April 28, AppleTalk Call Summary, Guest Speaker: David Rosenberger

AppleTalk Conference Call Summary
Tuesday, April 28, 2015, 8:00 – 9:00 AM
Guest speaker: David Rosenberger, professor emeritus, Cornell University’s Hudson Valley Research Laboratory
Presenter: John Aue, Threshold IPM
Moderator: Peter Werts, IPM Institute of North America; questions or comments, pwerts@ipminstitute.org

April 28th Call download: Click Here

Crop phenology 0:00
Across the region, many orchards have trees at half-inch green to pink. The short-term weather forecast reports cool nights will accompany warm daytime temperatures, which will may slow bud development into bloom.

Insect Management
Early season lepidoptera 3:20
Pheromone traps should be deployed for oriental fruit moth, redbanded leafroller and spotted tentiform leafminer. The larval stage of green fruitworm, forest tent caterpillar, obliquebanded leafroller and spring cankerworm are visible and can be found near flower and leaf buds (10x magnification may be necessary to see the small, freshly hatched larvae). Note: Lesser appleworm pheromone lures will also attract oriental fruit moth and vice versa. Lesser appleworm flights correspond with codling moth flights.

If early season lepidoptera, e.g., green fruitworm, has resulted in economic damage in the past a Bt (Bacillus thuringiensis) product, e.g., Agree, Dipel, Deliver, can be applied before bloom to reduce incidence of damage. If Bt is applied, it is critical larvae are present (verify by scouting) and are in their early instars. The temperature needs to be warm enough, after an application, for the larvae to be actively feeding on plant tissue to consume the insecticide. It is important to note that Bt rapidly photodegrades and is only active for three to five days after an application and is also prone to wash off during rain events. Bt needs to be consumed when larvae are small, it is not always effective to wait until petal fall or first cover to apply a Bt insecticide.

Apple rust mite 11:00
Apple rust mite (ARM) may be visible near flower and leaf buds. Although ARM does not pose a risk at this time it, ARM populations may indicate applications of dormant oil, e.g., BioCover or Damoil (mineral oil), were ineffective.

Tarnished plant bug 11:40
Tarnished plant bug (TPB) adults are active and feeding from pink through the 8-14mm fruit stage. Damage caused by TPB is not typically economic. Flower buds and fruitlets injured by TPB feeding will abort.

Note: Oil can still be applied for mites and scale. To prevent phytotoxicity only apply during fast drying conditions and use low concentrations.

Q&A with David Rosenberger, professor emeritus, Cornell University’s Hudson Valley Research Laboratory
Can you please explain the sooty deposits occasionally found on limbs near pruning cuts or damaged tissue? 15:00

Under the right conditions, xylem tissue can produce a sap flow from pruning cuts or damaged tissue. It is hypothesized the sooty deposits that sometimes form in these areas is saprophytic fungi (or mold) that colonizes the sap. This non-pathogenic fungi does not usually indicate damage to the vascular tissue. If a grower is concerned they can use a knife to peel the bark beneath these sooty areas, if the vascular tissue is green and healthy it is a good indicator that the fungi is superficial.

Can you please describe potential prebloom signs of fire blight? 18:45
In the April 6, 2015 Scaffolds Fruit Journal the article, “Prebloom Signs of Fire Blight”, highlighted several instances of sap leaking near the base of trees early in the season. The sap was examined at the lab and the results were positive for fire blight. Although visual symptoms of fire blight, e.g., trunk cankers, were not present it is understood that fire blight can persist systemically without causing symptoms; under optimum conditions it can remain systemic, without symptoms, for up to four years. It is unknown how widespread fire blight is in symptomless tissue, and although fire blight is present it may not be causing damage. Example: Trees damaged by Rely (glufosinate) were sent to the lab for analysis, trees had no symptoms of fire blight, test results were positive for fire blight.

Note: Fire blight needs to be introduced into actively growing tissue for an infection to occur. Following an infection other bacteria and fungi can quickly colonize the damaged tissue.

Note: Black stem borer (BSB) may serve as a vector for the transmission of fire blight. Trees that were damaged by BSB tested positive for fire blight. It is unknown if fire blight was present before the borer entered the tree or if the borer transferred the pathogen.

Can you identify bacterial ooze or sap in the field? 26:30
Bacterial ooze is typically more viscous than sap flowing from pruning cuts; sap from pruning cuts is of low concern. Sap flowing from cankers or vertical splits in the trunk is more concerning. Samples must be sent to a lab for confirmation, no affirmations can be made in the field.

What are the characteristics that can be used to identify bitter, black or white rot cankers? 34:30
White rot begins as a superficial canker that forms on the bark of the tree. If the tree is exposed to environmental stressors, e.g., drought, it can move into the vascular tissue and cause death of the cambium layer. The xylem tissue is usually still healthy as this occurs.

Black rot will typically result in blackened xylem tissue. Infections are a result of injury to the xylem, e.g., winter injury. Once xylem tissue is injured bract fungi (shelf fungi) will colonize the injury and their hyphae will travel into the cambium tissue, which will lead to black rot infections. It is recommended to remove as much injured wood as feasible to allow healthy, new growth to replace it.

Note: Black and white rot are fungal diseases produced by fungi ubiquitous in forests, orchards and woodlots. The genus of fungi responsible for these disease are decomposers and are not highly contagious. Unhealthy trees injured by environmental stressors, i.e., cold temperatures, drought or heavy fruit load, are prone to infection. Healthy trees are not usually affected by these diseases.

Strategies for using Maryblyt in your fire blight management program 47:10
If Maryblyt is predicting a high or extreme risk of fire blight infection, it is not recommended to wait until a rain event or heavy dew to apply streptomycin. Pollinators can transfer the fire blight bacteria from a block with a history of fire blight to blocks that have not had fire blight in the past. When applying streptomycin it is recommended to apply the antibiotic to the whole orchard, rather than making partial treatments.

Management timing of systemic fungicides for cedar apple rust and powdery mildew control 55:40
Cedar apple rust infections on fruit occurs from tight cluster through petal fall. Captan and mancozeb, e.g., Penncozeb, Manzate, applied through second cover will provide adequate protection.

Rally (myclobutanil) can be added to captan and mancozeb at petal fall to combat powdery mildew and is very effective at disrupting rust infections that occurred during bloom. Another option for powdery mildew control would be to tank-mix sulfur with captan and mancozeb at the tight cluster and pink, then apply captan, mancozeb and Rally at petal fall. Note: do not apply captan or sulfur with oil.

Fungicide recommendations to protect tissue before a large spore release? 62:15
It is recommended to look at long-term forecast, e.g., four to five days. If next wetting event will result in an infection period, e.g., 55°F, wet for 36 hours, look at the forecasted rainfall. If the forecast is calling for two to four inches of rain it is recommended to apply a high rate of Captan 80 (captan) and mancozeb. The idea is to preload the trees before the wetting period and heavy rainfall. If a short wetting period or low rainfall is forecasted a lower rate of a protectant can be used. If prebloom, an alternative would be to apply single-site fungicide that will be absorbed into the leaves, e.g., Syllit (dodine) or Inspire Super (difenoconazole, cyprodinil). Adequate coverage is critical to preventing an infection.

Additional resources