Production and pest update brought to you by the OMAFRA Apple Team:
Erika DeBrouwer, Tree Fruit Specialist and Kristy Grigg-McGuffin, IPM Specialist
Table of Contents
Growth Stage
Across the province fruit continues to size with discussions about harvest timing preparations due to the early season that has been seen across the province in other crops. We continue to progress 7 to 10 days ahead of normal in most areas.
Production
Leaf Tissue Sampling
Due to the advanced season, leaf sampling may be quickly approaching. Normally conducted within the last two weeks of July and into early August, leaf tissue sampling is recommended to occur once terminals are set, as this is when nutrients are most stable. Consistency is key and comparison from year to year should be done to give yourself a better idea as to tree health and nutrient flow.
To dust off the cobwebs – covering the What, Why, When, Where & How’s of Leaf Tissue Sampling, check out the article below.
For more information about leaf tissue ranges and nutrient availability please refer to the following links:
- Leaf Tissue Analysis | WSU Tree Fruit | Washington State University
- Publication 611: Soil Fertility Handbook | ontario.ca
Disease Development
Fire blight
With terminal bud set, the cell walls thicken, stomata on the shoot stem are no longer active and the base of the shoot starts to harden off and form bark. All of which results in a significant reduction in fire blight movement. This is a good time to start to prune out fire blight strikes if you haven’t been already. Choose days of dry weather and leave the pruning cuts in the row middles to dry up before mulching them down.
Looking for a quick refresher for pruning fire blight? An oldie, but a goodie – check out this video from Dr George Sundin, Michigan State University:
The unsettled weather we are experiencing may continue to bring hail, strong winds or heavy rains that could still trigger trauma blight from terminal set until harvest. These could be very isolated events, occurring in one area but not another nearby. Assess for signs of damage in all blocks following any storm.
Be sure to apply Streptomycin (PHI 50 days) or 0.5-0.8% Cueva as soon as possible after the trauma event, especially if foliage damage is extensive or fire blight is known to be active in the orchard (ie., cankers, etc). Ideal timing is 4 to 12 hours after a storm. Anything applied later runs the risk that the bacteria will have already established and begun to grow, reducing the efficacy of the product.
Summer disease
These hot, humid days and sporadic storms are also ideal conditions for summer disease, such as bitter rot, fly speck and sooty blotch. Be sure to keep up with regular fungicide applications while these conditions last. For more information on summer disease management, see the June 21st What the Crop?! apple update.
Scab
In orchards where scab is now present, a protective fungicide program should continue during periods of potential infection. Spores will be released from existing lesions during rain or other wetting events and infect surrounding leaf and fruit tissue. This secondary infection period will continue through to harvest.
Powdery mildew
In the earlier regions, terminal bud set has begun. Powdery mildew requires actively growing tissue to complete its cycle so fungicides with efficacy against this disease should continue until terminal growth stops. It is possible to see a flush of new growth later in the season so continue to monitor development.
Infected shoots will not cause damage to fruit at this point in the season. Fruit damage is a result of early infection that occurred in the flower buds. However, infected shoots will be the inoculum source for next year. Prune out any strikes that are present.
Insects of Interest
Apple maggot
Apple maggot have been caught throughout the province. Emergence is closely linked to soil moisture with flushes in flight often following periods of significant rainfall loosening soil. Those areas receiving good amounts of rain with the events rolling through may see a flush of apple maggot emergence in the coming days to weeks.
With catch on yellow sticky boards, it is important to differentiate between male and female adult flies. Males generally begin emerging before the females, but by peak emergence (August), the sex ratio is about 1 to 1.
(Photo: Dr. Rob Smith, retired, AAFC Kentville)
Timing for management depends on the type of trap:
- Sexually immature males and females are attracted to the yellow sticky boards, which mimic nectar sources. Insecticides are not needed until 7-10 days after first fly, particularly a female, is captured.
- Sexually mature females ready to lay their eggs are attracted to red spheres, which mimic ripe apples and indicate an insecticide should be applied immediately as damage is imminent.
Imidan has worked well for years as a border spray option for many growers. However, with the new label changes, all hand thinning activities must be finished before Imidan can be used. The main reason why Imidan can be used effecively as a border spray is its activity as a contact adulticide, killing adults as they fly into the orchard from surrounding areas. Not all alternative products registered for apple maggot have this same activity and therefore are not recommended in a border spray program.
In the table below, adapted from Dr John Wise at Michigan State University (2021), summarizes the characteristics of apple maggot products. Organophosphates (Imidan) and neonicotinoids (Assail, Calypso) are the only insecticide groups that have strong long-lasting activity on the adults as well as a curative effect on the eggs and larvae due to their ability to penetrate into the flesh of the fruit.
Summary of Insecticides Used to Control Apple Maggot
Product Name | Chemical Group | Life-Stage Activity | Efficacy | Residual Activity | Mite Flaring Potential |
Imidan | OP (1B) | Egg Larva Adult | Excellent | 14+ days | Low |
Ambush, Danitol, Perm-Up, Pounce, Ship, Up-Cyde | Pyrethroid (3) | Adult | Fair-Good | 7-10 days | High |
Aceta, Assail, Calypso, Cormoran, Theme | Neonicotinoid (4A) | Egg Larva Adult | Good – Excellent | 10-14 days | Low-Moderate |
Delegate, TwinGuard, GF-120 Fruit Fly Bait | Spinosyn (5) | Adult | Fair | 7-10 days | Moderate |
Altacor, Exirel, Harvanta, Vayego | Diamide (28) | Adult | Fair-Good | 10-14 days | Low |
Surround | Not classified | Adult (deterrent) | Fair | 7-10 days | Low |
Japanese beetle
Japanese beetle activity has started in many regions. The characteristic leaf skeletonization is quite distinct. Look for damage and congregations of this pest at the top of the canopy as damage often moves down the tree. Honeycrisp is often the most preferred variety.
Most insecticides applied for oriental fruit moth or codling moth should have good efficacy on Japanese beetle; however, the tendency of these beetles to move in from surrounding areas may make multiple applications necessary. If applying a control product, target timing for early morning while beetles are still relatively inactive on the tree. Once feeding begins, the sex pheromones emitted by females combined with what numerous studies believe to be feeding-induced plant volatiles attract more beetles to congregate in the feeding area. Achieving knockdown before this occurs could help reduce the number of individuals coming into the orchard from surrounding areas.
Good weed control in and around the orchard will also help reduce Japanese beetle pressure. Populations tend to be more abundant in orchards where there is poor control of wild raspberry, blackberry, Virginia creeper and wild grape.
San Jose scale
Most areas are starting to see a decline in first generation San Jose scale crawler emergence. The heat has helped move development along quickly. However, this also means second generation activity will likely be on the early side as well. In previous years, crawler emergence has generally begun late July to early August. Based on degree days (see table below), we seem to be about 1-2 weeks ahead of normal.
San Jose scale degree day accumulations as of July 4, 2024
Region | Current Degree Day Celsius (DDC) | Predicted Crawler Emergence – 2nd generation (806 DDC) |
Harrow | 678 DDC | July 13, 2024 |
London | 552 DDC | >14 days |
Delhi | 529 DDC | >14 days |
Grimsby | 573 DDC | >14 days |
Clarksburg | 467 DDC | >14 days |
Durham | 471 DDC | >14 days |
Fruit damage from first generation crawlers can be found in some orchards already, especially in those blocks with historically high pressure. Those that have a history of damage from this pest may want to consider managing this generation to prevent fruit damage close to harvest.
- Registered products include Movento, Sivanto Prime, Closer and TwinGuard.
- Weekly or bi-weekly applications of oil or soap may also provide some suppression but use caution with these products around certain fungicides.
- Always refer to the product label before use.
- For good resistance management, rotate to a different chemical group than what was used for the first generation.
- If using two consecutive sprays applied 14-days apart, be aware of the preharvest interval particularly on any early varieties.
Dogwood borer
Dogwood borer trap catch has peaked in early regions this week in orchards with a history of problems with this pest. Adult emergence will continue through to early September but management often targets peak flight or shortly after, as explained below. Throughout their activity, females will lay eggs on the surface of burr knot formations, pruning cuts, cankers, and wounded bark, after which the larvae use these as entry points to bore into the tissue to begin feeding.
Currently, pyrethroids, Altacor, Delegate and Rimon are registered for trunk application for control of borers:
- Pyrethroids at this timing can have significant impacts on the natural enemy complex.
- Rimon 10 EC is an insect growth regulator (IGR) that must be absorbed by eggs or ingested by larvae to be fully effective. The optimal timing for this product is around 25-75% egg laying, or approximately peak flight.
- Delegate and Altacor must be ingested by the larva in order to work; therefore it must be applied at the beginning of egg hatch, or a few weeks following peak flight.
- With all products, a repeat application 14 days later is recommended.
An alternative management option for dogwood borer next year is the mating disruption product, Isomate DWB. Dispensers (250-375 dispensers/ha) should be applied before adult borer emergence, or approximately the end of May. Researchers from Rutgers and Cornell University feel that Isomate DWB can adequately control light to medium dogwood borer infestations and give equal control to trunk drenches after multiple years of use.
Potato leafhopper
Potato leafhopper are quite active though little hopper burn and leaf cupping have been reported. This damage is caused by a toxin in the leafhopper’s saliva that blocks vascular system flow, preventing normal movement of water and nutrients to the affected area.
In most high vigour blocks, leafhopper damage is manageable, particularly once terminals harden off. However, nursery trees and non-bearing blocks require control at first sign of injury since vigour and shoot growth can be significantly impacted. With the first cut of hay happening in many regions, there may be a flush of potato leafhopper moving into orchards in the coming weeks.
Ambrosia beetle
Monitoring of ambrosia beetle is on-going in orchards across the province. The following graph shows the average trap catch per week since April 1st for each district. We are currently working through identification of each species. However, based on the activity to date, it is very likely the invasive black stem borer is present in most orchards being monitored.
As pests of hardwood, many species of ambrosia beetle may simply be present in the landscape surrounding your orchard. Higher numbers do not necessarily indicate damage; however, high numbers of certain species could potentially be problematic.
Damage can be tricky to find but look at the trunk for signs of oozing sap, discoloured or blistering bark and/or sawdust “toothpicks” from tunnel excavations that protrude from small holes. In most cases, ambrosia beetle infestation is often not detected until trees appear to spontaneously collapse.
Apple leafcurling midge
Orchards that still have not seen terminal set or are experiencing secondary growth may be noticing more apple leafcurling midge damage on the newest leaves. So long as there is new growth on either shoots or root suckers, leafcurling midge activity will continue into the fall. Watch young trees as this damage will impact growth and tree vigour.
Mites
The hot, humid weather has resulted in an increased activity of European red mite (ERM), two-spotted spider mite (TSSM) and apple rust mite (ARM) in some orchards. Those growers that are seeing populations reach threshold quickly are opting for miticides with relatively quick knock-down.
Keep in mind, thresholds for mites increases through the season as the tree canopy becomes more dense. From June to mid/late July, the threshold for most products is 7-10 active mites/leaf. Consider 5 mites/leaf for products like Nealta or Kopa. However, late July to August, the threshold for most products can be delayed to 10-15 active mites/leaf.
The table below lists registered miticides for summer management. When choosing a product, consider the abundant life stages that are present in your orchard. For instance, if you are seeing mainly eggs, Envidor may be an option as it is slower acting. However, if the population is mainly nymphs or adults, you may opt for a product that offers a faster knock-down. As mentioned earlier, products like Nealta or Kopa should be applied as populations are building.
Activity of Summer Miticides Registered on Apple in Ontario
Product | Target Species | Life Stage Affected | Knock-Down Activity |
Acramite 50 WS | ERM, TSSM | nymphs, adults | rapid |
Envidor 240 SC | ERM, TSSM, ARM | eggs, nymphs, adults (female) | slow |
Kanemite 15 SC | ERM, TSSM | all life stages | rapid |
Kopa (soap) | ERM, TSSM, ARM | nymphs, adults | intermediate |
Magister SC | ERM, TSSM, ARM | all life stages | rapid |
Nealta | ERM, TSSM | all life stages | intermediate |
Nexter | ERM, TSSM, ARM | nymphs, adults (ERM, ARM) | rapid |
Purespray Green Spray Oil 13 E | ERM (suppression) | eggs, some nymphs | smothers |
Suffoil-X | TSSM | eggs, some nymphs | smothers |
Vegol Crop Oil | ERM | eggs, some nymphs | smothers |
Despite the lush, dense foliage this time of year, do not let mite populations cause extensive damage. Late-season mite pressure and leaf bronzing can result in poor fruit finish and reduce winter hardiness.
North American Virtual Orchard Series
The 4th annual North American Virtual Orchard Series was held throughout June with a focus on water stress and precision irrigation. Recordings of each webinar can now be accessed in the YouTube playlist below:
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