Scaffolds Fruit Journal, Cornell University NYSAES

Diseases | Insects | Credits

Volume 6, No. 6							September 15, 1997


                                                    43°F             50°F
Current DD accumulations (Geneva 1/1-9/15):         3045             2041
Coming Events:                              Ranges:
San Jose scale 2nd flight subsides             2494-3257 	1662-2302
Apple maggot flight subsides                   2764-3656 	1904-2573
Codling moth 2nd flight subsides               2782-3693	1796-2635
Oriental fruit moth 3rd flight subsides        2987-3522	2018-2377
Redbanded leafroller 3rd flight subsides       3103-3433 	2013-2359
STLM 3rd flight subsides                       3235-3471	2228-2472
Lesser appleworm 2nd flight subsides           2775-3466 	2002-2460

TRAP CATCHES (Number/trap/day)
                                   9/2    9/5    9/8   9/11   9/15
Redbanded Leafroller               0.5      0    0.7    0.7    0.6
Spotted Tentiform Leafminer        228    665    627    513    480
Lesser Appleworm                   0.7    7.5   10.5   16.8   10.1
Oriental Fruit Moth (apple)        1.3   24.8   44.2   41.5   18.3
San Jose Scale                     0.3    0.5    1.7    0.6    1.3
Codling Moth                       9.0    2.2    3.0    3.0    1.4
American Plum Borer                1.0      0    0.2      0      0
Lesser Peachtree Borer             0.6      0      0      0      0
Obliquebanded Leafroller           0.1    1.0    0.2    0.7    0.1
Apple maggot                      0.55   0.25    0.5   0.17   0.44   



by Dave Rosenberger
Plant Pathology, Highland

"Every year is different," and such was the case again in 1997. Some were non-existent in 1997, whereas other diseases that are usually bit-players emerged this year as significant and interesting problems.

Many parts of the state had exceptionally high carry-over inoculum from 1996, so we anticipated that apple scab could become a major headache in 1997. Fortunately, prebloom weather favored fruit-growers rather than the fungus. Scab infection periods in most parts of the state were interspersed with good weather that allowed trees to be resprayed at appropriate intervals. As a result, scab was not a significant problem in 1997 except in the occasional block where it gained a foothold because of problems with sprayer calibration, fungicide timing, or spray coverage. The Champlain Valley was so dry that unsprayed trees in abandoned orchards did not develop any scab until several weeks after petal fall.

Mildew is often worse in years that are unfavorable for apple scab, and this year was no exception. Wetting periods are not required for dissemination or germination of mildew spores. Fungicides are often applied on extended intervals during dry seasons because most spray timing decisions are driven by apple scab. Furthermore, some growers who normally use SI fungicides opt to use only contact fungicides during "easy" scab seasons to reduce fungicide costs. (Except for sulfur, the contact fungicides are not effective against mildew, whereas the SI fungicides are good mildewcides.) All of these factors allowed mildew to become a significant problem on susceptible varieties in 1997.

The introduction of new cultivars has also helped raise the status of mildew as an important disease in some orchards. Gala, Braeburn, Cameo, and Shizuka are all mildew-susceptible, but Ginger Gold appears to have a special affinity for mildew. In test plots at the Hudson Valley Lab, 25 cultivars are being compared for susceptibility to apple diseases as part of the NE-183 project. In these unsprayed plots, 86% of the terminal leaves on Ginger Gold were infected with mildew when evaluated during late June of 1997, whereas the next most susceptible cultivars (Gala, SunCrisp, GoldRush) had only 47-51% of leaves infected. Thus, the relationship between Ginger Gold and mildew is analogous to the relationship between Jersey Mac and apple scab: Extra fungicide sprays may be needed to control the respective diseases because of unique cultivar susceptibilities.

The status of fire blight in 1997 remains unchanged: It is still the most poorly understood of the major tree fruit diseases. Fire blight caused extensive damage this year many orchards west of Rochester and in a few orchards in the Hudson Valley. The seasonal post-mortem on problem orchards has not yet been completed. Reasons for the sudden appearance of fire blight epidemics in previously unaffected orchards is difficult to explain. The MaryBlyte prediction program has become an important and useful tool for timing streptomycin sprays during bloom and for back-estimating when infections occurred after symptoms are first noted in orchards. However, following MaryBlyte does not guarantee control of fire blight. When new plantings contain highly susceptible cultivars like Ginger Gold, Gala, or Braeburn, large numbers of trees are usually lost if blight gets established in the orchard.

The unusually wet season in 1996 apparently favored the initiation of crown rot (caused by Phytophthora) in some orchards in eastern New York. Drought conditions in 1997 that extended from petal fall through at least mid-June (or until irrigation was initiated) may have further favored development of the disease by keeping trees under stress and reducing the ability of trees to "heal out" Phytophthora infections. Tree losses were noted in some two-year-old orchards and also in older blocks on M.26 and MM.106 rootstocks that did not have any history of crown rot problems. However, the incidence of crown rot was much lower in 1997 than during the severe epidemic that occurred in the Hudson Valley in 1982-83.

Bacterial diseases caused by P. syringae caused problems on pears (pear blast) and on some stone fruits in eastern New York. Cool, wet weather favored infection of pear flowers both in 1996 and again in 1997. Infection by P. syringae contributed to a very poor pear set in many Columbia County orchards in 1996. These conditions were repeated in 1997, but streptomycin sprays applied just prior to a light frost during early bloom in 1997 reportedly reduced the severity of pear blast this year.

P. syringae also affects stone fruits where it can cause a range of problems including canker, blossom blast, and spur blight. Weather conditions apparently favored severe blossom blast on apricots on Long Island. In several apricot orchards, most of the fruiting spurs were killed back to main limbs, leaving bare wood in the lower halves of the trees when they were observed in early June. To control P. syringae on stone fruits, copper sprays are recommended at leaf fall in autumn and again at bud break in spring. However, these copper sprays apparently are not effective under severe conditions such as those that occurred with apricots on Long Island last spring.

Black knot on tart cherry is becoming a major problem in western New York, and a peach twig die back caused by either Phomopsis or Fusicoccum is causing problems on Long Island. (The taxonomy of Phomopsis and Fusicoccum is confusing, and the pathogen causing the Long Island problem could be either or both species.)

Both black knot on tart cherry and the peach twig die back in Long Island may be occurring, at least in part, because of the recent introduction of effective new fungicides for controlling brown rot. The SI fungicides labeled for brown rot include Nova, Orbit, Elite, and Indar (although not all of these are labeled for all stone fruits). While this group is very effective for controlling brown rot, they may not provide the broad spectrum and long-residual disease control that was formerly achieved when Benlate, Topsin M, Bravo, captan, dichlone, or ferbam were used to control brown rot blossom blight or fruit rot. Although this hypothesis has not been proven, I suspect that diseases formerly suppressed by brown rot fungicides are re-emerging as newer and more narrow-spectrum fungicides are being introduced.

Low prices for tart cherries have also forced growers to economize on fungicide applications, thereby leaving trees less protected against black knot than in the past. In a recent report on research conducted in Ontario by John Northover and Wendy McFadden-Smith (Canadian Journal of Plant Pathology 17:57-68 [1995]), they reported that five applications of sulfur provided good control of black knot on tart cherry. Thus, sulfur might provide a low-cost approach for controlling this disease in the future.



by Dave Kain
Entomology, Geneva

Some of the most frequent comments and questions directed our way over the course of the season during a given year have to do with "how we're doing" on pest and tree development in comparison with last year, or with a "normal" year. Naturally, although some of this is only idle curiosity, sometimes a few good clues about the season can be gathered by comparing the relative timings of yearly events  - were the trees ahead of the insects, were some pests out of sync with the season while others weren't, was everything behind schedule? Despite the lack of any startling insight about how things went this year, we like to provide comparative listings of some of the pest events that occured this season (in Geneva) with those calendar and degree-day normals. (In alphabetical order, of course.) The values and dates are given +/- one standard deviation; i.e., events should occur within the stated range approximately 7 years out of 10.

                                                        DEGREE DAYS
                                 DATE                   (BASE 43°F)
                         _____________________    ______________________
EVENT                    Normal (+/-days) 1997    Normal (+/-DD)    1997

   1st catch             28-Jun  (+/-8)  7-Jul     1351 (+/-171)    1384
   Peak                   4-Aug (+/-14) 11-Aug     2365 (+/-189)    2298
   Subsiding              4-Sep (+/-10)   -        3065 (+/-286)     - 

   1st catch             18-May  (+/-6)  9-May      423 (+/-112)     360
   1st flight peak        3-Jun  (+/-6) 12-Jun      703 (+/-146)     733
   1st flight subsiding  30-Jun  (+/-7)  3-Jul     1367 (+/-218)    1296
   2nd flight start      11-Jul  (+/-4) 14-Jul     1613 (+/-250)    1550
   2nd flight peak       27-Jul  (+/-6) 31-Jul     2170 (+/-225)    2006
   2nd flight subsiding  14-Sep  (+/-8)  5-Sep     3394 (+/-247)    2841

   1st catch             19-May  (+/-7) 27-May      484 (+/-106)     426
   1st flight peak        4-Jun (+/-11) 16-Jun      794 (+/-194)     818
   2nd flight start      19-Jul (+/-14)  7-Aug     1900 (+/-340)    2181
   2nd flight peak       11-Aug  (+/-8) 11-Aug     2503 (+/-340)    2298
   2nd flight subsiding  12-Sep (+/-10)   -        3331 (+/-283)     - 

   1st catch              2-Jul  (+/-4)  1-Jul     1440 (+/-124)    1237
   1st flight peak        9-Jul  (+/-5)  5-Jul     1642 (+/-75)     1425
   1st flight subsiding  22-Jul (+/-10) 15-Jul     2003 (+/-130)    1585

   1st catch              9-Aug (+/-12) 15-Aug     2447 (+/-196)    2393
EUROPEAN RED MITE - Overwintered eggs 

   Hatch starts           6-May  (+/-4)  7-May      284  (+/-53)     280

   1st catch              4-Apr  (+/-9)  7-Apr       80  (+/-29)     124
   Peak                  15-Apr (+/-11) 24-Apr      138  (+/-56)     160
   Subsiding              7-May (+/-11) 15-May      342 (+/-114)     340


   1st catch             12-May  (+/-9)  5-May      394 (+/-160)     266
   1st flight peak       23-May  (+/-8) 30-May      572 (+/-179)     464
   1st flight subsiding  20-Jun (+/-10) 26-Jun     1154 (+/-246)    1096
   2nd flight peak       15-Sep  (+/-7)   -        3164 (+/-137)     - 

   1st catch             27-May  (+/-8) 30-May      584 (+/-150)     464
   Flight peak            1-Jul (+/-17) 12-Jun     1370 (+/-469)     733
   Flight subsiding       9-Sep  (+/-7)  5-Sep     3129 (+/-224)    2841


   1st catch             11-Jun  (+/-5) 19-Jun      921  (+/-88)     893
   1st flight peak       20-Jun  (+/-8) 23-Jun     1158 (+/-191)    1005
   2nd flight begins      7-Aug (+/-10)  4-Aug     2496 (+/-192)    2124
   2nd flight peak       22-Aug (+/-12)  5-Sep     2882 (+/-174)    2841

   1st catch              2-May  (+/-7) 15-May      297  (+/-95)     340
   1st flight peak       15-May (+/-11)  5-Jun      431  (+/-96)     565
   2nd flight begins      1-Jul  (+/-6)  3-Jul     1428 (+/-155)    1296
   2nd flight peak       10-Jul (+/-11) 10-Jul     1777 (+/-415)    1442
   3rd flight begins     12-Aug  (+/-9)  7-Aug     2545 (+/-257)    2181
   3rd flight peak       25-Aug (+/-16) 18-Aug     2894 (+/-322)    2470


   1st adult             30-Mar (+/-13)  7-Apr       66  (+/-36)     124
   1st oviposition        4-Apr (+/-11)  7-Apr       82  (+/-44)     124

   1st catch             17-Jun (+/-11)  9-Jun     1028 (+/-293)     646
   Flight peak            7-Jul (+/-21) 26-Jun     1552 (+/-516)    1096
   Flight subsiding      24-Aug (+/-13) 11-Aug     2827 (+/-313)    2298


   1st catch             18-Apr  (+/-7) 21-Apr      181  (+/-85)     141
   1st flight peak        4-May (+/-10)  1-May      302  (+/-82)     234
   2nd flight begins      2-Jul  (+/-6) 26-Jul     1481 (+/-230)    1096
   2nd flight peak       14-Jul  (+/-6) 14-Jul     1776 (+/-302)    1550
   2nd flight subsiding   4-Aug (+/-12) 25-Aug     2361 (+/-266)    2607
   3rd flight begins     21-Aug (+/-11)  2-Sep     2776 (+/-181)    2796

SAN JOSE SCALE - adult males
   1st catch             17-May  (+/-8) 30-May      478 (+/-119)     464
   1st flight peak        1-Jun  (+/-7)  9-Jun      684  (+/-51)     646
   2nd flight start      16-Jul  (+/-9) 21-Jul     1729 (+/-265)    1760
   2nd flight subsiding  31-Aug (+/-12) 28-Aug     2888 (+/-305)    2673

   1st catch             19-Apr  (+/-6) 21-Apr      175  (+/-66)     141
   1st flight peak        7-May  (+/-7) 19-May      332  (+/-87)     360
   2nd flight begins     15-Jun  (+/-7) 23-Jun     1065 (+/-127)    1005
   2nd flight peak        9-Jul (+/-10) 21-Jul     1648 (+/-237)    1760
   3rd flight begins      8-Aug  (+/-7) 11-Aug     2510 (+/-175)    2298
   3rd flight peak       22-Aug (+/-10) 28-Aug     2857 (+/-212)    2673
   3rd flight subsiding  12-Sep  (+/-7)   -        3311  (+/-96)     - 

                                                        DEGREE DAYS
                                 DATE                   (BASE 43°F)
                         _____________________    ______________________
CROP PHENOLOGY           Normal (+/-days) 1997    Normal (+/-DD)    1997

   Green tip             12-Apr  (+/-6) 11-Apr      113  (+/-40)     125
   Half-inch green       22-Apr  (+/-7) 21-Apr      173  (+/-28)     141
   Tight cluster         28-Apr  (+/-7)  1-May      230  (+/-22)     234
   Pink                   4-May  (+/-7) 12-May      299  (+/-31)     312
   Bloom                 11-May  (+/-7) 22-May      386  (+/-53)     381
   Petal fall            19-May  (+/-6)  2-Jun      494  (+/-47)     518

   Bud burst             23-Apr  (+/-6) 24-Apr      165 (+/-51)      160
   Green cluster          2-May  (+/-5)  5-May      241 (+/-29)      266
   White bud              6-May  (+/-7) 12-May      301 (+/-49)      312
   Bloom                  9-May  (+/-8) 19-May      352 (+/-51)      360
   Petal fall            16-May  (+/-8) 27-May      443 (+/-58)      426

   Bud burst             24-Apr  (+/-5) 24-Apr      173 (+/-28)      160
   White bud              1-May  (+/-5) 12-May      222 (+/-29)      234
   Bloom                  6-May  (+/-5) 19-May      267 (+/-34)      282
   Petal fall            14-May  (+/-5) 27-May      380 (+/-55)      360
   Fruit set             19-May  (+/-5) 22-May      443 (+/-50)      381

   Bud burst             28-Apr  (+/-6)  5-May      212 (+/-42)      266
   White bud              9-May  (+/-4)  8-May      279 (+/-23)      282
   Bloom                 12-May  (+/-4) 15-May      364 (+/-53)      340
   Petal fall            20-May  (+/-5) 30-May      463 (+/-57)      464
   Fruit set             29-May  (+/-5)  6-Jun      555 (+/-61)      585

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:

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Photographs courtesy of New York State Integrated Pest Management Program