The effect of petroleum oil herbicides on the growth of guayule and weed seedlings

Benedict, H.M.; Krofcheck, A.W.

The effect of petroleum oil herbicides on the growth of guayule and weed seedlings

1946

Benedict, H.M. | Krofcheck, A.W.

Results obtained with petroleum oils in controlling weeds in guayule seedings are reported in this paper. Adequate control of weeds in nurseries or field seedings was obtained by spraying the areas with a mixture of three-fourths stove oil and one-fourth diesel oil applied at the rate of 32.4 gallons per acre or 1.2 gallons per nursery bed 4 X 400 feet. It was necessary to make the first application of oil while the weeds were in the cotyledon stage or about 2 weeks after seeding when the weeds and also the guayule were susceptible to the oil. However, the guayule was so much more resistant to the oil that almost complete killing of the weeds and no killing of the guayule was obtained. Oil spraying resulted in a temporary set-back in the growth of the guayule, but by the end of the growing season there was no difference between the weights of the tops of plants in oiled and hand-weeded plots. Results from greenhouse tests indicated that guayule seedlings should be sprayed with the oil at air temperatures between 70 degrees and 80 degrees F. A great many plants were killed when sprayed with the oil at 50 degrees and 94 degrees F. The results also suggested that whenever the seedlings have been subjected to unfavorable growing conditions such as cold weather or drought prior to oil spraying, their resistance to the oil was greatly reduced. No difference was obtained between the growth of lettuce in soils that had not been sprayed with oil and those that had received a total of 250 gallons of diesel oil or 300 gallons of stove oil to the acre, thus indicating that there was no residual effect on the soil from applications of oil in much greater amounts than would be applied for weed control in guayule seedings.

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