Sectional notes

American Journal of Potato Research -     

Two-year development of southern pine seedlings and associated vegetation following spray-and-burn site preparation with imazapyr alone or in mixture with other herbicides

Eight herbicide combinations containing imazapyr alone or in mixture with glyphosate, triclopyr, or picloram+2,4-D were applied July–August 1991 at each of three upland sites in the southeastern U.S., with or without a subsequent broadcast burn in September. Seedlings of loblolly (Pinus taeda L.) or slash (P. elliottii Engelm. var. elliottii) pine were planted that winter. Second-year (August 1993) vegetation responses indicate that broadcast burning, in combination with herbicides, was associated with increased abundances of grasses, forbs, and shrubs and decreased abundances of vines and hardwood trees. In the presence of burning, imazapyr-in-mixture treatments were associated with a high abundance of grass (53% cover) and a mean size of pines less than that of seedlings growing in imazapyr-alone treatments. In the absence of burning, imazapyr-alone treatments were associated with a high abundance of blackberry (21% cover), an average height of hardwoods (131 cm) exceeding that of pines (71 cm), and a mean size of pines less than that of trees growing in imazapyr-in-mixture treatments. Hardwood height in the absence of burning was less when imazapyr was combined with glyphosate (75 cm) than with triclopyr (102 cm). Regardless of the presence or absence of burning, size of pines and abundance of shrubs and hardwoods did not differ between imazapyr rates of 0.56 and 0.84 kg acid equivalent/ha or among herbicides applied in mixture with imazapyr.     

The relationship between certain blood cations in cows with milk fever and both the state of consciousness and the position of cows when attended

In one study, a comparison was made of the concentrations and ratios of certain blood cations in 2 groups of cows with milk fever, one showing normal consciousness (n = 8) and the other depressed consciousness (n = 24). There were no significant differences in the mean concentrations of serum total calcium, plasma inorganic phosphorus and potassium, erythrocyte sodium and potassium, the serum calcium/serum magnesium ratio or the plasma sodium/erythrocyte sodium ratio. There were significant differences (all P less than 0.05) in the mean (+/- SD) concentrations of serum magnesium and plasma sodium concentrations, and the plasma sodium/serum magnesium ratio of 0.8 +/- 0.28 vs 1.2 +/- 0.37 mmol/l, 155 +/- 3.0 vs 147 +/- 6.4 mmol/l and 180 +/- 40.1 vs 116 +/- 34.1 for normal vs depressed cows, respectively. In a second study, a comparison was made of the concentrations and ratios of the same blood cations in 3 groups of cows in different positions when attended for milk fever, namely standing (n = 6), sternal recumbency (n = 24) and lateral recumbency (n = 31). There were no significant differences between the mean concentrations or ratios of any of the cations.     

Black soil blindness: A new mycotoxicosis of cattle grazing Corallocytostroma-infected Mitchell grass (Astrebla spp)

A new, fatal mycotoxicosis of cattle has been recognised in north-western Australia. A feeding trial confirmed the toxicity of a previously unknown species of Corallocytostroma that grows on Mitchell grass (Astrebla spp). The disease has been colloquially named ‘black soil blindness’ because its most prominent features are its confinement to pastures on black soil, and blindness and death of affected animals. Over 500 cattle have died and considerable subclinical disease is present. Above average wet season rainfall and extended growing seasons may explain the emergence of the fungus. The disease is important because cattle production in large areas of Australia utilise Mitchell grass pastures.