Jude Boucher, UConn Extension, 2014
Since it is time to order your sweet corn seeds for next season, you may want to take a minute to be sure that the varieties you pick have at least moderate resistance to the late season diseases, such as rust and Northern corn leaf blight. These two diseases have caused more and more problems in recent years, and seem to snowball as the season goes on, with some growers even losing late blocks of sweet corn. Other growers have had trouble selling ears with rusty or dead husk leaves, and can’t wait for the next block of resistant corn to mature to improve sales. Sometimes after very warm winters, Stewart’s wilt can kill many of the plants in early blocks of corn, reducing yields and sales.
The table below provides ratings for these three diseases on sweet corn varieties that are, or were, popular in New England. Additional information is available by Googling the “Midwest Vegetable Trial Report for 2010,” under “sweet corn.”
|Company||Genetics||Color||RM||Name/number||C. Rust||avir||D-vir||G-vir||NCLB||Ht gene||Stewart’s W|
|Rog||se+||Bi||4||BC 0805 A||Rp||0||4||0||7||7|
|MM||se||Bi||2||Bon Apetit TSW||6||6||6||6||5||6|
|MM||se||Bi||2||Bon Jour TSW||6||6||6||6||8||8|
|Rog||se||Y||5||Kandy Korn EH||4||4||6||5||4|
|Rog||se||Bi||5||Peaches & Cream||7||8||6||6||7|
|Cent||sh2+||Bi||3||Mirai 301 BC||6||6||6||5||7||3|
|Cent||sh2+||Bi||2||Marai 308 BC||4||4||4||4||6||5|
Dr. Jerald Pataky was a plant pathologist for the University of Illinois who recently retired after conducting sweet corn disease resistance trials on new varieties for 27 years. In 2010, he and Martin Williams (ARS) published a summary of their 27-years of results which included over 800 commercial and pre-commercial varieties. Most of the varieties were tested for a number of years and the average ratings were presented in his final report.
They inoculated the plants in the trials repeatedly with the following diseases and races to create uniform disease pressure: rust (races avirulent, D-virulent and G-virulent), northern corn leaf blight (races 0 and 1), Stewart’s wilt, maize dwarf mosaic virus, a couple of other less-common diseases and reactions to three post-emergence herbicides (Callisto, Laudis and Accent). Since the trials ended in 2010, some of the newest varieties that you may be trying or using on your farm’s, may not be included. Be sure to check the catalogue or ask your seed rep for information about resistance to rust and NCLB for varieties that have just been released, to assure great late-season performance.
Dr. Pataky and Williams rated each variety, for each disease, and sometimes for each race, on a scale of 0-9, completely resistant to susceptible: 1=resistant, 3=moderately resistant, 5= moderate, 7= moderately susceptible, 9= susceptible. Of the 800 varieties tested, only 12 sugar enhanced (se) and 120 shrunken-2 (super sweet) varieties had R to MR reactions to NCLB, but you should be able to pick a variety with at least moderate resistance to this disease. The first NCLB column represent varieties with partial resistance, which offers protection from more strains and reduces disease spread, but the plants may produce some small or fully developed lesions and spores. Those varieties with Ht or race-specific resistance to NCLB, may not provide resistance to all races of NCLB, but usually restrict lesions to small yellow spots that do not form spores, as opposed to five- or seven-inch long brown spots that spread up the plant rapidly.
Prevalence of new rust races has increased in recent years, so a combination or average rating is presented in the first column and individual races are rated in the next three columns. If the variety is marked with an Rp in the first column, then it has a single, or a combination of resistant genes that provide complete resistance to one or more races of rust (shown in the next three columns).
Company or seed sources: Cent= Centest, Cr=Crookham, HM= Harris Moran, IFS= Illinois Foundation Seeds, MM=Mesa Maize, Rog=Rogers (Syngenta), Sdw= Seedway, Sem= Seminis, Sto=Stokes.
Relative maturity is listed as RM: 1=first early, 2=second early, 3=midseason, 4=main season, 5 full season.