December 1, 1995
In field tests on Ruby Red grapefruit, the fungicides copper hydroxide (Kocide DF), benomyl (Benlate 50 DF), citrus spray oil, and fenbuconazole significantly reduced greasy spot severity and defoliation. Iprodione (Rovral 4 SC), fosetyl- Al (Aliette 80 WP), fluazinam, and myclobutanil did not control the disease or suppressed it only slightly. Of the nutritional products, Keyplex 350 at 2.0 gal/acre or at 0.5 gal/acre with citrus spray oil provided good control of greasy spot in field tests. Keyplex 445, Goemar MZ 63, and Tracite N also controlled greasy spot in field tests. In greenhouse tests with artificially inoculated rough lemon seedlings, copper hydroxide reduced greasy spot severity and defoliation much more than Keyplex 350, whether products were applied before or after inoculation. Tracite Zinc, Iron, and Manganese each suppressed greasy spot on inoculated rough lemon seedlings, suggesting the metals contained in nutritional products may be the active agents in these materials that suppress greasy spot development.