June 30, AppleTalk Conference Call

June 30, AppleTalk Call Summary
AppleTalk Conference Call Summary
Tuesday, June 30, 2015, 8:00 – 9:00 AM
Presenter: John Aue, Threshold IPM
Moderator: Peter Werts, IPM Institute of North America; questions or comments, pwerts@ipminstitute.org

June 30th Call download: Click Here

Procedure following severe hail
Several locations in the Upper Mississippi River Valley and near Chippewa Falls received severe hail on the evening of June 29.  Fire blight concerns increase following damaging hail and high winds since wounded trees are highly susceptible to infection.  Blossom or shoot blight symptoms do not need to be visible for the inoculum to be present and more bacteria is in the orchards now, then during bloom.  The best technique to combat infection is to apply streptomycin within 24 hours of a hail event.  Streptomycin can be effective in eliminating the initial infections.  It is recommended to apply at least 80-100 gallons of water per acre; thorough coverage of the scaffolds limbs and trunk is required for optimum performance.  If Streptomycin is applied with Regulaid (1 pint/ acre) the streptomycin rate can be reduced to 1 lb. per acre.  Important: Read product label. 

Fruit that is cut open at this time in the season will likely form callused scab.  Fire blight bacteria that enter damaged fruit will not likely result in systemic infections, rather infections will stay localized.  Infected fruit will appear grey, green or water soaked and later become shriveled, dark brown and mummified.  Bacterial ooze may become present in the next six weeks and this can spread innoculumn.

Black and white rot spores can easily infect damaged fruit and tissue.  It is recommended to apply a full rate of captan (4 lb. /acre) after damaging winds or hail.

Characteristic symptoms of fire blight and black rot may not develop on foliage following a mid to late season infection; symptoms may be expressed as the slow development of cankerous tissue.

Hail implications for apple maggot and codling moth management
It is recommended to increase apple maggot monitoring if hail damages fruit.  Unbaited traps can be used at this time and if there is a significant increase in trap captures, add baited traps to ensure trap efficacy.  During late-season hail, damaged fruit will release volatiles that become a significant attractant to apple maggot and other fruit flies in the genus Rhagoletis.  When this happens, unbaited spheres will become ineffective in catching apple maggot, due to the overwhelming volatiles produced by the injured fruit.  Use baited traps if hail occurs late in the season, e.g., late July or August.  We are not expecting a lot of volatiles to be released from the fruit damaged by this hail event.

Injury from codling moth may increase following hail due to the reduced ability of pesticide to adhere to damaged tissue.  Larvae are often seen entering into fruit on injured areas, e.g., hail, scab lesion, tarnished plant bug scar.  Scout for injury around these areas to determine performance of insecticides.  Initial entry wound is very small, e.g., pen-prick size, and may be surrounded by red tissue.  If CM has been a problem in the past look for CM damage near hail injury.

First generation codling moth wrap up
Base the decision to reapply codling moth (CM) insecticides using degree day accumulations from biofix and trap captures following the date of the first insecticide application.  Continue to closely monitor degree days and trap captures until 650-700 DD from biofix to determine the flight timing of a large cohort of moths.  Most flights should occur by 700 DD.

Look at the trap captures since you applied the first application and disregard counts from the first seven days after the application.  Eggs laid in first seven days will hatch in the second seven days after application.  Then count 250 DD after treatment to determine if another application is required at 14-17 days.  Checking traps more than once per week will allow more accuracy when determining to treat a cohort.  Note how many CM are alive when you check traps.

A high rate of Altacor (chlorantraniliprole) has been found to be effectiveness for up to three weeks with no rain.  A high rate of Delegate (spinetoram) will not provide protection past 14 days.  Lower rates will be effective, but for a shorter period of time.  Rate is also a function of CM pressure.  If you are treating eight moths per trap, could get good control with a middle rate, on the other hand if the cohort is 30-40 in a trap, then the high rate is required.

Consider setting a new biofix for each cohort that flies.  For example, if seven to 10-days from an insecticide, look at trap counts.  If there is a treatable population, i.e., more than five moth, set a second biofix and treat after 250 DD.  This cohort flew between day seven and ten of the application.  Moths will live 24-48 hours.  If moths are dead, they may be from a cohort from the last flight.

To assess efficacy of first generation codling moth control, check hot spots relative to trap captures.  Variable trap captures suggest CM are flying in from outside the orchard.  Uniform captures suggest an in-house population with minimal external pressure.  Dedicate time to scout fruit clusters or areas that may have received poor insecticide coverage.

Apple maggot
It is advised to hang yellow boards or red spheres by July 1.  Yellow boards can provide an early warning system by attracting apple maggot during their feeding period.  If bait is used in addition to visual traps replace volatile lures according to the manufacturer’s directions, e.g., seven to ten days.  A minimum of three traps per ten acres should be deployed at the beginning of July; trap density should gradually increase to one trap every 200-300 feet along the orchard perimeter, as the season progresses.  Locate traps along perimeter where wild hosts are present and near early ripening cultivars.  Hang traps at eye level, and make sure they are visible.  Traps can be placed in early season varieties that exist on the interior of block, since the trees can harbor resident populations that may not affect neighboring varieties.  Always apply more Tangle-Trap then you think is necessary, insect should be easily caught in the adhesive film.  If a spray-on formulation is used, it should begin to drip.  If you do not apply enough Tangle-Trap it can lose its tackiness and wear off in the rain.

Thresholds vary from one fly on unbaited traps to five flies with apple-volatile bait.  Treatment practices for apple maggot can include spot spraying perimeters and early-ripening varieties, and alternate-row-middle applications.  Consider applying traps to differentiate pressure between spray tanks: 20 (total acres) / 5 (acres per spray tank) = 4 monitoring blocks.  A block of attractive varieties, e.g., Redfree or Yellow Transparent, in the middle of a large block may require every row to be sprayed.  In majority of situations a full cover application is not necessary for effective control.

If apple maggot management overlaps with first generation codling moth, a neonicotinoid may be tank mixed with a codling moth material to target hotspots or perimeters.  An orchard-wide application of a neonicotinoid targeting AM is usually not necessary unless woolly apple aphid or San Jose scale are a concern.

Apple rust mites (ARM) are a common secondary pest that require high populations to cause damage; current threshold is 200 mites per leaf.  Damage can be observed as an olive drab color on the underside of leaves.  Populations will continue to grow once the terminals have set.  Not much of a concern on large established trees, yet can be harmful on young trees.  While scouting, turn over growing shoots and look for discoloration and scan leaf surface with hand lens to see if mites are present (requires 10x or greater magnification).  ARM damage may be more prevalent where nutrients are applied.  These mites are an important food source for numerous predatory arthropods

Two-spotted spider mites (TSSM) have a wide range of native host plants which includes broadleaves and red clover.  In dry years, TSSM may feed on tree foliage and can be as destructive as European red mites (ERM).  Damaging levels will be observed first near the trunk; where they travel into the tree. Damage can be observed as light green or whitish areas along the midrib.  Must use 10x magnification to see the two spots; are more difficult to identify then ERM.

European red mite thresholds are based on population densities and increase through the season, i.e., June, 2.5 mites/leaf; July, 5 mites/ leaf; August, 7.5 mites/leaf.  Although sampling can provide an accurate read on a population it does not always reflect actual pressure.  Visible damage can be present even if populations are under threshold.  If physical damage is observed, economic injury is occurring.  After significant bronzing develops it is too late to apply a material as mite populations will decrease naturally from starvation.

Dogwood borer
Use pheromone traps to sample presence/absence of dogwood borer (DWB).  If DWB are caught scout at least ten trees scattered throughout the block for infestation.  Focus on trees that are three to five years old grown on rootstocks susceptible to formation of burr knots, i.e., M.9, M.26 and Mark series.  Examine the trunk from the soil line to the first scaffold branch for frass protruding from borer holes, burr knots or damaged bark.  Fully remove trees guards while scouting.

Treatment options include a trunk application of Lorsban (chlorpyrifos).  Note: chlorpyrifos may not come in contact with bearing fruit and can be applied post-harvest.  Organic growers may choose to apply pure neem oil and paint, to the trunk.

Mating disruption is a viable option, but will not help manage existing larval infestations in the trees.  DWB are primarily attracted to root stocks which produce bur knots and may be a concern in many of the high-density orchards which are being planted.

Alternative insecticide options have been researched by Art Agnello, Cornell University, but do not offer an equal level of management that can be achieved by a single trunk application of chlorpyrifos.  Art’s research indicates that Avaunt (indoxacarb), Danitol (fenpropathrin) and Assail (acetamiprid) could provide suppression of DWB larva.  However none of these insecticides are labeled for DWB.

Cultural practices that reduce damage need to be implemented before infestations occur and include:

  1. Monitor adult population with pheromone traps.
  2. Identify and select rootstocks that have a lower tendency to producing burr knots. Rootstocks particularly susceptible to burr knot formation and attack by borers are M.9, M.26 and Mark.
  3. Trunk mounding around the exposed portion of the rootstock can reduce the initiation of burr knots. Where it is not possible to bury exposed rootstocks, the area around the trunk should be kept weed free to avoid shade and high humidity.
  4. Use wire mesh tree guards instead of solid guards.

Additional resource

April 20, 2015 Scaffold Fruit Journal