Bacterial Wilt.
Use resistant varieties as much as possible where disease is a problem. It is very important to control flea beetles early in the season. Use an insecticide at seedling emergence. Flea beetles transmit bacterial wilt disease (also known as Stewarts wilt) and are numerous after mild winters. Use Varieties resistant to bacterial wilt disease or those listed in the Sweet Corn varieties table. Treat susceptible varieties at spike stage when 6 or more beetles per 100 plants can be found.
Maize Dwarf Mosaic Virus.
This virus occurs on corn planted after July 1. The virus is transmitted by aphids to sweet corn from other infected weeds especially Johnsongrass. For control, keep fields as weed-free as possible, maintain strict aphid control, and plant resistant varieties for fall harvest.
Smut.
There is no real resistance to smut in sweet corn. Some varieties seem to escape infection due to differences in silk emergence and weather conditions. Since damaged tissue is more prone to infection, control corn borers as first tassel appears.
Leaf Blights.
For optimal control begin sprays before symptoms appear. In most years, chemical control is not needed for these diseases.
azoxystrobin (Quadris--9.2 - 15.4 oz 2.08F/A or Amistar--3-5 oz 80WDG/A) Apply on a 7- to 14-day schedule and do not make more than 2 consecutive applications without alternating with another fungicide, or
chlorothalonil (Bravo, Echo, Equus) (Do not apply to corn to be processed.) -- O.75-2 pt 6F/A (7-day schedule) or OLF, or
Headline--9-12 fl oz 2.1IEC/A (7-day schedule) or
mancozeb (Dithane, Manex II, Manzate, Penncozeb) -- l.5 lb 8OWP/A (5- to 7-day schedule), or
maneb -- 1.5 lb 8OWP/A (5- to 7-day schedule) or OLF, or
Tilt -- 2-4 fl oz 3.6 EC/A (7- to 14-day schedule)
Rust.
Rust occasionally can become troublesome with some varieties. Most years chemical control measures are not warranted. However, corn warrants spraying if infection occurs prior to the whorl stage. Observe fields on a regular basis, and if lesions are observed prior to the whorl stage, apply one of the following:
azoxystrobin (Quadris--6.2 - 15.4 oz 2.08F/A or Amistar--2-5 oz 80WDG/A) Apply on a 7- to 14-day schedule and do not make more than 2 consecutive applications without alternating with another fungicide, or
chlorothalonil (Bravo, Echo, Equus) (Do not apply to corn to be processed.) -- O.75-2 pt 6F/A (7-day schedule) or OLF, or
Headline--6-9 fl oz 2.1IEC/A (7-day schedule) or
mancozeb (Dithane, Manex II, Manzate, Penncozeb) -- l.5 lb 8OWP/A (5- to 7-day schedule), or
maneb -- 1.5 lb 8OWP/A (5- to 7-day schedule) or OLF, or
Tilt -- 4 fl oz 3.6 EC/A (7- to 14-day schedule)
Information provided is intended for consideration by the user, but is not intended to be a recommendation. Production decisions should be based on consideration of many types of information (scientific, experiential, economic, legal, etc.) available to the user.
Where trade names are used no discrimination is intended, and no endorsement by the Cooperative Extension Service is implied.
Dr. Alan A. MacNab, Professor, Plant Pathology
Penn State College of Agricultural Sciences
211 Buckhout Lab, University Park, PA 16802
Updated: Nov, 2005; EMH
Loaded: Nov, 2005; EMH