Eggplant, Pepper, and Tomato XXIV - Phytophthora Blight ...

High Plains IPM Guide, a cooperative effort of the University of Wyoming, University of Nebraska, Colorado State
University and Montana State University.
Eggplant, Pepper, and Tomato
Phytophthora Blight (Phytophthora Fruit Rot)
Howard F. Schwartz and David H. Gent
Identification and Life Cycle
Phytophthora blight is caused by the fungus-like organism Phytophthora capsici,
and is a widespread and often devastating disease of pepper and occasionally
tomato and eggplant. The pathogen has a broad host range and can attack many
vegetable crops, including cucumber, melon, squash, and pumpkin. P. capsici
can reproduce sexually (oospores) and asexually (zoospores and sporangia).
Sexual oospores can persist in the soil for several years, and serve as initial
inoculum. Asexual zoospores and sporangia are easily disseminated by wind,
splashing rain, and irrigation water. When zoospores or sporangia make contact
with a plant, they can infect any tissue. The pathogen survives between
susceptible crops in the soil as oospores and in contaminated seed.
Plant Response and Damage
Phytophthora blight can affect all plant parts. Root infections generally appear as
blackening of roots and crowns, causing a wilting of the plant. Stem infections
appear as distinctive black lesions. When spores are splashed from the soil onto
leaves, water-soaked spots form and enlarge quickly into pale green to brown
lesions. Lesions are often covered with white sporangia in moist weather,
especially on the bottom sides of leaves. Infected foliage becomes brown,
shrivels, and soon dies. Infected fruit are typically covered with white sporangia
and shrivel. The disease can be devastating when conditions favor the pathogen;
complete crop losses can occur in heavily infested fields.
Management Approaches
High Plains IPM Guide, a cooperative effort of the University of Wyoming, University of Nebraska, Colorado State
University and Montana State University.

High Plains IPM Guide, a cooperative effort of the University of Wyoming, University of Nebraska, Colorado State
University and Montana State University.
Biological Control
Soil solarization and incorporation of organic amendments can reduce soil
inoculum levels and subsequent disease development.
Cultural Control
Plant high quality seed free from P. capsici. Plant into well-prepared raised beds
and evenly leveled fields that promote rapid drainage of irrigation and rain water.
Use drip rather than sprinkler or furrow irrigation if possible. Prevent excessive
moisture. Avoid planting into fields with known salinity problems. Straw
mulches reduce splash dispersal of soilborne inoculum and can reduce foliar
infection. Practice a three-year or longer crop rotation between susceptible crops.
Plant resistant or tolerant varieties if available.
Chemical Control
P. capsici resistance to metalaxyl and mefenoxam is widespread in some regions,
and alternative fungicides and disease management strategies should be used if
resistant strains are present.
Product List for Phytophthora Blight:
Pesticide
Product per
acre
Application
Frequency (days)
Remarks
Famoxadone/Cymoxanil
Tanos 8 oz 5-7 days Rotate and rotato
with fungicides with
a different mode of
action such as
chlorothalonil or
mancozeb;
Maximum of 72
ounces per season; 3
day PHI
Mefenoxam
Ridomil Gold EC 1-2 pts Broadcast or banded
at planting;
High Plains IPM Guide, a cooperative effort of the University of Wyoming, University of Nebraska, Colorado State
University and Montana State University.

High Plains IPM Guide, a cooperative effort of the University of Wyoming, University of Nebraska, Colorado State
University and Montana State University.
Maximum of three
injections by drip
irrigation; maximum
of three pts per
season; 7 day PHI
Ridomil Gold GR 20 lbs Band (7”) or
broadcast and
incorporate with 0.5
to 1” of irrigation
water; a second
application can be
made; 7 day PHI
Maximum of 40
pounds per season;
7 day PHI
Ridomil Gold/Bravo 1.5-2.0 lb 7-14 days Make 3 total sprays;
14 day PHI
Ridomil Gold/Copper 1 pack/per 2.5
acres
5-14 days Make 3 total sprays;
14 day PHI
The information herein is supplied with the understanding that no discrimination is intended and that listing of commercial products, necessary to
this guide, implies no endorsement by the authors or the Extension Services of Nebraska, Colorado, Wyoming or Montana. Criticism of products or
equipment not listed is neither implied nor intended. Due to constantly changing labels, laws and regulations, the Extension Services can assume
no liability for the suggested use of chemicals contained herein. Pesticides must be applied legally complying with all label directions and
precautions on the pesticide container and any supplemental labeling and rules of state and federal pesticide regulatory agencies. State rules and
regulations and special pesticide use allowances may vary from state to state: contact your State Department of Agriculture for the rules,
regulations and allowances applicable in your state and locality.
Categories: Eggplant, Pepper, Tomato, Disease, Phytophthora Blight,
Phytophthora Fruit Rot
Date: 04/01/2007
High Plains IPM Guide, a cooperative effort of the University of Wyoming, University of Nebraska, Colorado State
University and Montana State University.