Small Grain Insects 



Armyworms are present in most thick, rank stands of wheat, barley, rye, and grass 

 in the southern half of the state. Only occasional fields have potentially damag- 

 ing numbers. Some fields of thick wheat averaged as many as 4 to 6 worms per 

 linear foot of row over the entire field, but this is still a borderline count 

 for treatment. In lodged spots, counts were as high as 15 to 20 worms per linear 

 foot of row. Populations of armyworms vary considerably from field to field, 

 and each field should be judged on an individual basis. In general, armyworm 

 development in southern sections is behind normal, while wheat development is 

 normal or slightly ahead. This could lead to more head-cutting by the worms if 

 the wheat begins to ripen before they mature. Also, there would be a greater 

 likelihood of armyworm migrations from wheat to corn under these conditions. 



South of Highway 50, armyworms are large enough in some fields for treatments to 

 begin this week; to the north of this line, armyworms are still small (1/4- inch) 

 and treatments should not be applied for another 10 days (May 29) or longer. 



Damage from mice or other rodents is noticeable in wheat fields. They cut the 



stems in 3- or 4- inch lengths and leave them in piles. This is not the work of 



armyworms. They strip the leaves and beards and sometimes cut the stem just be- 

 low the head. 



To find armyworms, examine lodged spots or the thick, rank areas first. Shake 

 the plants vigorously, and look on the ground for the worms. If small striped- 

 worms are present, they will probably be armyworms. Do not use this count as a 

 field average. If you find no armyworms in these spots, no further examination 

 is necessary. If you find lots of them, make several additional counts over the 

 entire field. No control is needed unless the population averages 6 or more per 

 linear foot. Even then, do not apply insecticides until most of the worms are 

 over one -half inch long. 



Apply 1 1/2 pounds per acre of toxaphene for armyworm control in small grains. 

 There are no restrictions on the use of the grain. Do not feed the straw to dairy 

 animals or livestock fattening for slaughter. Do not contaminate fish-bearing 

 waters with toxaphene. 



We have suggested that dairy farmers not use chlorinated hydrocarbons on their 

 farms. Toxaphene belongs to this group of chemicals. However, the official label 

 permits its use on dairy farms. If it is used on or adjacent to dairy farms, 

 avoid drift onto pastures and hay crops. 



Carbaryl (Sevin) , 1 pound per acre, may be applied to grain fields adjacent to 

 dairy pastures, but not after the heads have begun to appear. Use carbaryl on 

 grass pastures or hay fields if armyworms are extremely abundant, but warn area 

 beekeepers that you are applying carbaryl. Trichlorfon (Dylox) , an organic phos- 

 phate insecticide, at 5/4 pound per acre may be used to within 21_ days of harvest, 

 but the straw should not be used for livestock feed. 



Common stalk borers (whitish-brown, striped worms with a purple band around their 

 middle) and wheat stem maggots (pale-green maggot) feed inside the wheat stem caus- 

 ing the heads to turn white prematurely. Stalk borers concentrate more along 

 field margins, whereas stem maggots arc scattered throughout the field. Infesta- 

 tions are spotty and not of economic importance. 



