnification). ARM damage may be more prevalent where nutrients are applied. These mites are an important food source for numerous predatory arthropods.

Two-spotted spider mites (TSSM) have a wide range of native host plants which includes broadleaves and red clover. In dry years, TSSM may feed on tree foliage and can be as destructive as European red mites. Damaging levels will be observed first near the trunk; where they travel into the tree. Damage can be observed as light green or whitish areas along the midrib. Must use 10x magnification to see the two spots; are more difficult to identify then ERM.

European red mite thresholds are based on population density s and increase through the season, i.e., June, 2.5 mites/leaf; July, 5 mites/ leaf; August, 7.5 mites/leaf. Although sampling can provide an accurate read on a population it does not always reflect actual pressure. Visible damage can be present even if populations are under threshold. If physical damage is observed, economic injury is occurring. After severe bronzing develops it may be too late to apply a miticide as mite populations will decrease naturally from starvation.

Dogwood borer
Use pheromone traps to sample presence/absence of dogwood borer (DWB). If DWB are caught scout at least ten trees scattered throughout the block for infestation. Focus on trees that are three to five years old grown on rootstocks susceptible to formation of burr knots, i.e., M.9, M.26 and Mark series. Examine the trunk from the soil line to the first scaffold branch for frass protruding from borer holes, burr knots or damaged bark. Fully remove trees guards while scouting.

Treatment options include a trunk application of Lorsban (chlorpyrifos). Note: chlorpyrifos cannot come in contact with bearing fruit and can be applied post-harvest. Organic growers may choose to apply pure neem oil and paint, to the trunk.

Alternative insecticide options have been researched by Art Agnello, Cornell University, but do not offer an equal level of management that can be achieved by a single trunk application of chlorpyrifos. Art’s research indicates that Avaunt (indoxacarb), Danitol (fenpropathrin) and Assail (acetamiprid) could provide suppression of DWB larva. However none of these insecticides are labeled for DWB.

Cultural practices that reduce damage need to be implemented before infestations occur and include:
1. Monitor adult population with pheromone traps.
2. Identify and select rootstocks that have a lower tendency to producing burr knots. Rootstocks particularly susceptible to burr knot formation and attack by borers are M.9, M.26 and Mark.
3. Trunk mounding around the exposed portion of the rootstock can reduce the initiation of burr knots. Where it is not possible to bury exposed rootstocks, the area around the trunk should be kept weed free to avoid shade and high humidity.
4. Use wire mesh tree guards instead of solid guards.

Japanese beetle
• We have observed rather early Japanese beetle (JPB) pressure this year in southern Wisconsin and northern Illinois. Our thoughts are the good rainfall in September and October 2015, a mild winter and great conditions for grass to grow may be increasing 2016 populations.
• Insecticide options for this pest are rather limited. Neonicotinoids, e.g., Assail (acetamiprid), will offer good repellency if applied before large aggregations of JPB begin to appear. If populations are large, applying a “knock-down” or contact insecticide, e.g., organophosphate, pyrethroid or PyGanic, may offer good control.

Other resources
• Michael Phillips community orchardist newsletter: http://www.groworganicapples.com/community-orchardist-newsletter/Community-Orchardist-2016-06.pdf