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Cherryslug, Caliroa cerasi, is an important pest of organic pear production in New Zealand. It is reported to have two generations per year and cause severe leaf damage, particularly through the feeding of second generation larvae in mid to late-summer. This insect has been little studied in Central Otago. Adult cherryslugs were monitored with sticky traps in a block of ‘Taylor's Gold’ pears in the summers of 1999–2001 and the catches were used to assist in timing the single application each season of a range of organically-acceptable insecticides in randomized block experiments which included untreated control trees. The insecticides were: 1999–2000, ryanodine, lime sulphur, kaolin in January, kaolin in February; 2000–01, pyrethrum +mineral oil, lime sulphur, neem extract, kaolin in January. Efficacy was assessed using pre- and post-treatment larval counts and leaf damage. The impact of pre-treatment larval density on post-treatment efficacy was investigated to determine a preliminary spray threshold, specifically for pyrethrum+mineral oil. The adult monitoring indicated that cherryslug is univoltine in Central Otago, with the first adults appearing at the end of December. All the insecticides tested significantly reduced damage from cherryslug larvae and, if registered, could be used by organic growers. In both seasons, kaolin application in January, which targeted the adult cherryslugs, was more effective than all the other products, which were applied in February against the larvae. On the other hand, kaolin applied in February 2000 resulted in greater cherryslug damage than occurred with the other insecticides applied at that time. Larval density had a significant effect on the efficacy of pyrethrum+mineral oil, particularly when >10 larvae could be counted per minute on the trees before treatment. The implications of this result and the comparative efficacy of the different treatments are discussed in relation to organic pear production in Otago. [ABSTRACT FROM PUBLISHER]

Oystershell scale, Diaspidiotus ostreaeformis, is a pest of fruit crops in Otago and Canterbury that is well controlled within orchards but becomes a problem at harvest due to invasion from external host trees. Its major pest status on export crops comes from its being indistinguishable on harvested fruit from the critical quarantine pest San Jose scale Diaspidiotus perniciosus. Oystershell scale has a wide host range which includes trees frequently used as orchard shelter. The distribution of oystershell scale in apples adjacent to an infested shelter belt was investigated in Otago in 1995-96. Apple infestation was >90% next to the shelter and declined linearly to <1% 64 m away. The slope of this linear regression was similar on four cultivars of apple but infestation increased substantially from early- to late-harvested cultivars. The phenology of oystershell scale on apples in 1998-2000 was found to precede that on a range of other hosts, which extended the period of risk of fruit infestation by crawlers from December to April each year. Experiments were conducted in 1999-2000 on control of oystershell scale on a range of infested shelter trees using a vertical boom sprayer. Sprays timed for control of adult males and females in spring provided only a short-term reduction of winged males in sticky traps and failed to reduce crawler production and dispersal as measured by sticky bands and traps on tree branches. On the other hand, sprays timed for control of crawlers in mid-summer were effective in greatly reducing catches of crawlers. The options for management of oystershell scale on alternative hosts, particularly shelter, are discussed in relation to phenology, crop invasion by crawlers, host resistance and spraying. [ABSTRACT FROM AUTHOR]

Oystershell scale, Diaspidiotus ostreaeformis, is a pest of fruit crops in Otago and Canterbury. Spray programmes provide effective control of this pest in apple orchards but invasion of the crop from external host plants causes fruit infestation. Alternative hosts include deciduous tree species, many of which are used as orchard shelter belts. The abundance of oystershell scale was recorded on a range of deciduous and evergreen tree species in Otago in 1999-2000 as part of experiments on the management of oystershell scale on shelter. Scale insects on the trees were either counted during timed searches or scale crawlers were trapped and counted on sticky bands. Experimental design did not permit rigorous statistical analysis but the data indicated the potential susceptibility or resistance of the trees to oystershell scale. The majority of Betula, Alnus and Sorbus species studied were susceptible but resistance was indicated in B. papyrifera selections and B. platyphylla japonica. The hornbeam, Carpinus betulus, appeared resistant and no oystershell scale insects were found on any of the conifers studied. [ABSTRACT FROM AUTHOR]

Woolly apple aphid (WAA), Eriosoma lanigerum (Hausmann), and its natural enemies were monitored from 1994 to 2000 on apples at Clyde, Central Otago, New Zealand during the transition from conventional fruit production (CFP), which used broad spectrum insecticides, to integrated fruit production (IFP), which was based on selective insecticides. Populations were compared in orchard blocks under three management regimes: CFP; transition to IFP; and a biological fruit production (BFP) programme which complied with BioGro® organic certification. WAA remained at very low levels in the CFP programme, because of insecticides, and in the BFP programme, primarily because of natural enemies. Transition to IFP was accompanied by a surge in WAA and a slow colonization by natural enemies which took at least four years to reduce the aphid population to acceptable levels. The principal natural enemy that achieved this was the parasitoid Aphelinus mali (Haldemann), assisted by predators whose contribution remained obscure, including the brown lacewing Micromus tasmaniae (Walker) and the European earwig Forficula auricularia L. A single annual application of lufenuron within the IFP programme was not detrimental to any of these natural enemies, although further research is needed to confirm its lack of impact on the lacewing. Lufenuron reduced arboreal predator diversity, as measured by the Shannon-Wiener index, and this was in part due to decline in the populations of the generalist predator Orius vicinus (Ribaut) and the coccinellid mite predator Stethorus bifidus Kapur. Pirimicarb was an effective selective aphicide for integration with the action of the natural enemies of WAA, but a substitute is required, as its use is no longer permitted on export crops. The implications of these findings for the management of WAA in IFP are discussed. [ABSTRACT FROM AUTHOR]