Abundance and Spatial Dispersion of Rice Stem Borer Species in Kahama,Tanzania

Species diversity, abundance, and dispersion of rice stem borers in framer’s fields were studied in four major rice growing areas of Kahama District. Stem borer larvae were extracted from the damaged tillers in 16 quadrants established in each field. Adult Moths were trapped by light traps and collected in vials for identification. Results indicated the presence of Chilo partellus, Maliarpha separatella, and Sesamia calamistis in all study areas. The most abundant species was C. partellus (48.6%) followed by M. separatella (35.4%) and S. calamistis was least abundant (16.1%). Stem borers dispersion was aggregated along the edges of rice fields in three locations (wards) namely: Bulige, Chela, and Ngaya. The dispersion in the fourth ward, Kashishi was uniform as established from two of the three dispersion indices tested. Further studies would be required to establish the available alternative hosts, the extent of economic losses and the distribution of rice stem borers in the rest of the Lake zone of Tanzania.     

Evidence of genotype–diet interactions in the response of rainbow trout (Oncorhynchus mykiss) clones to a diet with or without fishmeal at early growth

This study examined the genetic variability and genotype × diet interactions during early growth (initial mean body weight 1.2 g) among seven heterozygous clones of rainbow trout, Oncorhynchus mykiss. The clones were hand-fed a diet containing either fishmeal or plant proteins during a 49-day trial divided into two periods (P1, 26 days, and P2, 23 days). Weight, variation of weight within clone, feed intake, feed efficiency and mortality were calculated for both periods.There was a highly significant effect of diet and of clone for all traits at both periods, except for feed efficiency and mortality at P1. Highly significant interactions between diet and clone were also recorded for all these traits, except for mortality at P1. The occurrence of genotype × diet interactions when feeding juvenile rainbow trout with an all plant-protein diet indicates that a highly performing genotype on a fishmeal diet may perform poorly when fed a plant-protein diet. Interactions were found for the two major determinants of growth, i.e. feed intake and feed efficiency, showing that the dietary response differs according to the genotype. Monitoring of the within-clone variability of weight showed that a plant-based diet is likely to enhance the overall phenotypic variance in a population, whatever its initial genetic variability.     

Polychlorinated biphenyls and other organic chemical residues in fish from major United States watersheds near the Great Lakes, 1978

Twenty-six composite samples of fish were collected during 1978 from United States watersheds near the Great Lakes and analyzed for polychlorinated biphenyls (PCBs) and related organic chemicals. PCB mixtures resembling Aroclor 1254 were found in all samples, and mixtures resembling Aroclor 1242 (or 1016) were found in 77 percent of the samples. Total PCB concentrations in the whole-fish composite samples ranged from 0.13 to 14.6 ppm; 65 percent of the samples contained more than 2 ppm PCBs. DDT and its metabolites were found in all samples. sigma DDT concentration was 1.66 ppm, and 81 percent of the samples contained less than 1.0 ppm sigma DDT. Chlordane ranged from less than 0.001 to 2.57 ppm in 38 percent of the samples. Hexachlorobenzene was found in 65 percent of the samples, ranging from less than 0.005 to 0.447 ppm. Other chemicals identified by gas chromatography/mass spectrometry included petroleum hydrocarbons and chlorobenzenes, chlorostyrenes, chlorophenols, and chlorinated aliphatic compounds. Fish from the Ashtabula River (Ohio), Rock River (Ohio), and Wabash River (Indiana) contained extremely complex residues of chlorinated and other organic chemicals.     

Some chemical and physical properties of epronaz,a new herbicide

A brief account is given of the work leading up to the synthesis of epronaz (BTS 30 843), 1-(N-ethyl-N-propylcarbamoyl)-3-propylsulphonyl-1,2,4-triazole, a new pre- and early post-emergence herbicide for annual grasses. The synthesis is described, together with the occurrence and isolation of all three possible positional isomers in the final (carbamoylation) stage. The evidence for the structure assigned to epronaz is presented together with that for the other two isomers, and their interconversion is described. Some chemical properties of epronaz are described, with particular reference to its hydrolysis and its ability to function as a carbamoylating agent, in relation to persistence in the environment and to mode of action respectively. Some physical properties are also reported, including vapour pressure, solubility, and spectra. The mass spectral fragmentation pattern is also discussed.     

Virulence associations in oat crown rust

ABSTRACT Isolates of Puccinia coronata obtained from natural populations of Avena sterilis in Israel, winter oat (A. sativa) cultivars in Texas, and spring oat cultivars in the Northern Plains states of Minnesota, North Dakota, and South Dakota were analyzed for significance of pairwise virulence associations. Isolates from all three regions were tested on 25 oat lines with single P. coronata (Pc) genes for crown rust resistance from A. sterilis and one line with a Pc gene from A. sativa. Isolates from Israel were tested also on 11 Iowa backcross lines with undesignated crown rust resistance genes from A. sterilis. Four associated virulence groups were identified from significant positive virulence associations that were consistent across all three regions. Group 38 included virulence to Pc-38, Pc-39, Pc-55, Pc-63, and Pc-71; group 45 included virulence to Pc-45, Pc-46, Pc-48, Pc-52, Pc-54, and Pc-57; group 58 included virulence to Pc-35, Pc-40, Pc-58, and Pc-59; and group 61 included virulence to Pc- 36, Pc-51, Pc-56, Pc-60, and Pc-61. Virulence to Pc-70 showed the strongest association to virulences in group 38 but also showed significant association with virulence to Pc-45, Pc-35, and Pc-58. Virulences in group 61 were consistently negatively associated with virulences in group 38 in each region. In Israel, virulences to five of the Iowa lines showed positive associations to virulences in group 61 and negative associations to virulences in groups 38 and 45. Close similarity of reactions of nearly all isolates to Pc-39, Pc-55, and Pc-71 suggest that these genes may be identical or nearly identical alleles.     

Economic and herbicide use impacts of glyphosate-resistant crops

More than 95% of United States maize, cotton, soybean and sugarbeet acres are treated with herbicides for weed control. These products are used to improve the economic profitability of crop production for farmers. Since their introduction in 1996, over 75 million acres of genetically engineered glyphosate-resistant crops have been planted, making up 80% of soybean acres and 70% of cotton acres in the USA. These genetically engineered crops have been adopted by farmers because they are perceived to offer greater economic benefits than conventional crop and herbicide programs. The adoption of glyphosate-resistant crops has saved US farmers 1.2 billion dollars associated with the costs of conventional herbicide purchases, application, tillage and hand weeding. With the adoption of glyphosate-resistant sugarbeets on currently planted sugarbeet acres, US growers could potentially save an additional 93 million dollars. The adoption of glyphosate-resistant crops by US agriculture has reduced herbicide use by 37.5 million lbs, although the adoption of glyphosate-resistant sugarbeets would dampen this reduction by 1 million lbs.     

Structure-activity relationships in a group of imidazole-1-carboxamides

Detailed structure-activity studies in a series of substituted imidazole-1-carboxamides culminated in the synthesis of N-alkyl-N-phenoxyalkyl substituted compounds and, eventually, prochloraz, a compound shown to give excellent broad-spectrum disease control in cereals. Subsequently, evidence was obtained which suggests that its mode of action is through the inhibition of ergosterol biosynthesis or, more specifically, through inhibition of sterol C-14 demethylation.     

Effectiveness of two anticoagulant rodenticides (chlorophacinone and bromadiolone) for Columbian ground squirrel (Spermophilus columbianus) control in eastern Washington

Over the years a number of techniques for control of ground squirrels have been developed and used with varying degrees of success. Some have used bait stations, others the broadcast application of chopped vegetable matter and cereal grains. No data were found on the broadcast application of pelletized materials. Two toxicants, chlorophacinone and bromadiolone, were mechanically broadcast over six plots during the summer of 1983. Results were good (70–80% mortality) with the mid-season application, and excellent (100%) with the late-season treatment. Problems of migration compounded part of the study which points out the need for complete coverage to achieve control.