Tree Fruit IPM Advisory

In this Issue:

• Pesticide Updates (Commercial growers)

• Dormant and Delayed-Dormant Treatments

• Other News
  

What to Look for/Do Now:

• Look for pear psylla eggs near the base of buds (the size and color of a grain of rice).
• Look for aphid eggs (creamy green to black) near buds and in cracks and crevices.
• Look for old fire blight infections (leaves are usually retained) and prune out.
• Watch bud development for swelling, indicating approach of delayed dormant treatment timing.
• Make sure all fruit trees are pruned properly.

Pesticide Updates (Commercial growers)

Movento/Ultor (spirotetramat, Bayer CropScience) lost its registration briefly in 2010, but is now available again.  In Utah, this product is most effective for woolly apple aphid applied at petal-fall stage.  It is also effective for San Jose scale and aphids on all fruit trees, and pear psylla on pear.

Isomate PTB-TT (Pacific Biocontrol) is a new twist-tie type mating disruption product for peach twig borer that lasts all season.  It should used only on orchards greater than 10 acres.

Thionex (endosulfan) is being phased out, with uses on cherry, peach, and plum ending July 31, 2012, uses on pear ending July 31, 2013, and uses on apple ending July 31, 2015. 

Guthion:  As you know, phase-out is in effect, and Guthion is not to be used after Sept. 30, 2012.  For 2011 through Sept. 30, 2012, the maximum pounds of product acre is:

• 3.0 on apple (1 spray at high rate)
• 2.0 on pear (1 spray at high rate)
• 1.5 on cherry (1 spray at high rate)
 

 Insect and Disease Activity/Info

DORMANT AND DELAYED-DORMANT TREATMENTS

Dormant sprays are targeted to insects that overwinter as eggs (mostly aphids), or as nymphs/adults withing trees (mostly scale).  Keep in mind that dormant sprays are not required every year.  You should keep track of your aphid and scale populations from year to year (by examining leaves and twigs for insects).  When damage is slight to non-existent, you can skip the dormant sprays.  The "aphid swarms" of fall 2010, however, may have led to a larger than normal population of eggs laid, and may require a dormant spray this year.

The ideal time to apply a dormant spray is after the buds of fruit trees have started to swell, and up to the point where leaves have begun to emerge. 

This is called the delayed-dormant timing.  Waiting for this timing rather than when buds are completey dormant is beneficial because eggs and overwintering adults become more "active" and susceptible to treatment.  Also, beneficial insects and pollinators are not affected, oils and other materials for this purpose are relatively inexpensive, and the developing ground vegetation will help to prevent runoff.  The exception to spraying only at delayed dormant is pear psylla, which would require one spray during dormancy (just before buds swell) and a second spray 2 weeks later.

Usually horticultural oil alone is sufficient for dormant or delayed dormant sprays, particularly for backyard growers.  Most oils are simply sold as "dormant oil" and the ingredients will be "98% (or higher) petroleum oil".  This type of oil is suitable for sprays in the dormant season (2% rate) as well as sprays during the growing season (1% rate). 

Commercial growers may consider mixing oil with an insecticide such as Lorsban.  When applying dormant or delayed dormant sprays, make sure you thoroughly cover all bark cracks and crevices.  Also, oils should be used when the air temperature is above 40 F and when there is no threat of freezing temperature for the following 36 hours.  Applying between 50 and 70 F on clear days is ideal.

The dormant and delayed dormant sprays can be effective against the following insects.

aphids: horticultural oil alone or with Lorsban (restricted use) at delayed-dormant timing; repeat if infestations were high last year	blister mites: these mites cause tiny galls on the leaves of apple or pear. Apply oil, or oil with Sevin at dormant or delayed dormant timing.
brown mites:  brown mites are related to European red mites, and overwinter as eggs in protected sites on trees.  Because of the past three cool springs, we are starting to see these mites more often in commercial orchards and more rarely, in backyard trees.  If this pest was a problem for you, oil alone at delayed-dormant timing should be sufficient.	peach twig borer: delayed dormant spray of horticultural oil plus spinosad targets overwintering larvae as they emerge to find food; this is a very important spray for managing peach twig borer
pear psylla: use horticultural oil alone; apply two applications starting at dormant timing	San Jose scale: horticulture oil alone or with pyriproxyfen (Esteem).  Apply at dormant or delayed-dormant timing.
soft scales:  horticultural oil is very effective on soft scales, particularly at delayed-dormant timing when temperatures have started to increase	shothole (coryneum blight of peaches, cherries): chlorothalonil (Bravo) at delayed-dormancy
fire blight:  copper spray at silver tip stage (late dormant timing) and when temperatures are above 45° (Bordeaux mixture, copper hydroxide, copper oxychloride, copper sulfate).  Do not apply copper after ¼-inch green leaf stage or when drying conditions are slow, as severe injury can occur.  Fixed coppers such as Kocide and C-O-C-S can be tank mixed with early season oil sprays, but do not combine copper sulfate alone with dormant oil.

In the next issue, we will start including bud stages and more information on dormant sprays.

Other News