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1996 - 199912000 - 20071

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Subject: search.filters.subject.Apples -- Diseases and pests

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    Host-finding behaviour of female apple leaf curling midge, Dasineura mali Kieffer (Diptera: Cecidomyiidae) : a thesis presented in partial fulfilment of the requirements for the degree of Masters [i.e. Master] of Applied Science in Plant Health at Massey University, Palmerston North, New Zealand
    (Massey University, 1996) Galanihe, Lalitha Damayanthi
    In the past few years New Zealand populations of apple leaf curling midge, Dasineura mali Kieffer (Diptera: Cecidomyiidae) (hereafter referred to as ALCM) have exploded, making control in commercial apple orchards more difficult. The present studies were initiated to generate information about the basic biology and behaviour of adult female ALCM. Experiments were conducted in the laboratory during two consecutive summer seasons in 1994/95 and 1995/96 at Massey University, Palmerston North and at HortResearch, Mt. Albert Research Center, Auckland, respectively. The diel emergence patterns of adult ALCM males and females were synchronized. Adults of both sexes started emerging at 05.00 h, with approximately 95% of adults emerging before noon. Females exhibited calling behaviour (a posture associated with the release of sex pheromone) within minutes after emergence. After mating females ceased calling. When tested in a wind tunnel containing apple foliage, mated females were rarely active before 10.00 h. After this, greater numbers of females flew upwind and landed on apple foliage, with peak responses to apple foliage occurring after 14.00 h. When given a choice between apple and pear foliage, female ALCM oviposited four times more eggs on apple than on pear. However, when given no choice between plant species females oviposited similar numbers of eggs on the two plant species. Female ALCM laid more eggs on immature apple leaves and buds than on mature apple leaves. Chemical cues from apple foliage were found to be of major importance in the host-finding behaviour of ALCM females. Volatile chemicals from apple foliage triggered upwind flight, approach and landing. Volatile chemicals from a non-host plant, pear, stimulated only half as many females to fly upwind and rarely stimulated approach or landing. Females were more responsive to chemical stimuli from immature foliage of apple than to stimuli from mature foliage. A dichloromethane extract of apple leaves increased the percentages of females flying upwind and approaching extract treated filter papers six and thirty times, respectively, over filter papers treated with dichloromethane. Out of the females that flew upwind to apple foliar extracts, 48.7% landed and 23% exhibited post-landing plant-examination behaviours. No females landed on filter papers treated with dichloromethane.
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    The influence of lime sulphur on the quality and sulphur content of organic 'Royal Gala' and 'Braeburn' apples : a thesis presented in partial fulfilment of the requirements for the degree of Master of Philosophy in Agribusiness at Massey University
    (Massey University, 2007) Ihringer, Diana
    Black spot or apple scab is a major disease in apple (Malus domestica) production. Its control is especially difficult in organic production systems that rely on copper- and sulphur-based fungicides which are not very effective and demand a high number of applications throughout the season. The most commonly used fungicide in organic apple production is lime sulphur, which is known to be phytotoxic, especially towards the cultivar 'Braeburn'. The influence of different application rates of lime sulphur (1% anti 2%) was evaluated when applied 11 times throughout the growing season from October to February. As varieties differ in their susceptibility to lime sulphur, the two cultivars 'Royal Gala' and 'Braeburn' were compared in this study. Black spot incidence and severity, russet development and postharvest quality parameters were evaluated. At harvest, residues of sulphur on and in the apple were determined as total sulphur, total water-soluble non-protein thiol compounds and cysteine content. Both cultivars behaved similarly to the application of lime sulphur, but 'Braeburn' was affected to a greater extent. Lime sulphur decreased background colour, blush, firmness, soluble solids content and dry matter content in both cultivars; fruit size in 'Braeburn' and titratable acidity in 'Royal Gala'. The changes observed can possibly be attributed at least in part to the decrease in the photosynthetic rate, which was especially drastic in 'Braeburn'. Lime sulphur caused increased russet on 'Royal Gala', but not on 'Braeburn'. Significant sulphur residues were found in the skin and flesh of both cultivars and part of the lime sulphur applied was metabolized into water-soluble non-protein thiols and cysteine. These results are of significant interest to the organic industry as the use of lime sulphur may compromise the residue-free status of organic apples and could have an influence on consumer acceptance and flavour.