Thursday, October 6, 2022

Postdoc Position in Horticulture and Plant Pathology


Postdoctoral Research Scholar in Horticulture and Plant Pathology

Available January 1, 2023:  Postdoctoral opportunity with a focus on vegetable horticulture and plant pathology.  This hybrid position includes a 50:50 split between laboratory and field research.  Principal project involves solarization as a means of managing soilborne pathogens such as Sclerotinia spp. and root knot nematodes.

This position can provide opportunities for independent ideas and contributions to a collaborative research and extension team.  A self-motivated candidate will have opportunities to learn new skills while working with diverse students, staff, and faculty in two interrelated disciplines. It also provides opportunities for applied research and first authored publications, particularly for a candidate who is interested in an extension career track.

Candidate must have an understanding of field plot design, execution, and analysis of field data. Field research experience is required, particularly in specialty crop production.  Candidate must also have basic pathology experience and proficiency in morphological and molecular pathogen identification, as well as ability to conduct conventional assays and experiments.    

PhD in horticulture or plant pathology is preferred, but experience in both fields is required.  Candidate must be able to work independently and creatively in a fast-paced environment.  Organizational skills and time management are a must.  Candidate must be agile and be willing to schedule time-sensitive tasks with regular research projects.  Excellent written and oral communication skills are mandatory, candidate should communicate regularly with the entire team, and research results should be published in a timely manner.  There will be opportunities for several first-authored publications for a motivated individual.  Candidate must be able to work with a diverse team, including interdepartmental collaborators, graduate students, and farm staff.  Ability to work without supervision is critical.  

This position is located at the University of Kentucky campus in Lexington. 

Salary $47,800.
Appointment 2 to 3 years, renewed annually, based on performance and grant funding.

To apply, send a CV, cover letter describing research experiences, example publications, and names/contacts of at least 3 references to Rachel Rudolph and Nicole Gauthier

Tuesday, February 22, 2022

Disease Management for High Tunnel Spring Tomatoes in Kentucky


Disease Management for High Tunnel Spring Tomatoes

By Dr. Nicole Gauthier and Dr. Rachel Rudolph


 Example management schedule assuming:

Week 1 (~April 1) transplant

Week 9 (~June 15) harvest

Week 16 (~Aug 15) crop termination



If tunnel has a history of timber rot (Sclerotinia spp), apply Contans pre-plant (see label)

Rotate out of tomato on a 3-year schedule, especially for sites with history of soilborne diseases

Space plants for maximum air circulation


Weeks 1-8 Vegetative Growth

Maintain RH <70% by opening end or side walls for air circulation! This is the most critical step for disease prevention and control.  If above 50 degrees F outside, it is safe to open the tunnels without damaging tomatoes. Install at least one humidity meter in each tunnel.

Sucker and prune tomato plants early while suckers are small to avoid creating open wounds. Use clean tools.

Practice good sanitation, remove diseased or senescing tissue regularly, remove clippings from tunnel.

Use preventative fungicides for bacterial and fungal diseases:

·         Low input:  Every week or two weeks (choose one or rotate)

o   OxiDate or ZeroTol or

o   OSO + copper or

o   Dexter Max (or mancozeb + copper)

·         Mid/high input:  Every week or two weeks, rotate among

o   Dexter Max (or mancozeb + copper)

o   Fontelis or Quadris Top*

·         Add targeted products, as needed, based on diagnostic results.

·         For timber rot, use Fontelis or Endura during April and May according to label.

·         For Botrytis gray mold, target applications in April and May.


Weeks 9-15 Harvest

Maintain RH below 70% all season.

Practice good air circulation. Unless there is extreme wind, the tunnel should be pretty much open all the time during this time period.

Sanitation is critical.

Continue fungicide applications:

·         Low input, every two weeks; mid/high input, every week

o   OxiDate or ZeroTol (0d PHI)

o   Optional, add Fontelis or Quadris Top* into rotation (0d PHI)

·         For leaf mold, target applications June/July through harvest


*Maximum 5 applications per season

Always read labels for specific use instructions

See spray guides for efficacy data.

Reminder:  From a pesticide application standpoint, high tunnels are considered greenhouses according to the Kentucky Department of Agriculture; use only greenhouse-approved products. If the label says that it is not permitted for use in a greenhouse, it is not permitted for use in a high tunnel.

Tuesday, January 23, 2018

Orchard Math

Orchard Math 101:
For Proper Spray Application

1.  Calculate GPA (gallons per acre) for the specific orchard. 

Begin with Tree Row Volume (TRV).  Refer to diagram on page 3.

TRV  =  Tree diameter (ft) x Tree height (ft) x 43,560
                                                      Row spacing (ft)

Use TRV to determine Gallons per Acre (GPA).  A dilute constant* should be selected:  0.5 for bare trees, 0.7 for sparse trees (minimum), or 1.0 for dense canopies (maximum).

GPA  =  TRV x (dilute constant*)
                                              1,000 cu ft

Proper GPA should give good coverage without over-dosing or under-dosing.  Refer to page 3 for recommended adjustments.

2.  Select appropriate nozzles to deliver proper gallonage. 

Convert GPA to Gallons per Minute (GPM).  Note:  For tractors without a speedometer, MPH calculation on page 3.

GPM  =  GPA x MPH x Row spacing (ft)

GPM is the total gallonage needed.  Now, divide by the number of nozzles.

GPM per Nozzle  =  _____GPM_____
                                                          Number of nozzles

Choose individual nozzles based on the GPM per Nozzle.  Know pump PSI (have a gauge).  Hollow cone nozzles are recommended for canopy sprays (airblast).  Hollow cone nozzles produce appropriate size droplets for canopy applications.  Flat fan nozzles are used for herbicides.  Ceramic nozzles are most resistant to abrasion and corrosion.  They are worth the extra cost.

See example Tee Jet selection guide below.

Check coverage and drift.  Calibrate sprayer.  Refer to recommended adjustments section below.

Check coverage, deposition, and drift.  Some recommendations include:

ü  Deposition should penetrate tree canopy but not blow through to the next row.
ü  Monitor deposition with water sensitive paper or photo paper, attach to poles in the center of tree row, stapled upward every 12 inches.  Also, use water sensitive paper in next row to monitor blow through and drift.
ü  Droplet size should be fine, but not aerosol.  If droplets are too big (>300µm), they will bounce from leaf surfaces.  If droplets are too small (<150 µm) they will drift without sticking.  Hollow core nozzles produce droplets within ideal range.
ü  Droplets density (droplets per cm2) should range from 20-30 droplets per cm2 for insecticides and 50-70 droplets per cm2 for fungicides.  There should not be streaks or overlapping spots.  Refer to label.  Sample data sheet from water sensitive paper attached (page 4-7).
ü  Adjust nozzle direction for best coverage.  Monitor by using poles with flagging (air direction) for even coverage.  70% of spray should cover the top half of the canopy.  30% of the spray should reach the lower half of the canopy.
ü  Calibrate sprayers annually by 1) confirming tractor speed (MPH), 2) calculating nozzle output (see page 1), and 3) checking nozzle outputs (see book Effective Orchard Spraying).  Error up to ±5%, adjust pump pressure or tractor speed.  Error over ±10%, replace nozzles.
ü  Most orchard pumps are too large for modern canopy architecture.  Ideal pressure is below 150 psi, but centrifugal pumps range from 150 to 200psi.  Diaphragm pumps have a wider range of adjustment, but they are more expensive.  It is critical to have a gauge to measure psi. Lower pressure by adjusting fan blade pitch, adjusting fan speed via PTO or separate pump.  Keep pressure as low as possible; high pressure creates horseshoe vortex and boundary layer.
ü  Adjust air volume via reducing intake (wooden donut) or reducing outlet (louvers) to eliminate blow through.
ü  Run a constant speed; faster travel speed causes turbulence.
ü  Calibrate nozzles and check for wear.  Change nozzles if ±10%.  Clean tank and nozzles often.
ü  Miles per hour (MPH) can be calculated by marking a 100 ft row, using a stopwatch to time the drive run, and then calculating    MPH  =  ­­­­___100 ft row x 60­­__
                                                     Seconds traveled x 88

Example:  from Syngenta website

Water-Sensitive Paper
What is water-sensitive paper?
Water-sensitive paper is a rigid paper with a specially coated, yellow surface which will be stained dark blue by aqueous droplets impinging on it. It has been developed for field use by Syngenta for the quick evaluation of LV sprays. For droplet assessment, aqueous sprays no longer need the addition of dye. Just place the papers in the target area before spraying. Following exposure to the spray the water-sensitive papers will be stained. Retrieve the papers as soon as they have become dry. Check the droplet pattern. For a quick estimate compare the exposed collectors with a known standard or count the droplets either using a hand lens or an automatic image analyzer.
Water-sensitive paper after exposure. (Courtesy Spraying Systems Co.)

Where to use it
Water-sensitive paper can be used for checking spray distribution, droplet density from aerial and ground spray applications and droplet sizing. 
Overdosing is a waste of product. With herbicides, it might result in crop damage and claims. With insecticides underdosing might not kill the pest. Calibrate the sprayer and check the spray pattern. Water-sensitive paper helps you to keep the environment clean.
Airblast sprayers in orchards: staple water-sensitive paper directly onto leaves at the periphery and inside the canopy at the top, in the center and lower part of the trees.

Number the collectors consecutively before placing them on the supports. This will help you to spot irregularities in your spray system when evaluating the exposed cards. 
The correct boom height can also be determined with water-sensitive paper. Insufficient overlapping of the spray pattern can be corrected by raising the boom. Excessive overlapping is leveled out by lowering the boom.

Visual assessment of droplet densities
Compare your spray samples with some known standard. The standard cards below and on the following page cover the range of acceptable droplet densities for coarse and medium LV spray. The droplet density in the target area should not be less than:

For routine checking of sprays you might also prepare your own standard cards by selecting spray cards with known droplet densities from previous spray operations.
Standard cards with a known droplet density per cm square
Computer-plotted standard cards displaying the expected number and sizes cards spraying at 3 different volume rates (20, 30, 40 l/ha) and using 3 different droplet spectra (VMD, 200, 300) assuming waters sprayed and the spread factor is two.

This handout was produced for the
 Kentucky Extension IPM Implementation Program, Fruit Crops Working Group
                By Nicole Gauthier, Extension Plant Pathologist and Ric Bessin, Extension Entomologist.

Assessing and Utilizing UK Extension Resources
Commercial Fruit Production

College of Agriculture publications website

Departmental sites (publications, fact sheets, videos)
                Ag Economics
                Biosystems Engineering (Ag Weather)
                Center for Crop Diversification                             
                Plant Pathology
                Plant and Soil Sciences

                Fruit Facts
                KY Pest News

Email Alerts (listserv)
                Contact Chris Smigel
                 Separate list servs for apple, peach, grape, blueberry, strawberry, brambles

Apps and Models
                Ag Models (Ag Weather)
                Disease and Insect Models (mobile version)    
                Scouting Guides (mobile version) and                                                             
Social Media
                Ag Weather
                Diseases of Ornamentals, Fruit, and Hemp
                Spotted Wind Drosophila in KY
                UK REC Hort
                UK Robinson Center
                University of Kentucky Ag Programs
                Center for Crop Diversification
                UK Extension @UKExtension
                UK Ag Weather Center @UKAGweather
                Ky-Bugs @KyBugs
                Southern IPM Center @southernipm
                Nicole Ward Gauthier @Nicole_WardUK
Lab Services
                Plant Disease Diagnostic Laboratory (free) submit samples through county extension office
                Soil Testing (fees vary) submit through county extension office.
                Food Systems
County Agents

                UK Extension Service 

Wednesday, December 7, 2016

Cold Temperatures Pose a Risk to Kentucky Strawberries

Chris Smigell, Extension Associate for Small Fruits/Vegetables, 
University of Kentucky  

A cold front forecast for Thursday night may bring temperatures down to 18-19 ºF for all of Kentucky.  Strawberry plants are not fully dormant by now, so it is important to have some frost protection in place.  

We recommend  applying straw over matted row strawberries when the air temperature first drops into the low 20ºs F.  Mulching actually has several benefits:

  • Protects the plant roots from frost heaving. Cycles of freeze and thaw, lift the soil and plants.  This can break roots off,  especially the very smallest root hairs, that are critical for nutrient uptake.  This reduces berry size and yields.
  • Protects the plant crowns from winter injury. Fully dormant buds in crowns are hardy down to about 10º F, but it takes several freezes and consistent cold to fully harden the plants.
  • Minimizes plant desiccation due to winter winds.
  • Minimizes risk of black root rot  

A standard  straw bale should cover about 50 square feet of bed. A 3-inch layer of straw on an acre requires 3 tons of straw.

Leaves are not recommended. They tend to mat down which  can cause rotting and limit light penetration in the spring.

Frost heaving is less common on coarsely-grained soils. Clay-based soils are finely grained.   Any practice that helps drain the soil, such as adding organic matter, trenching, or tiling, helps reduce the risk of heaving.

It can take temperatures much lower than 32  to freeze all of the water in soil, depending on soil type. Thus  even an inch of straw can help reduce the percentage of water frozen in a soil profile, and the less freezing, the less the amount of heave. The following article describes the frost heave process. 

Here's a guide to correctly applying mulch. (photos by John Strang)




Applying plastic mulch in plasticulture systems is a multi-person job, so line up a few helpers, and set out mulch and weights to hold down the sheets ahead of time. Rock bags tend to work better than sod staples or cinder blocks which can tear the fabric. Plasticulture growers that are using lighter weight covers (.5-.75 oz/square yard) could apply one layer now to help protect the plants and then follow up with a second application later in the month or early next year when the extended bitter cold temperatures usually begin.

"Why not just put down straw or apply row covers well ahead of any critically low temperatures?"   Covering plants too early (late October, early November) can prevent late plant growth on those sunny days when temperatures are in the higher 50's. Second, plants need to be in full dormancy once winter really sets in. It takes several freeze cycles and cold soil  to bring plants into full dormancy.  This process will be delayed by applying mulch or cover too soon.  Generally by late November, it is safe to do so. Plant color is another guideline - strawberry leaves should have a grey-green appearance, indicating onset of dormancy.

Tuesday, June 28, 2016

Using Resistant Cultivars to Manage Strawberry Diseases

From the Midwest Small Fruit Pest Management Handbook

In any IPM program, the use of resistant cultivars is an important consideration.  Many commercial cultivars have resistance and/ore tolerance to leaf spot, leaf scorch, red stele, and powdery mildew.  The more resistance within a program, the better.  Table 21 (page 27) lists ratings for disease resistance in several of the more commonly grown strawberry cultivars.


Thursday, May 5, 2016

Calibrate your sprayer now—Here is an easy way to do it 

From Erdal Ozkan, Professor and Extension Agricultural Engineer, The Ohio State University
Originally published as part of The Ohio State University Extension Vegetable and Fruit Newsletter Vol. 23 Number 3, May 3, 2016

Spraying season is just around the corner. Now is the time to pay attention to your sprayer. First, check all the components of the sprayer to make sure they are in working order. The next step in preparations for the season is to calibrate the sprayer. The only way you can achieve maximum accuracy from a sprayer is by calibrating it once before the spraying season starts, and recalibrating it frequently throughout the spraying season. While applying too little pesticide may result in ineffective pest control, too much pesticide wastes money, may damage the crop, and increases the potential risk of contaminating ground water and environment. The primary goal with calibration is to determine the actual rate of application in gallons per acre, then to make adjustments if the difference between the actual rate and the intended rate is greater or less than 5% of the intended rate. This is a recommended guideline by USEPA and USDA. Before starting calibration, make sure you have a good set of nozzles on the sprayer. Nozzles wear off through extended use, causing over application, or some nozzles may become plugged. Clean all the plugged nozzles. Check the output of all the nozzles for a given length of time at a given spray pressure. Compare output from each nozzle’s output with the expected output shown in the nozzle catalog for that nozzle at the same pressure. Replace the nozzles showing an output error of more than 10% of the output of the new nozzle. Once you do this, now you are ready to calibrate your sprayer. Calibrating a boom sprayer is not as difficult as it sounds. There are several ways to calibrate a sprayer. Regardless of which method you choose, only three things are needed: a timer (or watch or smart phone timer app) showing seconds, a measuring tape, and a jar graduated in ounces. Here, I will describe perhaps the easiest of all the methods to calibrate a sprayer.

Photo: Nicole Gauthier, University of Kentucky

To calibrate a boom sprayer for broadcast applications using this method, follow these steps:

1. Fill the sprayer tank (at least half full) with water.

2. Run the sprayer, inspect it for leaks, and make sure all vital parts function properly.

3. Measure the distance in inches between the nozzles.

4. Measure an appropriate travel distance in the field based on this nozzle spacing. The appropriate distances for different nozzle spacing is as follows: 408 ft. for a 10-inch spacing, 272 ft. for a 15-inch spacing, 204 ft. for 20-inch spacing, 136 ft. for a 30-inch spacing, and 102 ft. for a 40-inch spacing.

5. Drive through the measured distance in the field at your normal spraying speed, and record the travel time in seconds. Repeat this procedure and average the two measurements.

6. With the sprayer parked, run the sprayer at the same pressure level and catch the output from each nozzle in a measuring jar for the travel time required in step 5 above.

7. Calculate the average nozzle output by adding the individual outputs and then dividing by the number of nozzles tested. The final average nozzle output in ounces you get is equal to the application rate in gallons per acre. For example, if you catch 15 ounces from a set of nozzles, the actual application rate of the sprayer is equal to 15 gallons per acre.

8. Compare the actual application rate with the recommended or intended rate. If the actual rate is more than 5 percent higher or lower than the recommended or intended rate, you must make adjustments in either the spray pressure or the travel speed or in both. For example, to increase the flow rate you will need to either slow down, or increase the spray pressure. The opposite is true when you need to reduce the application rate. As you make these changes, stay within proper and safe operating condition of the sprayer. Remember increased pressure will result in increasing the number of small, drift-prone droplets.

9. Repeat steps 5-8 above until the recommended application error of +5% or less is achieved.