摘要:

The logarithm of the mean number of greenhouse whitefly (Trialeurodes vaporariorum) puparia per leaf, when sampled from a single leaf stratum of a greenhouse tomato crop, had a linear relationship to the proportion of infested leaves, on a complementary log-log scale. Whitefly puparia had a clumped distribution with strong correlations between adjacent plant rows and plants within rows. In order to sample most patches of whitefly but to minimise the impact of correlation between adjacent plants on the sample, sample plants were selected from a rectangular grid covering either the whole greenhouse or an infested area of a large house. The rectangular grids consisted of plants at fixed intervals (every 7–10th plant) along the chosen rows, spaced on odd number of rows (3, 5, or 7) apart. Each grid had a random starting point. Decision charts incorporating action thresholds can be constructed based on the number of infested leaves and the total number of leaves examined. Whether parasitism byEncarsia formosais above or below any preset threshold can be determined by plotting the number of leaves with whitefly puparia against the number of leaves with fewer parasites than the threshold. Using recording charts, an advisor to the grower will obtain information on the location of whitefly and whether parasitism is above or below the preset threshold. This information can be used to determine whether action is required and to assist in deciding the type of action to be taken.

ISSN:0114-0671    

DOI:10.1080/01140671.1989.10428019

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Wheat and barley seed treated with triadimenol+imazalil at three rates, (recommended, half-recommended, and twice recommended), and barley seed treated with imazalil in ethanol at three rates, was stored for 15 months at ambient temperature in the laboratory. At the recommended rates (15 + 5 g a.i./100 kg seed for triadimenol + imazalil and 6.25 g a.i./100 kg seed for imazalil in ethanol), germination over the 15 months of storage did not differ from that of untreated seed. There were no significant differences in field emergence after 3, 9, 12, and 15 months of storage. At twice the recommended rate, triadimenol + imazalil reduced barley germination after 12 months storage because of an increased number of abnormal seedlings. Field emergence was also significantly reduced. Seedling vigour, as determined by plumule length, did not differ for imazalil in ethanol treatments, but was reduced in both wheat and barley by all application rates of triadimenol + imazalil.

ISSN:0114-0671    

DOI:10.1080/01140671.1989.10428020

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Phenotypic stability and genotype × environment interactions of reproductive traits, yield, and yield components were estimated in pea by growing eight genotypes (cv. Ichiban, Huka, Maro, Birte, Progreta, Combi, Greengolt, and Carpo) in nine environments (three planting densities × three sowing dates). The regression coefficient (β) of the character against its average environmental performance of all lines was used as a measure of both stability and adaptation. Yield is likely to respond slowly to direct selection as indicated by a small genotypic effect and low broad dense heritability (h2bs). Broad sense heritability of number of ovule initials per pod was extremely high and there was no G×E interaction. The genotypic component of this character was very high. Early generation selection for number of ovule initials per pod is feasible. In contrast, the number of flowers, initiated pods, and flowers aborted per plant had low h2bsand a low genotypic effect, while the number of pods aborted per plant had medium h2bsbut a low genotypic effect with high G×E interaction, suggesting poor response to selection. Ovule abortion percentage had a high genotypic effect. The G×E effect was negligible for this character and it had high broad sense heritability. Breeding this character for low ovule abortion should be promising. Broad sense heritability of pods per plant was very low and G×E interaction was high. Breeding this character for specific adaptation and for stability across environments is not feasible with these lines. The number of peas per pod showed neither high genotypic effect nor G×E interaction effect. Progress in selection for this character would be slow. The effect of genotype was predominant for 1000 seed weight which had high heritability. Improvement of yield through selection for this character is possible.

ISSN:0114-0671    

DOI:10.1080/01140671.1989.10428021

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Root-weight densities (RWD; root weight per unit volume of soil) were measured in core samples taken from nine North Island kiwifruit orchards ranging in age from 1 to 52 years. Roots were divided into fine (< 2 mm diam.), medium (2–5 mm diam.), and large (> 5 mm diam.) fractions. In young plants, weight of fine roots was concentrated around the stem and RWD decreased both with soil depth and distance from the stem. In orchards older than 10 years, RWD of the fine-root fraction decreased with soil depth alone. Fine root weights generally conform to patterns of root-length density described by Gandar & Hughes (New Zealand Journal of Experimental Agriculture 16: 35–46, 1988). Although variability between orchards is large, the dry weight of fine roots appeared to reach a plateau of about 3 t/ha after 10 years, which corresponds approximately to the time taken for fine roots to explore the available soil volume beneath each plant completely. The combined weight of medium and large roots (i.e. structural roots) increased with increasing age. These roots made up more than 90% of root weight 15–20 years after planting.

ISSN:0114-0671    

DOI:10.1080/01140671.1989.10428022

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Feijoa sellowiana(Myrtaceae) was studied under cultivation in New Zealand, California, and Japan, to determine which floral visitors are the most effective pollinators. A large range of insects and birds visited feijoa flowers to collect pollen or feed on the sugary petals. Estimation of pollen deposited on stigmas showed that only large birds deposited sufficient compatible pollen to initiate fruit development. An exclusion experiment confirmed this. Observations of the behaviour and size of the floral visitors explained why insects and smaller birds are ineffective pollen vectors. In orchards with high densities of large birds, flowers were visited at earlier stages but, even at lower densities, visits were sufficient to ensure pollination. In orchards that lacked birds, fruit set was minimal. Bird visitation was greater at the edges of blocks and, in large blocks, fruit set was significantly lower in the centre of the block. Studies of animal movements indicated that large birds such as blackbirds (Turdus merula) and mynas (Acridotheres tristis) were the most efficient cross pollinators. Specific recommendations to growers are that large birds should be encouraged, honey bees should not be put in feijoa blocks, varieties should be interplanted within the row and blocks should be small (<0.5ha).

ISSN:0114-0671    

DOI:10.1080/01140671.1989.10428023

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Infection of wheat (Triticum aestivumL.) spikes with stripe rust (Puccinia striiformisWestend, f. sp.tritici) was widespread in crops of susceptible cultivars in the 1983/84 and 1984/85 seasons. In the 1983/84 season in Canterbury, infection was restricted to the cultivars Rongotea, Kopara, and Oroua. In Southland, most crops of ‘Tiritea’ and ‘Takahe’ inspected were infected. Percentage infection of florets was lower in both regions in the 1984/85 season. The lemmas were most often infected, but in severely infected florets the paleas and glumes were also often infected. Grains in infected florets weighed up to 77% less than grains in uninfected florets. The weight loss was related to the severity of infection of individual florets.

ISSN:0114-0671    

DOI:10.1080/01140671.1989.10428024

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The levels of resistance to stripe rust (Puccinia striiforrmsf. sp.tritici) in the leaf and in the spike were related in most wheat (Triticum aestivumL.) cultivars. Cultivars with seedling resistance to stripe rust were not infected in the spike. However, two cultivars, Otane and Advantage, with adult plant resistance on the flag leaf, were infected in the spike. In a susceptible cultivar, Takahe, infection of florets occurred from ear emergence until flowering. In susceptible cultivars, pustule formation began at flowering, approximately two weeks after infection, with the maximum percentage of florets with pustules occurring during milk development. A single application of triadimefon to heavily infected ‘Takahe’ wheat at full ear emergence reduced floret infection from 75% to 20% and increased crop yield by 34%.

ISSN:0114-0671    

DOI:10.1080/01140671.1989.10428025

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Maturation of perithecia ofMycosphaerella ribis(Fuckel) Kleb, in black currant leaf litter was studied for three winters at two sites (Edendale, Southland, 1981 & 1982; Palmerston, Otago, 1983). Ascospores began to appear in June and all perithecia contained ascospores by early September. In a spore trapping study at the same sites, and at Irwell, mid Canterbury in 1984, ascospore release always began in late August or early September, reached a peak between mid September and mid October, and declined to an undetectable level by mid November. The onset of ascospore release tended to coincide with bud burst on black currant bushes. To prevent primary infection in spring, fungicide protection should be maintained from the time leaves emerge until the grape stage of flower development

ISSN:0114-0671    

DOI:10.1080/01140671.1989.10428026

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A system was developed in New Zealand for the propagation and virus-screening of pome fruit and stone fruit cultivars imported from the northern hemisphere. By using imported scion material received in the mid to late southern hemisphere summer for both propagation and virus indexing, and using controlled environment conditions, it was possible to simulate two growing seasons and release material from plant quarantine within one year of importation, providing no infection by virus or viruslike diseases was found. Propagation plants were forced into growth using artificial heat and light until autumn, when winter dormancy was induced by placing the container-grown plants in a unit with a glass roof and fine mesh walls. Normal spring growth developed on the plants in the following season and continued through the summer. The technique of double budding was used in budding seedlings with buds from the import, and with indicator buds. These were given a winter dormancy, and in the following season the growth from the indicator buds was examined for virus symptoms. Some of the soft shoot growth made on the propagation plants in the spring was used as inoculum to mechanically inoculate herbaceous virus indicator plants. Virus and viruslike disease indicators are listed, and the use or non use of some important indicators is discussed.

ISSN:0114-0671    

DOI:10.1080/01140671.1989.10428027

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Ammonia volatilisation from nitrogen (N) fertilisers applied at 100 kg/ha N in spring to autumn-sown wheat was measured using a continuous air flow enclosure method. Loss from the bare soil surface was 21 and 29% of urea-N when broadcast in two seasons. Loss from broadcast ammonium sulphate was less than 1% and from urea placed 25 mm in the soil was 1% of applied N. The loss when wheat plants were present averaged two thirds the loss from bare soil. The total loss from the same soil type but with a history of crop or pasture was the same but loss occurred more rapidly from the pasture soil. Ammonia loss was also measured in one season using a micrometeorological technique (integrated horizontal flux). Both the total loss after 9 days and the daily pattern of loss were the same as estimated by the enclosure technique. The hydrolysis of urea and surface soil pH changes in both systems were similar.

ISSN:0114-0671    

DOI:10.1080/01140671.1989.10428028

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor