If you suspect or know that you have a resistant western or northern corn-rootworm 

 problem, and if you did not use an organic phosphate or carbamate insecticide at 

 planting time, apply one of these within the next two weeks. Use granules applied 

 at the base of the com plants, and cover them by cultivation. A special applicator 

 on the cultivator directs the phosphate granules at the base of the plant, and dirt 

 is thrown over this deposit. 



Organic phosphate or carbamate insecticides are the only effective means of con- 

 trolling resistant rootworms. The following materials have label approval for basal 

 application and are recommended for control of resistant rootworms in Illinois. 



Rate per 



Insecticide acre (lb.) 



*BUXten 1 



Diazinon 1 



Disulfoton (Disyston) 1 



Parathion (Niran) 1 



Phorate (Thimet) 1 



Carbaryl (Sevin) 2 



*Note: Effective June 1, 1969, BUXten 

 granular has been granted USDA 

 registration for use as a basal 

 application for corn rootworm 

 larval control in field corn. 

 For best results, make the ap- 

 plication before June 15. 



The emergence of European corn borer moths is almost complete in the southern section. 

 In the central section, pupation is complete and moth emergence is well underway. 

 Pupation is about 90 -percent complete in the northern section and moth emergence is 

 just starting. 



Egg- laying has been observed south of Route 50. These early counts show 55 to 65 

 egg masses per 100 plants. An estimated 10 to 15 percent of the pupae in old stalks 

 in the southern section have been killed by sunscald. In southern areas, egg-laying 

 will take place for another 10 days to two weeks. 



Watch closely for damage in fields that were planted very early . Fields averaging 

 30 inches in height now, with a tassel ratio of 5 to 10, may have a high level of 

 borer survival and could warrant treatment within two weeks, or perhaps sooner. The 

 survival of borers from eggs layed during the next two weeks will increase with corn 

 plant development. Economic damage may be prevented if we get hot, dry winds, which 

 will roll the egg masses off plants. Hard, beating rains would also help kill the 

 moths during peak egg- laying periods. Moths may be laying eggs on weeds and other 

 plants, and this would further reduce economic damage. 



r!uch of the com planted before May 10 in the northern half to two-thirds of the 

 state (except for localized areas in the east-central section) may develop economic 

 infestations of first-generation borers. Watch fields for damaging infestations... 

 in the south-central section beginning about June 12, in the central section about 

 June 18, and in the northern section about June 24. Plan to use insecticides if 

 needed. 



To decide whether an insecticide can be profitably applied, measure the tassel 

 ratio of the field and determine the percentage of the plants with recent feeding 

 in the whorl leaves. To determine the tassel ratio, measure the height of the 



