Chromista, Oomycetes Flashcards
Causal organism of damping off?
Pythium
What defines the kingdom Chromista?
Filamentus
Symptoms of damping off?
Seeds turn soft and mushy, no germination. Roots develop lesions, water soaked spots, and darkening. Stems develop necrotic spots, water soaking, and degradation. Older ants lose vigor. Produce water rot.
Signs of damping off?
White, fragile, slender mycelia growth (rare). Oospores in affected tissue.
Disease cycle of damping off?
Resting oospore - germinates around 68f producing sporangium - zoospores release - infect host - produce enzymes that cause tissue death - produce zoosporangia to produce zoospores and/or have sex to produce oospores
Favorable conditions for damping off?
Wet, cool.
Losses caused by damping off?
Seed, seedling losses, reduced stand, wilting and stunting of older, rotting of produce.
Management of damping off?
Sanitation, plant in correct conditions, do not over fertilize, seed treatment, improve drainage. No resistance available. Few fungicides affective against bc not a fungi.
Family if downy mildews?
Peronosporaceae
Significant about peronosporaceae?
Sporangea of determinate growth,wind borne, obligate parasites specialized to host.
Causal organism of downy mildew of grape?
Plasmopara viticola
Symptoms of downy mildew of grape?
Upper leaf surfaces - pale, bleached, yellow spots; spots become necrotic. Developing shoots are distorted. Berries wrinkle and toughen, develop reddish brown color.
Signs of downy mildew of grape?
Found on leaf undersides only in conditions of high moisture/ high humidity.
Disease cycle of downy mildew of grape?
Overwinters in woody stems or mycelium in infected parts; mycelium - symptoms and signs - cycle; oospores in debris - germinate in wet weather - form sporangia and oospores - wind borne/ rain borne - symptoms and signs - repeat at sporangia or senescence - sex - oospores.
Favorable conditions for downy mildew of grape.?
68-70f wet, high humidity
Losses from downy mildew of grape?
Plant vigor, quantity, quality.
Management for downy mildew of grape?
Resistance available especially in North American native varieties. Fungicide when needed - when wet at 7 to 10 day intervals. Bordeaux mixture.
Downy mildew of soybeans causal organism?
Peronospora manshrica
Symptoms of downy mildew of soybean?
Pale yellow spots on upper leaf surface.seed bleached. Some varieties have leaf and stem distortion.
Signs of downy mildew of soybean?
Sporangia on undersides of leaves.
Disease cycle of downy mildew of soybean?
Seed borne - systemic - symptoms and signs - sporangia and zoospores to repeat or oospores in debris; oospores in debris - germinate to sporangia and zoospores - infect to symptoms and signs - repeat or form oospores.
Favorable conditions for downy mildew of soybeans?
68-77f for infection. Wet high humidity. 50-80f for sporangia. Older leaves will develop resistance.
Losses from downy mildew of soybean?
Quantity and quality. Up to 20% loss in cool/ wet seasons.
Mangement of downy mildew of soybean?
Certified disease free seed. Rotate. Conventional tillage (debris management). No complete resistance but variations in susceptibility.
Causal organism of potato late blight?
Phytophthora infestans
Hosts of phytophthora infestans?
Solanaceae - tomatoes , potatoes peppers
Symptoms of potato late blight?
Water soaked spots on leaf edges, spots expand rapidly killing leaves. Plants die. Tubers affected with purplish blotches, water soaked spots and rot. Putrid odor.
Sign of potato late blight?
Downy white fungal growth on leaf edges.root lesions. In high humidity.
Disease cycle of potato late blight?
Overwintering in tubers –organism grows with sprout - sporangia - wind borne - zoospores germinate with water - can wash into soil
Favorable conditions for potato late blight?
Cool and moist 50-80f. Prolonged periods of wet.
Losses from potato late blight.?
Loss of vigor.decreased quantity, plant death. Tubers rot.
Management of potato late blight?
Resistance, sanitation, clean tubers, destroy cull pile. Fungicides.
Causal organism sudden oak death?
Phytophthora ramorum
Hosts of phytophthora ramorum?
Over 100 trees and ornamentals
.
Geographical distribution of sudden oak death?
Pacific coast and possibly Deep South.
Symptoms of sudden oak death?
Tree death. Cankers. Bleeding, necrosis. Defoliation.
Signs of sudden oak death?
May find sporangia on affected leaves.
Disease cycle of sudden oak death?
Over winters with chlamydospores(dark protective coating) - germinate to sporangia - wind borne - infect - cankers ooze - sporangia - repeat
Favorable conditions for sudden oak death?
Extended periods of moisture. Temp 60-70f for zoospores but 80ish for infection
Loses from sudden oak death?
Rapid plant death less than 2 years in mature oak less than one in woody ornamentals
Management of sudden oak death?
Eradicate burn infected. Monitor for disease and quarantine questionable shipment. Little can be done no fungicide.
Causal organism of potato late blight?
Phytophthora infestans
Hosts of phytophthora infestans?
Solanaceae - tomatoes , potatoes peppers
Symptoms of potato late blight?
Water soaked spots on leaf edges, spots expand rapidly killing leaves. Plants die. Tubers affected with purplish blotches, water soaked spots and rot. Putrid odor.
Sign of potato late blight?
Downy white fungal growth on leaf edges.root lesions. In high humidity.
Disease cycle of potato late blight?
Overwintering in tubers –organism grows with sprout - sporangia - wind borne - zoospores germinate with water - can wash into soil
Favorable conditions for potato late blight?
Cool and moist 50-80f. Prolonged periods of wet.
Losses from potato late blight.?
Loss of vigor.decreased quantity, plant death. Tubers rot.
Management of potato late blight?
Resistance, sanitation, clean tubers, destroy cull pile. Fungicides.
Causal organism sudden oak death?
Phytophthora ramorum
Hosts of phytophthora ramorum?
Over 100 trees and ornamentals
.
Geographical distribution of sudden oak death?
Pacific coast and possibly Deep South.
Symptoms of sudden oak death?
Tree death. Cankers. Bleeding, necrosis. Defoliation.
Signs of sudden oak death?
May find sporangia on affected leaves.
Disease cycle of sudden oak death?
Over winters with chlamydospores(dark protective coating) - germinate to sporangia - wind borne - infect - cankers ooze - sporangia - repeat
Favorable conditions for sudden oak death?
Extended periods of moisture. Temp 60-70f for zoospores but 80ish for infection
Loses from sudden oak death?
Rapid plant death less than 2 years in mature oak less than one in woody ornamentals
Management of sudden oak death?
Eradicate burn infected. Monitor for disease and quarantine questionable shipment. Little can be done no fungicide.
