April 29, 2019 VOLUME 28, No. 6 Geneva, NY

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IN THIS ISSUE...

DISEASES v Managing Fire Blight in 2019 v Weekly apple scab update

HORTICULTURE v NEWA Apple Carbohydrate Thinning Model, Improved

GENERAL INFO v Pest Management position available

UPCOMING PEST EVENTS

PEST FOCUS

INSECT TRAP CATCHES

PHENOLOGIES

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scaffoldsF R U I T J O U R N A L

Update on Pest Managementand Crop Development

scout for fire blight in apple blocks and note any potential failures of strepto-

mycin or antibiotic products. Send suspect samples in for isolation of the pathogen and testing the iso-lates for resistance – keep samples moist and viable, as if you were

planning to graft it or use it in a bouquet.

Present Season Currently, orchards in the Hudson Valley are beginning to reach bloom, but the sudden change to colder weather this weekend and at the beginning of the week is keeping the initial risk of fire blight low. In Western NY, with the sudden cool rainy weather, king bloom may be

MANAGING FIREBLIGHT IN 2019(Kerik D. Cox& Anna Wallis,Plant Pathology&Plant-Microbe

Biology, Geneva; Juliet Carroll,NYS IPM Program, Geneva;kdc33@cornell.edu,aew232@cornell.edu, jec3@cornell.edu)

2018 Fire Blight Season Recap vv The number and magnitude of fire blight outbreaks in NY was a little lighter than the previous years, yet some growers experienced significant losses due to the dis-ease. While production areas in the Hudson Valley experienced extreme risk of fire blight around the first week in May, production ar-eas in the rest of the state didn't reach bloom until after the third week of May. These pro-duction regions had low fire blight risk and cooler weather that delayed bloom further. Overall, 2018 was a fairly light fire blight sea-son for most of NY state. Younger plantings with vigorous growth and protracted bloom may have had problems around the end of May, but overall, we received few complaints of fire blight.

In 2018, fire blight samples tested for an-tibiotic resistance uncovered one occurrence of streptomycin resistance in a new planting. The CRISPR profile of this isolate matched those of the original outbreak in 2001, sug-gesting that strain from the original outbreak is still lurking in Western NY. As we ap-proach bloom in 2019, it will be important to

BY THENUM-BERS

DISEASES

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scaffoldsis published weekly from March to September by Cornell University—Cornell AgriTech at the NYS Agricultural Ex-periment Station (Geneva) and Ithaca—with the assistance of Cornell Cooperative Extension. New York field reports welcomed. Send submissions by 2 pm Monday to:

scaffolds FRUIT JOURNAL Dept. of Entomology Cornell AgriTech at NYSAES 15 Castle Creek Dr. Geneva, NY 14456-1371 Phone: 315-787-2341 FAX: 315-787-2326 E-mail: ama4@cornell.edu

Editor: Art Agnello

This newsletter available online at: http://www.scaffolds.entomology.cornell.edu/

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more than a week away. King bloom in the Champlain Valley region could potentially be two weeks away. While warm weather at bloom may be a week or two away, it will still be important to watch forecasts, check the dis-ease forecasting, and follow extension special-ists' alerts and bloom predictions. Keep track of first blossom open dates for each of your varieties, especially those that are susceptible to fire blight, and record them on a piece of paper or in Notes on your phone. Use these dates to run the NEWA fire blight model to increase precision. Don't use the model de-fault dates or generalized, region-wide dates.

As you consider disease forecasting out-puts from NEWA or other forecasting models using the NEWA weather data, here are some things to consider before making applications of antibiotics or other costly materials for blos-som blight: 1 - Predictions and forecasts are theoreti-cal. The theoretical models predicting disease risk use the weather data collected (or forecast-ed) from the weather station location. These results should not be substituted for actual ob-servations of plant growth stage and disease occurrence determined through scouting or monitoring. 2 - Consider the history of fire blight in the planting. If there was no fire blight the previ-ous season or if you have never had fire blight, do not let excessive model predictions or ex-tension alerts (including this article) "intimi-date you" into applying unnecessary antibiotics each time an alert is released. 3 - Consider the age and susceptibility of your trees. Age and variety can play a large role in the development of fire blight. Present-ly, none of the models consider these factors in a formal sense. Adjust your interpretations of model predictions based on tree age, variety and rootstock. If you have a young planting of a highly susceptible variety, it may be more im-portant to protect these blocks based on model

predictions than a 15-year-old 'McIntosh' plant-ing on resistant rootstocks, which may not war-rant the same level of protection during bloom and you no longer have a market for. A listing of susceptible cultivars and rootstocks is linked from the NEWA model page for fire blight. 4 - The models only identify periods of weather that are favorable for infection. All wetting events are now color-coded light blue in NEWA to draw attention to the weather factors that promote bacterial ingress into the flowers. Despite the use of words like "ex-treme" and "infection" colored in vibrant red, the models only predict infections based on fa-vorable weather conditions. If the apple vari-ety is not highly susceptible, if there is no prior history of fire blight, and if the trees aren't be-ing pushed into high vigor with nitrogen, the actual risk of fire blight infection may be low to non-existent. 5 - Weather forecasts and predictions can change frequently. Model predictions are based on weather predictions, so when fore-casts change, the model predictions and cor-responding risk will also change drastically. Bacteria double about once every 20 minutes

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under optimal conditions; for fire blight bac-teria this is warm weather >60ºF. The models use degree hours, not degree days, to accom-modate the rapid growth rate of these patho-gens. Check the fire blight predictions, espe-cially those in the forecasts, frequently. The 1- and 2-day forecasts are the most reliable; those at 3-, 4- and 5-days are less reliable as predictors. NEWA uses the National Weather Service forecasts. Compare these with your favorite local weather forecast provider.

Status of Antibiotic Resistance in 2018 Except for a single detection in Western NY in 2018, streptomycin resistance has not been detected in NY for the last four years. If we keep practicing resistance management by rotating bactericides and antibiotics with limited use of streptomycin application after bloom, we may never experience widespread outbreaks of streptomycin resistance as we did from 2011 to 2013. However, if blossom blight or trauma blight develop after strep-tomycin applications, it may be best to have some samples assessed for streptomycin resis-tance to ensure the future success of chemical management programs for your operation.

We have continued to refine and update our guidelines for managing fire blight in NY with an emphasis on young plantings. The guide-lines below are broken up into three sections: general guidelines for season-long manage-ment, additional guidelines for new plantings, and guidelines for on-farm nursery production:

General Guidelines for Season-Long Man-agement. 1 - All fire blight strikes and shoots with larger cankers should be removed during win-ter pruning. Remove any trees where the cen-tral leader or main trunk has become infected. Infected wood should be removed from the or-chard and either burned or placed where it will dry out rapidly. The fire blight pathogen can

withstand cold temperatures, but is intolerant to drying. 2 - Copper sprays should be applied at green tip. Processing varieties can be protect-ed with copper as late as 1/2-inch green, de-pending on requirements of the label. 3- Although we've previously mentioned the use of prohexadione calcium at pink to mitigate spread of blossom blight into the shoot tissues, we are not recommending this use pattern as a standard practice for managing fire blight in young plantings until we have a greater appreciation of the potential benefits and impacts on crop physiology. We are con-tinuing to test horticultural impacts on young plantings in several locations this season. However, growers using prohexadione calci-um at pink for the purposes of training narrow fruiting wall plantings may have reduced risk of fire blight development following such ap-plications. 4 - During bloom, when trees are at peak susceptibility, follow a blossom blight fore-casting modeling system such as the ones offered in NEWA (newa.cornell.edu/index.php?page=apple-diseases), Maryblyt™ 7.1 (http://grapepathology.org/maryblyt), or RIM-pro (http://www.rimpro.eu/). Time applica-tions during high risk weather only. If the orchard rarely has or never had fire blight, it may not be necessary to apply antibiotic each time a high-risk period is forecast. Regardless of model predictions, it is rarely necessary to make more than three applications of antibiot-ics for blossom blight. 5 - Begin antibiotic applications for blos-som blight with a single application of strep-tomycin at 24 oz/acre. Consider including the penetrating surfactant Regulaid (1 pt/100 gal of application volume) in the first application to enhance the effectiveness of streptomycin. Regulaid would be especially beneficial when applied under rapid drying conditions. Reg-ulaid can be omitted from subsequent appli-cations so as to minimize the leaf yellowing

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('strep burn') that is often associated with re-peated applications of streptomycin. If later antibiotic applications are needed, streptomy-cin or kasugamycin (Kasumin 2L 64 fl oz/A in 100 gallons of water) should be used. Consider making at least one application of Kasumin 2L for resistance management purposes. If there are concerns about the effectiveness of strep-tomycin or kasugamycin, contact the authors of this article to discuss the product failure and determine if it would be necessary to submit a sample for antibiotic resistance testing. The presence of shoot blight later in the season isn't necessarily an indication that antibiotics applied during bloom failed due to resistance. 6 - In the two weeks following bloom, scout for and prune out fire blight strikes promptly. Destroy pruned strikes by burning or leaving them out to dry. It is best to prune well back into healthy 2nd year wood, remov-ing at least 12 inches behind the water-soaked margin. Take care, as summer pruning may stimulate active shoot growth, leading to new susceptible tissues that could later become in-fected. If fire blight reaches the central lead-er, the tree should be removed. However, the spot in the orchard may be safely replanted. In no case should cuttings be dragged through orchard rows; it is a good idea to place them in the aisle between rows and allow them to dry out completely before removing them; alternatively, they may be bagged and then properly discarded. Pruning crews should sanitize equipment routinely with 10% bleach or 70% ethanol solution. Ethanol is preferred, as bleach can be corrosive to metal equipment. This is especially important during humid, wet weather when trees are moist and fire blight is active in the orchard. Otherwise, because fire blight bacteria don't survive drying condi-tions very well, the need for sanitizing pruning equipment may not be as important. 7 - Preventive applications of prohexa-dione-calcium (Apogee or Kudos) for shoot blight should be seriously considered, espe-

cially on highly-susceptible apple varieties and blocks with a history of fire blight, during shoot elongation beginning in late bloom. a - Best results with prohexadione-cal-cium are often achieved by applying 6–12 oz/100 gal (3–6 oz/100 gal for trees <5 years) when trees have 1–2" of shoot growth. A sec-ond application should be made 14–21 days later. b - Programs where prohexadione-cal-cium is applied at low rates slowly over the period of active shoot growth are gaining pop-ularity to provide disease control and reduce impacts on tree productivity. Specific pro-grams may vary slightly, but generally consist of three applications at 1–2 oz/100 gal on a 14-day schedule, beginning with early shoot growth in mid- to late bloom. Take caution, as such programs have not been widely validated over many seasons and locations. 8 - Preventive applications of copper can be used post-bloom and during the summer to protect against shoot blight infections. Cop-per must be applied before infection occurs as it will only reduce bacteria on the surface of tissues. Copper will have no effect on exist-ing shoot blight infections. Copper may cause fruit russet in young developing fruit. Apply with adequate drying time and use hydrated lime to "safen" copper. Terminal shoots can outgrow protective residues of copper. Hence, a low-rate fixed copper program consists of ap-plications on a 7–10-day schedule during high risk weather until terminal bud set. 9 - It may be possible to save plantings on resistant rootstocks that have a moderate amount of shoot blight. Apply a rescue treat-ment of prohexadione calcium at the highest rate to the planting (6–12 oz/100 gal) and al-low 5 days for the product to affect the tree. Afterwards, prune out existing and newly de-veloping shoot blight every two weeks for the rest of the season. Remove any trees where fire blight has reached the central leader. If

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pruning stimulates additional shoot growth, a second application of prohexadione–calcium could be warranted. 10 - If you need to interplant apple trees in existing orchards where fire blight was ob-served, replant in late fall to better synchro-nize bloom with the established trees in the following season.

Additional Guidelines for New Plantings (1–2 years) 1 - If possible, plant varieties grafted on fire blight-resistant rootstocks. 2 - Trees should be carefully examined for fire blight infections before planting. Any in-fected trees should be discarded. A few other conditions may cause symptoms similar to fire blight infections, including poor transport con-ditions, poor storage conditions, poor root de-velopment, or potentially unknown chemical treatments in the nursery. Correct diagnosis is important to prevent destruction of a valuable investment, but must be done rapidly to assure timely management of potentially infectious plants. Contact local experts and extension personnel to confirm diagnosis when needed. 3 - Immediately after planting and 14 days later, a copper application should be made us-ing the lower copper rates that are labeled for use after green tip. Ensure that soil has settled to avoid phytotoxicity to roots. 4 - Until we better understand the use pat-tern and impact on crop physiology, it is in-advisable to apply prohexadione-calcium to young plantings, especially at pink. 5 - Trees should be scouted at 7-day inter-vals for fire blight strikes until July 31st. In-fected trees should be removed as described above. Plantings also need to be scouted 7–10 days after hail or severe summer storms. The NEWA fire blight disease forecast tool (newa.cornell.edu/index.php?page=apple-diseases) can assist by providing an estimate of symp-tom emergence following a storm or other trauma event. Also, scout the planting at the

end of the season (mid-September). 6 - If possible, remove flowers before they open. New plantings may have considerable numbers of flowers the first year, and blossom removal may not be practical. If practiced, the blossoms should be removed during dry, cool weather to reduce risk of fire blight infection. 7 - Trees should receive an application of copper at a stage equivalent to bloom. Ob-serve the labeled REI and PPE before blossom removal. Protect any remaining bloom as de-scribed for mature plantings under season-long management.

Guidelines for On-Farm Nursery Produc-tion 1 - Collect budwood from orchards where fire blight is not established or from a neigh-boring farm without fire blight. 2 - Limit streptomycin and kasugamycin applications to 2–3 per season. These appli-cations should be timed according to a disease forecast prediction or CCE alert. 3 - When fire blight pressure is high and shoots are actively growing, apply copper at the lowest labeled rate to prevent shoot blight. 4 - Before conducting tree management tasks in the nursery, apply a copper product at the lowest labeled rate and observe the labeled REI and required PPE. 5 - Any pinching or leaf twisting should be practiced on dry, sunny days with low relative humidity, after the REI of a copper application has expired. 6 - When working in the nursery, field workers must wear clean clothing, and should wash hands and disinfect working tools often. 7 - If fire blight is found in the nursery, com-pletely remove the infected trees including the root system, and place them in trash bags be-tween rows. Subsequently, remove the culled trees from between the rows and discard them. Under no circumstances should infected trees be pulled between nursery rows when trees are

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wet, otherwise fire blight may be spread down the rows. 8 - Maintain weed control through cultiva-tion. Apply registered post-emergence herbi-cides using a shielded boom. There are some residual herbicides registered for use in nurs-eries. 9 - When trees have reached the desired height, consider applying the lowest labeled rate of Apogee (1–2 oz/100 gal) to slow growth and reduce susceptibility to shoot blight. 10 - Manage nitrogen levels to balance tree growth and fire blight susceptibility. vv

NEWA APPLE CARBOHYDRATETHINNING MODELNOW IMPROVED!(Dan Olmstead,

Juliet Carroll, NYS IPM Program, Geneva, and Mario Miranda Sazo, Lake Ontario Fruit Program, Newark; dlo6@cornell.edu, jec3@cornell.edu & mrm67@cornell.edu)

vv You've read about it in trade maga-zines, heard about in talks, and now it's be-come a reality with a v2019 upgrade released on Friday April 26! Terence Robinson has added important improvements to the apple carbohydrate thinning model on NEWA. Dr. Robinson (tlr1@cornell.edu) Professor of Horticulture, Cornell University, along with other horticulturists, developed the Malusim fruit thinning model. The Apple Carbohydrate Thinning Model on NEWA has continued to be researched and now the improvements from this research are being woven into a v2019 edition of the model, improving its precision.

How to Access the v2019 Apple Carbohy-drate Thinning Model on NEWA If you haven't already started your thin-ning program, access and use the v2019 apple carbohydrate thinning model using the same

dropdown list as the current apple thinning model. Click on 'Apple CHO Thinning v2019 NEW'.If you've already initiated your thinning pro-gram and are using the original 'Apple Carbo-hydrate Thinning' model, continue to use that one. All web browser bookmarks and website access points will remain intact for the remain-der of 2019.

Need more specifics? On NEWA's main menu, hover over or tap on 'Crop Management' to show the dropdown list. Then click or tap on 'Apple CHO Thinning v2019 NEW'. Click the link below for direct access.

Apple CHO Thinning v2019 (the upgraded version),http://newa.cornell.edu/index.php?page=ap-ple-thin-new Here is a summary of the upgrades in the Apple CHO Thinning v2019 NEW model. • The NEWA apple carbohydrate thinning model will get an updated look and provide more comprehensive information. • The data table will have a column of de-gree days (DD) base 4°C and will have color highlighting when we are in the sweet spot for thinning (200-250 DD from bloom). • The user will be required to enter the per-centage of spurs that are floral. • The new version will also give a Thinning Index composed of the average carbohydrate balance for the two days before, the day of thinning, and the next four days, providing a seven-day running average. • The thinning recommendations will be based on a new three-dimensional lookup table that takes into account DD from bloom, percent of spurs that are flowering, and the thinning index (i.e., the average carbohydrate balance over seven days).

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HORTICULTURE

THIN-WINSITUATION

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The thinning recommendation cells in the table will be color coded to indicate high risk of over-thinning (red), mild thinning efficacy (yellow), and good thinning efficacy (green).

In New York, please direct questions and comments regarding these important updates and changes to your Cornell Cooperative Ex-tension regional program extension educator listed below or to Terence Robinson. Mario Miranda Sazo, Lake Ontario Fruit ProgramMike Basedow, Eastern New York Commer-cial Horticulture Program (Champlain Valley)Dan Donahue, Eastern New York Commercial Horticulture Program (Hudson Valley)

In 2020, along with a brand new NEWA website, the upgraded apple carbohydrate thin-ning model will be implemented on NEWA and will replace the original version.vv

PEST MANAGEMENT POSITION AVAILABLE WITH CCE LAKE ONTARIO FRUIT PROGRAM(Craig Kahlke, LOFP, Lockport; ckj37@cor-nell.edu)

Cornell Cooperative Extension's Lake Ontar-io Fruit Program still has an opening for the position of Area Fruit Specialist/Extension As-sociate in Integrated Pest Management. The focus of this position is to provide commercial fruit growers, producers, consultants and in-dustry representatives with the knowledge and educational resources necessary to assess and adopt integrated pest management practices that will enhance their profitability and sustain the growth of the fruit industry in Western New York. Provide leadership for planning, imple-menting and evaluating educational programs that address producer identified needs and op-portunities. Emphasis is on the demonstration and adoption of Integrated Pest Management principles and practices leading to economical and environmentally sound use of pesticides to maximize fruit quality, profitability, and sus-tainability. For full details and to apply, go to: https://academicjobsonline.org/ajo/jobs/13132.

GENERAL

INFO

INSECT TRAP CATCHES(Number/Trap/Day)

Geneva, NY Highland, NY 4/22 4/26 4/29 4/15 4/22 4/29Green fruitworm 3.0 1.0 0.0 Green fruitworm 0.0 0.0Redbanded leafroller 4.0* 9.0 0.0 Redbanded leafroller 40.5* 64.0Spotted tentiform leafminer 0.0 9.0* 0.0 Spotted tentiform leafminer 5.5* 51.0Oriental fruit moth - 0.0 0.0 Oriental fruit moth 0.5* 0.0 *firstcatch

Geneva:Spotted Tentiform Leafminer 1stcatch4/26.

PEST FOCUS

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UPCOMING PEST EVENTS

43°F 50°FCurrent DD* accumulations (Geneva 1/1–4/29): 194.9 82.7 (Geneva 1/1–4/29/2018): 127.3 46.7 (Geneva "Normal"): 240.8 114.5 (Geneva 1/1-5/6, predicted): 261.2 117.8 (Highland 1/1–4/29): 356.1 172.0 Coming Events: Ranges (Normal ±StDev):Black stem borer 1st catch 256-364 111-195Comstock mealybug 1st gen crawlers in pear buds 215-441 80-254European red mite egg hatch 231-337 100-168Green apple aphids present 111-265 38-134Green fruitworm flight subsides 267-499 123-271Obliquebanded leafroller larvae active 158-314 64-160Oriental fruit moth 1st catch 221-321 96-160Pear psylla 1st egg hatch 174-328 60-166Redbanded leafroller 1st flight peak 232-382 105-201Rosy apple aphid nymphs present 134-244 56-116Spotted tentiform leafminer 1st oviposition 143-273 58-130McIntosh pink 267-316 123-158

*all DDs Baskerville-Emin, B.E.

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NOTE:Everyefforthasbeenmadetoprovidecorrect,completeandup-to-datepesticiderecommendations.Nevertheless,changesinpesticideregulationsoccurconstantly,andhumanerrorsarepossible.Theserecommendationsarenotasubstituteforpesticidelabelling.Pleasereadthelabelbeforeapplyinganypesticide.ThismaterialisbaseduponworksupportedbySmithLeverfundsfromtheCooperativeStateResearch,Education,andExtensionService,U.S.DepartmentofAgriculture.Anyopinions,findings,conclusions,orrecommendationsexpressedinthispublicationarethoseoftheauthor(s)anddonotnecessarilyreflecttheviewoftheU.S.DepartmentofAgriculture.

PHENOLOGIES

Geneva: Apple Current 5/6,Predicted (McIntosh): tightcluster earlypink(RedDelicious): tightcluster tightcluster(Empire): tightcluster earlypink(Idared): tightcluster earlypinkPear(Bartlett,Bosc): greencluster whitebudSweetCherry whitebud bloomTartCherry budburst whitebudPeach pink bloomPlum bloom bloom/earlypetalfallApricot bloom bloom/early petal fall

Highland:Apple Pear(McIntosh): 37%bloom (Bartlett): 69%bloom(GingerGold): 43%bloom (Bosc): 73%bloom(RedDelicious): 80%pink Cherry(Smoothie): 94%pink (BlackPearl): 83%petalfall(Empire): 56%bloom (EbonyPearl): 75%bloom(Zestar): 70%bloom (Regina): 86%bloom(JerseyMac): 60%bloom Peach 87-100%petalfall(Honeycrisp): 52%kingbloom(BrookfieldGala): 69%pink