GRUBS OR MAGGOTS INJURING STALK OR STEM 131 



The Wheat Straw-worm {Isosoma grande Riley) 

 In the wheat growing regions west of the Mississippi this insect 

 causes much damage. Its work is of two types. Overwintering, 

 mostly wingless adults lay eggs in April 

 in the tender tissues of young wheat plants. 

 The grubs that hatch from these feed in 



the crown of the plant, 



practically destroying it 



so that growth stops. 



After a pupal stage a 



second generation of adults 



in late May or June 



emerges. These are winged, 



and are apt to disperse 



rather widely. The female 



lays eggs in the wheat 



stem, below the head and 



just above the youngest 



joint that is not covered 



with a sheath of leaves. 



Larvae hatching from these 



eggs feed in the stem, and 



remain in the straw until 



the next season. The 



plant attacked will mature 



a head, but the kernels 



are apt to be small. 

 Rotation is important because it will prevent damage by the first, 

 wingless generation, which causes the more serious injury. The 

 overwintering larva can be killed by burning or otherwise disposing 

 of the straw and stubble. 



Fig. 111.— 

 Work of Iso- 

 soma hordei. 

 Original. 



Fig. 112. — Work of the 

 Wheat Straw-worm. Orig- 

 inal. 



The Wheat-stem Maggot (Meromyzn americana Fitch) 

 The evidence of the presence of the wheat-stem maggot is a char- 

 acteristic blanching of the heads of wheat, rye, oats, or other small 



