Scaffolds

Diseases | Insects | Credits


SCAFFOLDS Fruit Journal, Geneva, NY                          Volume 5 
Update on Pest Management and Crop Development               September 23,1996

Coming Events

                                                     43F       50F
Current DD accumulations (Geneva 1/1-9/23):         3374      2320
                       (Highland 1/1-9/23):         

Coming Events:                             Ranges:
Lesser appleworm 2nd flight subsides            2775-3466  2002-2460
Oriental fruit moth 3rd flight subsides         2987-3522  2018-2377



DISEASES

LAST WORD ON DISEASES

Dave Rosenberger, Plant Pathology, Highland

A Correction and a Caution on Postharvest Urea Sprays to Control Scab:

In last week's issue of "Scaffolds", I noted that scab inoculum was unusually high in many NY apple orchards this year, that postharvest sprays of 5% urea could be used to reduce inoculum levels for next year, and that 5% urea equaled 5 lbs of urea/100 gallons of dilute spray. Upon rereading the article after it was published, I suddenly realized that 5% urea on a weight/weight basis is not 5 lbs/100 gallons, but instead would be 40 lbs/100 gallons (since 100 gallons of water weighs about 800 lbs). On the other hand, 5% urea might be construed as 5 lbs/100 gallons if the percentage was calculated on a weight/volume basis. So what does the recommended rate of "5% urea" really mean in terms of a rate per acre?

I called Dr. Bill MacHardy at the University of New Hampshire for his opinion. Dr. MacHardy recently completed a 545-page book, titled "Apple Scab: Biology, Epidemiology, and Management", in which he reviewed and summarized all of the published literature on apple scab. He is also actively involved in research on reducing overwintering scab inoculum with various kinds of postharvest sprays. Dr. MacHardy indicated that the standard rate of urea that he and other researchers have tested in postharvest sprays is 40 lbs urea/100 gallons. He applies about 100 gallons of dilute spray per treated acre. Dr. MacHardy did not believe that 5 lbs urea/100 gallons would be enough to significantly reduce overwintering apple scab.

Unfortunately, postharvest application of 40 lbs of urea per acre could have negative horticultural effects. If the spray is applied to leaves on the trees, this rate of urea might result in reduced winter hardiness, especially if leaves remained on the trees for more than a week after the application, thereby allowing much of the nitrogen to be translocated into buds and twigs. Applying the urea to the ground after leaf drop might be safer, but leaf coverage and effectiveness of the treatment are likely to be lower than when the spray is applied to leaves on the trees. The effectiveness of ground treatments with urea is significantly reduced if the soil surface freezes soon after the application, because the microbial degradation process is then arrested before the full benefits of the urea application can be realized. Even when applied to the soil, 40 lbs urea/A might cause excess tree vigor the following year, especially in McIntosh trees where fruit quality becomes a problem with high nitrogen levels in leaves.

The bottom line is that the overall benefits of urea treatments applied to reduce scab inoculum are questionable. Low rates of urea may not be effective for reducing scab inoculum, whereas high rates that are known to be effective against scab might have adverse effects on apple trees in our northerly climates. Applying urea at 5-10 lbs/A might have some benefits if weather conditions following application were ideal for enhancing leaf degradation and if this low-rate application was combined with one of the other postharvest treatments (leaf chopping, liming, or 2,4-D application) that was outlined in last week's "Scaffolds". However, there is no data to document effectiveness of such combined treatments. Growers with high inoculum orchards may still wish to experiment with some combination of postharvest treatments to reduce scab inoculum, but the benefits cannot be accurately predicted.

Fall Copper Sprays for Stone Fruits:

Weather conditions during spring and early summer of 1996 were conducive for development of bacterial diseases on stone fruits. Bacterial leaf spot caused by Xanthomonas pruni is rarely a significant problem in upstate New York, but it caused serious problems in some peach, plum, and apricot orchards in 1996. In one case, apricot trees that escaped spring frosts and set a full crop for the first time in several years ended up with no marketable crop because the fruit were completely destroyed by the black bacterial lesions.

Xanthomonas pruni can infect leaf scars on twigs as leaves drop in the fall. Bacteria overwintering in the leaf scars will initiate infections again next year if spring weather conditions favor infection. Where bacterial leaf spot was a problem in 1996, growers should apply a copper spray at leaf fall to reduce overwintering populations of this bacterial pathogen. Copper sprays applied at leaf fall are also effective against peach leaf curl. Note, however, that other fungicides registered to control peach leaf curl will not control bacterial diseases.

A copper spray applied at 25-50% leaf drop has also proven effective for reducing bacterial canker of sweet cherry. Bacterial canker is caused by the bacterium Pseudomonas syringae. Bacterial canker on sweet cherries can be prevented by copper sprays applied either at leaf fall in autumn or before bud break in the spring. (Some Hudson Valley cherry growers apply copper sprays in both fall and spring.) However, a copper spray applied to cherries in early spring can have adverse effects on pollination and cherry fruit set in years when there is little rainfall prior to bloom. In such years, copper residues in trees can be high enough at blossom time to affect the viability of pollen. Cherry growers concerned about inadequate fruit set may wish to control bacterial canker of cherries by using a fall application of copper rather than the dormant application of copper in spring.




INSECTS

THE YEAR IN PERSPECTIVE

apple

Dave Kain and Art Agnello, Entomology, Geneva

As with our recollections of the year's weather, we're often surprised when we see our perceptions of pest events compared with hard data. Keeping this in mind, here is our annual comparison of some of the pest events that occured this season (in Geneva) with calculated "normals". In general, with the late spring and cool summer, most events occurred a week or so behind schedule for the entire season (unlike most years, when everything "catches up" after a little warm weather).


                             DATE                DEGREE DAYS (BASE 43 F)
                   __________________________  _________________________
EVENT              Normal (+/- days)     1996   Normal (+/- DD)     1996

AMERICAN PLUM BORER
1st catch             18-May (+/-7)    20-May     425 (+/-120)       379
1st flight peak        2-Jun (+/-6)    17-Jun     684 (+/-147)       962
1st flight subsiding  28-Jun (+/-7)     5-Jul     338 (+/-217)      1396
2nd flight start      10-Jul (+/-3)    18-Jul    1587 (+/-261)      1748
2nd flight peak       27-Jul (+/-6)     1-Aug    2183 (+/-241)      2092
2nd flight subsiding  13-Sep (+/-8)     9-Sep    3326 (+/-222)      3122

APPLE MAGGOT 
1st catch            28-Jun  (+/-8)     8-Jul    1336(+/-168)       1481
Peak                  3-Aug (+/-15)     8-Aug    2354(+/-194)       2292
Subsiding             5-Sep (+/-11)    26-Aug    2984 (+/-148)      2764

CODLING MOTH 
1st catch             8-May  (+/-7)    28-May     479 (+/-106)       510
1st flight peak       3-Jun (+/-12)    13-Jun     769 (+/-195)       851
2nd flight start     17-Jul (+/-14)    28-Jul    1843 (+/-350)      1998
2nd flight peak      10-Aug  (+/-8)    22-Aug    2475 (+/-369)      2649
2nd flight subsiding 10-Sep  (+/-8)    16-Sep    3142 (+/-237)      3257

COMSTOCK MEALYBUG - Adult males
1st catch             1-Jul  (+/-4)     5-Jul    1448 (+/-136)      1396
1st flight peak       8-Jul  (+/-5)    15-Jul    1639 (+/-82)       1661
1st flight subsiding 20-Jul (+/-10)     1-Aug    1983 (+/-137)      2092
Crawlers present      5-Aug (+/-12)    22-Aug    2397 (+/-186)      2649

GREEN FRUITWORM
1st catch             4-Apr  (+/-9)    15-Apr      79  (+/-28)        61
Peak                 15-Apr (+/-11)    22-Apr     140  (+/-62)       122
Subsiding             5-May (+/-10)    30-May     310  (+/-92)       527

LESSER APPLEWORM
1st catch            11-May (+/-10)    16-May     392 (+/-155)       283
1st flight peak      23-May  (+/-8)    24-May     599 (+/-193)       466
1st flight subsiding 20-Jun (+/-11)    17-Jun    1185 (+/-266)       962
2nd flight begins    10-Jul (+/-18)    15-Jul    1623 (+/-492)      1661
2nd flight peak      16-Sep  (+/-7)     9-Sep    3175 (+/-156)      3122

LESSER PEACHTREE BORER 
1st catch            26-May  (+/-8)     3-Jun     588 (+/-155)       602
Flight peak           5-Jul (+/-17)    17-Jun    1486 (+/-434)       962
Flight subsiding     10-Sep  (+/-8)     5-Sep    3140 (+/-192)      3011

DD models

OBLIQUEBANDED LEAFROLLER
1st catch            11-Jun  (+/-5)    17-Jun     917  (+/-86)       962
1st flight peak      20-Jun  (+/-8)    20-Jun    1163 (+/-195)      1034
2nd flight begins     7-Aug (+/-10)    22-Aug    2500 (+/-181)      2649
2nd flight peak      21-Aug (+/-13)     3-Sep    2882 (+/-191)      2957
 
ORIENTAL FRUIT MOTH
1st catch             2-May  (+/-6)     9-May     300  (+/-99)       227
1st flight peak      13-May (+/-11)    20-May     418  (+/-93)       379
2nd flight begins     2-Jul  (+/-6)     1-Jul    1441 (+/-162)      1305
2nd flight peak       8-Jul (+/-11)    29-Jul    1778 (+/-451)      2018
3rd flight begins    12-Aug (+/-10)    19-Aug    2594 (+/-251)      2561
3rd flight peak      24-Aug (+/-11)     9-Sep    2912 (+/-317)      3122

PEACHTREE BORER
1st catch            17-Jun (+/-11)    13-Jun    1061 (+/-290)       851
Flight peak          10-Jul (+/-21)     1-Jul    1666 (+/-515)      1305
Flight subsiding     26-Aug (+/-13)    26-Aug    2876 (+/-296)      2764

REDBANDED LEAFROLLER
1st catch            18-Apr  (+/-7)    22-Apr     185  (+/-87)       122
1st flight peak       4-May  (+/-9)    20-May     298  (+/-85)       379
2nd flight begins     3-Jul  (+/-6)     1-Jul    1515 (+/-225)      1305
2nd flight peak      14-Jul  (+/-7)    15-Jul    1783 (+/-328)      1661
2nd flight subsiding  5-Aug (+/-11)    25-Jul    2383 (+/-258)      1927
3rd flight begins    20-Aug (+/-12)    29-Aug    2758 (+/-208)      2841

SAN JOSE SCALE - adult males
1st catch            16-May  (+/-8)     6-Jun     475 (+/-116)       660
1st flight peak      31-May  (+/-7)     6-Jun     675  (+/-56)       660
2nd flight start     15-Jul (+/-10)    18-Jul    1686 (+/-203)      1748
2nd flight peak      14-Aug (+/-10)     5-Aug    2392 (+/-210)      2192
2nd flight subsiding 29-Aug (+/-12)    16-Sep    2857 (+/-305)      3257
         
SPOTTED TENTIFORM LEAFMINER
1st catch            19-Apr  (+/-7)    25-Apr     175  (+/-67)       136
1st flight peak       5-May  (+/-6)    20-May     313  (+/-75)       379
2nd flight begins    14-Jun  (+/-7)    20-Jun    1067 (+/-134)      1034
2nd flight peak      10-Jul  (+/-8)    11-Jul    1681 (+/-225)      1305
2nd flight subsiding 27-Jul  (+/-9)     1-Aug    2220 (+/-235)      2092
3rd flight begins     8-Aug  (+/-8)     8-Aug    2531 (+/-170)      2292
3rd flight peak      23-Aug (+/-10)    19-Aug    2878 (+/-207)      2561
3rd flight subsiding 12-Sep  (+/-7)    12-Sep    3311  (+/-96)      3197

                             DATE                DEGREE DAYS (BASE 43 F)
                   __________________________  _________________________
CROP PHENOLOGY     Normal  (+/- days)    1996   Normal (+/- DD)     1996

APPLE-MCINTOSH
Green tip            11-Apr  (+/-6)    22-Apr      108 (+/-42)       122
Half-inch green      21-Apr  (+/-7)    29-Apr      176 (+/-29)       158
Tight cluster        27-Apr  (+/-6)     9-May      228 (+/-24)       227
Pink                  3-May  (+/-6)    16-May      295 (+/-30)       283
Bloom                 9-May  (+/-6)    20-May      377 (+/-40)       379
Petal fall           17-May  (+/-5)    24-May      494 (+/-51)       466

stages of apple buds

PEACH 
Swollen bud           5-Apr  (+/-4)    25-Apr      126 (+/-38)        36
Bud burst            22-Apr  (+/-4)     2-May      136  (+/-5)       179
Half-inch green      27-Apr  (+/-7)     7-May      186 (+/-29)       209
Pink                 28-Apr  (+/-9)    13-May      215 (+/-31)       263
Bloom                 5-May  (+/-6)    16-May      298 (+/-58)       283
Petal fall           12-May  (+/-9)    24-May      406 (+/-123)      466

PEAR
Swollen bud          14-Apr  (+/-5)    22-Apr      123 (+/-42)       122
Bud burst            23-Apr  (+/-7)    29-Apr      159 (+/-52)       158
Green cluster         1-May  (+/-5)     9-May      240 (+/-30)       227
White bud             5-May  (+/-7)    16-May      297 (+/-53)       283
Bloom                 8-May  (+/-7)    20-May      344 (+/-50)       379
Petal fall           15-May  (+/-8)    24-May      436 (+/-57)       466

PLUM
Swollen bud          17-Apr  (+/-8)     2-May      148 (+/-38)       179
Bud burst            27-Apr  (+/-4)     9-May      173 (+/-49)       227
Green cluster         1-May  (+/-5)    14-May      239 (+/-35)       266
White bud             5-May  (+/-5)    16-May      239 (+/-17)       283
Bloom                 7-May  (+/-5)    20-May      329 (+/-49)       379
Petal fall           13-May  (+/-5)    24-May      393 (+/-53)       466

SWEET CHERRY
Swollen bud          12-Apr  (+/-5)    22-Apr      100 (+/-32)       122
Bud burst            23-Apr  (+/-6)    29-Apr      177 (+/-30)       158
White bud             1-May  (+/-6)     6-May      222 (+/-31)       206
Bloom                 5-May  (+/-6)    13-May      267 (+/-36)       263
Petal fall           13-May  (+/-4)    20-May      383 (+/-61)       379

TART CHERRY
Swollen bud          15-Apr  (+/-6)    22-Apr      117 (+/-61)       122
Bud burst            27-Apr  (+/-6)     2-May      210 (+/-42)       179
White bud             9-May  (+/-5)    13-May      281 (+/-26)       263
Bloom                11-May  (+/-4)    20-May      365 (+/-59)       379
Petal fall           18-May  (+/-4)    24-May      462 (+/-65)       466
deer

Scaffolds is published weekly from March to September by Cornell University -- NYS Agricultural Experiment Station (Geneva), and Ithaca-- with the assistance of Cornell Cooperative Extension. New York field reports welcomed. Send submissions by 3 p.m. Monday to:

Scaffolds Fruit Journal
Editors: A. Agnello, D. Kain
Department of Entomology, NYSAES
Geneva, NY 14456-0462
Phone: 315-787-2341 FAX:315-787-2326
E-mail: ama4@cornell.edu


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