How to scout for plant diseases

1
How to scout for plant diseases

• USDA-APHIS-PPQ-National Seed Health System
  phytosanitary inspection reference
• http//www.seedhealth.org/standardization/RMB0402.
  pdf

2
How do I start?

• Look the field over are there any spots you
  should focus on? (depends on what youre looking
  for)
• Low areas
• Edges
• Microclimates
• Decide on a sampling pattern
• Scout at the appropriate growth stage for the
  disease of interest
• Note symptoms and signs
• Get samples properly diagnosed if needed

3
Stagger X pattern
Equidistant passes pattern
4
Patterns of plant disease
x
Examples Wind-borne Seed-borne Soil-borne
(foci) - Rusts Stubble-borne Nematodes Contami
nated potato seed pieces Irrigation lines
(nozzles)
5
Sampling patterns
6
Other sampling patterns
(take a sample in each quadrat)
7
Arbitrary vs. Random

• Arbitrary choose plants as walk along pattern,
  perhaps at even intervals like every 3 steps
• Random must use a random number generator or
  other random method to select plants (eg. numbers
  in a hat)

8
How many samples should I take?
minimum of 95 confidence level in detecting an
infection level of 0.1