摘要:

Tarahe efficacy of four insecticide treatments—buprofezin, chlorpyrifos, 1 and 2% mineral oil, applied at four single, and a double application time, was evaluated against soft wax scale,Ceroplastes destructorNewstead, on ‘Seminole’ tangelo(Citrus paradisi(Macfadyen) ×C. reticulata(Blanco)) in Kerikeri, New Zealand. Settlement of the insecticide‐sensitive ray stage (1st instar and 2nd instar) onto leaves, and the later dispersal of rays onto the wood to form the wax‐protected peak stage (3rd instar), was monitored. Spray application times on 15 and 25 January, 12 February, and 2 March 1993 corresponded to 64, 96, 100, and 50% of total ray abundance on leaves in untreated trees. Maximum ray abundance, after correcting for natural mortality, was estimated to occur on 4 February. There was no significant difference between chlorpyrifos and both mineral oil treatments which resulted in 71 and 90% control of rays, when averaged over all single and double applications, respectively. The highest level of control was achieved about the time of maximum ray settlement and insecticides should be applied during the period, 18 days before and 28 days after maximum settlement. A longer‐term evaluation of the success of treatments showed that all treatments significantly reduced peak stages in April by 71%, averaged over all times of application. The 1 % mineral oil treatment was the preferred choice in an integrated pest management programme.

ISSN:0114-0671    

DOI:10.1080/01140671.1997.9514022

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Thrips were collected from flowers, immature and mature fruit from commercial citrus orchards mainly in the Northland region of New Zealand and c. 23 000 were identified to species.Thrips obscuratus(Crawford) comprised 84–100% of all thrips recovered from flowers of all citrus varieties. Infestation levels of adults and larvae were commonly c. 20 thrips/flower but they were not associated with damage to the rind of fruit.Megalurothrips kellyanus(Bagnall) was also commonly found in flowers, usually in association withT. obscuratus.The highest infestations ofM. kellyanusof 50 thrips/flower on lemons and 22 thrips/flower on tangelos occurred at times whenT. obscuratuswas present at a level of less than 1 thrips/flower. Approximately a third ofM. kellyanusin flowers were larvae and the remainder were adults indicating that breeding occurred in the flowers.M. kellyanuslarvae were commonly found on immature fruit of lemon, navel orange and tangelo, where their feeding caused scarring of the fruit. The low incidence ofM. kellyanuson mandarin and Valencia orange flowers was reflected in low numbers of larvae on immature fruit and little evidence of damage.Heliothrips haemorrhoidalis(Bouche) was commonly found on mature fruit of all citrus varieties where their feeding activity caused a whitening of the rind. Fruit of Valencia orange were particularly susceptible to damage by this species of thrips, with mandarin, navel orange, and tangelo also damaged. The tubuliferanNesothrips propinquus(Bagnall) was found on fruit of all citrus varieties, but there was no evidence of it producing any damage.

ISSN:0114-0671    

DOI:10.1080/01140671.1997.9514023

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The history of European pear(Pyrus communisL.) cultivars, and pear and quince(Cydonia oblongaMill.) rootstocks used in New Zealand during the present century was investigated in relation to their virus and phytoplasma disease status. Early attempts to control tree size and vigour using quince clonal rootstocks or seedlings of Oriental pear(P.pyrifoliaBurm. Nak.) were unsuccessful, in part because of the presence of these diseases, and pear trees were grown for most of this century on European pear seedling rootstocks. Testing of 12 older pear cultivars commonly grown in commercial orchards at the present time showed that most were infected with several viruses, and also with the phytoplasma disease apple rubbery wood. All of the 12 cultivars were imported before, or at the beginning of this century, and were likely to have been infected in their country of origin before being introduced to New Zealand. When freed from infection by heat therapy, some were successfully grown on the virus‐free East Mailing rootstocks ‘Quince A’ and ‘C, and on the French rootstock ‘Quince BA 29’ without incompatibility problems, but others required an intermediate such as ‘Beurre Hardy’ to overcome non‐pathogen induced incompatibilities.

ISSN:0114-0671    

DOI:10.1080/01140671.1997.9514024

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Changes in composition and sensory quality of buttercup squash(Cucurbita maximaDuch. ‘Delica') during fruit development and postharvest temperature and humidity conditions simulating shipment to Japan were studied at three representative growing sites in New Zealand. Fruit of a known setting date were harvested at 10‐day intervals and data were collected on heat accumulation, days after flowering, flesh colour, seed development, soluble solids, dry matter (DM) content, skin hardness, glucose, fructose, sucrose and starch content, and sensory properties before and after simulated shipment. Physical properties at harvest were related to sensory quality at the point of sale to identify an optimal harvest time. As fruit was left for longer on the vine the skin hardened, the flesh became redder, DM increased then decreased, the soluble solids and sucrose content increased and the sensory properties improved. Once harvested the flesh continued to become redder, sucrose and soluble solids increased, and starch and DM levels decreased. Starch and DM did not accumulate significantly after 40 days from flowering at any sites. Temperature accumulation affected the rate of increase in the maturity indicators measured. Sucrose levels, °Brix, and flesh colour varied too much with site and season to be used to indicate optimum harvest dates. Skin hardness and heat accumulation levels were the most effective means of estimating the optimum harvest date. The earliest time to harvest fruit to ensure an acceptable level of sensory quality after the simulated refrigerated shipment conditions imposed was at a skin hardness penetrometer score of 7 kgf. This point occurred between 240 and 300 growing degree days (base temperature 8°C) from flowering. Fruit harvested at this early stage required a postharvest ripening period to enhance sweetness and texture and to optimise sensory quality.

ISSN:0114-0671    

DOI:10.1080/01140671.1997.9514025

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A field study was carried out over two seasons to investigate the effects of maturity of onions(Allium cepaL.) at harvest and different curing conditions on bulb quality and the incidence of storage rots. Onion plants were lifted at one of three stages of maturity: 10, 70, or 90% leaf collapse (top‐down). Foliage was removed (topped) either before or after curing, and bulbs were subjected to one of three curing treatments: field curing with additional water, field curing without additional water, or heated forced air curing. Additional water applied during field curing increased the proportion of onions with stained skins and rots. Forced‐air curing of onions reduced the incidence of rots regardless of harvest method. Forced air drying also reduced skin staining in most harvest method treatments.

ISSN:0114-0671    

DOI:10.1080/01140671.1997.9514026

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

We demonstrate a quantitative framework for the study of yield‐density relationships of transplanted green asparagus (Asparagus officinalisL.). Such a framework is essential if new research is to make effective use of what is already known. We used quadratic equations to analyse data from 15 yield‐density studies with transplanted asparagus, in order to get indications of appropriate densities for new plantings in New Zealand and Western Samoa. In all instances the optimum density was close to or above the highest density used in the trial, so that optima were often poorly defined. We work with the density which gives 90% of the estimated optimum yield, which for practical application may be more realistic than the density which gives optimum yield. We give details of the methodology used for these estimates. Estimates of this 90% optimum, based on the cumulated yields over the first 3 years, varied from 8500 to 66 000 plants/ha. The optimum planting density estimated from cumulated yields to Year 3 gave an accurate estimate of optimum planting densities for cumulated yields to Year 7, and were substantially better for this purpose than cumulated yields to Year 2. No clear picture emerges of factors which may affect the optimum plant density for transplanted green asparagus, which clearly varies widely. There are too many factors which vary in an unsystematic manner between the different studies which we describe, or for which no information is given. We highlight deficiencies in trial planning and/or reporting which compromise the attempt to place individual trial results within a wider context. We make proposals for the conduct and reporting of future studies, which if followed will make the systematic overview of future trials more straightforward and productive.

ISSN:0114-0671    

DOI:10.1080/01140671.1997.9514027

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Field studies were conducted in southwestern Mexico to determine the effect of three plastic mulch colours (black, white, and clear) on aphid populations, soil temperature, and on fruit yield of watermelon(Citrullus vulgarisSchard.). Aphids were counted on alternate days in traps placed on the mulched beds. Aphids were least numerous on the clear mulch and most numerous on the bare soil. Maximum soil temperatures under clear polyethylene reached 38.5°C and were 1.0, 4.5, and 4.2°C greater than those under white, black, and 10 cm deep unmulched soil, respectively. Total soluble solids of fruits were not modified by different coloured polyethylene. Fruit length was increased with clear and white plastic. Plants grown on clear plastic mulch produced higher marketable yields than those grown on bare soil. Other colours (black and white mulches) were intermediate in their effects on aphid populations, soil temperature, fruit weight, and yield response. Marketable yields of 48.3, 43.2, 38.3, and 22.8 t/ha were achieved under clear, black, white, and unmulched soil treatments respectively. Clear plastic mulch increased fruit weight by 2.94 kg and watermelon yield by 25.5 t/ha in comparison with unmulched soil. All plastic mulches increased fruit weight and total yield as compared with production on bare soil. By delaying aphid population increases, use of mulches may reduce the need for insecticides targeted for aphid control. In conclusion, coloured polyethylene mulch has an important effect, and clear plastic could be a practical management tool for the increase of watermelon production and enhancement of fruit quality under tropical conditions.

ISSN:0114-0671    

DOI:10.1080/01140671.1997.9514028

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

‘Pink Lady’ is a late maturing ‘Lady Williams’ × ‘Golden Delicious’ apple (Malus domesticaBorkh.) cultivar developed in Western Australia and imported into New Zealand by the Ministry of Agriculture and Fisheries in 1986. We used trained and consumer panellists, and chemical and physical analyses, to compare the sensory quality of ‘Pink Lady’ with that of four standard late‐harvest apple cultivars. If acceptable, the new apple could usefully extend the harvest season of New Zealand apples. Trained taste panellists gave ‘Pink Lady’ apples similar ratings to ‘Braeburn’ and ‘Fuji’ apples for texture, sweet‐sour balance and flavour, but lower ratings for juiciness. ‘Pink Lady’ was a firm apple as measured by penetrometer, and Instron texture measurements indicated it was a hard, crisp apple. ‘Pink Lady’, ‘Braeburn’, and ‘Fuji’ apples were rated higher for acceptability than ‘Granny Smith’ and ‘Red Dougherty’ by the consumer panel, who said they would buy these cultivars and pay more for them. Consumers also preferred the appearance of ‘Pink Lady’ apples. Changes in sensory quality during storage (as measured by sweetness, flavour, crispness, and juiciness) were similar for ‘Pink Lady’ and the four late‐maturing commercial cultivars tested. ‘Pink Lady’ had a musty off‐flavour initially that disappeared during storage, whereas other cultivars developed metallic, “old”, and alcoholic flavours. ‘Pink Lady’ apples browned quite slowly when sliced. Compositional analysis snowed ‘Pink Lady’ was relatively high in dry matter, soluble solids, and titratable acids.

ISSN:0114-0671    

DOI:10.1080/01140671.1997.9514029

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The effects of four nitrogen (N) application rates (5, 10, 20, 40 g N/m2) and four potassium (K) soil levels (0.4, 0.8, 1.8, 3.2 me/100 g) on soil‐grownSandersonia aurantiaca(Hook.) stem and tuber production were evaluated. Leaf concentrations of N and K declined with plant age but were greater at the higher N and K levels, respectively. Small increases in some stem production indices (flower number, percentage side laterals) occurred with increasing N but declined with increasing K (stem length). Tuber weights declined with increasing levels of N and K with the largest tubers, 7.9 g produced at 10 g/m2N and 1.8 me/100 g K. This study indicates that moderate N and K nutrition rates should be used for soil‐grown sandersonia to optimise both stem production and tuber weights.

ISSN:0114-0671    

DOI:10.1080/01140671.1997.9514030

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

ISSN:0114-0671    

DOI:10.1080/01140671.1997.9514031

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor