362 PRINCIPLES OF SOIL MICROBIOLOGY 



season. 59 This is twice repeated; the common cycle being three years. 

 This white grub may become a limiting factor in continuous wheat pro- 

 duction in certain sections ; the infestation usually increasing with each 

 generation, so that it becomes necessary to rotate with a cultivated 

 crop. The green June beetle and muck beetle also (McCulloch) prefer 

 soils receiving heavy applications of animal manures. 



The cutworms hatch in September or October and become very 

 active during the following spring. They cut off young plants near 

 the surface of the soil and lap up the exuding sap. This is usually done 

 at night. 



Crop rotation, use of artificial fertilizers, fall plowing, 60 the use of 

 poisoned and other baits, 61 soil fumigants (CS 2 ) and insecticides (Paris 

 green) , 62 as well as the direct mechanical protection of plants, are among 

 the remedies suggested for these three pests. 



Insects may also inhibit the activities of certain specific soil organisms, 

 such as legume bacteria, by feeding on the nodules. This was pointed 63 

 out for the beet leaf larva Cerotoma trifurcata, and for the mealy bugs 

 Pseudococcus maratinus. 64 As many as fifteen bugs were seen on one 

 soybean nodule. 



In addition to the invertebrate, there exists also a vertebrate fauna 

 in the soil, including moles, blind mice, field mice, marmots, etc. 

 France suggests that there exists an association in soil (Edaphon) con- 

 sisting of bacteria, algae, fungi, diatoms, protozoa, rotatoria, nemato- 

 des, worms, myriapods and insects. The bacteria and fungi liberate 



59 McColloch, J. W., and Hayes, W. P. Soil temperature and its influence on 

 white grub activities. Ecology, 4: 29-36. 1923; Osborn, H. The problem of 

 permanent pasture with special reference to the biological factors. Proc. 39th 

 Ann. Meet. Soc. Prom. Agr. Sci., 7-18. 1919. 



60 Hyslop, J. A. Wireworms attacking cereal and forage crops. U. S. Dept. 

 Agr. Bui. 156. 1915; Hunter, W. D. Relation between rotation systems and 

 insect injury in the south. U. S. Dept. Agr. Yearbook, 1911: 201-210. 1912. 



61 Treherne, R. C. Wireworm control. Entom. Branch, Dept. Agr., Canada, 

 Pamphl. 33. 



62 Davis, J. J. Miscellaneous soil insecticide tests. Soil Sci., 10: 61-76. 

 1920. 



63 McConnell, W. R. A unique type of insect injury. Jour. Econ. Entom., 

 8: 261-267. 1915; Another nodule destroying beetle. Ibid., 8: 551. 1915; 

 Leonard, L. T., and Turner, C. F. Influence of Ceratoma trifurcata on the 

 nitrogen-gathering functions of the cowpea. Jour. Ajner. Soc. Agr., 10: 256- 

 261. 1918. 



64 Leonard, L. T. Mealy bugs on the roots and nodules of legumes growing in 

 the field. Science, N. S., 57: 671-672. 1923. See also Folsom, J. W. The 

 insect pests of clover and alfalfa. 111. Agr. Exp. Sta. Bui. 134. 1909. 



