Experiences of a West Texas Cotton Farmer with Phymatotrichum Root Rot Douglas Wilde Wall, Texas

Phymatotrichum Root Rot Indigenous soil born fungus Occurs in the Southwestern US and Mexico The fungus invades the cortical tissues of roots and damages the conducting system, induces severe water stress, and causes premature plant death by desiccation.

Symptoms Bronzing and Wilting

Symptoms Plants die suddenly Leaves remain firmly attached to plant

Symptoms Hyphal webs on infected roots

Root Damage

Susceptible Plants Trees Pecan Apple Peach Fig

Susceptible Plants Cotton Alfalfa Peanuts Vegetable Peppers Carrots

Susceptible Plants Shrubs Pomegranate Grapes Roses

Immune Plants Monocots are immune Palms, Yuccas, Agave Corn Grain Sorghum Wheat Sesame Grasses

Tolerant Plants Tolerant Dicots Mesquite, Strawberry, Prickly-pear cactus

Immune Soils Soils that have over 400 ppm of Na, (sodium) in the profile (3 ft.) – have almost no cotton root rot. Acidic soils

Favorable Disease Conditions High soil moisture High soil temperature Trapped CO2 Plant stress

Problems Harvest Yield Grade Planting

Harvest Problems Decreased harvest speed Increased harvest fires Increased wear on parts

Yield Decrease Up to 60% decrease in yield Up to 90% disease infestation in fields

Non-Diseased Area Diseased Area

Decreased Grade Decreased Micronare Decreased Staple Length Increased Leaf Increased Bark Grade Gr St Lf Mic Rmrks Strn Uni Loan Rate Diseased Areas 37 3 32 Light Bark 30.2 79.9 .5200 31 38 4 36 Light Bark 28.5 80.4 .5285 Non-Diseased Areas 31 37 2 42 30.6 80.2 .5850

Disease Management Increase Organic Matter Rotation Deep Plowing Hot Bed Manure Rotation Deep Plowing Avoid Infested Locations Fertilizer Application Decrease pH of soil

Disease Management Reduced plant stress Plant early and a fast variety Plant late and a fast variety

Current Research Projects Soil fungicide treatment Stem Drench Drip injection Biological management Genetic resistance Determining when fungus attacks plant

Conclusion No practical control for Cotton Root Rot Emphasis on genetic resistance Increase organic matter (microbes)

Thanks Rick Minzenmayer Dr. Tom Isakeit Arnold Matthiesen