Academic literature on the topic 'Stonefruit'

New Zealand flower thrips Thrips obscuratus (Crawford) (NZFT) feeds on the nectar and pollen of stonefruit flowers and was thought to then disappear from orchards for 23 months until the fruit ripen Aerial populations of NZFT were sampled in Central Otago orchards using white sticky traps Samples were taken in a peach orchard for 6 months from flowering until after harvest and in two cherry orchards for six weeks during harvest In all three orchards populations of NZFT reached high numbers in December In the peach block NZFT numbers peaked in December several weeks before the fruit began to ripen It was concluded that NZFT can live in stonefruit orchards probably feeding on newly emerged leaves of peaches or cherries or in the vegetation of the irrigated orchard floor Trapped thrips could also have come from other blocks within the larger orchard areas or from outside sources

Grapholita molesta (Oriental Fruit Moth OFM) primarily infests stonefruit but overseas it has adapted to pipfruit and become a major pest of apples and pears in some places The objective of this study was to determine the prevalence of OFM in New Zealand apple orchards Pheromone trapping was conducted in five apple growing regions in 201415 and repeated in Hawkes Bay and Nelson in 201516 No OFM was found in Gisborne (three orchards) Nelson (six) or Central Otago (seven) but it was recorded on one of six Waikato orchards In Hawkes Bay OFM occurred on 23/36 orchards although on 15 properties le;7 moths/trap/year were caught However traps in two orchards caught over 100 moths/year The few OFM collected on some orchards may have been strays from nearby stonefruit orchards but the high numbers in these two apple orchard blocks suggested the populations were established The implications of OFM becoming an apple pest or reaching the South Island are discussed

A Cytospora species isolated from infected tissues and sporulating stromata on diseased trees caused typical dieback symptoms when inoculated into Prunus species and was identified as the primary cause of stonefruit dieback in the Okanagan. Based on the morphology of the stromata, spore dimensions, and colony growth and color on malt extract agar, the fungus was identified as C. leucostoma (Sacc). After including the number of trees removed during the winter of 1985-86 and 1986-87 because of Cytospora sp., an average of 14.8% of the trees in 17 stonefruit orchards were affected by dieback from September 1985 to September 1987. The incidence of Cytospora sp. in the individual blocks ranged from 3.0-56.9%. In 11 of the 17 orchards surveyed in 1986 and resurveyed in 1987, dieback symptoms were evident on trees which had been symptomless in 1986. The percent of newly infected trees in these 11 blocks ranged from 0.4-8.8% and averaged 2.9%. The majority of sporulating Cytospora sp. infections were found on the scaffold limbs (69%) or trunks (28%) of infected trees. Pruning wounds (65%), rather than winter injury (25%), were the major infection courts. Fall and spring inoculations of a spore suspension (10³ spores/ml) of either a peach isolate (P8-19) to peach, or a cherry isolate (C9-23) to cherry revealed that intraspecies spread of the disease can occur at any time of the year. Although spring spore inoculations of the peach isolate to cherry or the cherry isolate to peach resulted in significantly (P = 0.05) more infections than the control treatments, identical fall inoculations did not. This suggests that spread of Cytospora sp. between cherry and peach is most likely to occur in the spring. The effect of temperature on spore germination and mycelial growth of Cytospora sp. in vitro was isolate-dependent. The minimum lag period for Cytospora sp. spore germination occurred at 27° C. Spores germinated at temperatures as low as 10° C, and remained viable even after exposure to -18° C for 1 week. The temperature optima for the in vitro growth of most stonefruit isolates in this study was 20-23° C. Viable Cytospora sp. spores were washed from infected trees (10⁵-10⁶ spores/ml) and adjacent healthy trees (10⁴ spores/ml) in mid-December and collected in funnel traps after the first rain the following spring (late April). Under Okanagan conditions, infection of fresh pruning wounds made in the spring can occur either by spores which overwintered on infected trees and were dispersed by spring rains, or by spores dispersed by fall rains to healthy trees on which they overwintered and infected following pruning. Benomyl (1 g a.i./L), dichlone (1 g a.i./L), flusilazole (0.01 g a.i./L) and ziram (5 g a.i./L) applied as water sprays did not significantly (P = 0.1) reduce the percent infection compared to the unprotected, inoculated controls. Of eight fungicide-pruning paste mixtures, only benomyl added to either Heal 'n' Seal or linseed oil significantly (P = 0.1) reduced the number of cankers which developed compared to the untreated control.
Land and Food Systems, Faculty of
Graduate

Total soluble solids (TSS) is a reliable indicator of melon eating quality, with a minimum standard of 10% recommended. The state of Australian melon production with respect to this quality criterion was considered within seasons, between growing districts and over seasons. It was concluded that improvement in agronomic practice and varietal selection is required to produce sweeter melons. The scientific literature addressing melon physiology and agronomy was summarised, as a background to the work that is required to improve melon production practices in Australia. The effect of source sink manipulation was assessed for commercially grown and glasshouse grown melon plants. The timing of fruit thinning, pollination scheduling, the application of a growth inhibitor and source biomass removal were assessed in relation to fruit growth and sugar accumulation. Results are interpreted against a model in which fruit rapidly increase in weight until about two weeks before harvest, with sugar accumulation continuing as fruit growth ceases. Thus treatment response is very dependant on timing of application. For example, fruit thinning at 25 days before harvest resulted in further fruit set and increased fruit weight but did not impact on fruit TSS (at 9.8%, control 9.3%), while thinning at 5 days before harvest resulted in a significant (Pless than 0.05) increase in fruit TSS (to 10.8%, control 9.3%) and no increase in fruit weight or number. A cost/ benefit analysis is presented, allowing an estimation of the increase in sale price required to sustain the implementation of fruit thinning. The effect of irrigation scheduling was also considered with respect to increasing melon yield and quality. To date, recommended practice has been to cause an irrigation deficit close to fruit harvest, with the intent of 'drying out' or 'stressing' the plant, to 'bring on' maturity and increase sugar accumulation. Irrigation trials showed that keeping plants stress-free close to harvest and during harvest, facilitated the production of sweeter fruit. The maintenance of a TSS grade standard using either batch based (destructive) sampling or (non-invasive) grading of individual fruit is discussed. On-line grading of individual fruit is possible using near infrared spectroscopy (NIR), but the applicability of the technique to melons has received little published attention. Tissue sampling strategy was optimised, in relation to the optical geometry used (in commercial operation in Australia), both in terms of the diameter and depth of sampled tissue. NIR calibration model performance was superior when based on the TSS of outer, rather than inner mesocarp tissue. However the linear relationship between outer and middle tissue TSS was strong (r2 = 0.8) in immature fruit, though less related in maturing fruit (r2 = 0.5). The effect of fruit storage (maturation/senescence) on calibration model performance was assessed. There was a negligible effect of fruit cold storage on calibration performance. Currently, the agronomist lacks a cost-effective tool to rapidly assess fruit TSS in the field. Design parameters for such a tool were established, and several optical front ends compared for rapid, though invasive, analysis. Further, for visualisation of the spatial distribution of tissue TSS within a melon fruit, a two-dimensional, or hyper-spectral NIR imaging system based on a low cost 8-bit charge coupled device (CCD) camera and filter arrangement, was designed and characterised.