Competition between Silene vulgaris (Moench) Garcke and alfalfa (Medicago sativa L.)

Growth indices describing the nature of the competitive relationship between Silene vulgaris and alfalfa during crop establishment were determined from experiments conducted outdoors in southem Manitoba in 1986 and 1987. The results of the experiments indicated that alfalfa dry matter yields were influenced more by intra- than interspecific competition. In comparison S. vulgaris was affected more by interspecific competition. Replacement diagrams and aggressivity indices both demonstrated that alfalfa and S. vulgaris were the aggressor and sub-ordinate species, respectively. Relative replacement rates for alfalfa versus S. vulgaris were significantly greater than unity, indicating that alfalfa exerted a greater replacement pressure on S. vulgaris than did S. vulgaris on alfalfa. Over time alfalfa could be expected to replace S. vulgaris as the dominant species within a population. Barley was more competitive than alfalfa with S. vulgaris. Not only was S. vulgaris shoot dry weight reduced more by barley than by alfalfa during the establishment year, but fewer S. vulgaris seedlings emerged the following year in plots that had been seeded to barley than in those that had been seeded to alfalfa.     

Phenological development and biomass allocation in Silene vulgaris (Moench) Garcke

Silene vulgaris (Moench) Garcke, grown from seed or from crown buds, exhibited three dis tinct growth phases; establishment, reproduc tive and post-reproductive. The establishment phase was characterized by rapid accumulation of shoot biomass, high relative growth rates (RGRs) and leaf area ratios (LARs). The sexual reproductive phase was characterized by a rapid increase in floral and seed biomass, minimal root development, and declining RGRs and LARs. In the post-reproductive phase, root and crown biomass increased rapidly concomitant with the development of regenerative buds; low RGR and LAR values occurred during this phase. Although similar growth phases were identified in both the first (grown from seed) and second years (grown from crown buds) of growth, LARs and RGRs were lower in the second than in the first year. In the second year of growth, plants exhibited a continual increase in below-ground biomass throughout growth, including the flowering period, a feature which was absent in the first year of growth.     

Effects of gamma radiation on the immature stages ofLiriomyza Trifolii

The effects of γ-radiation on the immature stages ofLiriomyza trifolii Burgess were studied with doses of 2000-25 Gy. The high doses were lethal to all stages. At doses of 750 Gy or less, larvae survived to pupate, but their number was reduced and the majority were either dead or deformed and did not give rise to adults. Eggs and prepupae were more susceptible to radiation than other stages. Larval radiosensitivity decreased with progressing instar, and pupal sensitivity decreased with increasing age. Contribution from the Agricultural Research Organization. No. 2922-E, 1990 series.     

Phagostimulants enhancing the efficacy ofBacillus Thuringiensis formulations against the Giant Looper,Boarmia (Ascotis) Selenaria,in avocado

In both laboratory and field trials, as well as in semicommercial scale applications, the minimum concentration ofBacillus thuringiensis (B.t.) required to secure satisfactory larval mortality ofBoarmia selenaria could be halved, from 0.5% to 0.25%, by addition of 1% of the commercial phagostimulant Coax. Another phagostimulant product, Gustol, was inactive. Coax did not attract caterpillars from a distance. However, individual, Coax-treated spots on the avocado leaf surface were consumed by the larvae to a significantly greater extent than control. The same difference in palatability was recorded when the spots were treated with a mixture of Coax and aB.t. formulation. This explains, at least partially, the aforementioned advantageous effect of Coax in practical control of the looper byB.t.     

Present status of Phytophthora species in the Mediterranean area,especially in relation to citrus1

Of the 44 currently accepted species of Phytophthora, 18 have been reported in the Mediterranean area. The status of each is briefly reviewed. On citrus, P. citrophthora and P. nicotianae var. parasitica are mainly responsible for foot rot and gummosis, and in addition P. hibernalis, P. syringae, P. cifricola and P. cactorum for brown rot of fruits. The incidence of these species is closely linked to their temperature requirements. The use of sour orange as a resistant rootstock has long provided satisfactory control of foot rot and gummosis, while chemical treatments are effective against brown rot. However, there are indications that, with changingcultural practices, the resistance of sour orange is less well expressed, and the species is incidentally also susceptible to citrus tristeza closterovirus. Alternative rootstocks are therefore being sought.     

Spread of phytophthora rot on stored citrus and its prevention by fungicide dips1

Oranges and lemons infected with Phytophthora citrophthora and P. syringae were placed among healthy fruits in boxes kept at 5, 10 and 14°C. The spread of the rot by contact infection was assessed after 3,6,12 and 18 days and again after 7 days' shelf-life at 17°C. P. citrophthora infected adjacent fruits after 12 days at 10°C and 3 days at 14°C. No infection occurred at 5°C. P. syringue infected the fruits at all the temperatures tested. On fruits kept for 6 days at 5°C, the rot developed after shelf-life. The presence of Phytophthora-infected fruits in orange and lemon packing boxes enhanced the development of penicillium rots. Post-harvest dips in metalaxyl at 0.05 and 0.1% concentrations and fosetyl-Al at 0.1,0.2 and 0.3% concentrations prevented the spread of P. citrophthora in packing boxes kept for 30,40 and 60 days at 11°C, but had no effect on penicillium rots. The mixture of the above fungicides with thiabendazole at 0.1%] or imazalil at 0.05%, concentrations gave best control against phytophthora and penicillium rots.     

Dynamics of antibody production in mice infected with Toxascaris leonina Linstow, 1909

Using counterimmunoelectrophoresis and ELISA tests the dynamics of antibody production in serum of mice experimentally infected with Toxascaris leonina was studied. The production of antibodies using both tests has already been detectable in serum of mice from 7 days post infection (DPI) and their level persisted till the end of the experiment, i.e. till 77 DPI. The most positive were reactions of sera with Antigens 1 and 3.     

Three species of the hair follicle mites (Acari: Demodicidae) parasitizing the sheep, Ovis aries L

Evidence of three distinct Demodex species parasitizing the sheep is given for the first time. A newly distinguished Demodex sp. is described, and diagnostic characters are compared for Demodex ovis Hirst, 1919, D. aries Desch, 1983, and Demodex sp. Information on prevalence, distribution in the tissues, and pathogenicity of these three Demodex species in 132 head of sheep in Czechoslovakia is presented, with a review of such data published to date.     

A new genus of capillariids from birds, Ornithocapillaria gen. n. (Nematoda: Capillariidae)

A new genus, Ornithocapillaria gen. n., belonging to the family Capillariidae and subfamily Baruscapillariinae is described and its diagnosis is given. The type species of the genus is Ornithocapillaria ovopunctata (Linstow, 1873) comb. n., other species are O. cylindrica (Eberth, 1863) comb. n., O. quiscali (Read, 1949) comb. n., and O. picorum (Rudolphi, 1819) comb. n. The new genus is characterized by a relatively large membranous pseudobursa, shape of processes supporting pseudobursa, and presence of a vulval appendage in female. It includes only species parasitic in the intestine of birds of the orders Passeriformes, Falconiformes, Strigiformes, and Piciformes.