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.

Leaf Spots (Alternaria and Cercospora)

Leaf spot fungi do not infect the root but infection can reduce yield, and blighted foliage can reduce the value of fresh-packed plants. To help reduce leaf spot, buy hot-water treated seed, reduce weeds and plow under crop debris in the fall.

azoxystrobin (Quadris): 12.3 to 15.4 fl oz/A (0 dh, REI 4h, Group 11). Apply at the first sign of disease and reapply after 7 to 14 days if necessary. Do not apply more than 2.88 qt/A. Do not rotate with other strobilurins such as Cabrio.

pyraclostrobin (Cabrio EG): 8 to 12 oz/A (0 dh, REI 12h, Group 11). Apply at the first sign of disease and reapply after 7 to 14 days if necessary. Apply only three applications per season or 48 oz/A. Do not rotate with other strobilurins such as Quadris.

Black Leg (Phoma Leaf spot and canker)

From foliar lesions, the pathogen spreads into leaf veins to the petioles and eventually the main stem. On root crops, such as rutabaga and turnip, a dry rot of the bulb or hypocotyl, develops. The neck and shoulder areas have large, brown lesions and an extensive dry rot deep into the fleshy tissue develops. Severely affected bulbs become shrivelled and dry, and are often invaded by secondary fungal and bacterial decay organisms. Start with certified disease free seed or treat seed with hot water or fungicides. Rotate to non-susceptible crops. Promptly incorporate infected crop debris after harvest. Apply foliar fungicides to protect susceptible cultivars.

iprodione (Rovral): 2.0 lb/A. (0 dh, REI 24h, Group 2). Apply immediately after thinning. A second application can be made up to the day of harvest.

Seed Decay and Damping-Off (Turnip only)

Buy treated seed. Do not use treated seed for food or feed.

White Rust, White blister (Albugo candida)

Yield reductions are rare but quality is reduced by the prominent signs of the pathogen. On radish, white rust can also infect flower shoots and cause root swellings. Use resistant cultivars where available and rotate to non-hosts where the disease is common. Proper fertility levels, especially of phosphorous and potassium, have been reported to reduce disease.

azoxystrobin (Amistar): 2-5 oz/A. (0 dh, REI 4h, Group 11). Do not make more than one foliar application of Amistar before alternating with a fungicide with a different mode of action.

mefenoxam (Ridomil Gold Copper): 1-2 pts/A. (REI 48h, Group 4). Pre-plant incorporate (broadcast or band) or soil spray (brodcast or band) and move into seed or root zone by mechanically incorporating or irrigating.