PLOTLESS ENUMERATION WITH ANGLE GAUGES

The basic method and theory for determining basal areas withangle gauges are explained. Limitations in use are pointed out,and modifications and developments discussed. An explanationis given of the use of the angle-gauge principle for determiningheight and volume. Next, the instruments themselves are discussedand finally the Spiegel-relaskop and its wide range of uses.For the future, the author considers consolidation of ideasmore likely than anyvery startling new developments. A fulllist of references to literature is given.     

A molecular genetic assessment of herbicide-resistant Sinapis arvensis

The acquisition of resistance to both the auxinic herbicide dicamba and the sulfonylurea herbicide chlorsulfuron has been recorded in Canadian populations of the weed species Sinapis arvensis L. (charlock, wild mustard) To study the effect of this selection for herbicide resistance on levels of genetic variation, polymerase chain reaction-based DNA fingerprinting techniques were used to characterize two herbicide-resistant and one susceptible population of S. arvensis . Analysis of the resultant DNA marker profiles revealed extensive polymorphism between individuals. However, segregation of the three biotypes was detectable despite high levels of intrabiotype polymorphism. No reduction in the levels of heterozygosity within the resistant populations were found compared with the susceptible population.     

A simulation model for forecasting the timing of attacks of Delia radicum on cruciferous crops1

The cabbage root fly (Delia radicum) is a major pest of cruciferous crops in temperate regions of the world. A model using weather data has been developed to forecast the timing of D. radicum attacks. The model simulates development of a field population of D. radicum, commencing with the overwintering stage (diapause pupa) and following development through the first, second and, where appropriate, third generation until autumn. The model is based on a series of rate equations which describe the relationship between the rate of development of D. radicum and temperature. The model uses soil temperatures in the simulation of the development of the egg, larval and pupal stages, and air temperatures with the adult-fly stage, taking account of periods of summer dormancy (aestivation) and the onset of winter dormancy (diapause). Using local weather data or standard measurements of air and soil temperatures taken at agrometeorological stations, the model can forecast D. radicum activity in any region.