Tree Fruit IPM Advisory

June 22, 2012

In this Issue:

• Insect/Disease Activity
  
  • Codling Moth
  • Spider Mites
  • Peach Twig Borer
  • Western Cherry Fruit Fly
  • Greater Peachtree Borer
  • Cherry Powdery Mildew
• Upcoming Monitoring/Insect Activity
• When Do I Spray?
  • Codling Moth
  • Peach Twig Borer
• Sprays-Commercial
• Sprays-Residential

What to Look for/Do Now:

• Powdery mildew continues to develop in cherries
• San Jose scale crawlers: Cache, Carbon, Uintah counties should treat June 26; make second application 2 weeks later in heavy infestations
• Iron chlorosis is evident on new foliage of peach, plum; consider getting leaf nutrition analysis in early August

Current Insect and Disease Activity

APPLES/PEARS

Codling Moth

Towards the end of June/early July, egg hatch for the first generation will be over in all areas of the Wasatch Front. Plan your last treatment accordingly. The start of second generation egg hatch will be about 7 or more days later, during which time the fruit does not need to be protected. The table on page 3 shows the dates for your area.

For those who have monitoring traps, you’ll notice that your weekly trap catch will do down dramatically this week in areas along the Wasatch Front, as all moths in the first generation have emerged. Second generation moth flight picks up speed around July 4.

Spider Mites

Spider mites on pear cause different symptoms than the typical stippling pattern on most fruit trees.

Spider mites were seen in some locations in Utah and Box Elder counties, primarily on the lowest leaves of the inner canopy.

Keep a close watch on your own fruit trees for build-up of spider mite colonies. Trees can tolerate a low to moderate population (7-10 mites/leaf). But hot temperatures and dust will increase mite development and reproductive rates. In addition, some insecticides like carbaryl (Sevin) and imidacloprid (Provado and generics) can actually promote spider mite reproduction.

Light infestations cause what is called stippling on the foliage. The spider mites feed with piercing mouthparts, and suck out plant cell contents, leaving behind tiny chlorotic (yellow) spots. Heavier feeding can cause the tissue to actually scorch, known as “mite burn.” On pears, mite feeding does not cause stippling, and sometimes it may not be obvious that spider mites are present without looking at the undersides of the leaves. Pear leaves may show slight scorching or blackening of leaf edges and petioles. Also, heavy feeding on older leaves can cause newly emerging foliage to be deformed or scorched.

Before making a decision on whether to treat for mites, look for predatory mites within the pest mite population. These are fast moving mites, about the same size, that can prevent spider mite densities from exceeding economic thresholds. If predators are present, then a treatment may not be necessary. When treating, good coverage is essential.

STONE FRUITS

Peach Twig Borer

    Look for peach twig borer damage on shoot tips now. Just the top inch or so
       will be affected, and the foliage will be wilted, underdeveloped, or crispy.

Larvae of the first summer generation are actively feeding within succulent shoots of apricot, peach, and nectarine. They bore into the tips of the shoots and feed just on the upper inch or so of growth, causing the leaves to wilt over. Feeding is almost always associated with some oozing at the shoot tip. Egg hatch of this first generation will be ending soon (late June to mid July, depending on your location). As with codling moth, time your last spray for 1-3 weeks before that “ending spray date” (depending on your product). The start of the second generation will be about 2 weeks later. See the table on page 4 for the dates for your area.

Peach twig borer larvae prefer feeding in shoots over fruit, but once the shoots harden off, adult moths instead lay eggs on the ripening fruit, which is why the second generation can be more damaging.

Western Cherry Fruit Fly

Many locations have harvested or will begin harvesting sweet cherries, with tart cherries not far off. If a spray is needed close to harvest, choose one with a short pre-harvest interval, like GF-120 (4 hours), Sevin (3 days), or Malathion (1-3 days). Note that the straight spinosad products (Success, Entrust) have a 7-day pre-harvest interval.

Greater Peachtree Borer

                     Ooze mixed with frass near the base of a peach tree.

A single peachtree borer was captured in a trap in Cache County, so bark treatments should start in all cooler areas of northern Utah (Cache, Carbon, Uintah, Wasatch counties). All other locations should have already started.

Again, sprays only need to be applied to the lower 12-18” of the trunk and any exposed roots. The residual material of the insecticide on the bark will kill the eggs and newly hatching larvae. Weeds should be cleared from around the base of the trunk so that the material can thoroughly cover the bark.

Cherry Powdery Mildew

Multiple  years of heavy cropping and powdery mildew can lead to decline in tart cherries.

Continue to keep an eye on powdery mildew on cherries. Many orchards have tart cherry trees loaded with fruit, and after several years of heavy crops, the added stress of powdery mildew preventing photosynthesis can result in a loss of vigor that could be severe. Powdery mildew does not need free water to spread, just humidity (which is raised just enough by microsprinkler irrigation), so don’t think that this dry weather means no disease.

Upcoming Monitoring/Insect Activity

Codling Moth - When to Spray

Codling Moth, First and Second Generations

First generation egg hatch is still underway; continue protecting fruit until the end of egg hatch. Then, start again for the second generation.
  

Peach Twig Borer - When to Spray

Peach Twig Borer, First and Second Generations

End of first generation egg hatch, where you should “keep fruit protected up to” is at 800 degree days. Second generation egg hatch, which will be occurring mostly on fruit, begins a few weeks after the first generation ends. Like the first generation, 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 1200 and 1300 degree days after biofix, or 5% and 16% egg hatch.
  

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 marion.murray@usu.edu. You may also access spray options at the guide’s companion website at intermountainfruit.org.

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.