****Important ****
Please note that the Update points out that the New England Apple Pest Management Guide is in conflict with the label of certain oil spray products commonly used pre-pink for European Red Mite management. The label is the law. Disregard any use listed in the Guide that is inconsistent with the label. Check the label of the oil product that you wish to use this season. It has come to our attention that some labels (e.g., Sunspray 6E, Spray Oil 6E) restrict use to "Dormant", "Delayed-Dormant", "Green Tip", or "1/2 Green".
Further note that the text under "Mite Management" in the UPDATE refers to the use of Apollo or Savey in combination with oil at tight cluster or early pink - - this would be in conflict with certain oil labels.
If you need a copy of the 1996-97 New England Apple Pest Management Guide, an order form is enclosed. There are a limited number in stock; they will be distributed on a first come, first servedâ basis.
Disease Management
Looking ahead at what we might expect for --
Apple Scab: One word can describe the 1996 growing season - - and that was WET. Some growers could not get into their orchard last spring to put on their first fungicide application when they wanted because the orchard floor was just too wet. And the wet weather during the remainder of the growing season was very favorable for scab development. Just how wet was it?? Based on our monitoring of infection periods, there were approximately 8 primary scab infection periods and 16 secondary scab infection periods in 1996 - - compare that to a total of 13 primary and secondary infection periods in 1995. In general, in Vermont and across New England and New York, more growers will be entering the 1997 growing season with a higher scab inoculum potential than what they have had in the past.
At this point in time, how can you reduce the amount of overwintering inoculum? There are two "sanitation" techniques developed and tested by Dr. Bill MacHardy and his colleagues at the University of New Hampshire. They are:
(1) a 5% Urea spray (42 lb. Urea/100 gal. water) applied to the leaf litter at 100 gal./A so that the leaf litter is thoroughly wet. This should be applied after snow melt but before bud break.
(2) flail mowing of leaf litter as soon as possible after snow cover is gone.
These practices can decrease the potential ascospore inoculum by 50-75%. This means that for any one infection period, there would be approx. 50-75% fewer scab lesions compared to the number of lesions that would develop if there had been no sanitation practice. Note that these practices are NOT a substitute for early season fungicide applications in moderate or high inoculum orchards but should be viewed as a cautionary measure if an infection period is inadvertently missed or there is poor spray coverage.
On the topic of the Potential Ascospore Dose or PAD, if you were using a SI fungicide program in 1996, we advise that you do not use the PAD threshold as described in the Guide. As was reported in January during the presentation on the results of the 'Whole Farm Apple Scab Integrated Pest Management' project at the New England Fruit School, Sturbridge, MA, questions have arisen on the potential impact of using an SI program on overwintering inoculum. In the two orchards that were on a SI program during the previous season, it is suspected that foliar scab was inhibited and not killed and that the lesions present in the autumn did not fully represent the latent infections that were actually present in the leaves. Thus, the PAD would underestimate the overwintering inoculum because not all foliar infections would be expressed as visible lesions at the time of assessment. Until we know more about the potential impact of a SI program on overwintering inoculum, we advise that you do not use the PAD threshold as outlined on page 13 of the Guide in SI blocks.
As is always the case, it would be good to take a few minutes before the season begins to review pages 7- 15 of the Guide which outline scab management strategies and information on ascospore maturation and infection.
Fire Blight (FB): In Vermont, it is very difficult to predict when this disease will cause significant damage. Almost every year, as one travels around the state, you can see a strike (i.e., a vegetative shoot that has become infected) here or there - - something that is easily pruned out as you walk through the orchard. In the past 12 growing seasons, the disease has caused extensive damage in only two orchards in the state of which we are aware. In 1991, a block of 13 year old Paulareds on M26 was hard hit with FB to the extent that the orchardist was contemplating pulling out the block, and last year, in 1996, an orchard with a number of cultivars on M 26 had extensive damage. In this orchard, 20 year old Macouns, McIntosh, Cortland, Gravensteins, Delicious, Empires, Golden Delicious plus Mutsu (Crispin) and Macouns trees in their fourth leaf had severe blossom and shoot blight.
What are some of the factors that increase your risk of fire blight?
(1) Susceptible Cultivars - - Please refer to Table 7 in the New England Apple Pest Management Guide for the ratings of susceptibility of the major cultivars. Note that Paulared, Fuji, Braeburn, and Idared are considered very susceptible to FB. Also note that a moderately susceptible cultivar such as Macoun or Red Cort becomes more susceptible on susceptible rootstocks.
(2) Susceptible Rootstocks - - M.9, M.26, and Mark rootstocks are considered very susceptible to FB.
(3) Succulent growth - - The bacterium that causes FB enters the plant through natural openings or wounds. Succulent tissue is tender and prone to injury in wind; it also is attractive to sucking insects such as aphids and leafhoppers, which can spread the bacteria.
(4) Inoculum Level - - The bacteria overwinters in cankers. If you had FB last year, you should examine your trees and cut out dead wood and cankers during winter pruning.
(5) Conditions favorable for infection - - The general weather requirements for blossom infection to occur are: the average of the high and low temperature of the day was 65 F or higher and relative humidity was at or above 60%. Dr. Paul Steiner at the U. of Md. developed a computer program called Maryblyt that rates the risk of fire blight blossom blight. The program assumes the bacterial pathogen is present and identifies an infection period when four requirements are met: (1) flowers are open; (2) at least 198 degree hours greater than 65F have accumulated after first bloom; (3) at least 0.01"rain or dew that day or at least 0.10" of rain fell the day before; and (4) an aver. daily temp. equal to or greater than 60F. When all of these conditions are met in sequence, the first symptoms of blossom blight is predicted to occur when an additional 103 degree days have accumulated (base 55F). The risk of infection is considered Îlowâ when one factor is present; Îmoderateâ when two factors are present; Îhighâ with 3 factors; and infection occurs when all 4 factors are present. We have been monitoring conditions at the UVM Hort.Res.Center for the past few years using the Maryblyt program. The following are the number of days during the bloom period of each year when the risk for infection was highâ and the number of days when all the factors were present for infection to occur.
1990 - 3 high risk days, 0 infection day 1991 - 4 high risk days, 1 infection day 1992 - 6 high risk days, 0 infection day 1993 - 4 high risk days, 2 infection days 1994 - 3 high risk days, 0 infection day 1995 - 1 high risk day, 1 infection day 1996 - 1 high risk day, 4 infection days
You can see that last year we had more infection days than the past 6 years combined but luckily for the industry as a whole, we did not see extensive disease except in one orchard. However, more FB was observed around the state which means that the potential carryover inoculum is greater this year. Weather conditions should be monitored closely during bloom to determine the risk of infection - - that coupled with the other risk factors listed here will help to determine your overall risk for this disease.
A Review of FB Management Options - -
Dormant Period
Remove Cankers
Growing Season
Silver Tip - 1/4" GT
Copper Spray (see pp. 100-101 of New Eng. Apple Pest Management Guide)
Bloom
Monitor temperature, rain, and relative humidity to determine conditions for infection
Streptomycin spray - - the following are some brief notes on the use of this material
*Timing is everything
*A spray will protect only blossoms that are open at time of application, providing 3-4 days of protection to those blossoms
*Can provide effective control if applied to a blossom within 24 hours after start of infection.
*must be absorbed by blossom; do not apply before or during rain
*need thorough coverage
*resistance concerns - limit use
Post- Bloom
Look for signs of infection (e.g., blossoms and/or shoots wilting, having a water soaked appearance; bacterial ooze, etc.)
Should you cut out the infected shoots? It depends on the degree of infection - - whether it is actually feasible given the number of strikes per tree, whether cutting out many strikes would stimulate further growth, whether cutting out infected shoots on young trees would help deter infection of central leader, etc. Please note the description of the "ugly stub" procedure for cutting out infected tissue on page 22 of the New England Apple Pest Management Guide.
The bottom line is to be aware that fire blight is a serious disease. It is important to assess your risk and know your management options.
An Additional Note on Fire Blight . . . Influence of Nutritional Factors
The following is an article written by Dr. Warren C. Stiles, Cornell University, entitled: "Nutritional and Other Factors Influencing Susceptibility of Trees to Fire Blight". It is reprinted here from SCAFFOLDS Fruit Journal, Vol. 6., No.1, March 24, 1997.
The high incidence and severity of fire blight that developed during the 1996 growing season has prompted concerns about the relationship between nutritional factors and this disease. It may be pertinent, therefore, to review some of its relationships with nutrition and other environmental factors that have been determined over the last 50 to 60 years.
SOIL TEXTURE. Several reports indicate that "heavy" poorly drained soils are more conducive to fire blight development than are well-drained coarser-textured soils. This difference is largely due to two factors: higher reserves of readily available nitrogen and higher water-holding capacity of the "heavier" soils. Both of these factors promote more succulent growth that is more susceptible to blight infections, not only during the spring but throughout the growing season.
SOIL pH, CALCIUM AND MAGNESIUM. Generally, fire blight severity is greater on acidic soils that are low in calcium and magnesium. Some workers suggest soil pH be maintained in the range of pH 5.5 to 6.5. We presently recommend maintaining the subsoil above pH 6.0 and the topsoil 6.5 to 7.0. Inadequate levels of calcium and magnesium, either in the soil or in the tree tissues, have been associated with increased susceptibility of trees to blight. Excessive nitrogen fertilization or availability, through its effect of stimulating excessive growth, is one of the major factors limiting levels of these elements in the tree. Maintaining soil and leaf contents of calcium and magnesium within presently recommended levels should minimize problems associated with inadequate supplies of these elements.
NITROGEN AND TREE VIGOR. Nitrogen status of the trees is consistently cited as a primary factor in blight susceptibility. This is a primary concern under New York State conditions. Excessive nitrogen stimulates excessively succulent growth that favors fire blight infection. This is a serious problem, particularly in young trees of blight-susceptible varieties that are being "pushed" with nitrogen in order to fill allocated space as rapidly as possible. Effects of excessive nitrogen can, in some cases, be moderated somewhat by increasing potassium, calcium and magnesium supplies. However, this approach is not likely to eliminate the problem. Maintaining a moderate nitrogen status and growth of the trees should be preferable to the alternative of losing the plantings to blight. Leaf nitrogen levels should be maintained no higher than 2.0 to 2.4 percent at normal sampling time, depending upon the variety, for both apples and pears if fire blight is of concern. Application of foliar sprays of nitrogen have been shown to increase the susceptibility of blossoms to fire blight and should not be used in orchards where blight potential is high.
POTASSIUM. Several studies have shown greater susceptibility of trees that are low in potassium. Our suggested levels of 1.35 to 1.80% appear to be in the optimal zone for minimizing susceptibility. Also, we must consider the Nitrogen/Potassium balance, and again our suggested ranges appear to be within reason. I am not aware of studies of the potential
effectiveness of potassium sprays as a supplement specifically with reference to fire blight.
MICRONUTRIENTS. There is little definitive data on relationships of levels of micronutrients to blight susceptibility. However, leaf tissue concentrations that we currently recommend fall within the ranges suggested in at least one report. In one study, low levels of boron in nutrient solutions were associated with reduced susceptibility to blight inoculations, but this effect appears to have been related to significantly reduced tree growth. Other reports suggest that leaf boron should be between 30 and 50 ppm. We suggest 35 to 50 ppm. It should also be stressed that the use of Bordeaux mixture (8-8-100) with oil between swollen bud and bud burst stages is still recommended as an effective treatment in blight infested orchards.
SUMMARY. Soil and nutritional factors that influence tree vigor can have significant effects on incidence and severity of fire blight in apple and pear trees. Avoiding excessive tree vigor and maintaining adequate levels of all essential nutrient elements as indicated by soil tests and leaf analyses appear to be the best approach in managing nutrition to minimize blight potential.
Arthropod Management
A Reminder . . . Silver Tip is the time to place traps in the orchard to monitor the following pests:
Tarnished Plant Bug - - white sticky traps hung at knee height
Thresholds:
- a cumulative 3 TPB/trap from Silver Tip to Tight Cluster or 5 TPB/trap from Silver Tip to Late Pink for Wholesale Market (mainly extra fancy fruit)
- a cumulative 5 TPB/trap from Silver Tip to Tight Cluster or 8 TPB/trap from Silver Tip to Late Pink for Retail Market (mainly #1 fruit)
Leafminers - - red rectangular traps on tree trunk at knee height
Thresholds: (Note: Work in Massachusetts suggests that the following thresholds apply to apple blotch leafminer and less so to spotted tentiform leaf miner. Vermont has both types of leafminers; at this point we do not have the details of species composition around the state.)
- For McIntosh - - a cumulative average of 4 moths per red trunk trap from Silver Tip to Tight Cluster or 9 moths per trap by Full Pink.
- For non-McIntosh trees - - a cumulative average of 8 moths per trap by Tight Cluster or 21 moths/trap by Full Pink.
Good News - - A New England-wide Apple IPM project Receives USDA funding
A project entitled: "AIM - - an interactive, dynamic, Apple Information Manager for New England" has received funding from the USDA IPM program. The goals of this two-year project are:
(1) Enhance apple IPM implementation in all six New England states by developing the Apple Information Manager (AIM) -- a New England Apple IPM site on the World Wide Web (WWW) that will exploit the ability of the WWW to serve as a comprehensive, frequently updated channel for transmitting information to, from, and among growers, industry service providers, and university personnel. AIM will provide apple growers and their advisors (i.e., IPM consultants) with access to communication functions, resource material, research reports, weather data, and daily updates of site-specific apple IPM decision support models. AIM will also serve as a "real-world" resource to students studying IPM.
(2) Compare relative performance of major apple pest decision support models using remotely generated virtual weather data versus weather data collected on site. This comparison will evaluate the potential of private sector site-specific virtual weather data for making key on-farm IPM decisions.
(3) Increase awareness and knowledge among New England commercial apple growers of WWW IPM resources and capabilities, and develop a participatory process to fully utilize this powerful new tool for education and information transfer to facilitate more extensive and intensive IPM adoption.
Project Participants/Cooperators include:
State University Participants Grower Cooperators Vermont L.Berkett , J.Clements, G.Demong, J.Gallot G.Neff Maine G.Koehler, J.Dill, J.Schupp R.Markley, E.Bunting, H.Ricker New Hampshire W.MacHardy E.Goodband, E.Leadbeater Massachusetts D.Cooley, R.Prokopy T.Clark, M.Tougas Connecticut L.Los, D.Kollas J.Bishop, J.Lyman, T.&S Muska Muska Rhode Island H.Faubert, L.Tewksbury J.Steere, P.Lamore
In addition to the growers listed above, we welcome and encourage your involvement in this project, which begins a new era of regional collaboration and application of technology to IPM information transfer and education delivery. We want your participation in shaping this Web site over the next two years. If you are not already hooked up to the Internet, a good resource to walk you through step by step is the book:
The Farmerâs Guide to the Internet By Henry James
Published by TVA Rural Studies
400 Agricultural Engineering Bldg.
The University of Kentucky
Lexington, KY 40546-0276
The cost of the book is $19.95 (plus shipping and handling) and can be ordered by writing to the above address or by calling 606/257-1872.
As stated in The Farmerâs Guide to the Internet, you will need the following to start using the Internet:
- A computer, modem and regular phone line
- The services of an Internet Access Provider or online service
- The Internet Access Provider or online serviceâs access telephone number
- Internet communications software (Trumpet, SLIP, or PPP)
- Internet application software (Eudora, Mosaic, or Netscape)
The book gives helpful, straightforward advice on each of these points.
We are looking forward to your input and involvement into the AIM project ! The new AIM Web site will be http://orchard.uvm.edu/AIM/
Update on UVM's Extension Fruit Specialist Position . . .
We are seeking a dynamic extension specialist who will continue to develop an integrated extension and applied research program that will serve the needs of Vermont's apple industry and contribute to the advancement of horticultural knowledge. The Department of Plant & Soil Science was not successful in filling the position with any of the top candidates that were brought to Vermont to be interviewed last summer. Although the situation is frustrating because we are eager to move ahead, this delay is not unusual when the goal is to hire the very best candidate for the position. The Search Committee is presently reviewing a new pool of national applicants. We will keep you posted on the status of the search and invite you to meet with the candidates when they are brought here to interview.
Member of the UVM Apple Team is graduating and "moving on" . . .
For the past two years, Terence Bradshaw, an undergraduate student in UVMâs Plant & Soil Science Department, has been a valued member of the UVM Apple Team. He has made significant contributions to the numerous research and extension projects that have involved the UVM Hort.Res.Center and commercial orchards around the state. We sincerely thank him for his hard work and dedication. In addition to his accomplishments with the apple program, Terry was awarded the W.H.Darrow Horticultural Prize last year and has been nominated to receive the C. Lyman Callahan Award this year. Terry will be graduating in a few weeks and has accepted a position as assistant manager of Tougas Family Farms in Northboro, MA, which produces apples, peaches, small fruits and pumpkins. We wish Terry much success·. he will truly be missed on the Apple Team. However, we will await his return to Vermont as an apple grower - -Terry has ordered apple trees for his family farm in Chelsea and has interesting plans for the future!! Best Wishes!!
The 1997 UVM Apple Team . . .
We remain committed to meeting the research and extension needs of Vermont's apple industry as best as we can. We look forward to having a new Extension Fruit Specialist here in Vermont as soon as possible. We do want to announce that a new undergraduate student, Roger Brouillette, has joined the UVM Apple Team.
Again, we greatly appreciate your continued support during this period of transition.
The following are our current phone numbers and e-mail addresses. Please do not hesitate to contact us with your questions or comments. Our mailing address is: Dept. of Plant & Soil Science, Hills Building, University of Vermont, Burlington, VT 05405-0082.
Lorraine Berkett 656-0972 lberkett@zoo.uvm.edu
Jon Clements 656-2924 jon.clements@uvm.edu
Gwendolyn Neff 656-0486 gneff@zoo.uvm.edu
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Where trade names or commercial products are used for identification, no discrimination is intended and no endorsement is implied. Always read the label before using any pesticide. The label is the legal document for the product use. Disregard any information in this newsletter if it is in conflict with the label.