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Ministry of Agriculture, Food and Rural Affairs

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Monitoring and Threshold Guide for IPM



When to look

Monitoring procedure

Threshold/application timing


Scale (San Jose scale, European fruit scale, oystershell scale)


When trees are dormant, check prunings for scale insect nymphs (San Jose and European fruit scale) or eggs (oystershell scale) on the bark. Use a knife to peel back the wood and look for discolouration of the underlying wood. 

Apply a dormant oil if harvest assessments from the previous year indicate scale injury or high levels of scale are found in the orchard early in the season.


Beginning mid May through June, and mid to late August

Wrap adhesive electrical tape on the trunks of trees with scale to monitor emergence of crawlers.  1st generation San Jose scale crawlers generally emerge  mid June, while 2nd generation are present in mid to late August. 

Apply control in high pressure orchards when crawlers are seen.


Fire blight


Note the presence of overwintering cankers in the orchard.

In orchards with a history of fire blight outbreaks, and/or overwintering cankers, use products to manage fire blight management on susceptible cultivars during bloom when weather conditions are optimal for the development of the disease. 


Bloom period to first cover

Monitor temperature, rainfall and stage of blossom development in susceptible cultivars. Use Maryblyt or Cougarblight models to predict when infections may occur.  Monitor for oozing cankers and infected blossoms.  Infected blossoms will often collapse after bloom.

Apply sprays beginning at first bloom until petal fall if one of the following conditions is met – temperatures >18°C accompanied by high humidity (>69%), heavy dews or rainfall. Based on the Maryblyt program, apply sprays when the epiphytic infection potential reaches 100 or more.

Fuji, Gala, Idared are extremely susceptible cultivars. Fire blight can be an issue with warm, rainy, humid periods during bloom.

During active shoot growth

Infected terminals exhibit a shepherd’s crook appearance.


Monitor and manage insect populations (leafhoppers) which may help spread disease.

European red mite/twospotted spider mite


Look for overwintering European red mite eggs by randomly selecting a total of 100 spurs from the inside and outside canopy of 10-20 trees throughout the block. Use a 10X hand lens to inspect small branches and the base of twigs and spurs for the presence of eggs.

If high numbers of eggs are present, apply superior oil to suppress egg hatch from tight cluster through pink. 

Healthy European red mite eggs are spherical and dark red. Non-viable eggs look empty or lighter in colour.

Tight cluster through petal fall

Examine fruit spurs for mite eggs, nymphs and adults. Collect 2 fruit spurs from 25 trees. Use a microscope to examine the underside of leaves for the presence of nymphs and adults. 


Thresholds vary depending on the product used. Apollo is applied at first egg hatch and before there are more than 3 active mites/leaf. For all other miticides the threshold is 5-7 nymphs/leaf and when 50% or more of the population is in the nymph stage.


Petal fall through early summer (June through early July)

Collect 2 leaves from 25 well-spaced trees on a weekly basis.

Apply when there are 7-10 active mites/leaf. Note: apply some newer miticides at 5 mites/leaf. See OMAFRA Publication 360 for more information on timing of specific products.

Twospotted spider mites are not usually present in the orchard until late summer.  Some products may work better against certain species of mites. 

Late summer (late July through August) through harvest

Collect 2 leaves from 25 well-spaced trees on a weekly basis.

Apply when there are 10-15 active mites/leaf. Note: apply some newer miticides at 5 mites/leaf. See OMAFRA Publication 360 for more information on timing of specific products.

Some products may work better against certain species of mites.


10-14 days after bud break

Monitor flower bud leaves for scab lesions.

Apply fungicides preventatively.

Scab lesions may be first seen on the underside of leaves.  McIntosh, Empire, Cortland and Jersey Mac are very susceptible.

Green tip through rest of season

Monitor leaves and fruit for lesions. Monitor daily temperature and leaf wetness. Initiate degree day model when 50% of McIntosh fruit buds are between silver tip and green tip. Base for degree day model is 0°C.

Apply fungicides preventatively when weather conditions are conducive to the spread of the disease. At 125 DDC, there is a higher risk of infections. At 418 DDC it is the end of the primary infection season provided sufficient rain has occurred. If scab is not seen in orchards for a week or so after the end of primary infection period, initiate a reduced spray program.

Often early season scab can be difficult to see on leaves. Scab lesions appear at the site of infection 10-28 days after infection.

Powdery mildew

Green tip to half inch green through to terminal growth set

Monitor leaves and terminals for powdery mildew during scouting.  Monitor susceptible varieties closely.

Apply pre-symptomatic sprays in blocks with a history of mildew problems.

Susceptible varieties include Cortland, Ida Red and Gala.

Tentiform leafminer
1st generation

Early April through petal fall

Place pheromone traps (optional) in orchards in early April to monitor for tentiform leafminer adults, and predict egg hatch. See guidelines for using pheromone and visual traps for more information. 

Collect a total of five fruit spurs from five well-spaced trees. Sample leaves from the lower part of the canopy (closest to the ground). Examine the undersides of the leaves under a microscope for the presence of eggs and sapfeeders. Determine the number of eggs/spur (total # of eggs/# of leaves examined).

Three or more eggs per spur or one or more sapfeeder per leaf after egg hatch has commenced.

Egg hatch generally occurs around petal fall.

Petal fall through July

Continue to monitor pheromone traps. After 1st generation egg hatch is detected (around petal fall), collect 5 leaves from each of 10 trees from the lowest limbs.  Using a microscope, count all eggs, sap feeders and tissue feeders on the undersides of the leaves.  Calculate the number of eggs per leaf and the number of sapfeeders per leaf.

After egg hatch begins, one or more sapfeeding mines per leaf.

Parasitoids can provide biological control of leafminers. Be sure to note the presence of parasitoids.

Tentiform leafminer
2nd generation

Mid to late June through July

Begin sampling for 2nd generation eggs and larvae after 2nd generation moth flight begins (mid- to late June). Collect a minimum of 50 shoot leaves (5 leaves from each of 10 trees) from lower limbs, i.e. below 1.5 m. Sample leaves from middle-aged leaves on extension/shoot growth. Using a microscope, count all eggs and sap feeders on the undersides of the 50 leaves collected and record.   Calculate the number of eggs per leaf and the number of sapfeeders per leaf.

2 mines/leaf (stressed trees)
4 mines/leaf (healthy trees)

Discontinue sampling once tissue feeding mines become predominant.

Leafminers are less of a concern in recent years, and may only need to be monitored closely in orchards with a history of problems.

Oriental fruit moth (OFM) 1st generation

Late April through mid June

Place pheromone traps in affected orchards in late April. Monitoring at this time can be critical since in cool seasons delayed emergence may require additional insecticide applications.

Terminal flagging, and damaged fruit from OFM may begin to appear in orchards in mid June

As a general rule, if pheromone traps are catching >10 moths each week, control measures are likely needed.  Insecticides for this generation are often applied 6-10 days after upswing in pheromone trap counts, which often coincides with petal fall.  A repeat application may be needed if emergence is extended.
A model has been developed to time the application of insecticides for OFM. Begin accumulating degree days (base 7.2ºC) at the first sustained moth catch (biofix).  For products targeting newly hatched larvae, timing is approximately 194-208 DDC for the first brood.

OFM is a regional pest and damage only occurs in Norfolk/Brant, Middlesex/London, Essex/Kent.

Oriental fruit moth
2nd to 3rd (partial 4th) generations

June through harvest

2nd generation flight begins in late June and lasts through to mid July.
3rd generation flight begins in August.

Apply insecticides three to six days after upswing in trap counts. If using the degree day model for OFM, apply insecticides at 805-833 DDC for the 2nd generation, and the 1st spray for 3rd generation at 1361-1389 DDC, followed by a 2nd application at  1611-1667 DDC. 

Mating disruption is an excellent tool in managing OFM.

Rust Diseases

Early pink

Monitor cedar branches for the emergence of fungal telia from cedar galls.

No thresholds exist for this disease. In orchards with a history of rust problems a fungicide program may need to be used to manage this disease.

Presence of cedar galls before and during bloom probably signals apple infection periods.

30 days post-bloom

Monitor apple leaves for the presence of yellow spots on the upper surface of leaves.


Fruit set to maturity

Monitor fruit, especially blossom end, for the presence of yellow spots.


Tarnished plant bug

Pink through to petal fall

Monitor for adults and feeding damage in orchards. Adults are not easily observed during monitoring since they are quick to take flight.  Look for oozing on or near flower buds.

There are no thresholds for this pest. Pre-bloom or post-bloom applications of some insecticides may control this pest.


Spring-feeding caterpillar

Half inch green through mid June

Larvae can be found feeding on leaves, fruit or blossoms. Examine 5 terminals and 5 blossoms on 10 trees on a weekly basis.

Apply control measure if 12-15 larvae are found in 100 terminals/blossoms.


Rosy apple aphid

Tight cluster to pink until mid season

Monitor 5 interior fruit clusters from each of 20 trees (100 fruit clusters total). A cluster with more than 20 aphids is considered infested. 

Apply controls if 5 or more infested clusters are present per 100 clusters examined.


Codling moth 1st generation

Bloom through to mid June

Place pheromone traps in orchard at bloom to monitor codling moth adults. See guidelines for using pheromone and visual traps for more information. Collect and input information on maximum and minimum daily temperatures into a degree day model.

Threshold for 1st generation codling moth is based on a degree day model. Apply insecticides targeting larvae at 125 DDC (base 10°C) after first sustained moth catch, and apply insecticides targeting eggs at 50 DDC (base 10°C). 


1st generation larvae are present in fruit from mid June to late August.  Fruit damage is obvious five or more weeks after petal fall.

Codling moth 2nd generation


2nd generation moths emerge in early August.

The Georgian Bay area only has one generation of codilng moth per season, all other areas have 2.

Apply 2nd generation codling moth insecticides targeting larvae at 600-625 DDC (base 10°C)

Mature larvae of the 2nd generation leave fruit as early as late August and well into October.

Mullein bug

Petal fall to two to three weeks after petal fall. 

Begin tapping around bloom and continue through until three weeks after petal fall. Make a total of 25 taps on randomly selected trees in orchard.

Apply products to control mullein bug 7-9 nymphs are caught per 25 traps. 

Susceptible varieties include Golden and Red Delicious, Gala, Spartan, Northern Spy, Empire, Courtland and Jona Gold.


Plum curculio

Bloom through to early summer

During weekly monitoring sessions, walk through the orchard exterior and keep a close eye out for damaged fruit. Monitor wild hosts near the orchard for the presence of this pest. 

Apply pesticides when the first injury is detected in the orchard perimeter or on nearby wild hosts. 

Adults become active around bloom but do not begin to attack fruit until petal fall. 

European apple sawfly

Pink through to  early summer

Monitor European apple sawfly adults using 3-D visual traps consisting of non-UV white sticky boards that mimic blossom colour.  Place traps in trees between tight cluster and pink stages, and check for adults twice a week. Apply insecticides pre-bloom and/or post-bloom. Fruit damage occurs two to three weeks after petal fall.

Pre-bloom insecticides to control spotted tentiform leafminer may also control sawfly. If a pre-bloom insecticide has been applied, apply post-bloom insecticides when six sawflies have been caught per trap. In orchards where no pre-bloom insecticides are used, the threshold for spraying post-bloom is three sawflies per trap.

This is a regional pest and in 2010 is only present in orchards east of Toronto.  For more information on it’s distribution contact OMAFRA’s Pome Fruit IPM Specialist.

Obliquebanded leafrollers - overwintering generation

Tight cluster  through to early June

Larvae emerge from tight cluster through bloom. Monitor 5 terminals and 5 blossoms on 10 trees (50 terminals total) for signs of caterpillar feeding activity and larvae.

Place pheromone traps targeting adults of the overwintering generation in the orchard at petal fall before adults are flying.



Threshold is reached when 1% to 2% of terminals or buds have larvae or damage, or if orchards have a history of damage. Apply sprays for overwintering larvae at petal fall.

Use pheromone traps to determine first sustained moth catch, and then count degree days using base 6.1° C. These models predict the timing of sprays for the summer generation.


Obliquebanded leafroller - summer generation

Early June through to late August

Summer generation larvae are present in orchards from June through late August. Summer generation adult flight occurs from mid August to late September, and larvae are present in the orchard until harvest, after which time they overwinter. Monitor 10 terminals on 10 trees for the presence of larvae.

Threshold is reached when 1% to 2% of terminals have larvae or damage, or when 240 to 280 DDC (base 6.1°C) have been reached after first sustained moth catch.

Late season sprays are not used to manage leafrollers as they are usually not effective.

White apple leafhopper

Pre-bloom through harvest

Nymphs begin to appear in orchards from pre-bloom through petal fall. Check 5 leaves from each of 20 randomly selected trees in an orchard block for the presence of nymphs and adults.  Give preference to older and mid-age leaves near the trunk area for first generation. 

2-5 nymphs per leaf



Green apple aphid

Bud break to harvest 


Monitor for aphid colonies. Check 10 terminals on 10 randomly selected trees for aphid colonies.  Be sure to monitor for the presence of beneficial insects.


Apply control measures if there are 400-600 aphids per terminal on 10% or more of the terminals. If predators are present on more than 20% of the terminals, delay the insecticide treatment, and check their effectiveness one week later. 


Aphid colonies are usually highest in July and August. Beneficial insects can reduce or eliminate the need for insecticide applications to manage aphids. 

Flyspeck and sooty blotch

Mid summer to harvest 


Check fruit for symptoms.

None exist. Maintain fungicide program at 540 hours of accumulated wetness after petal fall. Reapply fungicides in late August or September if more than 5 cm of rain have occurred since the last application, especially in orchards adjacent to hedgerows for woodlots that can provide abundant inoculum.

Moderate temperatures high humidity are optimal for this disease. Fruit symptoms can develop as soon as three to four weeks after petal fall, but are more common and severe by late summer or early fall. 

Blister spot

Petal fall through late July

Check fruit for symptoms.

None exist. Apply fungicides preventatively to susceptible varieties.

Susceptible varieties include Mutsu and Golden Delicious.

Potato leafhopper

Mid June through harvest 

Monitor for curled leaves and shoots, and the presence of adults and nymphs.

None exists but 1-2 nymphs per leaf can cause leaf curling.



Dogwood borer

June through to harvest

Adults begin to emerge in the end of June. Place four pheromone traps in orchards in June. Monitor peak flight of the adults (usually occurs around mid July). 

Apply insecticides to tree trunk seven days after peak flight of adults in orchards with a history of borer problems.


Dogwood borer is not a problem in all orchards.  To determine if it is a problem, monitor for frass and infested burr knots on tree. If evidence of feeding damage is found, consider implementing a management program.

Apple maggot

Early July through early September

Adults begin to emerge in mid July through August. Monitor adults using five yellow sticky traps baited with a synthetic fruit attractant (butyl hexanoate). Oviposition stings may appear on fruit 7-10 days after adult flight. Tunneling may be apparent 2-10 days after eggs are laid.  

Apply insecticides, targeting adults 7-10 days after the first adult apple maggot is caught on a yellow sticky trap.  Apply subsequent sprays every 14-21 days as trap catches warrant. 


This pest is an issue in all areas of the province with the exception of the Leamington area where sprays are seldom required.

Black rot

Black rot activity begins at the end of bloom and it continues to be a threat through harvest. Make note of infections on leaves, limbs and trunks and fruit. Make an attempt to scout surrounding woodlots and identify hardwood trees infected with the disease. None established.

The disease often first shows up on leaves one to three weeks after petal fall. The optimum temperature for leaf infections is around 26.6°C with 4.5 hours of leaf wetness.

Often fruit infections appear and black spots on fruit, just prior to harvest on susceptible varieties such as gala.

(European canker, anthracnose canker, fire blight)

Most infections occur when temperatures are 10-16°C and moisture is present. Cankers cause infection anytime after the emergence of green tip right up until harvest. Monitor trees for cankers throughout the season. Mark infected trees with bright coloured flagging tape or spray paint to make it easier to find them and prune out infected limbs during the dormant season. None established.  

Woolly apple aphid

End of tight cluster until mid-summer. Look for characteristic cotton, waxy covering around pruning cuts, limbs and trunks and at the base of young shoots and water sprouts in the spring and mid to late summer. There are no thresholds for woolly apple aphids. Consider management when infested twigs become swollen and galls form at feeding sites. Management is also necessary if colonies infest areas near fruit clusters or on young trees and nursery stocks. Damage is minimal when colonies remain on water sprouts and limbs away from the fruit clusters. This pest is not commonly seen in orchards, but has been increasing in numbers in recent years.

Calyx end rot (blossom end rot)

Infections usually occur during bloom or shortly after, although frequently symptoms are not visible until several weeks later. Rot symptoms usually become visible about one month after petal fall. Dry eye rot often develops later in the season (late July to early August) than calyx end rot which is often observed early to mid summer. During weekly pest monitoring examine fruit for the presence of lesions. None established. This is a sporadic problem in Ontario orchards, but can occur during seasons when cool wet weather occurs between bloom and first cover.