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COLLEGE OF 

 AGRICULTURE 

 UNIVERSITY OF 

 ILLINOIS AT 

 URB ANA-CHAMPAIGN 

 AND NATURAL 

 HISTORY SURVEY 

 URBANA, ILLINOIS 



^SECT WEED & PLANT DISEASE SURVEY BULLETIN 



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



FOR IMMEDIATE RELEASE 



No. 12, June 23, 1972 



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

 disease situation (fruit and commercial vegetables excepted) , along with suggested, 

 abbreviated, control measures. Each individual should check his own fields to deter- 

 mine local conditions. 



INSECTS 

 CORN INSECTS 



European corn borer moths are still present in northern Illinois. Egg-laying will con- 

 tinue for another week or ten days. Watch particularly advanced fields for signs of 

 economic infestations. Borer survival will be low in most fields, since the corn is 

 later than normal, and moth emergence and egg- laying are slightly earlier. However, 

 there may be a few very early corn fields in which moths could concentrate their egg- 

 laying. To determine whether enough borers are present to use chemicals, see Bulletin 

 No. 10 (June 9, 1972). 



Corn blotch leaf miners are becoming more common. They are not Of economic importance, 

 but can be confused with other problems. The adult, which is a fly, makes tiny elon- 

 gated punctures in groups about 1/16 of an inch long- -usually in the tip of the leaf. 

 The maggot mines between the upper and lower leaf surfaces. A dirty-yellow maggot can 

 usually be found in these mines. 



Leafhopper egg masses are appearing on corn leaves 

 with those of corn borers 



These masses are often confused 

 A leafhopper egg mass is usually fan- shaped. Each egg 

 represents a rib of the fan. The leafhopper masses are inserted into the leaf tissue, 

 and will not scrape off as corn-borer egg masses do. Leafhoppers do not represent a 

 problem. 



Garden symphylans , commonly called garden centipedes, are now being found in some corn 

 fields. These insect relatives are small (1/16 to 5/16 of an inch), white, and have 

 many legs. They move rapidly in the soil, attacking the roots. They prefer the root 

 hairs and tender new roots, but they will reduce the root system to a stub if the in- 

 festation is severe. Infested plants are stunted and may be killed. These pests feed 

 throughout the season, moving closer to the surface when conditions are moist and goin£ 

 deeper when they are dry. 



To check for centipedes, look in areas where the stand is irregular. Locate plants 

 that appear to be stunted. Dig up the plant with a spade full of soil, and place this 

 on a sheet of plastic or cloth. Examine the root system for feeding injury. Carefully 

 sort through the soil, breaking up the clods and watching for the white, moving centi- 

 pedes. It usually takes a hundred or more garden centipedes per hill to cause notice- 

 able injury. Do not become alarmed if you find five to ten in each hill. This number 

 is common in many corn fields . 



