Tree Fruit IPM Advisory

June 24, 2009 

In this Issue:

• Codling Moth 
• San Jose Scale
• Hail Damage
• Coryneum Blight
• Plant Bugs
• Degree Days and Insect Monitoring
• Spray Timing- Codling Moth
• Spray Timing- Peach Twig Borer
• Sprays-Commercial
• Sprays-Residential

What to Look for/Do Now:

• Watch crown area of peach, nectarine, and apricots for gummosis and frass, which is a sign of peachtree borer
• Watch peach, nectarine, and apricot fruit for purple coryneum blight lesions
• Continue to prune out fire blight strikes to reduce inoculum in the orchard

Insect and Disease Activity

APPLE/PEAR

Codling Moth

In conventional orchards, we have been seeing low moth trap catch in the last several weeks, and expected to see low numbers again this week because moth flight is almost at 100% in most areas.  But trap catch actually lurched up to the double digits.  My guess is that these are moths that have not been flying for the last several nights, and the remaining 5-15% are now all flying at once, desperately seeking a mate.

In Diane Alston’s (Extension Entomologist) research plots, she reports the good news that trap catch has been quite low for most of the first generation in mating disruption blocks.

To “wrap” up the first generation, go out and take a look at the fruit on your trees to determine the success of your program so far.  Do you have any stings or entries?  Look at the calyx end, where they will often enter when fruit is small, or look at areas where two fruits are touching, or where leaves are touching fruits.  Remove and destroy the damaged fruit as you see it. For homeowners, up to 10% damage is pretty good, and for commercial growers, up to 3% damage is good (0% of course, is best).

Second generation moth flight will begin soon, followed by another round of egg hatch.  The good news is that everyone gets a little break in spraying between the end of the first generation and the start of the second generation egg hatch.  So sprays are not necessary during this interval. (See spray table for dates in your area.)

Codling moth frass showing an entry on apple at the calyx end

Codling moth “stings” occur when larvae feed on the surface of the fruit and then stop, either from being killed or moving to a different location

San Jose Scale

San Jose scale (SJS) crawlers have been active for the last week or two, and now is the optimal time for all growers in northern Utah to treat (except Cache and Carbon counties and Tremonton, which will be one week from now).

SJS attacks most fruit trees, and apple is the most common host in Utah.  The crawlers are the mobile stage of this insect.  The adult female lays approximately 200 live crawlers 4-6 weeks after mating.  They are bright yellow, and slow moving.  They 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 allowed to build on a tree, effects include reduced tree vigor and a decline in yield.  It is primarily a problem in standard-sized, poorly pruned trees.  For cases like these, conduct dormant pruning to remove infested limbs, and apply a spray of oil plus Esteem at half-inch green.


Hail Damage

This has been an interesting spring with cool days and nights, above average rains, and severe storms.  Hail storms have occurred sporadically throughout northern Utah in the last month, causing quite a bit of damage--not only physical damage to fruit, but in spreading fire blight bacteria to succulent shoots.  Growers in Cache, Box Elder, Davis, and Utah counties are reporting damage.  Sadly, a few commercial growers are possibly facing a total loss of their apple and sweet cherry crops due to storm-damaged fruit.

Because of the repeated wind, hail, and rain, many growers are seeing lots of “shoot strikes” of fire blight

PEACH/NECTARINE/APRICOT

Coryneum Blight

Severe shot hole on foliage results in brown spots, holes, and yellowed leaves that drop prematurely

Cherry harvest is about upon us, and you may see some shot hole infections that look like this

Plant Bugs

For commercial growers: Stink bugs and lygus (tarnished plant bug) may soon start feeding on developing peach fruit.  Orchards that border open hillsides and alfalfa fields should be watched closely in the next few weeks as the vegetation dries or the fields get cut.  You can also use a sweep net to monitor for lygus bugs in orchard groundcover or roadside vegetation to get a feel for population density. 

If you have problems every year, or are seeing problems now, consider a border spray of a pyrethroid, spinetoram (Delegate), or flonicamid (Beleaf).

 

Degree Days and Insect Monitoring

Monitoring/Insect Activity

Degree Day Accumulations (March 1 - June 24)

 Spray Timing - Codling Moth

Codling Moth, First Generation

“Start sprays” occurs at 220 DD.  The period of greatest egg hatch occurs from 340 DD - 640 DD.  “Last spray” occurs two weeks prior to the end of egg hatch.  If you are using a material that lasts 2 weeks, it should be applied on this date.
 

 Spray Timing - Peach Twig Borer

  

Peach Twig Borer, First Generation

(If you had moderate to severe PTB damage last year, use the earlier spray date; if you had very little PTB damage last year, use the later date to start sprays.  These two dates correspond to 300 and 360 degree days after biofix, or 5% and 16% egg hatch.  The “last spray date” is the date 2 weeks prior to end of egg hatch, when the last spray (if your material lasts 2 weeks) should be applied.

Spray Materials - Commercial Applicators

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

 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.