Early harvest and ensilage of forage sorghum infected with ergot (Claviceps africana) reduces the risk of livestock poisoning

Sorghum ergot produces dihydroergosine (DHES) and related alkaloids, which cause hyperthermia in cattle. Proportions of infected panicles (grain heads), leaves and stems were determined in two forage sorghum crops extensively infected 2 to 4 weeks prior to sampling and the panicles were assayed for DHES. Composite samples from each crop, plus a third grain variety crop, were coarsely chopped and half of each sealed in plastic buckets for 6 weeks to simulate ensilation. The worst-infected panicles contained up to 55 mg DHES/kg, but dilution reduced average concentrations of DHES in crops to approximately 1 mg/kg, a relatively safe level for cattle. Ensilation significantly (P = 0.043) reduced mean DHES concentrations from 0.85 to 0.46 mg/kg.     

Rhizomania disease of sugar beet in England

Rhizomania disease was first detected in the UK in 1987, in a single crop in Suffolk. Affected plants had pale leaves, often upright, narrow and rolled; roots were small, often with constrictions, warty outgrowths, proliferation of fibrous roots, and vascular staining. Disease occurred in strips at right angles to one another, parallel with directions of cultivation, suggesting that the previous beet crop had also been infected. Beet necrotic yellow vein virus was detected by ELISA, by electron microscopy, and by transmission to indicator species. It was sometimes associated with beet soil-borne virus. The affected crop was destroyed with herbicide. No other outbreaks were detected in subsequent surveys of crops in 1987.     

On difficulties with allelopathy methodology

Summary. The main techniques and the common experimental methods used in studying allelopathy are reviewed. Problems associated with both methodology and conclusions drawn based on certain techniques are discussed. The accuracy obtained using these techniques is evaluated and show that some of the techniques could be a misleading tool. Some changes are suggested.     

Possible rôle of allelopathy in the competition between tomato, Senecio vulgaris L. and Chenopodium album L.

Summary. The allelopathic effect of Chenopodium album L. (fat-hen) and Senecio vulgaris L. (groundsel) on tomato ( Lycopersicon esculentum Mill cv. Ailsa Craig) plants was investigated under glasshouse conditions. A new technology was used to separate competitive from allelopathic effects. These experiments suggested that C. album had an effect on tomato through allelopathy. C. album leach-ates significantly reduced shoot fresh and dry weights and the accumulation of N, P, K, Ca and Mg of tomato shoots. No effect was found on the quantities of these elements in tomato roots. Leachate of five plants of C. album per pot was sufficient to reduce tomato growth. Addition of 10 or 20 g kg⁻¹ of C. album dried shoots to the soil mixture significantly decreased the fresh and dry weights of tomato plants. S. vulgaris leachates did not show significant effects on the growth or nutrient accumulation of tomato plants.     

The influence of inoculum concentration, relative humidity, and temperature on infection of greenhouse tomatoes by Botrytis cinerea

Botrytis cinerea causes serious crop losses in greenhouse tomato crops through infection of flowers and stem wounds. Experiments were carried out to determine the effects of inoculum concentration, relative humidity (RH), and temperature at these two infection sites. Infection of permanent flower parts increased as a function of inoculum concentration and both length of exposure to high RH (approximately 100% for 0–36 h) and specified continuous RH (56–100%). A low level of infection was still evident under continuous 56% RH. Interruption of periods of high RH with breaks of low RH did not reduce infection. Infection of stem wounds was less dependent on inoculum concentration or RH. Factorial combinations of inoculum concentration, RH, and temperature produced significant interactions. Higher temperature increased infection of flowers but reduced infection of stem wounds. The main implications for control in commercial crops are as follows. Lowering the aerial spore concentration by maintaining the disease at a low level will reduce flower infection. Lowering RH will reduce but not eliminate flower infection but will have only a small effect on stem infection. Raising the temperature (from 15 to 25°C) will reduce stem infection, and whilst flower infection increases, this is counteracted by increased flower production and a decrease in the proportion of infections reaching the peduncle and stem.     

Vegetation and Environment in Afforested Sand Dunes at Newborough, Anglesey

Newborough Forest was planted with pines, chiefly Corsican pine,during the period 1947–65. In 1986, its soils and vegetationwere surveyed and related to the preplanting condition of thedunes, inferred from air photographs. The youngest dunes contained4 per cent calcium carbonate in the top 30cm; the oldest wereacid, with no free calcium carbonate. There was little acidificationof the soil and no extra leaching of calcium carbonate due tothe pines. Vegetation under trees varied according to the ageand pH of the dunes. Young dunes were almost bare except formoss; older dunes had been colonized by ferns and brambles.All plant species of the original open dune system had apparentlysurvived in unplanted slacks or on road verges; some had increased.Many new species had invaded, including woodland mosses, ferns,orchids and two species of Pyrola.     

Inactivation of infectious pancreatic necrosis virus for vaccine use

Abstract. Formalin and β-propiolactone (BPL) were compared for efficacy in inactivating infectious pancreatic necrosis virus (IPNV) for vaccine use. Incubation with a 1:200 dilution of formalin at 20°C for four days or longer, or a 1:200 dilution of BPL at 4°C for six days or longer, completely inactivated the virus infectivity. However, whereas treatment with formalin caused only a slight reduction in anti-genicity as titrated by in vitro tests, treatment with BPL destroyed over 50% of the antigenicity of the virus. Virus inactivated with formalin also proved highly effective at inducing high titres of neutralizing antibody in trout.     

A NEW TECHNIQUE FOR THE ACCURATE AERIAL APPLICATION OF HERBICIDES TO DRAINAGE CHANNELS WITH NEGLIGIBLE SPRAY DRIFT

Summary. Difficulties of access met with in Britain when applying dalapon to emergent water weeds in drainage channels led to work starting in 1964 on the development of a method of accurate aerial application of aqueous solutions of herbicide. The narrow, sinuous nature of the targets and the proximity of susceptible crops made it necessary to minimize spray drift and maintain a constant height and a slow speed. Nozzles designed to give large droplets were tested for droplet size and distribution. Selected nozzles were then tested from a helicopter in the field and the effect of their spray characteristics on the biological performance of dalapon was assessed. No daman occurred as a result of spray drift and satisfactory control of Phragmites communis, Typha angustifolia and T. latifolia was achieved with a lower dose of dalapon in a lower volume of spray than previously considered necessary for ground applications.
Une nouvelle technique pour l'application précise d'herbicides par voie aérienne sur les canaux de drainage, avec des risques négligeables d'entrainement     

The significance of leptospiral titres associated with bovine abortion

To investigate relationships between serological titres to 2 serovars, pomona (L. pomona) and hardjo (L. hardjo), of Leptospira interrogans and abortions, log linear and logit models were fitted to herd and individual cow data from cattle serologically negative for brucellosis. Serological titres to both serovars were significantly related to abortions in individual cows, with L. pomona having a stronger relationship than L. hardjo. L. hardjo was not significant when herd data were analysed. Differences between dairy and beef cattle in the serological titres found to both L. pomona and L. hardjo were detected when data sets of all cattle or cattle with no history of abortion were analysed. The beef/dairy differences may be due to different management practices and/or to different geographical distributions of both serovars and populations of beef and dairy cattle. If there are no cattle in a herd with a reciprocal titre of 3000 or greater for L. pomona, it is unlikely that L. pomona is associated with the abortion problem. There was no specific L. hardjo titre which separated high and low probabilities that the serum came from a cow or herd with an abortion history.