Vermont Apple IPM Alert

L.P.Berkett, IPM Specialist

April 23, 2002

 

Stage of Development:  Tight Cluster  to  early Pink on McIntosh at UVM Hort.Res.Center.

Disease Management

 Apple Scab – Included in the chart is the predicted date on which 300 DD will have been accumulated.  This would be the start of the “accelerated phase” of ascospore maturity which is when a high percentage of this season’s ascospores will mature and will be released.   Needless to say we are in a high risk period for scab infections.

 

2002 Estimated Degree-Day Accumulation (Base 32F, from McIntosh Green Tip) and

Cumulative % Ascospore Maturity for Selected Vermont Sites1

Date

4/22

South

Burlington

(GT=4/13)

Elev. 71 M

Shoreham

 

(GT=4/12)

Elev. 107 M

South Hero

 

(GT=4/14)

Elev. 54M

Bennington

 

(GT=4/10)

Elev. 370 M

Dummerston

 

(GT=4/13)

Elev. 171 M

DD

250

287

220

304

271

Maturity

 10-25% 10-25% 10-25% 10-25% 10-25%

Predicted date to reach 300 DD (start of “accleration phase”

  

4/27

  

4/24

  

4/29

  

4/22

  

4/25

1Degree Days received from Skybit E-Weather Service: http://www.skybit.com/

 

Fire Blight:  Bacteria overwinter in cankers.  During warm weather in the pre-bloom period the bacteria actively multiply and ooze from the edge of cankers.   However,  cold weather (like we have had in the past few days) will 'knock down' bacterial populations.  The 2000-2001 New England Apple Pest Management Guide, pages 22-24, gives a good overview of disease management including information on predictive models. We will be monitoring bloom conditions in 5 orchards around the state to determine the likelihood of infection. In general terms,  warm (65-85F), wet and humid weather during bloom favors blossom blight infections. Streptomycin remains the primary defense agains fire blight.   

 

Arthropod Management Update:

 

2002  Estimated Degree-Day Accumulation (Base 50F, from Jan. 1) for Selected Sites1

Date

UVM HRC

South Burlington Chittenden Co.

Elev. 71 M

Shoreham 

Addison Co.

Elev. 107 M

South Hero

Grand Isle Co.

Elev. 54M

Bennington

Bennington Co.

Elev. 370 M

Dummerston

Windham Co.

Elev. 171 M

4/22

 126

138

112

133

 150
1Degree Days received from Skybit E-Weather Service: http://www.skybit.com/

The following are some arthropod 'events'  that are expected at different degree-day accumulations:

Tarnished Plant Bug -  1st observed                                                                  43-171

Obliquebanded Leafroller - 1st overwintered larvae observed                               64-160

European Red Mite - egg hatched observed                                                       100-168

Spotted Tentiform Leafminer - 1st generation adult peak flight                              112-214

Codling Moth  -  1st adult catch                                                                         185-325

 

Running Out of Time to Apply Oil

For a number of reasons (availability of oil, accelerated tree growth, current cold temps, etc.),  getting on oil this year may be difficult.   Apollo or Savey are options at pink but, to address resistance development, you should not use them if you had used either of them last year.   An option just after petal fall is Agri-Mek.   Agri-Mek also has activity against leafminers.

 

Coming Events:

Early Pink - - Place EAS traps in orchard

Late Pink - -Check TPB and LM Red Sticky Traps to determine if thresholds have been reached

Bloom - -Place CM pheromone traps in orchard.  Begin to inspect fruit for PC injury during late bloom

 

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