Evaluation of Ryania for the Protection of Stored Wheat and Shelled Corn from Insect Attack

Excerpts from the report: This report is the third of a series presenting results of tests with various insecticidal dusts and sprays applied to stored grain for protection from insect attack. It summarizes the tests with ryania begun in September 1952 and concluded in January 1956. Ryania is a tropical American genus of shrubs and small trees belonging to the family Flacourtiaceae, the principal source of the insecticide being the stem wood of Ryania speciosa Vahl, a species native to Trinidad. Other species occur in different areas of northern South America and in the Amazon basin. The studies were conducted under actual storage conditions both on the farm and at CCC bin sites. At the latter tests were made with wheat and shelled corn stored in the standard circular 3,250-bushel metal bins of the Commodity Credit Corporation, U. S. Department of Agriculture, and also on shelled corn in 3,000-bushel rectangular wooden bins. After the dusts were applied, the grain was sampled monthly to determine the insect population trends and the moisture content of the grain. These samples were used to estimate the levels of residue, to observe any change in the potency of the residues in bioassay tests, and to establish commercial grades. In tests with wheat, the level of residue was also traced through the milling process. Application rates of ryania ranged from 20 to 100 pounds per 1,000 bushels in wheat, and from 20 to 60 pounds in corn. These rates practically eliminated any initial insect populations, and kept the grain almost insect-free for as long as 33 months. Milling tests showed that 80 to 90 percent of the ryania could be removed in the scouring process preparatory to milling, and that relatively small amounts were carried into the feed and flour fractions.