introduction to pecan diseases and general...
TRANSCRIPT
Introduction to Pecan Diseases and General Management
Original Presentation by Damon Smith/Jen Olson
Modified and Presented by Jackie LeeHorticulture IPM Extension Specialist
Little Rock, AR
Contact InformationJackie LeeUniversity of ArkansasCooperative Extension Service2301 S. UniversityLittle Rock, AR 72204
501-671-2191 [email protected]
Infectious Disease Agents(Pathogens)
• FUNGI: cause the great majority of plant diseases; thousands have been reported
• BACTERIA: six genera are known to cause plant diseases
• VIRUSES: Submicroscopic obligate parasites• NEMATODES: small nonsegmented worms• PHYTOPLASMAS and SPIROPLASMAS:
submicroscopic obligate parasites• PROTOZOANS: motile microscopic animals• PARASITIC PLANTS: use feeding structures to
feed on plants
Fungi
• Most common of plant pathogens• Attack all plant parts• About 16,000 fungal plant pathogens• Unit of infection = spore or mycelium• Multi-celled• Visible, microscopically• E.g. Pecan scab, Powdery mildew• Spread by wind, splash, insects, water,
tools
Mycelium on leaf surface
SPREAD OF FUNGAL SPORES
•Air currents of 1 MPH or more can carry fungal spores long distances
•Spores often form during the night hours when humidity is high
•Become detached with dropping humidity in the morning hours as temperatures rise and air movement increases, and are borne aloft by convection currents created by warming of soil
Spore germination and infection
• Spores require high humidity for development (>90%)
• Spores require water film on the host tissue to germinate
• Many germinated fungal spores penetrate plant tissue directly, or enter through the leaf pores (stomates) or wounds.
• Most conidia can survive from several hours to several days if conditions necessary for germination are not met.
Fungi
Powdery mildew
Pecan scab
PecanHost
Pathogen Environment
Plant Disease Triangle
Example
Fungus: Cladosporium caryigenum
Periods of extended leaf wetness; cool to moderate temperatures
Pecan Scab
Manipulate the Host Component
Host
Pathogen Environment
Host
Pathogen Environment
• Genetic resistance most powerful disease management tool
• Native trees (fewer disease problems)• Plant stress management – Stress
predisposes plants to disease
Manipulate the Environment
• Do not over fertilize – many diseases are more severe when there is an excess of nitrogen available
• Reduce competition for water, light, nutrients
• Provide adequate air movement and light penetration
Host
Pathogen Environment
Host
Pathogen Environment
Reduce Amount of Pathogen
Host
Pathogen Environment
Host
Pathogen Environment
• Exclusion – Preventing the introduction of a pathogen (verify clean planting stock)
• Eradication – Constant observation and early diagnosis is critical
• Sanitation – Removing pathogen infested plant material from the area
• Pesticide Use
Pecan Scab
Jackie Lee, Horticulture IPM Extension Specialist
Pecan Scab Cycle
Fusicladium effusum
Fusicladium effusum
Overwinters as stroma on shucks, petioles, and stems
Spores produced in spring with warmer temps and rainfall
PecanHost
Pathogen Environment
Plant Disease Triangle
Example
Fungus: Cladosporium caryigenum
Periods of extended leaf wetness; cool to moderate temperatures
Pecan Scab
Native vs. Cultivars
Scab Management for Native Pecans
• Open up groves to air and light; remove heavily scabbing trees; promote drainage
• Assess crop load while scouting for casebearer & make spray decision
• Make fungicide applications
Fungicide applications for Native Pecans
1. First casebearer (pollination complete)
2. 1st Cover (2-3 weeks after first casebearer)*
3. 2nd Cover (2-3 weeks later)*4. Subsequent cover sprays as
needed*
Cultivars: More Intensive
Scab Management For Cultivars
• Plant resistant cultivars• Open up orchards to air and light;
promote drainage• Implement a fungicide spray program
1. Phenological Scheduling Method(based on plant growth stage)
2. Pecan Scab Model ???? (weather-based, Internet accessed)
Resistance
Highly susceptible Moderately susceptible Low susceptibility (resistant)
Burkett Caddo BartonSquirrel’s Delight Colby Choctaw
Western Creek GrakingWichita Giles Kanza
Kiowa LakotaMaramec MountMohawk NaconoOconee Osage
Shawnee PeruquePawnee Stuart
Native Trees
Phenological/Plant Growth Method of Fungicide Application
1. Pre-pollination ( ~”parachute” stage of development)
2. First casebearer (pollination complete) 3. 1st Cover (2-3 weeks after first
casebearer)* 4. 2nd Cover (2-3 weeks later)*5. Subsequent Cover sprays as needed*
Scab influence on yield (Bill Reed)
Pecan Scab Advisory Needed
1. Weather-based disease advisory, Internet accessed, location specific
2. Uses weather data from 115 weather stations in the Mesonet system
3. Calculates # scab hours (hours during which temp > 70 F and RH > 90 %) accumulated in last 14 unprotected days towards fungicide application thresholds
4. Also has information on using the advisory, cultivar susceptibilities, fungicide application thresholds, fungicides and rates
Scab Advisory Spray Thresholds
• Highly susceptible cultivars 10 scab hours• Moderately susceptible 20 scab hours• Natives, low susceptibility 30 scab hours
ProductsProduct Active FRAC Rate/AcreTilt propiconazole 3 4-8 fl ozStratego Propiconazole +
trifloxystrobin3,11 10oz
Orbit 45WPAGPAK/SuperTin
Propiconazole+triphenyltin
3,30 Refer to label
Headline SC pyraclostrobin 11 6-7ozMerivon Fluapyroxad+pyra
clostrobin7,11 5-6.5oz
Adament 50WG Tebuconazole+trifloxystrobin
3,11 3-8oz
Topsin M 70WDGTopsin M 70WP
Thiophanate-methyl
1 1lb
Super Tin 80WP Triphenylin hydroxide
30 5-7.5oz
***Labels change, Refer to label before application. Restrictions on numbers of applications and timing (shuck split)
Products
• http://www.uaex.edu/publications/pdf/mp154year2016/mp154completebook2016.pdf
• MP154 Arkansas Plant Disease Control Products
In the future….
Produce decision aides and educational materials
What is needed?????
Farm visits: [email protected]
Questions?