Fruit IPM Advisory • Fruit 2017

Backyard: San Jose Scale, Greater Peachtree Borer

June 13, 2017
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In this Issue

  • Codling moth: updated spray dates table
  • San Jose scale:  treatment time coming up (if present)
  • Peach twig borer: updated spray dates table
  • Greater peachtree borer:  begin protecting lower trunks soon
  • Western cherry fruit fly:  treatment starts when fruits turn salmon blush color

ALSO WATCH FOR

  • On apples and pears, prune out fire blight strikes
  • On peaches/nectarines and apricots apply Spectracide Immunox fungicide after rains for coryneum blight

APPLE, PEAR

Codling Moth

After first generation egg hatch, inspect your trees for any damaged fruit and remove them.

View a pdf of the spray timing table. Be sure to read the instructions at the top of the page, for how to read the table.

At most sites, codling moths are finishing up the “period of greatest egg hatch,” where 75% of all eggs for the first generation are hatching.  In high population areas, time your last spray of the first generation to protect fruit up to the end of egg hatch as shown on the table.

Your next application should occur at the date for the start of second generation egg hatch, or if you can tolerate higher injury or have a low population, apply your next spray at the start of “second generation peak egg hatch”.

Treatment

San Jose Scale

San Jose scale is an immobile insect that sucks sap from tissues. Fruit can often become infested.

Scales are immobile insects with a hard “shell” that feed on tree sap through a straw-like mouthpart.  They are often difficult to see with the naked eye; a 10-20x hand lens helps.

San Jose scale (SJS) primarily occurs on apple. It looks like a small pimple or large pepper flake.  It can be found on fruit, twigs, scaffold branches, and the main trunk.

If your trees have SJS and you applied a dormant oil spray, most overwintering adults will have survived that spray. Therefore, a treatment targeting newly hatched nymphs (called crawlers) will need to be applied. Each adult female lays about 200 eggs.  The crawlers walk or are windblown to new sites to settle on twigs or fruit, insert their mouthparts, and feed for the remainder of their lives. Once they form their hard outer covering, they are more resistant to pesticides.

If the scale population is left untreated, the fruit becomes small and deformed. The tree loses vigor and branches may start to die. It is primarily a problem in standard-sized, poorly pruned trees.

Treatment timing windows:
  • Cache and northern Box Elder counties, and high elevation areas: June 23 – 29
  • Warmer Wasatch Front locations:  June 15 – 20
  • Cooler Wasatch Front locations:  June 18 – 24
  • Carbon and Iron counties:  June 18 – 24
  • Washington (New Harmony; not St. George): June 14 – 18
Materials to use:
  • Organic:  insecticidal soap (apply three times 5 days apart); horticultural oil (apply 3 times 5-7 days apart)
  • Conventional:  Ortho Flower, Fruit & Vegetable (apply once); Spectracide Triazicide (apply once)

PEACH, NECTARINE, APRICOT, PLUM, CHERRY

Peach Twig Borer

Peach twig borer

View a pdf of the spray timing table.  Be sure to read the instructions at the top of the page, for how to read the table.

The first peach twig borer sprays should be on this week in the Wasatch Front area, and in later weeks in cooler areas.

If you have apples and are treating for codling moth, you can use the same material for peach twig borer.  Generally for backyard settings, one application per generation is sufficient.

Greater Peachtree Borer

Greater peachtree borers feed on wood at the crown and in the upper roots.

We have not yet detected greater peachtree borer (trunk borer, crown borer) in our monitoring traps. However, we predict that treatment should begin as shown:

  • Cache and northern Box Elder counties, and high elevation areas: July 1
  • Warmer Wasatch Front locations:  June 20
  • Cooler Wasatch Front locations:  June 24
  • Carbon and Iron counties:  June 23
  • Washington (New Harmony; not St. George): June 15

The female moth lays eggs on the lower trunk (4” high at most) or exposed roots only. The larvae that hatch immediately bore into the tree trunk and feed on the inner bark and cambium.

There they stay until the following spring. Young trees can be girdled and killed in one season, while older trees can usually withstand a few attacks.  Trees with borer may have gumming mixed with frass at the base of the trunk, or even just below the soil line. If you
see these symptoms, plan on implementing a management program.

Treatment

Spray the lower 18″ of the trunk, exposed roots, and the ground around the base of the tree.  Keep all weeds, grass, and mulch away from the trunk.  For conventional products listed below, repeat applications monthly, with the last one in late August.

  • Organic:  nematodes
  • Conventional:  Hi Yield Permethrin (a few options); Spectracide Triazicide; carbaryl

Western Cherry Fruit Fly

Western cherry fruit fly adults lay eggs inside ripening fruit.

In most areas, cherry fruit has colored up, and fruit should be protected from western cherry fruit fly.  This insect lays eggs inside fruit (that become maggots), so treatments target the adults.

Western cherry fruit fly is a serious pest of tart and sweet cherries. Although you may be able to tolerate several wormy cherries, please keep in mind that a commercial growers’ crop can be rejected by the processing plant if worms are detected. If your backyard trees are adjacent to commercial orchards, they should be treated for cherry fruit fly, or else removed.

Treatment

Protect fruit until harvest.

  • Conventional:  Ortho Max Flower, Fruit, and Veg. (apply every 14 days); carbaryl (every 10-14 days); Spectracide Triazicide (every 14 days); malathion (every 7 days)
  • Organic:  Safer Neem