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SCAFFOLDS Fruit Journal, Geneva, NY                     Volume 5
Update on Pest Management and Crop Development         June 3, 1996


COMING EVENTS

43F 50F Current DD accumulations (Geneva 1/1-6/3): 602 329 (Highland 1/1-6/3): 916 519 Coming Events: Ranges: American plum borer 1st flight peak 360-962 134-601 Plum curculio oviposition scars present 448-670 232-348 Lesser appleworm 1st flight peak 455-851 255-471 Pear psylla hardshell present 463-651 259-377 Spotted tentiform leafminer 1st flight subsides 489-978 270-636 Redbanded leafroller 1st flight subsiding 518-893 255-562 Codling moth 1st flight peak 547-1326 307-824 Peachtree borer 1st catch 565-1557 299-988 San Jose scale 1st flight peak 581-761 308-449 Mirid bug hatch complete 610-720 330-390 Obliquebanded leafroller pupae present 612-860 330-509 Obliquebanded leafroller 1st catch 686-1059 392-681 European red mite summer egg hatch 773-938 442-582 Spotted tentiform leafminer pupating 778-807 454-456 TRAP CATCHES (Number/trap/day) Geneva: 5/16 5/20 5/24 5/28 5/30 6/3 Green Fruitworm 0 0 0 0 0.3 0 Redbanded Leafroller 0.8 6.2 5.5 1.1 0 0.1 Spotted Tentiform Leafminer 76 641 627 88 13.5 63.4 Oriental Fruit Moth 0 3.6 3.4 1.0 0 1.5 Lesser Appleworm 0.3* 9.0 10.4 5.5 1.5 5.3 Codling Moth 0 0 0 1.6* 0 6.3 San Jose Scale 0 0 0 0 0 0 American Plum Borer 0 0.1* 0 0.3 0 11.6 Lesser Peachtree Borer (cherry) 0 0 0 0 0 0.1* Lesser Peachtree Borer (peach) 0 0 0 0 0 0 Highland (Dick Straub, Peter Jentsch) 4/29 5/6 5/13 5/20 5/28 6/3 Green Fruitworm 0.2 0 0.1 0 0 0 Redbanded Leafroller 14.7 8.1 0.9 1.0 0.6 0.6 Spotted Tentiform Leafminer 15.3 15.6 16.4 4.7 5.1 0.3 Oriental Fruit Moth 0.3 4.4 4.5 1.0 0.9 1.2 Lesser Appleworm - - 0 0.1* 0.2 0.2 Codling Moth - - 0 0.1* 2.8 4.1 Fruittree Leafroller - - 0 0 0 0 Tufted Apple Budworm - - 0 0 0.4 0.8 Obliquebanded Leafroller - - - - - 0 Sparganothis Fruitworm - - - - - 0 * = 1st catch Pest Focus Highland - Adult 17-year Cicada emergence near peak 1st Rose Leafhopper adult on multiflora rose



DISEASE UPDATE

By: Dave Rosenberger, Plant Pathology, Highland

Blossom Blast

Pear blossom blast appeared in several pear orchards in Columbia County during the last two weeks. Blossom blast is a bacterial disease caused by Pseudomonas syringae. Pseudomonas syringae is favored by cool, wet weather (as compared with fire blight bacteria, which are favored by warm, wet weather). Pseudomonas syringae survives and grows on the surface of many different plant species and is distributed by splashing rain and by insects. Severe outbreaks of blossom blast on pears are usually associated with spring frosts because frost injury provides entry sites for infection. In the Columbia County orchards I observed, many of the developing fruitlets had frost rings, indicating that fruit were damaged by a frost (probably on May 14). However, less than 5% of the flower clusters were affected by blast.

Symptoms of blossom blast include blackening of the calyx end of individual fruitlets, blackening of entire blossom clusters with cluster leaves remaining unaffected, or complete death of clusters including both the blossoms and the leaves. Young leaves near affected clusters may have small nondescript necrotic leaf spots. Unlike fire blight, blossom blast does not spread into larger limbs or cause extensive damage to pear trees. However, heavy infections can seriously reduce fruit set.

Nothing can be done to change the course of the disease after symptoms of blossom blast appear, and no further spread of the disease will occur after bloom. When anticipated in advance, the severity of blossom blast can be decreased by a combination of a delayed-dormant copper spray plus two streptomycin sprays applied during bloom (See Plant Dis. Reptr. 61:311-312 [1977] and The GoodFruit Grower, 1 July 1986, pages 22-23). Unfortunately, streptomycin sprays timed to control fire blight infection periods will usually be applied too late during the bloom period to provide complete control of blossom blast. One of the Columbia County orchards affected this year had been protected with copper plus two streptomycin sprays timed for fire blight.

In its early stages, when clusters of blossoms are just beginning to turn black, blossom blast can easily be confused with fire blight. However, symptoms of blossom blast are likely to appear earlier in the season than would be expected for fire blighted blossoms. (The expected appearance of blossom blight symptoms associated with fire blight can be determined using the MaryBlyt program.) Fire blight bacteria produce a toxin that is rapidly transported to adjacent leaves and causes blackening of leaf veins, whereas perfectly healthy leaves are often found just below clusters of flowers killed by blossom blast. Clusters affected by fire blight frequently have drops of bacteria ooze on their surface, sometimes visible only with a hand lens, whereas ooze is not visible with blossom blast. Although no fruit grower is ever happy about having diseases in their trees, most pear growers are happy when someone diagnoses dead flower clusters as resulting from blossom blast rather than from fire blight.

Comparative Susceptibility of 25 Apple Cultivars to Powdery Mildew and Cedar Apple Rust

Regional research project NE-183, "Multidisciplinary Evaluations of New Apple Cultivars," was initiated in 1995 to allow uniform comparisons of promising new apple cultivars in multiple locations. Cooperators from 18 states and two Canadian provinces established a total of 28 uniform plantings. Multiple plantings were established in some states to allow evaluations under varying climatic conditions within the state or to allow more complete collection of both horticultural and pest susceptibility data. Cultivars chosen for evaluation were selected by a group of fruit breeders and horticulturalists representing all geographic regions and headed by Duane Greene from Massachusetts. The apple trees were all propagated at Adams County Nursery, Aspers, PA on M.9 EMLA rootstock and were planted at the various locations during April or early May of 1995. The experimental design was a randomized complete block design with five single-tree replicates.

During the summer of 1995, trees at four sites were evaluated to determine the incidence of powdery mildew and cedar apple rust that developed on the foliage. Disease incidence data were collected by Richard Kiyomoto, Connecticut Ag. Exp. Station, from a planting established near New Haven, CT; Keith Yoder, Virginia Polytechnic Institute & State University, from a planting near Winchester, VA; Alan Biggs, West Virginia Agricultural Experiment Station, from a planting at Kearneysville, WV; and Dave Rosenberger, Cornell University's Hudson Valley Lab, from a planting near Highland, NY. Statistical analysis of the compiled data was completed by Ron McNew at the University of Arkansas. Means separations among varieties were determined using multiple t-tests at the 5% significance level.

In most locations, one or two applications of Captan were made in May or early June to suppress scab. Mildew inoculum levels were high in VA, moderate in NY and WV, and low in CT. Cedar apple rust inoculum is abundant at all test sites. Grand means for data from all four sites is present in the data table along with the individual means for the planting in New York. Mutsu and Gala (Fulford strain) were included only in the New York planting and therefore are not included in the statistical analysis.

Ginger Gold was the most susceptible to mildew. Goldrush, Shizuka, and BC8M15-10 were the most susceptible to rust. The location-by-cultivar interaction was significant (P<0.001). Arlet developed the most mildew in CT but was only moderately affected in the other locations. Shizuka was severely infected with mildew in VA and NY but had relatively little infection in WV and CT. Shizuka is of particular interest in this planting as a POSSIBLE substitute for Mutsu (the fruit are reportedly quite similar) that would not be susceptible to blister spot.

Cultivars that are highly susceptible to rust or mildew in this comparison are likely to need special fungicide applications to prevent these diseases in commercial plantings. When planning new orchards, growers may wish to group mildew-sensitive or rust-sensitive cultivars together whenever possible so as to make it easier to apply special sprays to highly susceptible cultivars. Rust-sensitive cultivars should be located well away from border areas where cedars might provide rust inoculum. Pest evaluations on these plantings will be continued over the next four to eight years and will include evaluations for susceptibility to apple scab, mites, aphids, leafminer, and possibly other pests.

Table 1. Relative susceptibility of 25 apple cultivars to cedar apple rust and powdery mildew as determined at four locations in 1995, when trees were in their first leaf.

________________________________________________________________________
                     Percentage of 1995 terminal leaves with
                     Powdery Mildew         Cedar Apple Rust
                  _____________________   ____________________
                     All        NY           All         NY
Cultivar          Locations   29 June      Locations   12 July
__________________________________________________________________
Ginger Gold        29.1 a     45.4 a       7.3 cd      8.6 bc
Goldrush           18.6 b     24.2 bc     12.9 a      29.1 bc
Shizuka            17.6 b     31.3 ab     15.3 a      20.1 a
BC8M15-10          16.7 b     19.8 bcd    12.4 ab     12.9 ab
Orin               15.6 bc    15.2 c-f     4.4 de      4.9 cde
Suncrisp           14.8 bc    13.1 c-g     1.0 ghi     0.3 fg
Pioneer Mac        14.0 bcd   15.4 cde     0.3 ghi     0.4 fg
Golden Del         13.2 b-e   11.3 c-h     6.2 cde     7.9 bcd
Mutsu*                        11.0*                   24.2*
Gala (Fulford)*                8.5*                    0.8*
Honeycrisp         12.1 b-f    7.9 d-i     3.6 ef      3.5 c-f
Carousel            9.9 c-g    7.7 d-i     8.2 bc      6.3 b-e
Arlet               8.3 d-h    3.7 f-i     7.1 cd      7.9 bcd
Golden Supreme      7.9 e-i   11.0 c-h     0.0 i       0.0 g
Sansa               7.3 f-i   5.2 e-i      0.0 i       0.0 g
NY 429              6.8 ghi   7.3 e-i      0.0 i       0.0 g
Pristine            6.4 ghi   6.2 e-i      3.7 ef      7.2 bcd
Enterprise          5.5 g-j   3.1 ghi      0.1 hi      0.4 fg
Braeburn            5.2 g-j   5.0 e-i      3.9 def     7.1 bcd
Senshu              5.2 g-j   4.2 f-i      1.7 fg      2.1 efg
Gala Supreme        4.4 hij   1.3 i        0.7 ghi     0.0 g
Sunrise             3.8 ijk   2.3 hi       0.2 hi      0.3 fg
NY 75414-1          3.6 ijk   6.9 e-i      0.0 hi      0.0 g
Yataka              2.2 jk    0.6 i        1.6 fg      2.9 c-f
Fuji Redsport #2    1.0 k     0.0 i        1.1 gh      2.7 def
______________________________________________________________________

Means separation is by the 5% level t-test; values in the same column without a common letter are significantly different. Asterisks (*) indicate cultivars included only in the New York planting and not included in the statistical analyses.




GROUP SHOTS

By: Art Agnello, Entomology, Geneva

OBLIQUEBANDED LEAFROLLER

Various field reports confirm that, although the numbers and general infestation levels don't yet appear to be as high as normal this season, there are some patchy concentrations of good-sized overwintered larvae now evident in fruit clusters. Although the economics of controlling this brood don't always work out in terms of early-season damage prevented, many growers like to hedge their bets against the summer brood numbers by including something in the petal fall spray to take care of as many susceptible larvae as possible. For problem blocks, we would recommend Dipel, Lorsban or Lannate (in order of increasing harm to predator mites), together with the usual advice to be timely with summer brood sprays when they become necessary.

Apropos of which, we haven't yet heard anything official, but we do expect the Section 18 application for Confirm to be approved quite soon, and certainly in time for use against the July brood that causes the most problems. Harvey Reissig and I have talked continuously with the people at Rohm and Haas about the best strategy for using this product when it becomes available, and the following points outline the gist of what we all feel is the best way to proceed with Confirm, which is a very different kind of leafroller material than any other we've worked with before: - Although it's a little academic since it probably won't be approved in time for use against the petal fall generation, Confirm is not recommended for the overwintered brood, as it would certainly be getting tank-mixed with something else like an OP for your other petal fall insect concerns, and the overall result will be an increased selection pressure for the insecticide resistance that we'd like to delay for as long as possible. - Its recommended use is for problem blocks where the previously available materials are not able to provide less than 3-5% fruit damage during a normal year. Start with a spray at the 1st hatch of the summer brood, normally assumed to occur 7-10 days after the first regional moth catch (about 360 DD base 43F if you're picky; we'll be monitoring this event in many areas to let people know when the optimum recommended time arrives). This application should be followed by a second one 14 days later, and in all likelihood, a third one 14 or so days after that (we'll probably know more about the necessity for this third spray by the end of this season, but this is not the best time to take chances). - It would be of interest to check the terminals a few days after the second spray, just to see what visible effects the material is having on the larvae still present. It must be noted that this product does not kill the larvae immediately, but feeding ceases during the first 24 hours after the sprayed tissue is ingested; death comes slowly, taking as long as 5-7 days or more, depending on larval size. If you see live larvae after the second spray, don't panic, and if you want to see whether they're still feeding, throw a few into a container with apple foliage for a day to see whether they continue to eat it. With any luck, no larvae you find at this point will be able to feed. - No orchard on a Confirm schedule should have any problem with codling moth, but this material will not affect apple maggot, so keep in mind the need for an OP around the time of the third Confirm spray, which should normally coincide with maggot season. This product has not been shown to be effective against oriental fruit moth, so a separate material will be necessary if you feel OFM pressure is high, especially in any blocks near peach plantings, for instance. - You may hear stories about how well Confirm works on tufted apple bud moth. For unkown biological reasons, this product will not necessarily wipe out all the OBLR on your farm, but it is at least as effective as any other available material that's still giving good control, and it has the advantage of not adding to the selection pressure for resistant populations. Plus, it's probably one of the best choices in terms of selectivity and compatibility with predator mites.

MITES

Despite the cold and damp spring weather, European red mite eggs that weren't treated at all before bloom (which may have happened in a number of orchards because of the poor spraying conditions) seem to have had no trouble hatching during the past couple of weeks. This makes it all the more important to treat these orchards soon with some early season material, before things get out of hand and you're faced with threshold populations and no way to handle them. Some suitable options include: - Agri-Mek, particularly in any problem blocks that almost always need special attention. Get the necessary paperwork from the NYS Hort Society Office (315/787-2404); fill it out and notarize it, and send it back with the appropriate fee. Apply with highly refined oil, according to label directions, preferably within the first 2 weeks after petal fall. - Summer oil, applied in three sprays on a 10-14-day interval. See last week's issue for details. - Kelthane remains a very good alternative in blocks where a) you've never noted resistance problems, and b) you've had failures that may have been resistance-related, but haven't used it since then for 5-6 years. We've had some promising results mixing the 50WP formulation with a low rate (0.75-1.0%) of summer oil.

ROSY APPLE APHID

Some field reports alert us to the presence of substantial RAA numbers in parts of Western New York, particularly in late-blooming varieties such as Ida Red. Although these insects are difficult to control by the time petal fall arrives, an honest effort to keep colonies down might be worth the effort. Since we didn't find many during the pink-to-bloom window, we wouldn't expect to be seeing much fruit damage later on, but infestations of terminals and watersprouts can become messy. Provado and Thiodan are both recommended for any aphids present at this time, and Provado will additionally control white apple leafhoppers and any spotted tentiform leafminers that may have actually survived the poor spring weather.

PLUM CURCULIO

This is the designated period for controlling plum curculio in most tree fruit crops. We've heard from points east that populations appear to be high this year, so a timely OP spray after the petals are gone will be the first step of this task. As to whether another spray might be needed, it all depends on the temperatures from here on out. A developmental model tested for several years by Harvey Reissig and Jan Nyrop says that if, by the time 10-14 days have elapsed since your petal fall spray, we've accumulated 340 DD (base 50F), you won't need to make an additional application. If we haven't gotten that number of heat units, a 1st cover spray or at least an application of the border rows should be made. Now, granted that petal fall is an amorphous event at best, and that most growers probably have too much to think about at this time to track degree days anyway, what does this mean in practical terms? Briefly, if the next 7-10 days are generally warmer than normal, you're probably going to be safe with just the petal fall spray; if colder than normal, the curcs will still be moving into the orchards to lay eggs by the time of a 1st cover timing, and it's best to be on the safe side. We'll give you our reading on the situation in another week.

CHERRY FRUIT FLIES

No adults have been reported caught on sticky boards yet, but because of the zero tolerance in cherries for insect damage or presence, this absence does not diminish the need for sprays in your cherries now (for these pests as well as for curculio). Guthion, Imidan (tart cherries only), Sevin, the pyrethroids, or Penncap-M are all effective treatments. Sevin, Imidan and Penncap-M will also control black cherry aphid.




POSITION ANNOUNCEMENT

CORNELL COOPERATIVE EXTENSION - PA#15A Commercial Fruit Agent

Duties Plan, implement, and evaluate educational programs for the commercial fruit industry in Columbia and other contracting counties. Develop educational strategies, maintaining direct linkage with Cornell faculty and program units. This may include conducting applied research in conjunction with faculty and developing written materials for publication. Develop strategies for implementing programs that utilize a variety of proven educational methodologies and that consider the diversity of the community. Develop networks of volunteers and/or professionals to extend program implementation efforts. Coordinate efforts with Program Leader, agricultural program committees, and the fruit advisory committee. Also coordinate efforts with Eastern New York Fruit Program serving as a resource in the area of pest management of fruit crops.

Minimum Qualifications Masters degree with coursework in pomology, soils, plant physiology, pest management and irrigation. Three years of progressively responsible experience in Cooperative Extension or equivalent professioinal experience in the field of education, human service, or related industry.

Salary $33,000, commenusurate with qualifications. Apply by June 27, 1996 by sending a letter of intent indicating the title and number of the position, a resume, and college transcripts to:

Cornell Cooperative Extension Staffing and Professional Development
Cornell University
365 Roberts Hall
Ithaca, NY 14853-4203


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: art_agnello@cornell.edu


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