The wireworm survey in the Eastern Counties revealed many cases where the observed wireworm damage failed to correspond with the estimated field population. A possible explanation for this was the inaccuracy of counts made by picking wireworms out of the soil samples by hand. Tests showed that such methods recovered an extremely variable proportion of the wireworms in the‐ samples and, on the average, only two‐fifths of the larvae were obtained. A modified form of the washing and flotation technique used by Salt & Hollick (1944) was introduced for large‐scale work and is described. By this method, ten samples of soil (4 in. diam. and 6 in. deep) bulked together are examined at a time and can be dealt with at the rate of 13 samples per man per hour with an efficiency of 95‐100% in the extraction of wireworms. The populations estimated on 600 fields sampled between December 1942 and May 1943 have thrown more light on the size and composition of the wireworm population in grass and arable fields. Inspection of the crop results on fields tested by the washing process showed a much closer relationship between wireworm population and wireworm damage than had been obtained by the hand‐sorting method in the previous year.

A study was made of the numbers and kinds of microorganisms in the root zone of wheat and soybeans grown in the greenhouse at three ranges of temperature: 55–60°, 70–75°, and 85–90 °F. Numbers of bacteria in the rhizosphere and rhizoplane of wheat decreased as the temperature increased, whereas numbers in the root-free soil and on soybean roots increased with increased temperature. The same relationships held for methylene blue reducing, glucose-fermenting, and ammonifying bacteria and those requiring amino acids for optimal growth. Generic analysis of bacterial isolates showed that the percentage of Gram-negative rod-forming organisms increased with a rise in temperature in root-free soil and on soybean roots but decreased on wheat roots. On the other hand, the incidence of Gram-positive and pleomorphic organisms decreased in soil and on soybean roots with higher temperature and increased on wheat roots.Fungal isolations from washed root segments showed a greater incidence of Mucor, Rhizopus, Rhizoctonia, and Gliocladium on soybeans at the high temperature whereas species of Fusarium and Cylindrocarpon were more prevalent at the low temperature. With wheat the most striking feature was the predominance of non-sporing dark species at the high temperature and of non-sporing hyaline types at the low temperature.The number of soil nematodes decreased in the rhizospheres of both plants with increased temperature, the effect being more pronounced with soybeans. With this crop all except one of the genera recognized decreased in number, whereas with wheat, the incidence of certain nematodes such as species of Helicotylenchus, Boleodorus, and Aphelenchoides did not change with temperature.The results suggest that temperature exerts a direct effect on the microorganisms in the root zone and an indirect effect by influencing plant growth.

The number of nematodes in the rhizosphere of wheat, barley, oats, soybeans, and peas is greater than in the adjacent root-free soil. Pratylenchus sp. is present in the rhizosphere of grains in greater numbers than in the rhizosphere of legumes; Paratylenchus sp. on the other hand showed a preference for legumes. Other genera identified were more abundant in the rhizosphere than in root-free soil, but were not as numerous as Pratylenchus or Paratylenchus, nor did they show a preference for any of the plants tested. One nematode species (Tylenchorhynchus) was present in small numbers and was equally abundant in the rhizosphere and in root-free soil. The consistent distribution pattern of nematodes in the rhizosphere of wheat and of soybeans, observed at high levels of illumination (1200 foot-candles), was not maintained when the illumination was reduced to 300 ft-c or less.

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The influence of actinomycetes and fungi isolated from soil and from plant roots on Rhabditis (Cephaloboides) oxycerca de Man, a bacteria-feeding nematode, was studied. A striking accumulation of nematodes occurred in the vicinity of colonies of certain species of these organisms growing on agar media. There was little evidence of repulsion of the nematodes. Shake-culture filtrates of a large percentage of the actinomycetes tested strongly attracted the worms and none repelled or was toxic to them. It is suggested that the commonly observed attraction of nematodes to plant roots may be due not only to root diffusates but also to the abundance and activity of the soil microorganisms in the vicinity of the roots.