Vermont Apple IPM Alert

L.P.Berkett, IPM Specialist

May 10, 2002

 

 

Stage of Development:  Bloom on McIntosh at UVM HRC.

Disease Management

 Apple Scab –   The good news is that if your weather is similar to what we have experienced at the UVM Hort. Res. Center,   we have had only two infection periods so far, both when the trees were at Green Tip(4/13-14;   4/14-15).    Any other rains which measured over 0.01"  were enough to release mature ascospores but no infection should have taken place.   As of today, no scab lesions have been seen on non-sprayed McIntosh trees at the UVM HRC.   Hopefully, you also will find no lesions in your orchard -- but keep checking the top and bottom surfaces of leaves over the next few weeks.   As the table below shows,  we are still in the 'accelerated phase' of ascospore development which is a period of high risk.   Please refer to the April issue of the Vermont Apple Newsletter  for  fungicide strategies.

 

 

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

Cumulative % Ascospore Maturity for Selected Vermont Sites1

 

Date

5/08

So.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

457

494

430

501

491

 

Maturity

50% - 75%

50% - 75%

25% - 50%

50%- 75%

50% - 75%

 

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

 

 

Fire Blight:  Using the Maryblyt program, infection is predicted if the following four requirements are met:   (1) flowers must be open with stigmas and petals intact;   (2)  accumulation of at least 198 degree hours > 65 F after first bloom;   (3)  a wetting event occurring as dew or  at least 0.01" of rain, or at least 0.1" of rain the previous day (allows the bacteria to move from the colonized stigmas to the nectarthodes);  (4)  an average daily temperature of at least 60F.    As of May 6, we had not met all of these conditions in the above sites we are monitoring with Skybit E-Weather and the Maryblyt program.   Be on the alert if the weather turns warm and wet.

 

Arthropod Management Update:

 

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

for Selected  Vermont Sites 1

Date

 

So.Burlington

 

 Shoreham 

South Hero

Bennington

Dummerston

 

 

05/08

 

166

 

179

 

151

 

170

 

197

 

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

 

Arthropod 'events' associated with degree-day accumulation:

STLM - 1st generation adult peak flight                  112-214

San Jose Scale (SJS) - 1st adult catch                  181-321

CM - 1st adult catch                                              185-325

STLM -1st sap-feeding mines observed                 165-317

PC - 1st oviposition scars observed                        249-323

 

 

Trap captures of Spotted Tentiform Leafminer,    Tarnished Plant Bug and  European Apple Sawfly are all low and below threshold so far at the UVM Hort.Res.Center.     Low insect activity has also been reported in Massachusetts.   However,   be prepared to come in with your Petal Fall spray for Plum Curculio -- Dr. Ron Prokopy reports that as of May 7th,  he has seen two large migrations of adults into his monitored blocks in Massachusetts.   This is an indication that they may be active early in the orchard this year.  As mentioned in the March issue of the Vermont Apple Newsletter,  PC will actively feed and lay eggs when the barometric pressure drops or is low, particularly when there is also high humidity or rain.  When these conditions are present, there is a greater chance of fruit damage the higher the temperature is above 65F.

 

Note: We have caught the first Codling Moth adults in pheromone traps at the UVM HRC and will be tracking degree-day accumulation to predict best time for treatment where CM is a problem.

 

 

 

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