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) Geneva: 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.
DISEASES CAUSED BY PSEUDOMONAS SYRINGAE
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.
OTHER STONE FRUIT DISEASES
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 ), 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
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 APPLE MAGGOT 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) - AMERICAN PLUM BORER 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 CODLING MOTH 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) - COMSTOCK MEALYBUG - Adult males 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 COMSTOCK MEALYBUG - Crawlers 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 GREEN FRUITWORM 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 LESSER APPLEWORM 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) - LESSER PEACHTREE BORER 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 OBLIQUEBANDED LEAFROLLER 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 ORIENTAL FRUIT MOTH 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 PEAR PSYLLA 1st adult 30-Mar (+/-13) 7-Apr 66 (+/-36) 124 1st oviposition 4-Apr (+/-11) 7-Apr 82 (+/-44) 124 PEACHTREE BORER 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 REDBANDED LEAFROLLER 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 SPOTTED TENTIFORM LEAFMINER 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 APPLE (MCINTOSH) 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 PEAR (BARTLETT) 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 SWEET CHERRY (WINDSOR) 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 TART CHERRY (MONTMORENCY) 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