Table of Contents:
- 2021 Degree Day Accumulations
- Apple - Scab
- Apple - Powdery Mildew
- Fire Blight - Orchard Management
- Apple - Black Rot/Frog-Eye Leaf Spot
- Apple - Brooks Spot
- Apple - Flyspeck and Sooty Blotch
- Apple - Bitter Rot
- Stone Fruit - Brown Rot
- Apple Insects
- Leafhopper
- Aphids
- Codling moth
- Mites
- Leafroller
- Apple maggot
- Honeycrisp Leaf Chlorosis
- Solstice Reminders
- Pruning and Training
- Young Trees
- Calcium Nutrition
- Weed Management
- Nursery Trees
- Mowing
Events and Notices
- Bitter rot and apple scab samples for AAFC
- Perennia has moved to downtown Kentville!
- Agricultural Clean Technology Program
The above-average trend continues.
Figure 1: Heating degree day accumulations for plant (above 5°C) and insect (above 10°C) development from March 1st to July 5th for the past 17 seasons. Provided by Jeff Franklin (AAFC).
- Approximately 14% more plant development heat units compared to the 5-year average, and 12% more compared to the 10-year average.
- Approximately 12% more plant development heat units compared to 2020, and 30% more compared with 2019.
- Approximately 18% more insect development heat units compared to the 5-year average, and 16% more compared to the 10-year average.
Diseases
Apple – Scab
Where primary lesions are present, secondary infections have been occurring and will continue during wetting events of sufficient duration. The minimum wetting required for secondary infections is 3 hours less than the wetting required for primary infections.
Recommendations:
- Plugged sprayers warning - You are already aware that water soluble packaging should not be tank mixed with boron and that the tank should be rinsed well before and after boron. Sometimes boron is not the target nutrient in a product but it is included. Please carefully review nutrient formulations that might contain boron in small quantities.
- Folpan cautions - Folpan is not a new product but it is new for use in the industry. It is considered a cousin to Captan and is similarly a hot product that has the potential to cause fruit russetting. Do not use Folpan close to oil sprays or products containing surfactants. Also, be wary of tank mixes with liquid nutrients that are formulated to maximize uptake.
- Hand thinning REI reminder - Be very aware of the re-entry periods on the new captan-containing product Maestro 80 WSP for planning ahead to hand thinning. High-density plantings with a maximum canopy width of 2 m have an REI for hand thinning of 15 days. Otherwise, low-density plantings have an REI of 24 days for hand thinning.
- Do not reduce fungicide spray intervals until you can identify your pressure from secondary scab lesions. Also note the risk of summer diseases if spray programs are stretched to the limit.
- The pre-harvest interval for EBDC fungicides (e.g. Manzate, Dithane, Polyram) for fruit destined for the United States is 77 days versus 45 days for the domestic market. An application of EBDC on July 6th would require until September 21st to meet pre-harvest requirements for the United States.
- Always tank mix single site fungicides with a group M for resistance management.
Apple – Powdery Mildew
Recommendations:
- Powdery mildew pressure is high this year. On young trees, monitor for active mildew to determine the need to protect new terminal growth. Only group 3, 7, and 11 fungicides have activity and resistance is a concern in group 11. This issue of not having enough groups is widespread across apple growing regions.
- Powdery mildew will continue to spread until terminal bud set. Remember that late summer sprays are protectants for new tissue and they are not eradicants on previously infected tissue.
- Pay particular attention to susceptible and high-value varieties such as Honeycrisp and Gala.
Fire Blight - Orchard Management
Recommendations:
- Continue to monitor for signs of fire blight blossom infections, especially in young blocks.
- Canker blight and shoot blight symptoms should also be visible by now.
- In blocks with historically high pressure, prune only when the forecast calls for at least 2 days of sunny, dry weather. As an extra precaution, disinfect tools after working in a block with fire blight pressure.
- When pruning, remove fire blight strikes at least 2-4 ft below active infections to remove the leading edge of the bacteria. Being aggressive at the first sign of symptoms will help prevent the re-occurrence of symptoms and the need for continuous cutting back. Leave prunings in orchard alleyways to dry thoroughly for several weeks.
- Cut out infections when a period of 2 dry days are in the forecast. Drop shoots into the laneways to let dry thoroughly. If cutting a whole tree consider letting it dry while attached to the trellis. Don’t make piles that will prevent the wood from drying.
- Monitor for shoot blight on suckers that can infect the rootstock.
- For on-farm nurseries, consider applying a copper product at the lowest labeled rate prior to training trees and follow the labeled REI. Make cuts on only dry and sunny days.
Apple - Black Rot/Frog-Eye Leaf Spot
This disease has been an issue in certain orchard blocks. Varieties most prone to infection include Honeycrisp, Northern Spy, Delicious, Sunrise, and Ginger Gold. Infection can develop on fruit after about a 9-hour wetness period at an average temperature around 20-24C.
Dr. Sajid Rehman and Dr. Paul Hildebrand have been exploring the black rot disease. Research they reviewed from North Carolina (Sutton 1980) suggests the following:
- The total spore load is highest for a period from petal fall to 4-6 weeks later. However, spores are likely active beginning at green tip.
- Spores are produced for at least 6 years in dead wood that researchers had tied to trees.
- As little as 0.25 mm of rainfall triggered spore discharge.
- Spores are detected during the first hour of rainfall.
- Spore concentration increased as the rain continued.
Recommendations:
- The heaviest spore release is believed to occur for a four to six week period following petal fall. If considering when to apply the second and final Captan on a low-density block, any time prior to a rainfall would be appropriate. Be cognizant of the REI for hand thinning activities.
- Fungicides are protectants because they prevent spore germination on plant tissues so for protection from this disease the fungicides would need to be applied prior to the wetting event.
- Do not reduce rates of Captan after bloom in high density orchards that have a history of black rot. Consider this recommendation where practical in terms of new label restrictions. Pristine and Merivon would also have good protective activity but these chemistries should not be overused and they also have a hand thinning REI of 12 days.
- Check for nearby brush or wood piles because they serve as a major source of inoculum. Remove the brush pile to reduce the chance of infection.
Apple - Brooks Spot
Apple - Flyspeck and Sooty Blotch
Apple - Bitter Rot
The bitter rot disease is a localized issue in Nova Scotia orchards during most years. Many different species under the genus Colletotrichum can infect apple fruit. When the organisms are present, infections can develop during hot and wet weather after fruit set during the summer. Bitter rot symptoms usually appear on the sun exposed side of the fruit and when cut through the lesion the rotted area is V shaped. The most susceptible varieties are Honeycrisp, McIntosh, Sunrise, Paulared, Jonagold and Empire.
Local Research
- Symptomatic apples were collected from three separate sites in the summer of 2019 by Dr. Shawkat Ali's research program at AAFC. They identified three separate species of Colletotrichum from these samples and made the following preliminary observations:
- "The first and most common species was C. Fioriniae, which has been previously reported to cause Bitter Rot in Atlantic Canada. We also found C. Nymphaeae, which had previously been isolated from symptomatic apples in the southeastern United States but not in Canada. Finally, two of the samples were identified as C. Salicis, which has been reported to cause Bitter Rot in Europe and Oceania, but to our knowledge has not previously been reported from symptomatic fruit in North America. All three species were also pathogenic on strawberry."
- "Our early fungicide sensitivity assays demonstrate significant differences in fungicide sensitivity between species. So far we have just tested Pyraclostrobin and Difenacanozole and currently have an experiment running for Mancozeb. There have been minor differences in fungicide sensitivity between isolates of the same species, but more pronounced differences between species."
- View the full research update here. To participate in future work under this research, see the invitation under Events and Notices. Participants who provide a site for collection of bitter rot samples will have the species in their orchard identified and they will be informed of the fungicide sensitivity profile for that species.
Stone Fruit - Brown Rot
As sweet cherries begin to ripen they become more susceptible to brown rot infection. The interval between fungicide applications will need to be shortened as the fruit softens. Check the Stone Fruit Management Guide for fungicide options and always check the pre-harvest spray intervals when selecting the fungicide.Insects
Apple Insects
- White apple leafhopper:
- Monitor for white apple leafhopper that has been enjoying this heat. Sevin XLR applications will control leafhopper but monitor untreated plants for leafhopper.
- The first generation is nearing the end when there will be only adults on trees. The nymphs will start to appear again and cause feeding damage in early August so the second generation is the next treatment opportunity. If treatment is required, a neonicotinoid, Sivanto Prime, or Exirel would control leafhopper and also pick up aphids.
- Aphids:
- Rosy apple aphid pressure is slowing down. Winged adults are leaving apple trees to go to their alternate hosts, and natural predators are cleaning up colonies. Asses trees for active colonies before determining the need to treat for this insect.
- Monitor for green apple aphid. In young trees the aphids can disrupt shoot growth. Monitor nursery plantings as well. In bearing plantings the aphids can colonize fruit clusters and damage fruit. Green aphid will move back into orchards that were treated previously so continue to monitor. Assail and Calypso also have activity on codling moth, apple maggot and leafhoppers. Be cognizant of REIs if installing trellis.
- Codling moth:
- Approximately a week after application of an OP insecticide, clean out the trap and start monitoring the trap. The capture of an additional 10 or more moths would indicate that a second treatment is required.
- Codling moth treatments can be washed off by 12.5-25 mm (0.5-1 inch) of rain. Note that some regions had significant rainfall over the weekend of 1-2 inches. A heavy rain just after application is more concerning than a late application because it would wash off and reduce the residual life of the insecticide.
- Mites:
- Scout your orchards or check your scouting reports to see if there is a treatable population. Mites thrive in warm and dry weather.
- Both European red mite and two-spotted spider mite are controlled by the products Acramite, Apollo, Kanemite, and Nealta. All three mite species are controlled by Nexter and Envidor.
- This is the time of year to get rust mite under control instead of mid to late August when the foliage has become bronzed.
- Mites have many generations per year and therefore have a high potential to develop resistance. For resistance management, it is critical to rotate miticide classes. The use of dormant oil applications will also help to delay resistance selection for European Red Mite.
- Obliquebanded leafroller: Monitor or check scouting reports for larval populations.
- Apple Maggot: In 2012 that had similar heat to this year, the first capture of apple maggot in a heavily infested orchard was reported on June 29th. Captures in commercial orchards were more common around July 10th. In blocks that are still being treated for codling moth, the control is extended to early maggot flies. No captures have been noted yet for this year by Dr. Suzanne Blatt at the research station. Emergence should start any day now.
- The economic threshold is 1 maggot fly per orchard on a yellow sticky board. Apply a treatment 7-10 days after the first fly is captured on a yellow sticky board or immediately after a female is captured on a red sphere.
Horticulture
Honeycrisp Leaf Chlorosis
- There is the potential for early and noticeable symptoms of Honeycrisp leaf chlorosis this year.
- Leaves start out chlorotic and by the end of the season they turn brown and dry. The symptoms commonly form on the edges of the leaf and progress inwards. Not to worry though, this genetic trait of Honeycrisp shows up at the end of every season, and severe symptoms do not appear to negatively affect the health of the trees.
- It’s tempting to think the discolouration is related to a nutrient deficiency because the resemblance is strikingly similar, but the scientific consensus is that a nutrient deficiency is not involved. Honeycrisp leaves become discoloured when export of carbohydrates from the leaf becomes partially disabled. Carbohydrates accumulate and interfere with chloroplast function. As a result, the chloroplasts break down and the green pigment is lost.
- Symptoms tend to appear after shoot growth is complete. Growing points like shoot tips, and storage organs like roots and fruit all attract carbohydrates for their own use. When shoot tips stop growing, there is less demand for carbohydrates... allowing it to accumulate to excess levels in Honeycrisp leaves. The severity of the leaf chlorosis varies by rootstock.
- Years that are sunny and warm encourage excess carbohydrate production and may cause more severe symptoms. Also, light crop loads will show more symptoms.
Solstice Reminders
- If granular fertilizer is applied now, the risk is that any dry weather in July will slow the release. Late release will prevent trees from hardening off before the winter. Top dressing is not recommended after the end of June.
- Around July the trees are storing reserves in the roots for next year’s growth. When they are storing reserves, late glyphosate applications can be damaging if taken up by root suckers and transported to the root system. Avoid the risk by avoiding glyphosate applications after the end of June.
Pruning and Training
- If bamboo is limited because of COVID delays, we recommend looking at other options in the meantime. As young trees grow more foliage they are more susceptible to sailing in the wind. Consider running wire supports or new solutions to support trees. The hurricane season has begun and even the risk of high wind events is cause for concern.
- Prioritize trees that are known to be brittle at the union, including many of the new Geneva rootstocks (G.11, G.41, G.16 etc).
- Train and support young trees as soon as possible. Remove competing terminals. Work in dry weather especially if the block has historically high risk of fire blight.
Young Trees
- Broadcasting grass seed is not recommended for establishing grass in the alleyway. Direct seeding is recommended to confine the grass seed to the alleyway and avoid spread to the tree row. The herbicide gramoxone used to provide good control of bluegrass species but post-emerge products for grass control are now limited.
- Ensure that deer fencing is installed as soon as possible to protect new growth on young trees. Deer are browsing young plantings and causing damage. Thiram is no longer an option to deter feeding while the fence is being installed. Another deterrent product called Bobbex is available for nonbearing trees.
- Remove root suckers. Suckers compete with the main tree for water and nutrients. They harbour pests, and they are an entry point for fire blight. Pull or break off suckers because otherwise cutting them would let them rebound. If necessary, AIM herbicide is registered for control of suckers but avoid drift onto young trees and apply only near mature brown bark.
Calcium Nutrition
- Note that nutrient product formulations with calcium may contain boron that would interact poorly with water soluble packaging.
- The goal of Ca sprays is to increase the concentration of Ca in the fruit and reduce bitter bit incidence.
- Calcium applied at two-week intervals is better than occasional, high-rate applications.
- The recommended rate is 4 to 14 pounds of elemental calcium per acre in a season spread over six to eight cover sprays. The percentage of elemental calcium will be listed on the label.
- Ca has very low movement within the tree and needs to be applied directly to the fruit surface to be absorbed. Therefore, thorough coverage is important to cover developing fruit.
- Calcium chloride flake (77% Ca) is the most economical Ca material to use but also the highest risk for foliar burn. Apply calcium chloride flake at no more than 4.5 kg per 1000 L of spray solution. The risk of leaf or fruit damage from calcium is highest in hot and dry weather. Susceptible varieties can develop lenticel spotting if damaged. Target fast drying conditions for applications.
- Risk of leaf injury may be enhanced by Captan. Incompatibility has been observed with Epsom salts, and liquid or emulsifiable pesticide formulations in some cases. Do not apply calcium with apogee.
Weed Management
- Note that 2,4-D has an 80-day PHI.
- Prevent herbicide drift by avoiding sprays during wind gusts, periods of dead calm, wind speeds above 16 km/hr, and temperatures above 25°C.
- Remember the importance of weed control in nurseries and young plantings. Management practices now will impact the outcome of the final tree. Encourage the growing point to be successful.
Nursery Trees
- Scion leaders will need support.
- Aim is registered for nurseries but it is a hot product and caution is recommended around green tissue. The product is not volatile but green tissue is very sensitive on contact.
- Monitor for aphids, leafhoppers, and tarnished plant bug.
- Strip the lower leaves on nursery rootstock before they become woody.
Mowing
- As grass becomes long the extra surface area increases transpiration. Keep grass mowed to conserve moisture.
- Keeping the orchard floor cover mowed will minimize dandelion flowers that attract bees, which increases the safety of insecticide applications.
Pest Management Guides 2021
The pest management guides are available online for download. All changes new to 2021 are made in red text.
- Download the 2021 Pome Fruit Schedule
- Download the 2021 Organic Apple Schedule
- Download the 2021 Stone Fruit Schedule
- Download the 2021 Thinners and Growth Regulators Schedule
- Download the 2021 Tree Fruit Weed Management Guide
Events and Notices
For upcoming events, visit the ‘Events’ tab on the NS Tree Fruit Blog. Specific events will be described here when available.
Bitter Rot and Apple Scab Samples for AAFC
The Plant Pathology Lab of Kentville’s Agriculture and Agri-Food Canada is looking for apple growers who will participate in a province-wide study of the fungal pathogens responsible for bitter rot and apple scab disease in apple. One of the goals of the research is to look at the fungicide resistance profile to find out which fungicides are still effective or not. This is an industry and AAFC funded project.Growers who notice either bitter rot or apple scab appearing in their orchard are invited to contact Dr. Shawkat Ali (shawkat.ali@canada.ca) or Shayne McLaughlin (mc615708@dal.ca). Researchers will then monitor the orchard to collect diseased leaves or fruit from the orchard for further study. Samples cannot be collected from the orchard floor due to rapid deterioration. The industry needs your help in identifying sites where samples can be taken.
Perennia office has moved to downtown Kentville!
We are now located at 28 Aberdeen Street in downtown Kentville. Our office phone number stays the same: (902) 678-7722. Please note, we are not open for visitors until July 5th. You can access the building from Aberdeen Street and walk through to the back parking lot where our entrance is or enter the back parking lot (turn left beside the Independent grocery store off Webster Street) where we have designated parking and our own separate entrance. For those of you familiar with Kentville over the years, we are in the old Access Nova Scotia space.Agricultural Clean Technology Program
This adoption stream will support the purchase and installation of commercially available clean technologies and processes with a priority given to those that show evidence of reducing greenhouse gas (GHG) emissions, and other environmental co-benefits. Funding will be specifically allocated towards projects under the priority of green energy and energy efficiency. There is a maximum contribution of 50% from the program for For-Profit operations and up to 75% for Not-For Profit organizations. For specific examples, check out the applicant guide.Perennia Food and Agriculture Inc.
