Disease management in high tunnels and greenhouses Downy and powdery mildew on squash ANR East Update Clark Co., KY October 26, 2016 Emily Pfeufer Ph.D. Extension Plant Pathologist Vegetables and Tobacco University of Kentucky Leaf mold on tomato

Today’s topics Fungicides in protected structures Principles of IPM Powdery mildew Fungicides in protected structures Principles of IPM Labeled products Application frequency Fungicide application Small scale sprayers Nozzles and booms Pressure and coverage Calculating rates Late blight of tomato Summary and discussion

Plant disease occurs when a pathogen infects a susceptible host under conducive environmental conditions Botrytis spp. Fulvia fulva (Cladosporium) Pythium spp. TSWV Pathogen Excessive moisture Wet leaves Saturated soils Disease Plant host Environment Tomato Cucumber Greens High humidity Saturated media Plant nutrition

Protected ag structures provide an edge over the environment Benefits Temperature control (especially if there is a heating unit) Moisture control via irrigation Reduction in leaf wetness Higher-value produce Botrytis gray mold

Protected ag structures provide an edge over the environment Drawbacks Intermediate expertise needed: fertigation, varieties Higher humidity Soil quality issues Smaller equipment needed More expensive Insect and disease management differ

Using principles of IPM helps you get the most out of chemical applications Toxicity increases as you approach the top Chemical management is most effective when integrated with other methods Graphic from environtechgreenhouse.com

Products labeled for greenhouse / high tunnel use Protectant fungicides – prevent infection Copper Mancozeb Systemic fungicides – prevent infection and slow advance of colonization Groups 3, 7, 9, 11, etc. General modes of action: effective against many pathogens *Must be on plant surfaces prior to pathogen arrival for efficacy Specific modes of action: only work against certain pathogens *Taken up into plant tissue and move in some cases

Fungicides commonly used in KY greenhouses From ID-36, pg. 18

Fungicides commonly used in KY greenhouses Botrytis gray mold on greenhouse tomato Pfeufer Fungicides commonly used in KY greenhouses From ID-36, pg. 18

Application frequency and spray programs Most spray programs start by using a protectant fungicide on a regular schedule Low risk of resistance Manage wide range of pathogens Inexpensive Once a disease is identified, systemics are incorporated Higher risk of resistance Smaller range of affected pathogens More expensive -> How does fungicide breakdown differ between the field and the greenhouse?

Mancozeb inhibition of Alternaria spores on muskmelon leaves under dry conditions 85% inhibited after 9 days 50% inhibited after 29 days Suhari and Latin, 1991. Plant Disease 75: 1013-1015.

Copper fungicide retention on orange leaves and fruit Retention inversely associated with rainfall Deposition and persistence of cuprous oxide, copper hydroxide, and copper oxychloride were similar Residues were reduced 48 – 60% over 14 days, when 3 – 4 in. rain fell; very little residue loss without rain Schutte et al. 2012. Crop Protection 42: 1-9.

Penthiopyrad (Fontelis) uptake, retention, and efficacy in wheat leaves, against Septoria tritici 50% taken up in 3 hrs Surface residues significantly reduced after 5 days Fungicide retained in treated tissue 14 days Infection inhibited 28 hrs – 21 days Sweets, Univ. Missouri IPM Pils et al., 2011. Phytopathology 101:S141 and S142.

IPM for tomatoes in the greenhouse Consider biocontrols of virus-vectoring insects Eliminate condensation dripping from ceiling Remove last year’s debris, sanitize trellis materials Only use transplants that appear healthy Graphic from environtechgreenhouse.com

Greenhouse tomato spray program Modifications Transplanted March 1, expect to harvest until July Tighten application interval to 10 days if disease pressure mounts Weeks after transplanting 3 Mancozeb or copper 5 7 9 Fontelis or Switch or Quadris Top or Inspire Super Weeks during harvest 11 Copper 13 15 17 19 Introduce earlier if fungal leaf spot symptoms develop Do not use mancozeb during harvest; PHI = 5 days Choose a second systemic fungicide if intend to grow >4 mo.

Systemic fungicide options for greenhouse tomatoes: Choose 2 products with active ingredients from different groups Assign one as Specific fungicide 1, the other as Specific fungicide 2, then alternate with copper every 2 wks Labeled for greenhouse use: Fontelis (Group 7) Switch (Group 9 + Group 12) Pageant Intrinsic (Group 11 + Group 7) Scala (Group 9) Not prohibited for greenhouse use: Inspire Super (Group 3 + Group 9) Quadris Top (Group 11 + Group 3) Revus Top (Group 3 + Group 40) Example specific fungicides for rotation (not an exhaustive list!): Switch + Quadris Top Fontelis + anything but Pageant Intrinsic Scala + anything but Switch or Inspire Super

Questions / comments ? TSWV TSWV

Today’s topics Fungicides in protected structures Principles of IPM Powdery mildew Fungicides in protected structures Principles of IPM Labeled products Application frequency Fungicide application Small scale sprayers Nozzles and booms Pressure and coverage Calculating rates Late blight of tomato Summary and discussion

Basic components of a sprayer Adapted from Bell, Henderson, and Zalam, UC Davis

Selecting equipment for small scale applications

Small scale equipment comparisons CO2 backpack Blower/mister Electric backpack Hand pump backpack Pressure source Compressed gas Gasoline 12V battery and compressor Hand-powered Pressure consistency Good Average Poor Nozzle selection None Somewhat limited Appropriate for Fungicides, insecticides, herbicides, fertilizers Fungicides, insecticides Herbicides and fertilizers Approx. cost (R&D Sprayers; Gempler’s) $700 - $1200 $720 $135 - $1285 $70 - $350 Ease of use Intermediate Lower skill Lower skill-intermediate

Booms with spaced nozzles allow for better coverage of trellised plant foliage

Nozzles and accessories Fungicides are typically applied with hollow-cone or flat fan nozzles - Small orifices create finer sprays Water-sensitive paper is used to help evaluate spray coverage Sprayers101.com

Pressure and volume for vegetable fungicides Pressure: 30 – 50 psi Do not use higher pressure than nozzle rating Higher pressure, smaller droplets, better coverage Lower pressure, larger droplets, poorer coverage Field volume: 10 – 50 gal/A 1 gal / 1360 sq ft in greenhouse Depends on plant size: more volume for larger plants

Converting fungicide rates for greenhouses Greenhouses are much smaller in area than fields Fungicides labeled for use in the greenhouse often have a greenhouse rate listed For those without a greenhouse rate, a ratio calculation is necessary: Field rate / acre = Greenhouse rate / treated area EXAMPLE: Inspire Super is labeled for 16 oz / acre. 1 acre = 43,560 sq ft. The area of the greenhouse to be treated is 30 x 72 ft = 2160 sq ft 16 oz / 43,560 sq ft = x / 2160 sq ft

Calculating fungicide rates x = 0.79 oz (from previous page) Some growers use ‘teaspoons:’ there are 6 tsp in 1 fl oz 4.75 tsp = 0.79 oz Use a similar ratio to calculate the amount of water needed. 40 gal / 43560 sq ft = x / 2160 sq ft x = 2 gal water Fusarium crown and root rot

Test yourself: calculating fungicide rates Example 2: The fungicide rate for Quadris Top on field tomatoes is 8 oz / acre. The greenhouse is 22’ x 96’. Since the plants in the greenhouse are large, the grower wants to apply the equivalent of 50 gal / acre. What is the volume of water to apply? How much Quadris Top should be added? What would that be in tsp? 0.4 oz Quadris Top in 2.4 gal 2.4 tsp

Test yourself: calculating fungicide rates Example 3: The fungicide rate for Switch on field tomatoes is 11 - 14 oz / acre. The greenhouse is 30’ x 72’. Since the plants in the greenhouse are small, the grower wants to apply the low rate at the equivalent of 20 gal / acre. How much water is needed? How much Switch? What would that be in tsp? 1 gal water 0.55 oz Switch = 3.3 tsp Switch

Disease management in greenhouses isn’t easier, it’s just different Use IPM principles to get ahead of disease Fewer fungicide options are available for the greenhouse Fungicide applications can be stretched to 10-14 days in most cases Different equipment and rates are necessary Smaller sprayer Vertical boom (with flat fan nozzles?) Smaller aliquots and volumes Questions or comments? Emily Pfeufer, Ph.D. epf222@uky.edu (859) 218-0721

Gabriel Joseph Kelly Son of Andy Kelly and Emily Pfeufer Born 8/19/2016 6:26 am 8 lb, 11 oz 21 in. long