Tree Fruit IPM Advisory

April 26, 2012

In this Issue:

• Insect/Disease Activity
  • Codling Moth
  • Fire Blight
  • Green Peach Aphid
  • Coryneum Blight
    
• Upcoming Monitoring/Insect Activity
• Codling Moth-When to Spray
• Sprays-Commercial
• Sprays-Residential

What to Look for/Do Now:

• Codling moths were caught in many locations along the Wasatch Front, and we can now provide spray dates in the table below.  We expect to know more details of remaining locations by next week.
• Fire blight risk is EXTREME today, and with threat of rain, an antibiotic is recommended.
• Continue to examine apple, peach, and cherry leaves for new colonies of aphids forming; oil can be used on aphids at 1% rate anytime during the growing season

Current Insect and Disease Activity

APPLES/PEARS

Codling Moth

With the hot weather we had over the past weekend, most areas along the Wasatch Front reported biofix (first moth trap captures).  With the knowledge of first trap catch, we can now start to use the codling moth model to determine the date at which egg hatch begins, which corresponds to when to start sprays.

Most other areas of northern Utah may see first moth flight within the week, but the cooler weather and rain coming may prevent flight.

When codling moth adults emerge in the spring, they mate, and females lay up to 70 eggs on fruit or on foliage near fruit. Depending on temperature, eggs hatch in approximately in 6-20 days, and larvae bore into the fruit, feeding mainly on the seeds. One to two more generations follow in northern Utah, and two-three in southern Utah.

The table below provides dates to start sprays.  There are two management strategies included: 

• Option A is a recommendation out of Washington State University.  It is a little more complicated, but may result in a slight cost savings and possibly improved control.  With Option A, you use horticultural oil (1%) to kill eggs at the date corresponding to the timing just before they start to hatch.  Good coverage of the oil (to dripping) is very important.

Assuming the oil kills all the eggs, any new eggs that get laid will not start hatching for 6-20 days, so the actual first cover spray is then delayed to the date corresponding to when that egg hatch would begin (which will be provided in the next advisory).  The later application of the traditional insecticide is close to the timing of “peak egg hatch”, when about 50-75% of eggs hatch in a 1-2 week window of time.

• Option B is the traditional date to start your codling moth sprays--when eggs start hatching in the spring.  

After the first insecticide spray has been applied, continue to apply your chosen material(s) at the interval provided on the label (usually every 7-14 days), until the end of the first generation.  Then, you will start back up for second generation egg hatch.

Fire Blight

Apples are still in bloom, and fire blight should be on everyone's mind.  Fire blight can be prevented by using antibiotics only during bloom.

Due to the hot weather of the last several days, all locations in Utah are at EXTREME risk for fire blight infection.  With rain coming today and tomorrow, an antibiotic should be applied asap where you have had fire blight problems in the past. 

New infections, if they have happened, will show up within about 1-2 weeks.  If you have the time and resources, one of your best defenses against fire blight is to prune out new infections in the very early stages.

new fire blight infections can be seen on the fruit stems; look for browning of the stem and oozing bacteria	if you find new infections early (before it has moved into the wood), you can prune off the fruit cluster; remove at least twice the length of the visible infection

PEACHES/NECTARINES

Green Peach Aphid

A few peach growers have found that green peach aphids have really become a problem, and we have seen that they are already starting to curl the leaves.  The weather conditions of the last two years have favored aphids, so it is not surprising that they might have built in numbers.

When the leaves start to curl, treatment with contact sprays (horticultural oil, insecticidal soap) is not as effective, unless you can get good coverage of all the upper and undersides of the leaves.  The other option is to use as systemic (imidacloprid) where direct contact of the aphids is not as important. NOTE:  do not use during bloom.

For commercial growers, that would be Admire Pro or any of the (many) generic options labeled for peach. 

For residential growers, that would be Bayer Advanced Fruit, Citrus & Vegetable Insect Control.  Note:  The label states to stop use within 21 days of harvest, but because this product is a systemic, we recommend limiting its use to this time of year.

Coryneum Blight (Shot hole)

Shot hole lesions are starting to appear on leaves at this time. Shot hole (or coryneum blight) overwinters in buds and spreads from there to leaves and later in the season, to developing fruit. On the leaves, you will see small round holes that may be purplish or tan in color. The center of the lesion will sometimes still be attached. Cool, wet weather contributes to spread.

At the shuck-split stage, you can use Bravo (chlorothalonil, Daconil for residential use), Abound, Captan, Ziram, or Pristine.  Chlorothalonil should not be used after the shuck split stage.  For residential growers, the only option during the growing season is Captan (it would be used if you continue to have infections at times when 4-6 hours of moisture occur).

And keep in mind that the most important treatment is an application of copper at 50% leaf drop in the fall.

Upcoming Monitoring/Insect Activity

Codling Moth - When to Spray

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 kill 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.

Spray Materials - Commercial Applicators

Spray materials for commercial applicators may be accessed from the Utah-Colorado Commercial Tree Fruit Production Guide companion website at the following links:

Apple, petal fall (aphids, powdery mildew)

Apple, fruit present (codling moth)

Peach, shuck split (aphids, peach twig borer mating disruption, coryneum blight, powdery mildew)

Spray Materials - Residential Applicators

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

If your trees are in bloom, we do not recommend applying any pesticides unless you are controlling fire blight with antibiotics.  Although it is accepted to use “softer” materials such as Bt or spinosad during bloom, we still recommend either:  waiting until the petal fall stage or apply at dawn or dusk when pollinators are not active.