TrAU 1 



COLLEGE OF 

 AGRICULTURE 

 UNIVERSITY OF 

 ILLINOIS AT 

 URBANA-CHAMPAIGN 

 AND NATURAL 

 HISTORY SURVEY 

 URBANA, ILLINOIS 



NSECT WEED & PLANT DISEASE SURVEY BULLETIN 



fATE/COUNTY/LOCAL GROUPS/U.S. DEPARTMENT OF AGRICULTURE COOPERATING 



-77V. 



FOR IMMEDIATE RELEASE 



ML .? 1371 " 



No. 11, June 11, 1971 



This series of weekly bulletins provides a general look at the insect, weed, and 

 plant disease situation (fruit and oommeraial vegetables excepted) , along with 

 suggested, abbreviated control measures. Each individual should check his own 

 fields to determine local conditions. 



INSECTS 



CORN INSECTS 



Wireworms . This pest continued to damage corn this week, but the problem seems 

 to be lessening. Wireworm damage usually declines by mid- June because the worms 

 go deeper into the ground when the soil becomes warmer and drier. 



In cases where replanting is necessary, use one of the organic phosphate 

 insecticides --Thimet, Dyfonate, or Dasanit at 1 pound or diazinon at 2 pounds per 

 acre of actual chemical. These will control small wireworms, but may not control 

 the large ones. A rain after application is helpful. 



Black cutworms . A few scattered reports of damaged corn were received this week. 

 Continue to be on the lookout for damage. Control suggestions were given in Re- 

 port No. 9. 



European corn borers . This situation will need to be watched for the next three 

 weeks . In general, the development of these borers appears to be slower than nor- 

 mal this year, which would allow for greater survival. 



In the southern section of Illinois, egg-laying reached its peak this week. The 

 tiny borers now present in the whorls of corn under 40 to 45 inches in height 

 (from the ground to the tip of tallest leaf) will die 

 is 50 inches or taller, check for borer infestations, 

 make the application this week. 



In fields where the corn 

 If treatment is justified, 



In the central section, moth- emergence is well along and egg- laying has 

 started. The earliest time for treatments, if needed, would be in about ten 

 days (June 21 or after). In the northern section, the moths are just beginning 

 to emerge. 



To determine the need for treatment, first check the tassel ratio. Dig up a 

 plant and measure from the bottom of the plant to the tip of the longest leaf. 

 Split the plant and find the developing tassel. Measure from the bottom of the 

 plant to the tip of the tassel. Divide the tassel height by the plant height 

 and multiply by 100. If the tassel ratio is 30 or over and if 75 percent or 

 more of the plants have corn-borer feeding on the whorl leaves , the field should 



