July 30 Apple Talk Conference Call

AppleTalk Conference Call Summary
Tuesday, July 30, 2019, 8:00 – 9:00 AM
Guest Speaker: Kristin Krokowski, UW-Madison Extension Waukesha County
Presenter: John Aue, Threshold IPM
Moderator: Peter Werts, IPM Institute of North America;
questions or comments, pwerts@ipminstitute.org


Due to a problem with the our conference-call provider, there is no call recording for the July 30 conference call.

Regional update

Location Degree Days 7/29/2019 (Base 50°F) Petal Fall Date (NEWA) Total leaf wetting hours, from petal fall Total potential infection event hours, from petal fall CM Biofix (NEWA) Accumulated DD (Base 50°F) from CM biofix
Eau Claire, WI 1278 5/28/2019 249 228 6/8/2019 961
Gays Mills, WI 1478 5/30/2019 230 201 6/6/2019 1104
Hastings, MN 1434 6/1/2019 132 106 6/7/2019 1080
Harvard (Royal Oak), IL 1440 5/23/2019 296 279 6/6/2019 1083
Lake City, MN 1436 6/1/2019 185 152 6/3/2019 1145
Mauston (Northwoods), WI 1414 6/1/2019 156 131 6/7/2019 1060
Mequon (Barthel), WI 1205 6/6/2019 125 107 6/15/2019 868
Preston, MN 1388 5/31/2019 201 181 6/3/2019 1104
Rochester (Ela), WI 1327 5/23/2019 238 216 5/30/2019 1106
Trempealeau (Eckers), WI 1419 5/31/2019 185 164 6/6/2019 1086
Verona, WI 1475 5/30/2019 161 132 6/5/2019 1125
White Bear Lake, MN 1379 6/3/2019 154 125 6/8/2019 1025
Woodstock, IL 1578 5/26/2019 173 146 5/28/2019 1298

Table 1. Degree-day accumulation and leaf wetness hours to 7/29/2019.  Note: Degree days for codling moth are estimated by NEWA.  Actual dates must be entered by users and are not saved.  This year DD are as much as five days off grower-observed codling moth flights. *All degree days are calculated using a lower-temperature threshold or base temperature of 50°F.  *Leaf wetness events are periods of four or more hours.

The forecast throughout the region calls for highs in the 80s and lows in the 60s.  There is not a substantial chance of rain for most locations until early next week.  Most days will be sunny with low wind.

FSMA discussion with Kristin Krokowski
General background information on produce safety
There has been a large educational effort in Wisconsin regarding the Food Safety Modernization Act (FSMA).  There are seven parts to FSMA, with product safety being the focus of this conversation.  FSMA was passed almost ten years ago, but enforcement via the FDA just recently began.  The reasoning is it took several years to modify several of the rules to ensure the end product was enforceable and effective.  The Produce Safety Rule applies to any food that is sold for human and/or animal consumption.  All farms must have one-lead person who completes a required one-day training that covers worker health and hygiene, water testing, compost use, and building sanitation.  There are a few exemptions to the produce safety rule, depending on the commodity and average annual produce and food sales.  Determining if you have an exemption is essential to know how your farm must comply with FSMA.  The following are compliance dates based on average annual produce sales:

For covered activities, other than those involving sprouts (which have additional requirements and earlier compliance dates):

  • January 26, 2018: Covered farms for which, on a rolling basis, the average annual monetary value of produce the farm sold during the previous 3-year period is more than $500,000.
  • January 28, 2019: Covered farms for which, on a rolling basis, the average annual monetary value of produce the farm sold during the previous 3-year period is more than $250,000 but not more than $500,000 (small businesses).
  • January 27, 2020: Covered farms for which, on a rolling basis, the average annual monetary value of produce the farm sold during the previous 3-year period is more than $25,000 but no more than $250,000 (very small businesses).

If you have an exemption, the FDA still requires you to keep detailed documentation and you must display the farm name and address at all point of food or produce sales on the farm, restaurant, farm stand or concessions.  If a farm makes less than $25,000, then they are exempt from the rule.  To calculate average produce income, growers must take the last three years of total income and determine an average.  The idea behind the exemption for those farms under $25,000 is the cost of regulation would be unreasonable in comparison to total income.  This cutoff number is also adjusted for inflation, with the latest for Wisconsin being $26,999.

Even with these exemptions, growers must keep records broken down by product sold selling and whether it is wholesale or directly to consumers, which started in 2015.  Farms that fall between $25,000 and $500,000 in food sales can qualify for an exemption if half of all sales go toward a qualified end user (sold directly to the consumer), e.g., pick-your-own, farmers market, grocery store.  These sales must be within the residing state lines or within 275 miles of the farm location.  All farms that generate over $500,000 in sales cannot qualify for an exemption.

Instead of complying with the entire rule, which is extremely record-keeping heavy and includes an inspection, with an exemption farms must only display the name and address of where the produce is grown and must keep records of sales.  This is to ensure that if a consumer gets sick, it can be quickly traced back to where the product originated. However, farms can easily lose their exemption if it is determined unsanitary conditions or poor food handling processes exist.


Grower question: If someone is selling bagged apples to a grocery store and the store does not have signage but the names and locations are on the bags, does this still fall into compliance?

  • It is the grocery stores responsibility to be able to trace back to the origin of food products sold. Your traceback is only from the point of sale, e.g., on your farm or from your farm stand.  As long as there is a sign with your farm name and address, you will fall under compliance.  Another point to bring up is selling produce at your farm stand or store that wasn’t grown on your farm, e.g., growers that ran out of apples and are selling apples from another farm.  Bottom line is you must know where the product came from and your farm name and location must be present at the point of sale.  This also doesn’t qualify as a direct sale and cannot qualify count toward the exemption.  Essentially, if a consumer falls ill from a product that was sold on their farm, the grower must know where the product originated.

Question: Our farm lies almost directly on the Illinois and Wisconsin border, so as long as we are within 275 miles from our farm, we can count it towards the exemption?  What if we have sales outside of this limit?

  • Some sales may be beyond the 275 mile limit, but the number is taken as a whole of all food sales. It is important to monitor your sales and possibly hold off on a wholesale option if this will push you out of the exemption.  Several growers have done this and will instead donate to a food pantry to ensure qualification for the exemption.

Water testing
If your farm does not qualify for an exemption, you are required to do water testing of both production and post-harvest water.  Production water allows a certain level of E. coli presence as it can often be killed before harvest which is based on the geometric mean and the statistical threshold.  The geometric mean of samples is 126 or less CFU of generic E. coli per 100 mL of water, and the statistical threshold of samples is 410 CFU or less of generic E. coli in 100 mL of water.  Post-harvest water has a zero tolerance for E. coli, e.g., water used for washing hands during and after harvest, water used directly on produce during or after harvest and water used for sprout irrigation.

When testing untreated surface water used during production, the FDA requires farms to use a minimum of 20 samples during the first two to four years.  Once the initial survey has taken place, an annual survey with a minimum of five samples per year is required.  These tests must be taken when the crop is in the field.  If municipal water supply, just need copy of their testing.  For untreated ground water used during production, the FDA requires farm to use a minimum of four samples collected near harvest.  After the initial survey, a minimum of one sample per year is required.  If irrigation water doesn’t come into contact with fruit, this water doesn’t require testing.  Any water that comes into contact with fruit between bloom and harvest does require testing.

As stated previously, post-production water has a zero tolerance for the presence of E. coli.  All post-harvest water must be tested at least four times during the growing season and these results will be used to determine if the water can be utilized or not.  If the initial testing results in zero presence of E. coli, one sample can be taken once annually.  If E. coli is present in the sample, farms must test at least four times per growing season until results are clean.

Question: What if two wells are interconnected through pipeline but only one is used in production?

  • If backflow prevention is present, then you just need to test the well-used for production in the state of Wisconsin.

Question: John: Do water testing rules not apply if don’t you have qualified exemption, correct?

  • Yes, this is correct, though would be smart to test once or twice to make sure they are clean. Just need to keep track of financial records and have the sign up with farm name and address.  How much does it cost for one water test? – 30-35 dollars in Wisconsin, for quantifiable test.  There is a presence absence test, would run the quantifiable test first.  FDA can pull exemption at any time if feel that you are not using good food handling practice.  The more you have done to make good food-safety on the farm, the less likely they will pull the exemption.


If growers have any further questions on FSMA, call or email Kristin:

  • Phone: 262-548-7768
  • Email: krokowski@wisc.edu

Second generation codling moth
Most locations have now accumulated the 1000 degree days between first generation codling moth biofix and second-generation biofix.  Not all locations are reporting a biofix and sometimes can come as late as 1200 DD from the first generation biofix.  Most of the time trap counts drop off and we can see a distinct gap in the flights.  However, for some growers with high pressure, the flights never drop off to zero.  This is when we need to use our degree days to decide on when a flight is now part of the second generation and to switch insecticide modes of action.

Unlike in the spring, insecticides targeting second generation codling moth should not be delayed past 250 degree days (DD), base 50°F, from biofix, which takes 10-12 days of degree day accumulation.  We are able to delay in the spring, because adverse weather conditions and rain during the first flight often reduce the fecundity of female codling moths.  In late summer, we have excellent weather for codling moth mating and can expect a strong flight to require treatment at 250 DD, base 50°F.  Peak egg hatch for the generation will likely not occur until two to three weeks into August and right up until Labor Day.  On average, 650 DD accumulate during the month of August.

The treatment threshold is five moths per trap and after a biofix has been established, blocks that do not go over threshold may not require treatment.  This could be helpful as we near harvest and allow for spot treatments only of blocks which caught five moths or more in a weeks’ time.  While recording trap numbers are important, codling moth injury to fruit is also a great indicator of potential second-generation population presence in the orchard.

One larvicide application, no matter what product, will not carry you through August and into the first week of September especially if significant rain occurs.  If rain is forecasted, do not apply the highest rate of the material even if it has been three weeks since the last application.  Apply a low application and follow up if need be.  Keep in mind that Altacor (chlorantraniliprole) has a minimum interval of 10 days.  Excluding neonicotinoids, at this stage it is a good idea to incorporate a sticker with an insecticide application.  If growers are catching 5-15 moths, this is not a massive threat.  John considers catching 20+ moths to be more of a threat in terms of urgency to apply an insecticide.

Lesser apple worm
The second flight of lesser apple worm (LAW) has begun in several orchards, some upwards of 35 trap catches in the last week or so.  There is no strict threshold, but John considers 10 trap catches in a week to be a potential for economic injury.  If LAW numbers are high, growers can apply a larvicide late next week.

Obliquebanded and redbanded leafrollers
The second-generation of obliquebanded leafroller (OBLR) will begin to hatch in August and can continue through Labor Day.  This generation typically feeds on ripening fruit rather than on vegetative tissue.  The OBLR larvae will only grow to a few millimeters in length before developing a pupa and going into diapause, where the OBLR’s growth and development is suspended until spring.

The CM larvicides, e.g., Delegate (spinetoram), Altacor (chlorantraniliprole), will control these larvae, whereas the neonicotinoids, e.g., Assail, Admire Pro (imidacloprid), do not.  Managing the second generation now, will reduce the overwintering population that may need to be controlled next spring. Three to five percent injury is possible at harvest and scouting needs to be used to determine if a treatment is warranted.  A mistake with OBLR may discount an apple from US Fancy grade but is not usually a real problem when selling the fruit since the injury is so tiny and there is no worm in the apple. Two traps per 20 acres is adequate to determine where treating is necessary.

Apple maggot
In August, Assail (acetamiprid) is often a preferred insecticide for combined management of apple maggot and codling moth.  If a different insecticide is being used for second-generation codling moth, then imidacloprid products may be used for apple maggot management.  The neonicotinoids have limited mortality on adult AM (two-to-three days) and increased mortality on eggs and their ability to hatch, plus repellency and avoidance of egg laying (up to 14 days).  Rainfall following an application will impact efficacy.  If Assail was applied with the dual purpose of controlling CM, reference John Wise’s article below to determine when to reapply.  A final AM application of the season should be a material that has efficacy on the adult fly as well, like Assail (acetamiprid), Imidan (phosmet) or carbaryl.  If a final product is applied that doesn’t have efficacy on adults, this will result in maggots hatching out when residue efficacy is diminishing and may lead to metabolic resistance.

Note: Since neonicotinoids do not perform well against adult flies, trap captures will not be impacted by an application, whereas they would have been if a broad-spectrum material, e.g., Imidan (phosmet), were used.  If pressure is localized spot spraying may offer adequate control.

Note: The fruit essence on baited traps is viable for one week and should be changed accordingly.


Grower question: Does Bt have any efficacy on apple maggot?

  • No, Bt does not offer efficacy against AM but will be effective when OBLR begin to hatch.

Fruit rots and summer diseases
Bitter pit
Adapted from August 11, 2015, AppleTalk Conference Call with guest speaker Dr. Amaya Atucha, University of Wisconsin- Madison.

Calcium (Ca) is important and necessary to maintain fruit quality.  The majority of Ca is absorbed into the fruit during the cell expansion phase lasting from petal fall to the end of July (~50 days after petal fall).  After this period, the xylem in the fruit losses efficiency, especially in the calyx end.  Calcium does not easily move into the fruit from the soil and is relatively immobile within the tree.  Concentrations can vary between foliage, fruit and soil.  Note: Foliar Ca levels will be greater than what is in fruit because leaves have a high transpiration rate and accumulate more Ca material.  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.

Strategies for 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/micronutrients 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 the growing season.
  3. Reduce excessive vegetative growth.  Reducing vegetative growth will redirect the transport of Ca from foliage to fruit.  Apogee (prohexadione calcium) can be applied to curb vegetative growth.  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 must contact fruit to be effective.  The recommended rate is one-to-two pounds of Ca per 100 gallons of water.  If visible symptoms of bitter pit are present, it is not too late to apply Ca to prevent further injury.

Bitter rot
Bitter rot has been discussed extensively this season, even though incidences of the disease remain limited to date.  However, we are now entering the portion of the season where orchards with high inoculum are at a greater risk of infection.  Like sooty blotch and fly speck (SBFS), bitter rot has more genetic diversity than previously thought and while not completely immune to resistance, we currently are not very concerned about the current treatment programs resulting in fungicide resistance.

The visual symptoms of bitter appear as a orange, slimy mass that is almost salmon-colored.  Black rot and white rot make black fruiting bodies but do not make orange slime.  Bitter rot makes a sharper V-shape into the fruit, when cut in half, when compared to black and white rot.  This disease can cause problems on other fruit crops, weeds, lilac, trees and hedge rows, which suggests it has a wide host range beyond apples.  Spores likely enter orchards early in the season (June) through either fire blight infections or some other source.  For example, we know that SBFS come off brambles in the woods and hedge rows adjacent to orchards.

Fruit infected with bitter rot are often observed in groupings and clusters on several branches.  While bitter rot does not cause big cankers, it can infect quickly.  This suggests the source of inoculum is nearby, e.g., overwinter drop, mummied fruit, fire blight canker, rather than a pathogen that has spread via wind or rainstorms.  The pathogen can overwinter mummified in fallen fruit and in trees.  Rotten fruit tend not to decay very well on herbicide strips.  Fruitlets on the ground after hand thinning can also become infected and release spores.  Dead wood, e.g., infected by fire blight, can become colonized and sporulate by late-July.  In strawberry and blue berries, infections can happen in four-to-six hours during wetness, which is relatively fast for a fungus.

Even though the fungus requires vegetation to reproduce, the disease can appear after fruit have been harvested. Heat-stressed fruit also seems to be more susceptible.  When humidity is high, evapotranspiration is reduced, slowing fruit cooling.  Therefore, growers should ensure trees are well irrigated going into hot weather.

Management options:

  • Applying an SDHI, Strobilurin and Captan are best options for bitter rot.
  • Phosphorous acid fungicides are not effective on bitter rot.
  • Organic options are limited.  Results from trials at UW completed by Patty McManus found that Liquid lime sulfur (LLS) had 9% injury, Serenade Optimum 10%, and the control had 7% bitter rot injury.  This suggests that none of these fungicides performed better than the control.
  • Cultural controls: Removing and mowing over is likely just fine, the key is getting fruit to decompose, which will destroy the inoculum.  A flail mower is likely to destroy the fruit better than a rotary mower.

Sooty blotch and flyspeck
Growers using leaf-wetness sensors from NEWA stations or Spectrum Technologies stations should have made their first applications at 175 LWH from petal fall.  This same accumulation of LWH can be used to determine when we can conclude sprays this fall.  From your last SBFS spray, track wetting hours up to harvest, and if only 150 have accumulated at the start of harvest, you are likely fine.  However, if accumulations of hours are low, an additional spray prior to harvest may be beneficial. While SBFS is not disfiguring, it can eat away the waxy cuticle, causing fruit to dry out.  There are currently no resistance concerns since the diseases are coming from beyond orchard perimeters.  If a Strobilurin application is planned, be aware that most of these fungicides have a 14- to 30-day PHI.

Plant growth regulators

  • Blush (prohydrojasmon) can enhance color development, especially on the backside of the fruit that does not color well. Blush does not accelerate ripening. Some growers prefer to not apply blush to Honeycrisp, so pickers can use visual cues based on harvest parameters.
  • ReTain (AVG-HCl) reduces amount of ethylene produced to prevent the abscission layer from forming between the fruit stem and spur. The general recommendations for use of ReTain on Honeycrisp are to apply a half rate 30 days before harvest. Other recommendations would allow a ¼ rate to be applied within 14 days of harvest or to include NAA, e.g., Fruitone, at 10 PPM with the ¼ or ½ rates. Honeycrisp does not produce a lot of ethylene and therefore is more sensitive to Retain. This means that a “half rate” is essentially a full rate. The use of Retain with NAA can extend harvest another seven to ten days. The combinations can continue to promote ripening and also inhibits separation at the abscission zone.

It is not recommended to apply these materials in complicated tank mixes and to also read product label for compatibility statements. When first using these materials experiment with application timing and rates for specific varieties to help determine what works best for you orchard.