Influence of aldicarb on root lesion nematodes, leaf disease and root rot in wheat and barley

The effects of aldicarb on populations of root lesion nematodes (primarily Pratylenchus penetrans ) and on grain yields of spring barley and wheat were examined in the field over 3 years, 1981*83. The incidence of barley net blotch ( Pyrenophora teres ), wheat leaf blotch ( Leptosphaeria nodorum ), and common root rot ( Cochliobolus sativus ) was also recorded in 1982 and 1983. Aldicarb treatments reduced the size of root lesion nematode populations in soil and roots in all years, except in the mid-season soil sample in 1983. The severity of leaf disease was decreased only in 1982, but the incidence of root rot was not significantly affected by the nematticide. Although aldicarb increased cereal grain yields by approximately 15% there was no significant relationship between numbers of root lesion nematodes in roots and soil and fungal disease symptoms on barley and wheat.     

THE PATTERN OF MIXTURES

The authors consider the main reasons which may justify theplanting of mixtures rather than pure crops, e.g. the provisionof nurses, intermediate returns, continuity of employment, biologicalconsiderations, health, fuller utilization of the site, improvementof form, &c., and give four examples of possible patternsfor mixtures in strips to suit varying circumstances.     

Responses to Pathogen-induced Disturbance: Decomposition, Nutrient Availability, and Tree Vigour

In the Oregon subalpine zone, extensive dieback occurs in relativelypure stands of 150 to 250-year-old mountain hemlock growingon very infertile soils. Tree death is caused by a root-rotfungus, Phellinus weirii. Young trees that become establishedfollowing death of the original forest are apparently not reinfectedby the pathogen until 80–140 years later. whereon mortalityoccurs again. We examined the effects.of this natural disturbanceand subsequent regrowth on a number of ecosystem characteristics. Decomposition rates and nitrogen availability measured by insitu exchange resins increased in the zones of young regrowth,but dropped to values common for old growth as the forest agedand the canopy closed. Phosphorus and potassium accumulationon exchange resins showed trends opposite to nitrogen, and mayhave been associated with changes in biomass. Increased nitrogenconcentrations and decreased lignin concentrations in fine rootsin the zone of young regrowth suggested improved tree nutritionunder conditions of higher N availability and lower leaf areaindex. Tree vigour, estimated as wood production per unit leafarea, also was significantly increased in the zones where youngforests grew. Circumstantial evidence suggests that increasesin nutrient availability and light following death of the matureforest improved photosynthesis leading to increased resistanceof young trees against infection by the pathogen.     

Knowledge Networks in an Uncompetitive Region: SME Innovation and Growth

Knowledge networks are now recognised as a crucial element underlying the economic success and competitiveness of geographic locations, in particular regions. The aim of this paper is to assess the types of knowledge networks utilised and formed by knowledge‐based small‐ and medium‐sized enterprises (SMEs) in the relatively uncompetitive regional setting of Yorkshire and Humberside in the UK. It explores the relationship between knowledge networking activity and the levels of innovation and growth achieved by these SMEs. It is found that SMEs tend to utilise and value more knowledge networks with actors outside the region. However, more innovative SMEs possess a balance of inside and outside the region knowledge networks. Knowledge networking activity is sometimes negatively associated with growth, suggesting that networks with certain actors, such as public sector support agencies, may be formed by SMEs when they are facing competitive pressures. In terms of policy implications, the paper recommends a shift from the cluster policies implemented by many regional authorities to a regional innovation systems approach, focusing equally on the regional and more global dimensions of knowledge networks. It is concluded that regional public policy makers need to renew their efforts to support SMEs in creating and sustaining their knowledge networks.