The Effect of Phorate Applied to Seed on the Growth, Development and Insects Attacking Grain Sorghum1

Abstract

Seed of sorghum variety RS610 was treated with phorate (Thimet 44-D) at the rate of 0.5, 1.0, 2.0 and 4.0 pounds of active ingredient per 100 pounds of seed, with and without Arasan 75 at 10-2/3 ounces. Additional treatments included Arasan 75 and Sticker 25-1 alone and in combination. In field tests the 2- and 4-pound rates seriously reduced stand and delayed plant development as measured by pollen shedding. Plants from seed treated with the 0.5- and I-pound rates shed pollen earlier than the untreated. Highly significant differences in seed yield were associated with differences in stand. The plots receiving the phorate treatments had significantly less yield than the untreated. In greenhouse tests, germination was reduced by the higher dosages and prolonged about 3 days. Treated seed, after 10 months storage, showed a great reduction in germination. Per cent germination under greenhouse conditions was highly significantly correlated with the field stand. Arasan reduced the toxic effect of the phorate. The sticker showed some deleterious effect on germination, which was reduced when combined with Arasan. The higher dosage rates controlled the corn leaf aphid, Rhopalosiphum maidis (Fitch), during the earlier period of growth. However, the phorate treatments gave no control of aphid populations on bagged heads of sorghum in the field.