May 27, AppleTalk Call Summary

AppleTalk Conference Call Summary
Tuesday, May 27th, 2014, 8:00 – 9:00 a.m.
Presenter: John Aue, Threshold IPM.
Moderator: Peter Werts, IPM Institute of North America; questions or comments, pwerts@ipminstitute.org

May 27th Call download: Click here

Tree phenology
Orchards in southern Wisconsin and northern Illinois are nearing petal fall.  In the Upper Mississippi River Valley, trees are at petal fall, while orchards near Eau Claire and the Twin Cities are in full bloom.  Warmer days and cool nights have lowered stress levels, producing healthy bloom and foliage.  The warmer weather creates favorable conditions for pollination and the immigration of beneficial insects into orchard.

Fungicide and bee toxicity
Research on fungicide toxicity suggests products containing chlorothalonil, i.e., Bravo (chlorothalonil), and pyraclostrobin, i.e., Pristine (boscalid, pyraclostrobin) and Merivon (fluxapyroxad, pyraclostrobin), have the highest toxicity to pollinators.  The QoI and SDHI/QoI class fungicides are not recognized as being toxic to pollinators.  Regardless of product toxicity, it is wise to apply fungicides during evening, night or early morning hours to reduce contact with pollinators.

Codling moth monitoring and management
Pheromone traps are the primary tool used to monitor, determine biofix and thresholds, and effectively time insecticide applications for codling moth.  The key to successful codling moth monitoring is trap density and placement.  The minimum rate is one trap per five acres (20% of acreage) and two traps per block.  Orchards under five acres should still hang two traps.  Locate traps three to four rows from the orchard or block edge and position in the top third of the tree canopy.  The traps should be free from any obstructing foliage or branches.  Trap location is crucial since the pheromone lure will only sample a one-acre radius and the majority of mating and egg lying happens higher in the canopy.  If no codling moths are caught during first generation, change the trap location for the second generation, or for the following year.  It is important to change lures at the appropriate time and to the keep adhesive card clean.  Red pheromone codling moth lures should be replaced every three to four weeks.  Growers using the grey CML2 lure may replace them every sixty days.  Note: Traps placed on edges of deciduous forest may have greater trap catches, if wild apple trees are present.

Biofix needs to be established to effectively time a pesticide application.  Biofix is the first sustained flight and can be established by catching one codling moth in a trap on successive nights.  Newer products used for codling moth target the larvae or eggs and rely on a growing degree day (GDD) model, base 50, from biofix, to time the application of an insecticide.  Most larvicides are applied beginning at 250 degree days.

Example:

Trap ID

5/23/14

5/24/14

5/25/14

5/26/14

5/27/14

5/28/14

5/29/14

A

1

1

1

2

1

3

4

Biofix
Trap ID

5/23/14

5/24/14

5/25/14

5/26/14

5/27/14

5/28/14

5/29/14

A

1

0

1

0

0

3

4

No biofix Biofix

 

Plum curculio monitoring and management
Scouting is the primary tool for monitoring and determining threshold for plum curculio.  At petal fall, scout for crescent-shaped oviposition scars and adult weevils on outside rows of early season varieties.  Beating trays can aide in scouting.  The recent warm weather may cause plum curculio movement beyond the outside rows and scouting further into the orchard may be necessary.  The threshold for plum curculio is one oviposition scar or one adult weevil.  Once this threshold is reached an insecticide can be applied.  For organic management apply Pyganic (pyrethrins) to the outer rows on a warm night.  Surround WP (kaolin) should be applied on interior rows.  Note: All insecticides targeting plum curculio should be applied on a warm night, when plum curculio is most active, and to prevent contact with pollinators.

Cornell carbohydrate thinning model
The MaluSim Model (Cornell carbohydrate model) is used to time thinning applications by calculating tree stress.  Thinning products can be applied at different rates depending on variety and accompanying tree stress.

Day and night conditions

Corresponding tree stress

Thinning response

75°F sunny and 45°F clear

Low

Low

75°F cloudy and 60°F cloudy

Moderate

Moderate

45°F cloudy and 40°F cloudy

High

High

The weather conditions on the previous two days and the successive four days, of the prospective thinning date, need to be considered if using the MaluSim Model to thin.

Additional Articles and Resources
How to optimize placement of codling moth pheromone traps.
http://msue.anr.msu.edu/news/how_to_optimize_placement_of_pheromone_traps_in_your_orchard

 Wild Pollinators of Eastern Apple Orchards.  Includes chart on toxicity of pesticides to bees.  http://www.fruit.cornell.edu/tree_fruit/resources/wild_pollinators.pdf