Tree Fruit IPM Advisory

USU Tree Fruit IPM Pest Advisories provide nearly weekly updates on current insect and disease occurrences, biology, and treatment recommendations for Utah. Updates run from mid-March through September.

To subscribe to this advisory (link to this newsletter sent to your email inbox), click here.

Gummosis of Stone Fruits

pdf version

June 2, 2011

In this Issue:

What to Look for/Do Now:

  • Codling moth spray timings updated in table below
  • If any infections have occurred due to fire blight, they will be showing up soon, as wilted shoots.  Prune these out as you see them, about the same distance into healthy wood as the length of the shoot.
  • Watch peach fruits for powdery mildew lesions as the fruit starts maturing.
  • Brown mite (a cool season mite related to spider mites) has started showing up in some orchards.
  • Western cherry fruit fly will not be an issue until fruit has developed a salmon blush color (several weeks away).

Current Insect and Disease Activity


Codling Moth

Because of the cool, wet spring, codling moth emergence has been very sporadic. Biofix (first trap catch) is about 2 weeks later than last year in most locations. Adults only fly at night, looking for mates and egg-laying sites, when temperatures are above 50 and when there is not a pouring rain. The weather has surely prevented mating, and thus egg-laying from happening so far. Eggs within females are only viable for about 3-4 days, so if they cannot mate with males, eggs do not get laid. We are hoping that this means a “light” population for the first generation flight. Updated spray timings are posted below.


Peach Twig Borer

Peach twig borers spend the winter as small larvae in galleries within the tree cambium.  Larvae have emerged and moved to newly expanding shoots where they bore into the tip to feed, causing the typical “shoot strikes.” They will pupate within the shoots and emerge soon as adult moths, to lay eggs on shoots.  Later generations feed on the fruit. We have not caught any moths, and when we do, we will be able to provide dates for starting sprays.



black cherry aphid leaf curl plum aphid

Aphid eggs that survived your dormant oil sprays have hatched and are multiplying now, including green peach aphid, leaf curl plum aphid, and black cherry aphid.  Be sure to examine the aphid colonies closely for beneficial insects, as they are also increasing in population. 

Green peach aphid is the most damaging, especially to nectarines, in that feeding can result in deformed fruit.  All three species leave their tree fruit hosts for the summer to vacation on alternate plant hosts, returning at the end of the season to mate and lay eggs.

Oil (1%) or insecticidal soap are the best options for residential growers.  Once leaves are tightly curled, aphids are more difficult to treat, so thorough coverage is important.


With the warming temperatures comes the flow of sap, especially noticeable in stone fruit trees (cherry, apricot, peach, and plum). The oozing is sometimes generically referred to as gummosis (although back East, “gummosis” refers to a disease caused by a fungal pathogen). The sticky, oozing gum can be clear or amber in color, and by the end of the summer, it will have become almost rock-hard.

oozing gum on stone fruit trees can be caused by a variety of factors ooze from bacterial canker (apricot) is milky in color
ooze from cytospora canker is amber in color, and often occurs in association with wounds, like improper pruning cuts by scraping the outer bark away, you can see the dead phloem tissue adjacent to the healthy, cream-colored tissue
oozing from shothole borers is a response to push out the insect flatheaded borers attack trees under stress that often do not have the reserves to exude sap
 clear oozing may be a result of a wound by scraping the bark away, we see that the phloem underneath is healthy

Although most people suspect borers when they see oozing, it can actually be caused by a variety of other factors, such as:

1. A plant pathogen

a)  Cytospora canker, caused by Leucostoma cincta, invades and kills bark and cambial tissue through wounds such as pruning cuts, sunscald, hail, etc. Gumming from cytospora is dark amber in color, and if you scrape the outer bark, the dead phloem will appear cinnamon brown in color. Cytospora canker is an opportunistic pathogen, meaning that it invades trees through wounds. It can be found almost everywhere, so prevention is the key to management.

Management for cytospora includes:

i. in normal pruning operations, make proper cuts (i.e., do not leave stubs or do not make “flat cuts” that remove the branch collar where healing would normally occur) and do not prune in wet weather;
ii. use white tree wrap or 50/50 latex paint/water to prevent sunscald injury
iii. prune affected limbs back to healthy wood and sterilize tools with 10% bleach between cuts;
iv. remove severely affected trees;
v. keep trees healthy with optimal watering, mulching, nutrition, etc.

b)  Bacterial canker, caused by Pseudomonas syringae, is more common on cherry, but has been identified from peach in Utah. Gumming from bacterial canker can also be amber in color, but may appear milky. Exposed phloem will have a slight fermented smell. Pseudomonas is also opportunistic, entering the plant tissue through tiny wounds. The bacteria can survive as a non-pathogenic epiphyte on leaf and bark surfaces of peaches, cherries, and many other plants including weeds.

Infections occur in late fall just prior to winter, and symptoms appear the following spring. Late season rainfall spreads the bacteria from leaf surfaces to buds where the infections take place. Infections are inconspicuous in the fall and winter but become more obvious in the spring, with dead buds that often exhibit signs of gummosis. Flowers and foliage may be infected under rainy conditions, resulting in wilting of shoots and oozing. Once within the branches, the bacteria invades the phloem, causing cankers

Management is the same as for cytospora canker, with the addition of copper sprays in the fall (2-3 applications beginning at 10% leaf drop to just after full leaf drop) and early spring prior to bud break.

2.  Greater peachtree borer.

If you see gumming at the base of the tree (no higher than 8-12”), the gumming may be caused by this borer, and is not a canker. Peachtree borers attack the crown of the tree, and healthy trees can withstand attack. Tree can be protected with a properly timed insecticide (more information in future advisories).

3.  Flatheaded or shothole borers.

These types of beetles will only attack weakened trees or wounds such as where sunscald has occurred. Attacks on healthy trees are usually unsuccessful because the tree will exude enough sap/ooze to flush out the insects. Ooze is often clear in color, and limited to beetle entry holes. Weakened trees that are attacked may actually not ooze as much because they do not have enough reserves to waste on this response. Management of these pests is difficult, and may include bark sprays of permethrin May through August.

4.  Wounds

Wounds from frost crack, bark injury, cat scratching, hail, etc. may exude gum in spring. Gummosis not caused by a pathogen will run somewhat clear in color (but will dry to amber).

5.  Other climatic or physiological problems

Factors such as planting too deep, excessive irrigation, severe pruning from April - August, or over-bearing have all been cited as possible causes of abiotic gummosis.

If you are not sure that a pathogen is causing the gummosis, scrape the outer bark away. If the inner bark is still cream-colored (healthy), the oozing is caused by a non-living factor, and there is nothing you should do. If the wood is tan to brown, it is dead, and was most likely killed by a pathogen.

Coryneum Blight


Coryneum blight (also known as shot hole) infections on fruit are showing up now, especially on apricots. The cool wet weather has been ideal for spread of this disease. As mentioned in earlier advisories, the optimal timing for coryneum is at the shuck split stage of fruit development.

Coryneum blight is caused by a fungus that overwinters in buds, causing small gummy cankers. From there, it spreads to leaves and later, to developing fruit. Infections on the leaves cause small round holes, with the center of the lesion sometimes barely attached. On fruit, lesions vary from dark colored warts to sunken lesions (depending on time of infection). Look for developing lesions (holes in the leaves and purplish spots on fruit) and treat if necessary to protect fruit for later in the season.

Keep in mind that future infections will occur whenever there is a 4-hour window of moisture.

Management for residential growers: If your peaches are at the shuck-split stage (currently only cooler areas such as Cache County, northern Box Elder County), you can use chlorothalonil (Fertilome, Bonide Fungonil). If your fruit is beyond this stage, you cannot use chlorothalonil. The only other easily available option is captan (Bonide). If you can find it, Ziram is very effective, and if you can afford it, so is Pristine.

Management for commercial growers: Ziram and Pristine are most effective, Abound is somewhat effective.

For all growers: an application of copper at 50% leaf drop in the fall is an excellent option for control of coryneum blight.

Peach Leaf Curl


Peach leaf curl is showing up in many places this spring due to the cool wet weather. Peach leaf curl is a fungal-caused disease that affects peach and nectarine. Infection occurs just as the leaves are opening, and causes puckering and distortion of the leaves. The affected area is pink at first, and then turns green, then brown. Leaves will eventually drop. Infections only occur when temperatures are below 79 F in the presence of moisture. Once the temperatures rise, further infections of leaves and fruit will end.

If you see these symptoms, note that there are no fungicides that can be applied at this time. The best treatment is a single application of a fixed copper applied at leaf fall.

For now, maintain tree vigor of infested trees by thinning more fruit than normal, reducing drought stress with irrigation (if soils ever dry up), and apply extra nitrogen fertilizer.


Upcoming Monitoring/Insect Activity

Pest Host Appearance/Management
Apple powdery mildew apple Look for small white lesions on new foliage
Codling moth apple fruit Egg-hatch approximately 2 weeks after emergence
San Jose scale apple mostly Treat crawlers in late June/early July
White apple leafhopper apple Look for nymph activity on the undersides of leaves
Green peach aphid peach, nectarine Look for colonies on peach and nectarine
Peach twig borer peach, nectarine, apricot Moths typically start flying in early to mid June; treatment is 1-2 weeks later
Black cherry aphid cherry Watch terminals for leaf-curling and feeding
Cherry powdery mildew cherry Look for small white lesions on new foliage near the base and interior of the tree


Degree Day Accumulations and Insect Development

Click here for information on degree days.

March 1-May 31

Location Codling Moth, 1st Generation
DD (post biofix) % Moth Flight % Egg Hatch
Box Elder
Perry 42  0
River Heights 16 2 0
Smithfield 13 1 0
Davis Kaysville 59 7 0
Grand Castle Valley 376 73 25
Iron Cedar City 60 7 0
Salt Lake Holladay  109 17 0
West Valley City 106  16 0
West Jordan  67 8 0
Tooele 130  17 0
Uintah Vernal 91 13 0
Utah American Fork 17 2 0
Genola  106 15 0
Goshen  36  4 0
Lincoln Point 40 4 0
Lindon  82 10  0
Payson  59 7 0
Santaquin-West 58 7 0
West Mountain 66 8 0
Weber Pleasant View 52 6 0
Wasatch Heber City 20 2 0
Wayne Capitol Reef  112 17 0


Spray Timing

The table below shows two options for the first spray of the first generation. Option A may provide a slight cost savings, and can be repeated at the beginning of the second generation.  It uses horticultural oil (1%) to target eggs before they have started to hatch.  The second spray will then be about 7-12 days later, and will coincide with the period when eggs would normally be rapidly hatching.  Option B is the traditional date to start sprays--when the eggs start hatching. 

Good residue (insecticide) coverage is important at this timing. After the first insecticide spray has been applied, continue to apply your chosen material(s) at the interval provided on the label.


  Option A  Option B  
County Location Apply Oil
(200 DD)
Apply delayed 1st cover
(350 DD)
Traditional Start Date (220 DD,
1% egg hatch)
Period of Greatest Egg Hatch (340-640 DD)
Box Elder
Perry June 11 June 20 June 13 June 20 - July 5
River Heights June 15 June 25 June 17 June 24 - July 10
Smithfield June 15 June 24 June16 June 23 - July 8
Davis Kaysville June 9 June 17 June 10 June 17 - July 1
Grand Castle Valley past past past May 28 - June 13
Iron Cedar City June 10 June 19 June 11 June 19 - July 3
Salt Lake Holladay June 5 June 13 June 6 June 13 - June 26
West Valley City June 6 June 15 June 7 June 14 - June 28
West Jordan June 8 June 17 June 10 June 16 - June 30
Tooele June 5 June 13 June 6 June 13 - June 27
Uintah Vernal June 8 June 18 June 9 June 17 - July 4
Utah American Fork June 12 June 21 June 13 June 20 - July 4
Genola June 7 June 16 June 8 June 16 - July 1
Goshen June 11 June 19 June 12 June 17 - July 1
Lincoln Point June 11 June 20 June 13 June 20 - July 4
Lindon June 7 June 15 June 8 June 14 - June 28
Payson June 10 June 18 June 11 June 18 - July 2
Santaquin-West June 10 June 19 June 11 June 19 - July 3
West Mountain June 8 June 17 June 10 June 16 - June 31
Weber Pleasant View June 9 June 18 June 11 June 17 - July 1
Wasatch Heber City June 16 June 27 June 18 June 26 - July 14
Wayne Capitol Reef June 5 June 12 June 6 June 12 - June 25


Spray Materials - Commercial Applicators

 The options provided below are not all-inclusive and are not endorsements of USU.  Please check the label before mixing.

Target Pest Host Brand Chemical Amount
per acre
REI Comments
Codling Moth apple Altacor 35WDG chlorantraniliprole 3.0-4.5 oz 4 h  
Assail acetamiprid 1.7-3.4 oz 12 h
Belt SC flubendiamide 5 oz 12 h
Delegate 25WG spinetoram 6-7 oz 4 h
Imidan 70W phosmet 3.5-5.3 lbs 3 d
Voliam Flexi thiamethoxam +chlorantraniliprole 4-7 oz 12 h
Rosy apple aphid apple Assail acetamiprid 1.7 oz 12 h apply post bloom only if scouting shows that this pest is present
Beleaf flonicamid 2-2.8 oz 12 h
Calypso thiacloprid 2-4 oz 12 h
Clutch clothianidin 2-3 oz 12 h
Provado imidacloprid 4-8 oz 12 h
Pear psylla pear Assail acetamiprid 1.7-3.4 oz 12 h oil alone is also effective, or add oil to one of these products
Centaur WDG buprofezin 34.5-45 oz 12 h
Delegate spinetoram 4-7 oz 4 h
Powdery mildew apple Flint trifloxystrobin 2-2.5 oz 12 h apply starting at open cluster stage and repeat every 7-14 days if necessary
Kaligreen potassium bicarbonate 2.5-3 lb 4 h
Pristine boscalid/ pyraclostrobin 14.5-18 oz 12 h
Procure triflumizole 8-16 oz 12 h
Rally myclobutanil 5 oz 24 h
Rubigan fenarimol 12 oz 12 h
Green peach aphid peach, nectarine Assail acetamiprid 8 oz 12 h apply to nectarines if >1 colony/tree and peaches, >2 colonies/tree
Provado imidacloprid 4-8 oz 12 h
Lygus bug peaches Aza-Direct azadirachtin 1-2 pints 4 h OMRI certified organic
Baythroid beta-cyfluthrin 2-2.4 oz 12 h restricted use product
Pyganic pyrethrin 4.5-18 4 h OMRI certified organic
Tombstone cyfluthrin 2-2.4 oz 12 h restricted use product
Coryneum blight peaches. nectarine, apricot


captan see label 24 h  
Pristine boscalid+ pyraclostrobin 10.5-14.5 oz 12 h  
Ziram/Thiram  ziram 6-8 lbs 48 h  

Spray Materials - Residential Applicators

Note that these treatments are only recommended if you know you have the particular pest in your trees.


Target Pest Host Chemical Example Brands
Codling moth apple, pear Conventional  

acetamiprid:  every 14 days
carbaryl:  every 14 - 21 days
malathion:  every 7 days
gamma-cyhalothrin:  every 14 days

bifenthrin:  every 14 days; pears only

hort. oil:  lasts 5-7 days for killing eggs; use at beginning of each generation; apply at 1% rate only when temperatures are below 80; follow up with a different product

spinosad:  every 7 days

codling moth virus can only be purchased online

acetamiprid Ortho Max Flower, Fruit, and Veg.
carbaryl Sevin, Bonide Fruit Tree Spray, etc.
malathion Malathion
gamma-cyhalothrin Spectracide Triazicide
bifenthrin Ortho Max Lawn and Garden Insect Killer
hort. oil (1%) Many products
spinosad Green Light Lawn and Garden Spinosad; Gardens Alive Bull’s Eye; Ferti-Lome Borer, Bagworm, Leafminer & Tent Caterpillar; Monterey Garden Insect Spray; Natural Guard
codling moth virus Virosoft, Cyd-X
Aphids all fruit trees carbaryl Bayer Advanced

start with a single application


bifenthrin Ortho Bug-B-Gone
malathion Bonide, Malathion
neem oil Green Light
permethrin Lilly Miller
Powdery mildew apple, cherry bayleton Bonide

do not apply lime sulfur when temperature is over 75 degrees F

Neem oil and Kaligreen are organic options

lime sulfur Lilly Miller
propiconazole Ferti-Lome
neem oil Garden Safe
potassium bicarbonate Kaligreen
Coryneum blight peach, nectarine captan Captan

If your fruit has not passed shuck split stage, use chlorothalonil, otherwise, use captan if necessary;
Neem oil is organic, but provides only poor-fair control

neem oil Various brands

Precautionary Statement:
  Utah State University Extension and its employees are not responsible for the use, misuse, or damage caused by application or misapplication of products or information mentioned in this document.  All pesticides are labeled with ingredients, instructions, and risks.  The pesticide applicator is legally responsible for proper use.  USU makes no endorsement of the products listed herein.