SUMMARYWeighed amounts of lightly pulverized soil were drawn through a perforated aluminium plate and impacted on agar media in Petri dishes. This was done by placing the dishes in an Andersen air sampler, through which air was drawn at 14 l./min. The sampler was operated so that the soil was dispersed uniformly into 400 equally sized units/dish, each unit weighing 0·125 mg. These were transferred either to water‐agar medium to detect Pythium spp., or to Dox‐yeast‐agar medium for Fusarium oxysporum. The amount of each fungus in the soil was estimated from the frequency it was recovered from the transferred soil units. Results were more reproducible than by the usual soil‐dilution methods, and the method gave more uncontaminated cultures of Fusaria and Pythia.
The annual recurrence of the mosaic disease in epiphytotic form in the canning tomato crop of Indiana has made it highly important to ascertain the mode of overwintering of the causal virus. It seemed within the realm of possibility that the virus might be perpetuated over winter in hothouse tomato crops, in tomato seed, in related perennial weed hosts, and by insects. The agency of insects in this connection has not been studied. The work of MCCLINTOCK and SMITH (9) on aphids as carriers of spinach blight would indicate that such insects might perpetuate other mosaic viruses, but MCCLINTOCK (io) has been unable to find this true for tomato mosaic. DOOLITTLE'S (7) work on cucumber mosaic has failed to incriminate any of the insects studied in connection with that disease. The present work has to do mainly with the second and third possibilities just mentioned. Hothouse tomatoes as carriers The mosaic disease has been found very commonly in hothouse tomato crops, and in the immediate neighborhood of hothouses it is possible that the disease may be carried from the late hothouse crop to the field crop plant-beds. This danger is very great in cases in which the plants for the field crop are started in hothouses or coldframes adjacent thereto. In one case noted in June I920 at Kokomo, a severe early infestation of mosaic was present in a field, the plants for which had been grown in part of a hothouse occupied by a tomato crop. In fact, mosaic was found on many of the tomato plants left in the plant-bed. Hothouse tomatoes, however, are grown only in a relatively few localities in the state, and are usually near the towns and cities. The canning tomato crop, on the other hand, is contracted primarily among general farmers
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