Disease Control in Leafy Brassica Greens Control in...Disease Control in Leafy Brassica Greens Steve...
Transcript of Disease Control in Leafy Brassica Greens Control in...Disease Control in Leafy Brassica Greens Steve...
Disease Control in Leafy Brassica Greens
Steve Bost Extension Plant Pathologist
University of Tennessee
Presented at 28th Annual Southeast Vegetable & Fruit Expo December 4, 2013 Myrtle Beach, SC
Tennessee has some large leafy greens operations. Most plantings are small scale, hand-harvested.
What are the major diseases of brassica leafy greens? How to identify them? How to control them?
Cercospora leaf spot
Tan spots, may have yellow haloes.
Cercospora leaf spot cont’d
Spots may be smaller or may show rings
Alternaria leaf spot
Definite rings. Alamo turnip pictured.
Anthracnose
Small lesions
Anthracnose cont’d
Lesions on stems and veins are diagnostic
Anthracnose cont’d
Downy mildew
Diffuse yellow spots. May advance to necrotic.
Downy mildew cont’d
White tufts of spores may be seen on the undersides of lesions. Can be difficult to see.
Downy mildew cont’d
Spores on undersides may appear gray, such as on these collards.
Diseased leaves may remain in canopy, causing a quality problem in harvested product.
Powdery mildew
Southern Giant Curled mustard and Alamo turnip growing side-by-side. Mildew very light on turnip.
Southern Giant Curled mustard
Bacterial diseases
Black rot Xanthomonas campestris pv. campestris
Leaf spots Xanthomonas campestris pv. campestris
Xanthomonas campestris pv. armoraciae
Pseudomonas syringae pv. maculicola
Pseudomonas syringae pv. alisalensis
Bacterial leaf spots Symptoms vary. Easier to see lesions on undersides of leaves.
Bacterial leaf spots Can resemble nutritional problems or fungal diseases
Both of these are bacterial leaf spot diseases.
Bacterial leaf spots cont’d
Vein necrosis distinguishes them from fungal diseases, but often not seen.
Black rot Bacteria become systemic in plant.
V-shaped lesions
Black rot cont’d Bacteria spread rapidly by rain splash.
Bacterial disease control
Sources of infestation are contaminated seeds and infected weeds. So:
• Treat seeds. Hot water seed treatment kills internal and external bacteria, whereas disinfestants such as bleach and trisodium phosphate only kill surface bacteria. Seed company service preferred to do-it-yourself.
• Control cruciferous weeds in and around field.
If disease is found:
• Copper and/or Actigard sprays may suppress the severity of the disease, but often do not suppress incidence, i.e. the number of diseased leaves.
• Incorporation of post-harvest crop debris into soil will hasten decline of bacterial populations.
• Long crop rotations are not necessary, but cole crops should be limited to one crop per year. Longer rotations may be needed if other diseases are a problem or if cruciferous weeds persist.
Pythium root rot. Don’t grow
transplants in float beds.
Fungicide Trial, Highland Rim REC, Springfield, TN Spring, 2013
Product, rate/acre (application number)
Cercospora leaf spot (% leaf area affected)
Turnip Mustard
Check 35.0 a 30.0 a
Quadris, 6 fl oz (1,3); Kocide 3000, 0.5 lb (2) 16.5 b 7.5 b
Fontelis, 1 pt (1-3) 2.8 c 1.8 c
Fontelis, 1.5 pt (1-3) 4.3 c 1.5 c
Downy mildew trial, Highland
Rim REC, Springfield, TN
Fall, 2011
Fungicide Trial, Highland Rim REC, Springfield, TN Fall, 2011
Product, rate/acre Leaf area affected (%)*
Check 16.3 a
Fontelis, 1 pt 22.5 a
Fontelis, 1.5 pt 20.8 a
Endura, 8 oz 15.8 a
Quadris, 6 fl oz 4.5 b
* Primarily downy mildew, some Cercospora.
Controls Chemical
Caution: Be careful where you get your information! Every product used must be registered with EPA!
The Southeastern US Vegetable Crop Handbook http://www.thegrower.com/south-east-vegetable-guide/
Cultural
Plow-down crop debris at end of year.
Rotate with non-cruciferous crops.
Control cruciferous weeds*.
Use treated seed and buy transplants from trusted source*.
* Particularly important for bacterial disease control.
Scenes from a garden center.
Garden center suppliers must be held
accountable for diseased transplants.
Anth Cercos Downy Powd Bacter Collard Kale Mustd Turn grns Turnip
Actigard X X X X X X X
copper X X X X X X X X
Forum X X X X X
Presidio X X X X
Ranman X X X X X
Reason X X X X
Revus X X X X
Ridomil X X X X X
Zampro X X X X
Endura X X X X
Fontelis X X X X X X X X
Inspire Super X X X X X X X
Quadris X X X X X X X
Quadris Top X X X X X X X
Cabrio X X X X
Switch X X X X X X
Procure X X X X X
sulfur X X X X X X
tebuconazole X X X X X X
Flint/Gem X X X X
Partial list of registered products. X = Registered for use.