Studies on the effect of Bladex and Etazine on bacterial indices of pollution
The effect of the triazine herbicides Etazine and Bladex on coliform and fecal streptococci groups was studied in Nile river water, Nile water seeded with sewage, and autoclaved Nile water. The results indicate the fecal streptococci were able to persist and multiply in Nile water containing Bladex or Etazine and seeded with sewage. The successive addition of Bladex and Etazine (up to 10 mg/liter) increased its degradation rate and had no inhibitory effect on the bacterial parameters.
Ecological Distribution of Pesticides in Lake Poinsett, South Dakota
Abstract Ecological distributions of chlorinated hydrocarbon residues in Lake Poinsett, South Dakota were studied from June, 1967 to June, 1968. Components of the ecosystem analyzed were water, bottom sediments, zooplankton, benthic algae, crayfish, aquatic insects and fish. Concentrations of aldrin, p,p'-DDD, p,p'-DDE, p,p'-DDT, dieldrin, endrin, heptachlor, heptachlor epoxide, lindane, methoxychlor and toxaphene were determined by gas chromatography and thin-layer chromatography. DDT and its metabolites, DDD and DDE, were the highest residues detected in all trophic levels examined. Heptachlor, heptachlor epoxide, aldrin, dieldrin and lindane were present in the majority of sample types, while neither endrin nor methoxychlor was detected above analytical confidence limits in any sample. Toxaphene was present in four fish. DDT and metabolites increased in percentage of total residue, while the ratio of DDT to DDD plus DDE decreased with increase in trophic level. The ratio of the epoxide form of heptachl...
The infection process, sporulation and survival of Alternaria helianthi on sunflower
SUMMARY 
 
Electron microscopy was used to study the infection of sunflower leaves by Alternaria helianthi. Conidia germinated by producing one to many germ tubes which grew across the leaf surface before forming appressoria. The fungus directly penetrated its host through the cuticle and epidermis. Entry into the host through wounds and stomates was also observed. Extracellular sheaths were found to be associated with germ tubes and intercellular hyphae of A. helianthi. Conidiophores developed through collapsed stomates, from leaf veins, trichomes and also from mycelium growing across the host leaf surface. Microcylic conidia were produced directly from parent conidia under certain conditions. Studies using a volumetric spore trap showed that the airborne spore concentration followed a distinct periodicity with peaks occurring between 0900 and 1100 h each day. Laboratory studies showed that safflower, noogoora burr and bathurst burr could serve as alternative hosts for A. helianthi. The pathogen was readily isolated from sunflower crop debris from a diseased crop that had been harvested 1 yr earlier.