You can apply 2,4-D on wheat, oats, barley, or rye between milk stage and harvest. 

 But 2,4-D does not kill weeds rapidly, and they may still be green at harvest time. 

 Some weeds may curl enough so that the combine can be set to miss them. Spraying 

 small grains much earlier to prevent yield reduction because of weed competition 

 and harvesting losses is usually the best practice. Very few acres of small grains 

 are sprayed for weeds in Illinois at present. If weeds are a problem now, this 

 practice may be worth considering next year. 



PLANT DISEASES 



SPRAYING FOR SOUTHERN CORN LEAF BLIGHT 



Consider economics first . Race T of the southern corn leaf blight fungus (Helmin- 

 thosporium maydis) is infecting many susceptible corn fields in Illinois. Other 

 leaf blights--the yellow, northern, and eyespot--are also present. 



Illinois com growers have an average cash investment of $40 to $50 an acre in their 

 crops. With favorable growing conditions and prices, they have a potential return 

 of as much as $100 an acre. 



The thorough and timely application of fungicide sprays may help insure a major part 

 of this potential return from field corn infected with the southern com leaf blight 

 or with other leaf blights. The key question is: "Will fungicide sprays reduce the 

 loss in grain yield enough to cover the cost of spray materials and of application?" 

 To be economic- -that is, to maximize expected net returns --fungicide sprays should 

 be used when increased yields resulting from the use of fungicides are worth more 

 than the cost of the chemical plus the cost of application. 



Not all farmers will want to use this basis to make the decision . Instead, to avoid 

 uncertainties, they may wish to follow the insurance principle and take a known loss 

 now-- the cost of spraying if blight hits their crop- -in order to avoid a larger, cat- 

 astrophic loss. The profit prospects from spraying can be estimated by calculating 

 the break-even yield increase necessary to offset the cost of fungicide and appli- 

 cation and comparing this figure with the expected yield response. 



A reasonable spraying cost estimate is $3 to $4 per acre per application- -including 

 the cost of materials and of application with either ground or aerial equipment. 

 Three sprays would cost $9 to $12 an acre. With a net corn price of $1.30 per bushel, 

 only 7 to 9 bushels per acre are required to cover the cost of spraying. 



In estimating yield response to spraying, farmers must consider many factors- -including 

 the expected weather pattern, present disease situation in the field, and suscepti- 

 bility of the crop. Dry weather will help reduce spread of the disease as well as 

 the number of sprays needed. Warm, rainy conditions favor rapid blight development, 

 and more sprays would be required. The greatest yield response would probably be from 

 an intermittent wet and dry weather pattern that allows enough time for the protective 

 spray to dry on the leaf surfaces. After drying, the fungicide is more resistant to 

 the diluting effect of rainfall. 



Weighing the economic factors is important in making the decision of whether or not 

 spraying for corn leaf blight will pay. If the decision is to spray, consider timing, 

 materials, rates, and methods of application to get the greatest protection. 



Give highly susceptible T hybrids priority when spraying. Less-susceptible T hybrids 

 and fields planted with blended seed would come next in order of priority. As a 

 general rule, it will not pay to spray normal (N) corn, except for seed production 



