August 11, AppleTalk Conference Call

AppleTalk Conference Call Summary
Tuesday, August 11, 2015, 8:00 – 9:00 AM
Guest speaker: Dr. Amaya Atucha, University of Wisconsin- Madison
Presenter: John Aue, Threshold IPM
Moderator: Peter Werts, IPM Institute of North America; questions or comments, pwerts@ipminstitute.org

August 11th Call download: Click Here

Regional disease and insect update
Cool weather over the past week has induced coloring on several varieties; many early season apples need additional time to reach harvest maturity. Codling moth and apple maggot are continuing to fly, pressure from these pests will likely continue through the beginning of September.

Codling moth
Higher numbers of codling moth (CM) caught during second generation may suggest an in-house population; generally, low trap counts represent a migrant population. Second generation flights will likely continue until the end of August. It is recommended to set a biofix for second generation control. If initial flights are lite and then increase substantially consider resetting biofix, or delaying larvacide application until 350 DD from first biofix. Active larvacide present in mid- to late August will also control hatching obliquebanded leafroller (OBLR) larvae. Scout terminals and fruit clusters to time pesticide targeting OBLR; bio control may adequately control this pest. A lot of predatory insects can still be seen in orchards and may continue to control woolly apple aphids, spotted tentiform leafminer and spider mites populations.

Mites
If mite populations exceed August 1- 15 sampling threshold of 7.5 mites per leaf consider applying a miticide. Mite days are likely high if it has taken populations this long to build up. A long period of feeding from below threshold numbers can still result in economic injury. European red mite can lay eggs on fruit, causing superficial injury. Dry weather will likely push two-spotted spider mites from orchard floor into tree canopies.

Apple maggot
Continue to monitor traps through the first week of September. Clean traps 10-12 days after an insecticide application or one inch of rain to determine if a reapplication is necessary.

Neonicotinoids have limited lethal action on adult apple maggots, but provide strong curative activity on eggs and larvae. It is recommended to apply neonicotinoids as full cover spray to blocks that exceed threshold. Alternate-row-middle applications will not provide adequate control. For more information visit: http://msue.anr.msu.edu/news/managing_apple_maggots_with_insecticides

Apple scab and summer disease
If scab lesions are present on foliage and/or fruit it is critical to maintain fungicide treatments as cooler, wet weather will create desirable conditions for the development of conidia. Use caution if stretching out fungicide, e.g., captan, coverage for more than two weeks if scab is a concern.

Growers with history of summer diseases are recommended to monitor leaf wetting hours. Fruiting bodies can appear post-harvest. It is recommended to apply Captan 80 (captan) at a minimum of 2 lbs. /acre for control of summer disease. Consider applying a fungicide that will control summer disease if apples will be on trees for another 30 days. For protection against black and white rot infections, which can occur from wind damage, a minimum of 2.5 lbs. /acre is recommended.

Pre-harvest interval

Click to enlarge image.
Click to enlarge image.

Maintaining tree health through harvest and maximizing winter hardiness with guest speaker Dr. Amaya Atucha, University of Wisconsin- Madison
Bitter pit
• The majority of calcium (Ca) is taken into the fruit from petal fall to the end of July.
• Calcium is relatively immobile within the tree and concentrations can vary between foliage, fruit and soil. The following factors can influence Ca levels and incidence of bitter pit: Nutrient imbalances with nitrogen (N), potassium (K) and boron (B), soil moisture levels and fruit size.

Keys to reducing bitter pit
1) Submit foliar, fruit and soil samples for nutrient and pH analysis. It is recommended to test samples for all available macro/micro nutrients as many complex interactions exist. For example: an excess amount of magnesium (Mg) or potassium (K) will compete with Ca for uptake.
2) Keep soils adequately hydrated throughout entire growing season.
3) Reduce excessive vegetative growth; Apogee (prohexadione calcium) can be applied to curb vegetative growth. Reducing vegetative growth will redirect the transport of Ca from foliage to fruit. The pre-harvest interval for Apogee is 45 days.
4) Lite crops or excessive thinning can result in large fruit. Calcium levels can be diluted in large fruit; Ca concentrations typically vary from stem to calyx end (location where bitter pit symptoms are most pronounced), excessively large fruit usually have exacerbated symptoms.
5) Calcium sprays can begin at petal fall and continue to end of August; up to six applications may be necessary. Coverage is important, Ca most contact fruit to be effective. The recommended rate is 1-2 lb. Ca per 100 gallons of water. If visible symptoms are present it is not too late to apply Ca to prevent further injury.

Tips for promoting winter hardiness
• Keep soils adequately hydrated throughout entire growing season to help regulate soil temperatures and reduce tree stress.
• Consider using mulch to protect trees in years without snow. Modify rodent control if mulch is used.
• It is not recommended to apply nitrogen before harvest to promote fruit bud hardiness, more research is needed to determine rates and timing; if too much N is applied terminal buds will reinvigorate.
• Applying potassium for cold hardiness is a myth. If soil has adequate nutrients, there is no need to apply more than the crop needs. Note: If yield is 1500 bushels/ acre, approximately 80 lb. of K is removed from soil. Soils typically have high concentrations of K. Potassium is mobile and readily available.
• Newly planted trees are more sensitive to cold temperatures and extreme temperature fluctuations than established trees since they are already being exposed to replant stressors, e.g., soil pathogens. Mulching can help reduce stress.
• Terminal buds should be set one month ahead of the first frost. Apogee (45 day PHI) can be applied to halt vegetative growth, effects should be visible within a week following application.