Residual Red Morningglory (Ipomoea Coccinea) Control with Foliar- and Soil-Applied Herbicides

Research was conducted to evaluate residual activity of herbicides applied postemergence (POST) and preemergence (PRE) for red morningglory control. Atrazine at 2.24 kg ai/ha controlled 30- to 60-cm red morningglory 78% 10 d after treatment (DAT) but control was greater for carfentrazone at 0.035 kg ai/ha, diuron plus hexazinone at 1.57 + 0.44 kg ai/ha, flumioxazin at 0.14 kg ai/ha, and sulfentrazone at 0.32 kg ai/ha (88 to 93%). At 28 DAT control with diuron plus hexazinone, flumioxazin, and sulfentrazone, reflective of both the initial POST control and soil residual activity, was equivalent to that of atrazine at 3.36 kg/ha (92%), but control was 34 to 66% with carfentrazone at 0.009, 0.018, and 0.026 kg/ha, hexazinone at 0.56 kg/ha, pyraflufen at 0.007 and 0.015 kg ai/ha, and trifloxysulfuron at 0.016 kg ai/ha. In another study to evaluate residual control with soil-applied herbicides, red morningglory was controlled at least 87% 35 DAT with atrazine at 2.24 kg/ha, diuron plus hexazinone at 1.57 + 0.44 kg/ha, flumioxazin at 0.14 kg/ha, sulfentrazone at 0.16 kg/ha, and metribuzin at 1.68 kg ai/ha. Control 35 DAT was 78% for atrazine at 1.12 kg/ha, 84% for diuron plus hexazinone at 1.05 + 0.30 kg/ha, and 63% for flumioxazin at 0.07 kg/ha. By 49 DAT only sulfentrazone controlled red morningglory 80% or more and by 63 DAT, control with sulfentrazone at rates of 0.21 kg/ha and higher was 83 to 88%. At 77 DAT sulfentrazone at 0.21 kg/ha controlled red morningglory 78% and no other herbicide treatment provided more than 46% control. In another study red morningglory control did not change from 49 to 63 DAT when sulfentrazone at 0.28 to 0.42 kg/ha was applied PRE following trifluralin preplant incorporated (PPI), but control decreased from 49 to 63 DAT when sulfentrazone was incorporated with trifluralin.

Light and electron microscopy of teliospores and teliospore germination in the rust fungus Coleosporium ipomoeae

A combination of light, scanning, and transmission electron microscopy was used to examine teliospores and teliospore germination in the rust fungus Coleosporium ipomoeae (Schw.) Burrill, a parasite of the wild morning glory Ipomoea coccinea L. Telia developed on abaxial surfaces of infected leaves and appeared as orange, waxy crusts usually associated with uredinia. Mature teliospores were cylindrical to slightly clavate in shape and thin-walled. The presence of chitin in the spore wall was demonstrated using wheat germ agglutinin gold labeling. Teliospores were surrounded by an electron-dense extracellular material. Each spore possessed a large prominent nucleus containing synaptonemal complexes indicative of prophase I meiotic nuclei. Following hydration, the nucleus of each spore completed meiosis and the spore was divided into four uninucleate compartments by the formation of three transverse septa. Each compartment gave rise to a germ tube into which the nucleus and cytoplasm migrated. Germ tubes developed into long slender sterigmata that grew through the extracellular material within the telium to become exposed on the leaf surface. A basidiospore then developed at the tip of each sterigma. Once the nucleus moved from the sterigma into the spore, a septum formed to delimit the spore from the tip of the sterigma.Key words: fungal spores, transmission and scanning electron microscopy, high pressure freezing.