Disease Control

NOTE:  For the products for disease control listed below, one product trade name and formulation is provided for each active ingredient (common name) as an example of rates, days to harvest (dh), REI, and special instructions. In many cases there are other products available with the same active ingredient. Please see Table 22 and Alphabetical Listing by Trade Name for more information on products with the same active ingredients.

Alternaria Damping Off

Buy seed certified as disease-free or treat with hot water at 122°F for 25 minutes (see Seed Treatments). Cole crop seed is susceptible to seed vigor loss from hot water treatment. Seed should be treated as close to planting as possible.

Mycostop (Streptomyces griseoviridis): 3 g/lb seed (REI 12h). Place seed in a jar, cover, add Mycostop and mix until seeds are coated. For planter box treatment, fill box half full of seed, add half the required amount of Mycostop, mix thoroughly with paddle. Add remainder of seed and Mycostop and mix thoroughly. Use within a day or two and keep cool and dry. May also be used as a drench. See label for directions. Mycostop is distributed by AgBio Development Inc., 9915 Raleigh Street, Westminster, CO 80030. (303) 469-9221.

Alternaria Leaf and Head Rot

Leaf spot and head rot are caused by at least three species of Alternaria and may be seed-borne. Start with certified disease-free seed. Destroy diseased crop residues after harvest. Differences in cultivar susceptibility exist. Avoid overhead irrigation for broccoli head rot.

azoxystrobin (Quadris): 6.0 to 15.5 fl oz/A (0 dh, REI 4h, Group 11). Apply preventively or at the first sign of disease. Do not repeat the application or rotate with other strobilurins. See label for list of allowed brassica crops.

chlorothalonil (Bravo Weather Stik): 1.5 pt/A (7 dh, REI 12h, Group M5). Apply at the first sign of disease; repeat at 7- to 10-day intervals.

maneb (Maneb, Manex): Rates vary depending on the formulation. See Table 23.

Black Leg (Phoma lingam)

Use three to four year crop rotation. Start with certified, disease-free seed. Remove and destroy infected seedlings in seedbeds. Improve  soil drainage and air circulation. Eliminate Brassica weeds. Avoid working in fields when they are wet. Promptly incorporate plant debris after harvest.

potassium bicarbonate (Armicarb 100): 2.5 to 5.0 lb/100 gal (0 dh, REI 4h, Group M1). Start application at the first sign of disease and continue at 7-14 day intervals while conditions remain favorable for disease development.

thiram (Thiram 50 WP): 8 0z/100 lb seed. (REI 24h, Group M3). Seed treatment.

Black Rot (Xanthomonas)

Use a four-year rotation of seed beds. Start with certified disease-free seed or treat seed with hot water. Eliminate cruciferous weeds and volunteers. Do not work in wet fields. Maneb or manex (see Table 19) can be mixed with a copper material such as cupric hydroxide to improve activity against bacteria (7 dh, REI 24h). Note: not all crucifers are on the maneb or manex label.

copper hydroxide (Kocide 3000): 0.5 to 0.75 lb/A. (0 dh, REI 24h, Group M1). Apply on a 7- to 10-day interval as soon as disease appears. Do not apply in a spray solution having a pH less than 6.5 or tank mix with Aliette.

Club Root (Plasmodiophora brassicae)

Maintain soil at a pH of 6.8 or higher. Apply 1,500 lbs. of hydrated lime six weeks prior to planting to raise pH to 7.2 or more. At present, if club root is introduced into the soil, it can only be delayed, not defeated. A four-year rotation is recommended for cole crops. If club root is detected, increase to a seven-year rotation. The PCNB and pH adjustment then may reduce the viable club root spores to below economic threshold levels of infection for many growing seasons to come. Cold, wet soils favor club root and its spore survival. Resistant cultivars of some crucifer crops are available. Prevent the movement of infested soil into unifested fields.

PCNB (Terraclor 75WP): 2 lb/100 gal water (REI 12h, Group 4) applying 0.5 to 0.75 pt per transplant; or apply 30 lb/A (13,100 linear feet of row for cabbage and broccoli; 10,900 linear feet of row for cauliflower). Apply at planting only. Thoroughly mix Terraclor with soil for effective control.

Downy Mildew (Peronospora parasitica)

Improve air movement around plants by proper plant density and row orientation. Irrigate early in the day to speed drying of foliage. Plant resistant varieties. Treat seed with appropritae fungicides.

azoxystrobin (Quadris): 6.0-15.5 fl oz/A. (0 dh, REI4h, Group 11). 

chlorothalonil (Bravo Weather Stik): 1.5 pt/A (7 dh, REI 12h, Group M5). Apply at the first sign of disease; repeat at 7- to 10-day intervals. “Premium Crop” and “Headline” broccoli are tolerant to downy mildew. Read label for replant restrictions.

copper hydroxide (Kocide 3000): 0.5-0.75 lb/A. (0 dh, REI 24h, Group M1). Do not apply in a spray solution having a pH less than 6.5 or tank mix with Aliette.

fosetyl aluminum (Aliette WDG): 2 to 5 lb/A (3 dh, REI 12h, Group 33). Apply as a foliar spray when conditions favor disease development (high moisture, moderate temperatures) and continue on a 7- to 21-day interval. Do not mix with copper fungicides. Lower rates of Aliette (2 to 3 lb) can be used when tank mixed with another fungicide labeled for downy mildew control.

mandipropamid (Revus): 8.0 fl oz/A. (1 dh, REI 12 h, Group 40). A spreading/penetrating type adjuvant must be added. Do not make more than two consecutive applications before alternating to a fungicide with a different mode of action. Can be tank mixed.

maneb (Maneb, Manex): Rates vary depending on the formulation. See Table 23.

mefenoxen plus chlorothalonil (Ridomil Gold/Bravo): 1.5 lb/A (7 dh, REI 48h, Groups 4 & M5). Apply when conditions are favorable for disease or as soon as disease first appears. Repeat at 14-day intervals. See label for plant-back restrictions, and restrictions on certain crucifers.

potassium salts of phosphorous acid (Phostrol, Fosphite, ProPhyt): Rates vary according to formulation. See labels. (0 dh, REI 4h, Group 33). Systemic action by enhancing plants’ natural defense system.

potassium bicarbonate (Armicarb 100): 2.5-5.0 lb/100 gal. (0 dh, REI 4h, Group M1).

Fusarium Yellows

The pathogen is soil-borne and may also be seed-borne. Plant resistant varieties. Prevent the movement of infested soil to clean fields. Provide adeqaute fertility; potassium deficiency increases disease severity.

Seed Decay

Buy treated seed. Do not use treated seed for food, feed or oil purposes.

Wire Stem (Rhizoctonia)

Rhizoctonia is a natural inhabitant of the soil and can survive there indefenitely. Practice good sanitation throughout crop cycle. Successful sanitation in transplant production prevents further need for fungicide drenches. Use treated seed for direct seeding into field. Avoid planting transplants too deeply. Rotate crops. Do not plant susceptible crucifers in fields with undecomposed crop residues. Fungicide treatments in the field have limited effectiveness.

PCNB (Terraclor 75WP): 12.2 to 18.4 oz/1,000 row feet, 15 to 20 lb/A (REI 12h, Group 4). Apply as a broadcast or row drench at transplant or seeding only.

Streptomyces griseoviridis strain K61 (MycoStop): 0.13 oz/lb seed.

Turnip Mosaic Virus

Turnip mosaic virus can infect most brassica crops but it is most commonly seen in Chinese cabbage and bok choy. It is spread by aphids in a nonpersistent manner; therefore, insecticides are of little or no value in controlling its spread. This virus survives the winter in perennial weeds. It is spread by many species of aphids. Resistant cultivars include: Nabyeng, Kongng, Tip Top and Ta Feng. These cultivars may not be completely resistant and may have some intolerance to heat.