June 27, AppleTalk Conference Call

AppleTalk Conference Call Summary
Tuesday, June 27 2017, 8:00 – 9:00 AM
Presenter: John Aue, Threshold IPM
Moderator: Peter Werts, IPM Institute of North America; questions or comments,

June 27th Call Stream: CLICK HERE

Note: There will be no AppleTalk schedule for Tuesday, July 4, 2017.  The next AppleTalk will be on Tuesday, July 11, 2017.

Dogwood borer
The last couple of weeks has been an excellent time to scout for active dogwood borer (DWB) larvae.  Overwintered larvae are currently large (~0.5”) and reddish brown, gummy and/or crumbly frass can be found where they are feeding.  This frass looks very similar to what we see from codling moth larvae.  The standard recommendation is to scout for larvae in blocks with trees on dwarfing rootstocks that are prone to producing burr knots, e.g., M.9, M.26, since DWB females find these burrknots to be an attractive medium on which to lay their eggs.  Another critical area to scout is beneath tree guards on all dwarf trees even if they don’t look in decline or have reduced vigor.  Tree guards, regardless of style, e.g., wraps, corrugated, grow tubes, can cause the “protected” bark to remain humid and damp long after the surrounding environment dries.  The dampness can be exacerbated by tall weeds or grass in the tree rows.  These conditions can cause the bark to crack or degrade, which create an area for the female moths to lay eggs and hatching larvae to burrow into the bark.  When scouting for larvae also look for empty pupae casing near to or protruding from borer holes.  Even if borers are not found other surprises may exist below the tree guards, e.g., woolly apple aphids, ants, etc.

Usually DWB injury is found right above or around the graft union.  DWB have also been observed in the scaly bark that is not covered by tree guards, e.g., winter injury or herbicide injury, or even on pruning cuts just above the tree guards.  Small diameter dwarf tree are more prone to girdling that can be caused by continuous infestation; feeding often needs to happen for several years before trees shows decline in vigor and possible death.  Even if feeding does not impact the vigor of the tree it can produce an entry point for disease, e.g., black or white rot.

The IPM Institute has been in communication with Pacific Biocontrol Corp (Pacific Bio), the manufacture of DWB mating disruption and other Isomate products.  Pacific Bio is planning to submit a registration application to Minnesota and Wisconsin for the 2018 growing season.  It is currently only approved for use in Michigan and about a dozen Mid-Atlantic and New England states.  The current recommendation is to hang 100-150 disruptors per acre at chest to shoulder height; $200 for 500 pack = $40-60.  Management in year one of mating disruption should include 150/acre and can be decreased in subsequent years.  DWB are pretty easy to disrupt, e.g., similar to OFM mating disruption and because they are pretty good fliers, they are easy to disrupt.  The recommended block size is between five and ten acres and where you are surrounded by lots of wild hosts, mating disruption is not going to prevent mated females from flying in and laying eggs.  Many growers have mixed age and rootstocks in blocks, e.g., trees ranging from three years to 20+ years.  While we may not need to spray trunks of old trees mating disruption may need to be hung on all trees in the block to reach our minimum of five acres of mating disruption.

For more information and photos visit:

 

Codling moth
We are still quite concerned about codling moth (CM), even though trap captures have dropped off over the last few weeks.  The many rain events across the region have washed off larvacides from the fruit surfaces.  When considering whether to reapply it is essential to look at your trap counts 250 – 350 DD ago, e.g., 10 – 14 days ago.  This is the flight that would be hatching right now.  If you have no protection in the orchard and had trap counts were over threshold, i.e., 5 CM/trap/week, several weeks ago, this would be a good reason to reapply a larvacide.  The larvacides need to be on during egg hatch and because of wash-off risk, as little as a 0.5” of rain within 24 hours of an application could justify the need to reapply the insecticide.  If you have been using an insect-growth regulator, e.g., Esteem (pyriproxyfen) or Rimon (novaluron), and the application made contact with the eggs, these applications should have worked, even if they get washed off at a later date.

Younger trees on trellis will be exposed to equal amounts of rain and washoff potential, comparatively, a tree with a large canopy may not experience the same level of wash off on the interior of the canopy and we know the female codling moth lay eggs on the interior of the canopy.

The recent week of cooler weather has slowed down degree day accumulations to 15 – 20 degree days per day, whereas during our heatwave at the beginning of June we were accumulating closer to 20 – 25 DD per day.  It is important to keep in mind there are around 1000 degree days between first and second generation biofix and can be used to help determine when to rotate your insecticide mode of action or set second generation biofix.

Rainfast characteristics of insecticides on fruit, May 30 2017, John Wise, Michigan State University Extension, http://msue.anr.msu.edu/news/rainfast_characteristics_of_insecticides_on_fruit

 

Station Location CM Biofix Date DD Accumulation Base 50°F
Woodstock, IL 5/24/2017

605
Verona, WI 5/19/2017

614
Gays Mills, WI 5/15/2017

654
La Crescent, MN 6/1/2017

521
Lake City, MN 6/6/2017

414

Table 1. Codling moth DD as of 6/28 based on grower reported codling moth biofix dates

Pheromone trap maintenance
The lifespan of our pheromone traps is dependent on three primary factors, the amount of pheromone load, the lure material or medium which regulates the pheromone release and the ambient temperature which can degrade pheromones during extended periods of high heat.  Several extended-life lures exist with varying life spans.  These should all be replaced at the beginning of July, and depending on their life span, they may last the rest of the season or may need to be replaced mid-August.  Any 1x lure used for codling moth, obliquebanded and redbanded leafrollers, oriental fruit moth, lesser appleworm and dogwood borer should expect a lifespan of two to three weeks during periods of extended heat in July and August.

 

Lure Type Lifespan for 1st Generation Lifespan for 2nd Generation
1x red septum1

3 weeks

2 weeks
10x red septum2

3 weeks

2 weeks
Super Lure2

6-8 weeks

6 weeks
MegaLure (Trece)1

6 – 8weeks

6 – 8 weeks
Biolure CM10x (Suterra brand)2

4 – 6 weeks

4 weeks
CMDA combo lure

8 weeks

Probably less than 8 weeks3
Biolure CM1x (Suterra brand)1

6 to 8 weeks

Probably closer to 6 weeks3
CM L21

8-12 weeks

Probably closer to 8 weeks3

Table 2. Codling moth lure lifespan for first and second generation flights.
1 http://msue.anr.msu.edu/news/using_pheromone_traps_to_monitor_moth_activity_in_orchards1
2 http://entomology.tfrec.wsu.edu/stableipm/WorkshopPDFs/cmmonitoring.pdf
3 No data was available on the lifespan during second generation, but we should presume decreased life of these pheromones based on average temperatures in July and August that have potential to decrease duration of pheromone release.

Apple maggot
If you have had issues with AM or have early ripening cultivars, e.g., Lodi, yellow boards or red spheres for AM monitoring can begin to be deployed.  Yellow boards can provide an early warning system by attracting AM during their pre-oviposition 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.  It is advised to set up a minimum of three traps per ten acres 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.

The treatment threshold is dependent upon whether or not baited or unbaited spheres are used.  The threshold established by researchers at Cornell suggest an average of one apple maggot fly per trap, across three traps per ten acres of orchards.  Where baited spheres are used, the threshold increases to an average of five apple maggots per trap, across three traps in a ten acre block.  In orchards where apple maggot is managed every year, populations do not reside within the orchard.  The unbaited sphere will only attract apple maggots within three or four feet of the fruit and better reflect the probability of apple maggots finding fruit to oviposit on.  Baited spheres can attract apple maggots from well outside the perimeter of an orchard, but can be helpful to better establish how large a population is where hail has damaged fruit.  Baited spheres can also be helpful where reproducing populations reside within the orchard or if apple maggots have been allowed to leave fruit and pupate in the soil beneath the apple trees.  If you have not had recent hail injury or do not have a population established within the orchard, unbaited spheres are recommended.

Woolly apple aphid
The insecticides Movento (spirotetramat) and/or Beleaf 50 SG (flonicamid), remain the best insecticide options to manage woolly apple aphid (WAA) and needed to be applied at petal fall or first cover to offer best performance.  If these applications were not made, assessing WAA pressure now is critical.  If areal colonies are observed and still remain small and isolated and you still have growing terminals on trees, an application of Beleaf 50 SG may offer some efficacy or slow down population growth enough to allow beneficial insects to keep populations low later in the summer.  Both Beleaf 50 SG and Movento are sequestered into the tree through young and succulent growth.  Once terminal buds are set and shoots stop growing, it is less likely for these two insecticides to offer their desired level of management.  We have some excellent biocontrol options for WAA, but the last several years these populations have emerged late, compared to emergence of WAA populations and have not always been able to keep the populations down.  These beneficial insects include syrphid fly larva and the parasitic wasp (Aphelinus mali).  Most of the traditional insecticides for WAA control are not used any more, e.g., pyrethroids and organophosphates and were not necessarily all that effective on WAA.  Azadirachtin, e.g. Neem oil are probably the best option for organic producers.