greenhouse sanitation jean williams-woodward extension plant pathologist uga
TRANSCRIPT
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GREENHOUSE SANITATIONJean Williams-Woodward
Extension Plant Pathologist
UGA
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Disease Triangle
WATER! (wet foliage or soils, high humidity, poor air circulation)
Stressed or injured plant
Capable of causing disease (many are host specific)
Host Pathogen
Environment
Disease
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Plant diseases are caused by…
• Fungi • Bacteria• Viruses• Nematodes• Phytoplasmas
• Aster Yellows
80%
10%
5%
5%
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Pathogens are spread by…
• Foliar pathogens:• Water• Wind• Insects• Grafting• Pruning/pinching• Vegetative propagation• Seed • Worker activity
• Soilborne pathogens:• Soil• Water • Insects• Plants • Seed• Worker activity
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Scouting for Plant Disease
• Disease control relies on prevention• You cannot cure a plant of a plant disease• You cannot manage diseases by reacting to symptoms
• The time between infection and symptom development may be 21 days or more
• By the time you see symptoms, it is too late to manage the disease on that plant
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What to look for…• Concentrate on entryways into greenhouse (doors, open vents, walkways)
• Concentrate on incoming plants• Look for out-of-the-ordinary plants
• Stunted• Off-color• Yellowing• Wilting• Browning• Distorted• Leaf spotting
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Diseases may be overlooked…
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Look more closely…
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Closer… Notice the defoliation, leaf spotting
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Downy mildew on Knockout Rose
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Turn leaf over and look for sporulation
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Botrytis blight
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Signs of wet environments
• Presence of fungus gnats and shore flies indicate high soil moisture• Insects can spread
root rot pathogens
• Algae growth on pots, soil, benches, etc. indicates high moisture environment
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Root disease
• Plant wilting, off-color, etc.• Pythium, Phytophthora, Rhizoctonia, Thielaviopsis
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• Damping off (both pre- and post-emergence)
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• Root death, sloughing, discoloration – WET substrate
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• Graded, gravel beds or ground-cloth covered gravel can reduce root disease incidence
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• Phytophthora and Pythium are water-molds• Require water to spread and infect.• Puddles saturate the rooting medium, as well as channel Phytophthora inoculum
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Phytophthora infected rhododendrons
• Discard dying plants quickly to reduce spreading disease to adjacent plants
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• Potential rooting medium contamination from cull piles or incorporation of non-composted material
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Home-made steam sterilizer
• Clean or sterilization rooting medium and containers is essential in reducing Rhizoctonia
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Bacterial slime/ooze
Xanthomonas bacterial wilt of banana
Ralstonia
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Acidovorax anthurii on Anthurium
• Scout for disease twice a week
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Scout plants, provide good air flow
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Drip irrigation to keep foliage dry
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Wash hands immediately after touching infected plants
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Sanitation!• Follow good sanitation practices• Use clean pots, rooting medium, benches, tools, etc.• Disinfest tools, benches, everything
• Bleach • quaternary ammonium• hydrogen dioxide
• Begin a habit of washing hands after handling infected plants
• Remove infected plants immediately• Inspect newly arriving plants – don’t bring in diseases
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Disease Management Principles
• Eliminate initial inoculum (pathogen survival)• Sanitation• Scouting for early detection
• Reduce pathogen spread• Water splash• Plant-to-plant contact• Wind dispersal• Vectors (insects, workers, tools)
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Use Fungicides to Increase Lag Phase of Epidemic
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No fungicideSpray #1Spray #2Spray #3Spray #4