An Experiment to Control Fomes annosus in Second Rotation Pine Crops

Stump removal was found to singnificantly reduce killing byFomes annosus in second rotation crops of pine. Poisoning andgirdling of trees prior to felling and also stump poisoningfailed to control the disease. In this experiment no significantdifferences were detected in the susceptibility of Scots andCorsican pine to attack. Increasing periods of delay beforereplanting resulted in less mortality. An equation is presented,based on factors of the first rotation crop which may be usedto predict losses likely to occur when a site is replanted.Root attack by F. annosus results in reduced growth and yieldas well as mortality. The results from the experiment are discussed in trems of themangement of pine crops attacted by F. annosus in Theford Chase.     

MICRO-STRUCTURAL DIFFERENCES BETWEEN ARABLE AND OLD GRASSLAND SOILS AS SHOWN IN THE SCANNING ELECTRON MICROSCOPE

The scanning electron microscope has been used to compare the microstructure of an old grassland soil with that of an arable soil of the same soil series. The micrographs give more direct evidence than previously available of the presence of an adherent, presumably organic, matrix binding the clay and other particles of the old grassland soil. Fungal hyphae were also observed. Neither of these features was present to the same extent in the old arable soil.     

Comparison of laboratory methods for assessing numbers of apple rust mite (Aculus schlechtendali) overwintering on apple

During the winter of 1980/81 apple shoots from the preceding season's growth were collected from 19 orchards in Kent and East Sussex. Five buds from each of 10 shoots per orchard were dissected under a stereoscopic microscope at × 30 magnification and apple rust mites ( Aculus rchlechtendali ) were counted. These dissected buds were then used to test a more rapid method of extraction and counting. The buds were added to methanol and mixed with a vibrating machine, mites were then collected in sieves and counted. Counts of mites by this method were similar to those of the first method when there were fewer than 100 mites on 50 buds, but there was greater variation when mites were more numerous.
An even more rapid method using five other buds from the same 10 shoots was also tested; the buds were bisected, then vibrated in methanol, and the mites were collected in sieves and counted. Results were comparable with those obtained by the dissection/methanol method and can be used with similar confidence in advisory work on apple rust mite.     

SOIL STRUCTURE AND CROP YIELD

Relatively little has been published in Great Britain relating yields with quantitative assessments of the structure of soils. This paper gives examples of the kind of correlations found, a selection from many years' observations. Where the quantity of soil nutrients or disease was not a limiting factor, the yields of cereals, peas, and red beet were related to the stability of the structure which in turn depended on the number of years the soil had been out of grass. On a soil of weak structure it was found that stabilizing, with a conditioner, the structure developed by cultivation at a moisture content below field capacity resulted in a marked increase in both yield and size grade of cauliflowers.     

Spring Frosts Affecting the Establishment of Second Rotation Crops in Thetford Chase

Spring frosts in Thetford Chase cause a major reduction in thegrowth of young Corsican pine and very severe frosts or repeatedfrosting may kill the trees. Records of temperatures taken ona range of sites and in different conditions have shown that(a) spring frosts occur every year at Thetford, but the severefrosts which kill trees outright may only occur once every fewyears, (b) frost damage to plants mainly occurs when the treesare less than 18 in (45 cm) tall, (c) forest clearings largerthan 5 acres (2 ha) do not act as artificial frost hollows,(d) cold air flows down slopes of more than 1° and accumulatesat the bottom, forming a frosty zone. Studies showed that frost damage can be minimized by (a) completecultivation, (b) deep ploughing, (c) underplanting, and (d)strip felling. The benefits of these measures are demonstratedby temperature records and by measurements of tree growth. Methods of reducing frost damage are necessary in areas proneto spring frosts if crops of Corsican pine are to be successfullyestablished at low cost.     

Tubed Seedling Research and Development in Britain

Based initially on Canadian practice, research on the productionand use of tubed seedlings in Britain has been in progress for3 years (1968–70), and was begun because of their potentialadvantages as planting stock. Polythene greenhouses are usedto produce pine and spruce seedlings grown in small plastictubes filled with fertilized peat-sand compost, and plantingis possible 8 weeks after sowing. On ploughed peat-land, step-plantedseedlings are capable of high survival and vigorous early growth,with an effective planting season from mid April to late August.Animal browsing is the main adverse factor encountered, buthas been less serious than expected. Very high planting ratesare possible with a special tool. Seedling use could lead tolarge savings in peatland afforestation costs, and large-scaletrials are planned. In contrast, seedling performance on ploughedmineral soil has been unsatisfactory due to severe frost liftingand poor height growth. Results in reafforestation trials havenot been very promising.     

Poliovirus inhibitor from the central nervous system of the Rhesus monkey

The production of riboflavin by Eremothecium ashbyii is appreciably reduced by 3-amino-1,2,4-triazole at concentrations of inhibitor which do not inhibit growth. Corn and pea leaf tissues which are albinistic as a consequence of treatment with this compound have a greatly lowered riboflavin content.