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.

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San Jose Scale, Pear Psylla, Cat-facing Injury

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July 20, 2012

In this Issue:

What to Look for/Do Now:

  • Spider mite populations are starting to build
  • Second generation San Jose scale crawlers emerging soon
  • Iron chlorosis is evident on new foliage of peach, plum; consider getting leaf nutrition analysis in early August
  • If 4-6 hr rains occur during peach ripening stage, may need to apply fungicide to prevent coryneum infection

Current Insect and Disease Activity


Codling Moth

Except for the coldest areas (Cache, Wasatch counties) all other areas are in the middle of second generation egg hatch, so maintain protection of fruit. The end of egg hatch for this generation will occur August 11 - 20. There will be a full third generation this year, with no real “down time” between the second and third. So basically, in those areas that have high pest pressure, keep fruit protected from now through the middle of September (when you can stop, even if harvest has not begun yet).

San Jose Scale

San Jose scale will have a second emergence of crawlers, coming up soon in may areas. This pest is usually treated primarily with the dormant oil spray and with treatment of the first crawler emergence. But if you have a heavy infestation, or missed the window for the first emergence, consider a treatment for the timing below. One treatment is all that is necessary, with 1% horticultural oil (evening or early am to avoid 85+ temps) or Esteem.

Box Elder: July 22 - 25
Cache: August 6 - 10
Davis: July 24 - 28
Iron: July 30 - August 3
Salt Lake: July 22
Tooele: July 21 - 24
Utah, Uintah: July 25 - 29
Wasatch: August 17 - 21

White Apple Leafhopper

Where present, leafhopper feeding damage on leaves can now be seen. The second generation has begun, and nymphs are active on the undersides of leaves. If you saw heavy leafhopper earlier, now would be a good time to treat because the nymphs are more susceptible and easier to treat than the adults. Adult activity will become very noticeable by mid to late August.

Feeding on the foliage will not affect apple yield or tree health, but this pest can become a nuisance to pickers late in the season during apple harvest.

Pear Psylla

If you had not noticed the presence of pear psylla this spring, damage is evident now. They are active from spring to fall, and if left unchecked, can build to damaging levels. Not only do they excrete honeydew, but their feeding kills the plant tissue.

At this point in the growing season, adults, eggs, newlyhatched nymphs and older nymphs can be found. The best timing for treatment is in spring, but if necessary, horticultural oil can be applied (when temperatures are below 85-90F). Commercial growers can use Assail, Centaur, Clutch or Provado.


Peach Twig Borer

Most areas are at he beginning of or are just approaching second generation egg hatch for peach twig borer. Peach twig borer larvae prefer feeding in shoots over fruit, but once the shoots harden off, adult moths will instead lay eggs on the ripening fruit, which is why the second generation can be more damaging.

Most growers can get away with one spray (on the appropriate date) per generation. But keep in mind that the warmer summer will speed up egg hatch and larval development, and if you are harvesting peaches late into August and/or early September, you may need to apply a second application to protect the ripening fruit.

Peach Silver Mite


Peach silver mite is a microscopic eriophyid mite that feeds on the bottoms of leaves. Where it occurs, it is present all season, but only becomes noticeable in mid summer when populations build to high numbers in the heat. Their feeding causes leaves to look silvery in appearance.

Trees can tolerate high populations, but when leaves start to droop and fall, a miticide or 0.5 - 1% horticultural oil application should take care of the problem. Alternatively, they can be treated in early spring (at budbreak) with oil.

Spotted Wing Drosophila Update

Spotted wing drosophila (SWD), an invasive vinegar fly that was introduced into the U.S. in 2009 and has since spread to almost two dozen states, was detected in Kaysville in August 2010. There were a few detections in 2011, in three sites in Davis County.

This season, Cory Stanley, USU Coordinator for the Cooperative Agricultural Pest Survey (CAPS) program has set up traps throughout Davis County and southern Weber County. Trapping sites include areas where raspberries, sweet cherries, tart cherries, and peaches are grown, as well as fruit stands. Traps are baited with yeast and sugar solution, which is replaced weekly when trap contents are removed and examined for SWD presence.

To date, no SWD have been confirmed yet this year

Spider Mites

The spider mite species that cause damage to fruit trees in Utah are two-spotted and McDaniel, with two-spotted being the most common. They share the same life cycle and appear similar.

Spider mites can be found in large numbers by this time of year, as they thrive in hot, dusty conditions. Their feeding causes leaves to look stippled with tiny white spots. In heavier feeding, leaves will start to bronze. Monitor for spider mite damage on all fruit crops by looking at the undersides of the leaves for a dirty appearance, and use a hand lens to get an estimate of the number of mites per leaf. If you see approximately 1 predatory mite per leaf and/or fewer than 5-10 damaging mites per leaf, then there is no need to spray. But by the time damage is obvious, the population is much greater than this.

Ideally, spider mite populations are held in check by the presence of the western predatory mite (Galendromous occidentalis). Predatory mites are very sensitive to certain insecticides, especially pyrethroids (any ingredient ending in “-thrin”, which is why we recommend keeping pyrethroid sprays to a minimum (especially early in the season).

Predatory mites are teardrop shaped, translucent in color, and usually have longer legs. They can be spotted easily with a hand lens because they move rapidly through the slower-moving spider mite colonies.

Cat-facing Injury

                             Stink bug nymphs can be seen in the orchard now.

Cat-facing injury is a generic term used to describe a symptom caused by feeding of true bugs (lygus and stink bugs) on young fruit. Although these insects are considered minor pests, most commercial and residential orchards will see a certain level of damage each year.

True bugs feed by inserting their proboscis into the fruit flesh. They excrete a salivary enzyme that breaks down the cells, and then suck up the dissolved food juices. The damage caused to the fruit will look different depending on when the feeding occurred. Trying to distinguish which insect may have caused the damage is almost impossible to discern because their feeding habits are so similar. Scouting for adults throughout the season will help to determine which is most common in your tree or orchard.

Both lygus bugs and adult stink bugs can feed on very young, developing fruit, but they leave the orchard for other crops (alfalfa, weeds) to breed and feed until later in the season. When alfalfa is cut or weeds die back, lygus and stink bugs will come back to the orchard as adults.

If your orchard is bordered by lots of weedy areas, watch closely for signs of feeding damage on the fruit. By late-August, stink bugs move on to overwintering sites.

Severely dimpled fruit indicates that feeding occurred earlier in the season. Early to mid-season feeding by lygus bugs will cause strings of oozing gum and sometimes, a water-soaked appearance. Feeding closer to harvest does not cause gumming, and may not be noticeable until later, when the flesh appears brown and corky or even decayed. Sometimes, injury does not show up until fruit is brought out of storage.

If possible, remove weed hosts in the orchard (mullein, ironweed, horse-weed) or keep them mown within and on orchard edges.

The most effective products on adult true bugs are the broad spectrum insecticides (carbaryl and pyrethroids). Only consider a treatment if it is worth the cost of killing beneficial insects that may be feeding on other pests.

Post-harvest Control of Western Cherry Fruit Fly

Tart cherry harvest began last week, and will continue for another few weeks. If sprays need to be applied, consider spinosad (or GF-120) or carbaryl (Sevin) where the pre-harvest interval is short (0 days or 3 days).

After harvest is finished, commercial growers that still have fruit remaining on the trees should consider a post-harvest application to clean up later emerging flies. Cherry fruit flies become more numerous later in the season, and females will continue to lay eggs in ripe/overripe fruit as long as possible. Protecting unharvested fruit is wise because you are decreasing the overwintering population in your orchard.

For commercial growers, dimethoate is the best option (costwise), as is a generic imidacloprid registered on fruits.

Homeowners should remove and destroy all fallen fruit (including sweet cherries), and if possible, pick your cherry trees clean to remove egg-laying sites for late-emerging fruit flies.


Even though this summer has been dry, European earwig populations are still high, especially due to the moist seasons of 2010-11. They do not like dry conditions, so they concentrate in areas that are irrigated and have moist, cool places to hide during the day. They feed mostly at night, leaving behind trails of black frass. Keep in mind that earwigs are omnivorous, and can be considered beneficial insects in that they feed on insects such as aphids and insect eggs.

We mostly see earwigs on peaches. They will usually not start feeding on fruit until it softens. Often they enter fruit through the stem end, and feed around the pit. They may exit through the stem end or through a new exit hole. You may also see shallow gouges on the fruit surface or a single deep hole. The riper the fruit, the more appealing it is to feeding.

To manage earwigs, use a variety of options:

1.  Trap regularly. Options are: cat food or tuna cans, with 1/2-inch of fish or bacon oil in the bottom;rolled-up newspaper; rolled up corrugated cardboard; bamboo sticks; or short pieces of hose. Place traps on the soil or wrapped around the tree trunk and empty traps into soapy water, or change them out, daily. Continue until you are no longer catching earwigs.

2.  Remove refuge sites. Keep mulch away from trees, remove weedy growth or groundcovers from the base of trees.
Remove tree suckers or any limbs touching the ground.
Remove loose bark on fruit trees where earwigs can hide.

3. Pick fruit as soon as they start to ripen.

4. Insecticides. Spinosad kills earwigs when they feed on the residual material. It can be used either as a spray or bait sprinkled at the base of trees (Sluggo Plus). (In this method, the bait must be used before the earwigs enter the tree. Otherwise, sprinkle bait in tree crotches.) Carbaryl (Sevin) can also be used, applied to the tree trunk and scaffold limbs, but again, it must be applied as soon as earwigs are starting to enter the tree.

Iron Deficiency

Iron chlorosis is common this season, as it is almost every year. The problem is not caused by a lack of iron in the soil, but rather the soil pH (which ranges from 7.5 to 8.5). In high pH, iron is insoluble, and therefore not available for root absorption. Because irrigation water is also very alkaline, trying to manage iron deficiency by reducing soil pH is impossible.

Iron deficiency is exacerbated by frequent springtime irrigation, prolonged soil wetness, or an uneven root to shoot ratio.

Iron is a nutrient necessary for the formation of chlorophyll. Lack of chlorophyll means reduced photosynthesis, and reduced tree vigor. Iron-deficient leaves have interveinal chlorosis (yellowing between veins). In severe symptoms, leaves may show blackened scorching, curling, or premature drop. Some trees are genetically more susceptible to nutrient deficiencies than others.

To prevent or treat iron deficiency, chelated iron should be applied to the soil in spring before budbreak. Usually one application is good for the entire season, but must be repeated again the following spring. Adding iron to the soil later in the season is also an option, but takes longer to see results. Foliar sprays (0.1%) with a spreader-sticker provide quick results but must be reapplied at approximately 10- to 21-day intervals. The drawback of foliar sprays is that staining of fruit can occur.

Iron amendments for high pH soil should be chelated, meaning that it is readily available for absorption, and not affected by soil pH. The best form of chelated iron to use is EDDHA, sold as Sequestrene or Miller’s Ferriplus.

To be sure of the correct nutrient deficiency, the USU Analytical Lab (435-797-2217) can test foliar and soil samples. Iron chlorosis symptoms usually show up later in the season, but research has shown that nutrient analysis of peach flowers in spring can be used for predicting iron deficiency.

Upcoming Monitoring/Insect Activity

Pest Host(s) Monitoring Action
San Jose scale apple mostly Crawler emergence early June; treat in late June
White apple leafhopper apple Adults of first generation form in late June; nymphs of second generation start showing up in mid-July
Cat-facing insects (lygus, stink bugs) peach As peaches start to ripen, these piercing-sucking insects will become attracted to feeding on the flesh


Codling Moth - When to Spray

Codling Moth, Second and Third Generations

Second generation egg hatch is still underway; continue protecting fruit until SEPTEMBER 15. The content below is for information purposes only because there is no long “break” between second and third generations.

County Location Beginning of 2nd Generation Egg Hatch: End of 2nd Generation Egg Hatch (2100 DD): Beginning of 3rd Generation Egg Hatch (1150 DD):
Box Elder Perry passed August 12 August 14
Tremonton passed August 21 August 24
Cache River Heights July 21 after August 22 after August 22
Smithfield July 20 after August 22 after August 22
Carbon Price passed August 20 August 22
Davis Kaysville passed August 13 August 14
Iron Cedar City passed August 20 August 23
Salt Lake All Regions passed August 5 August 7
Tooele Tooele passed August 8 August 10
Uintah Vernal passed August 17 August 19
Utah Alpine passed August 22 August 25
American Fork passed August 14 August 16
Genola passed August 12 August 13
Lincoln Point passed August 12 August 14
Orem passed August 14 August 16
Payson passed August 16 August 18
Santaquin passed August 15 August 17
Weber Pleasant View passed August 11 August 12
Wasatch Heber City July 25 after August 22 after August 22


Peach Twig Borer - When to Spray

Peach Twig Borer, Second and Third Generations

End of second generation egg hatch, where you should “keep fruit protected up to” is at 1900 degree days. Third generation egg hatch, which will be occurring only on fruit, begins a few weeks after the second generation ends. Like prior generations, if you had moderate to severe PTB damage last year, use the earlier spray date to start again. If you had very little PTB damage last year, use the later date to start sprays. These two dates correspond to 2140 and 2250 degree days after biofix, or 5% and 16% egg hatch.

 County  Location Start Protecting Fruit 2nd Generation: Keep Fruit Protected Up To (2nd Generation): Start Protecting Fruit 3rd Generation:
Box Elder Perry passed August 9 August 20-24
Tremonton July 24-27 after August 22 after August 22
Cache River Heights July 27-31 after August 22 after August 22
Smithfield July 28-August 1 after August 22 after August 22
Carbon Price July 24-27 after August 22 after August 22
Davis Kaysville passed August 8 August 17-21
Iron Cedar City July 20 August 15 after August 22
Salt Lake All Regions passed August 12 August 10-14
Tooele Tooele passed August 4 August 13-17
Uintah Vernal passed August 12 after August 22
Utah Alpine July 22-23 August 22 after August 22
American Fork passed August 11 August 21-25
Genola passed August 9 August 19-22
Lincoln Point July 20 August 12 August 22-27
Orem July 20-23 August 15 after August 22
Payson passed August 11 August 23-26
Santaquin July 20 August 12 August 22-27
Weber Pleasant View June 20 August 11 August 21-26
Wasatch Heber City August 5-9 after August 22 after August 22


Spray Materials - Commercial Applicators

Please look up spray material options in the 2012 Utah-Colorado Tree Fruit Production Guide. If you do not have a copy and would like one, contact You may also access spray options at the guide’s companion website at


Spray Materials - Residential Applicators

Note that these treatments are only recommended if you know you have the particular pest in your trees. We recommend learning about specific pests, and scouting your trees at least once/week. Products are listed by Conventional (usually broad-spectrum pesticides that are effective, but harmful to beneficial insects), or Soft/Organic (not as effective, but safer for environment and humans). Products are listed in order of efficacy.

Target Pest Host Chemical Example Brands Comments

Both codling moth


Peach twig borer (except Cyd-X)

apple, pear Conventional  

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

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 (codling moth only)  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
hort. oil (1%) Many products
spinosad Green Light, Gardens Alive Bull’s Eye, Monterey
codling moth virus Cyd-X
Coryneum blight peach, apricot captan Captan use as a preventive before a rain

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.