Summary1. Natural enemies may reduce the effectiveness of weed biocontrol agents and can also cause environmental damage, for example to a shared native insect host through apparent competition. Indeed, successful biocontrol may rely on enemy-free space and avoidance of apparent competition in the area where the biocontrol agent is introduced. 2. We surveyed parasitism in 28 insects released for weed biocontrol in New Zealand (NZ). We reviewed the global literature and databases to complement this survey, and to collate records of these insects being parasitized in their area of origin. We also collated records of native insects that feed on weeds targeted for biocontrol in NZ to test Lawton's (1985) hypothesis that, to find enemyfree space, selected agents should 'feed in a way that is different' and 'be taxonomically distinct' from native herbivores in the introduced range. 3. We found that 19, mostly native, parasitoid species attack 10 weed biocontrol agents in NZ, of which 15 were confined to five agents that possessed 'ecological analogues', defined as a native NZ insect that belongs to the same superfamily as the agent and occupies a similar niche on the target weed. Parasitoid species richness in NZ was positively correlated to richness in the area of origin. However, only agents with ecological analogues contributed significantly to this pattern. 4. A review of NZ weed biocontrol programmes indicated that parasitism is significantly associated with the failure of agents to suppress weed populations. 5. Synthesis and applications. Although our conclusions are based on an unavoidably limited data set, we conclude that biocontrol agents that escape attack from parasitoids are more likely to suppress weed populations and should be less likely to have significant indirect non-target effects in food webs. Biocontrol practitioners can reduce the chance of weed biocontrol agents attracting species-rich parasitoid faunas after introduction by (i) selecting agents that have species-poor parasitoid faunas in their area of origin, and ⁄ or (ii) avoiding agents that have 'ecological analogues' awaiting them in the introduced range.

Phytophthora root rot (PRR), caused by P. cinnamomi, is a primary constraint on avocado productivity in Australia. Numerous field trials at sites in northern NSW and southern QLD have demonstrated significant variation in tree health amongst commercial rootstocks and recently selected material, grown under high PRR disease pressure. Selections 'SHSR-02', 'SHSR-04', ungrafted 'Hass' (rooted cuttings from clonal propagation) and the commercial rootstock 'Dusa™' were significantly healthier over time than other rootstocks, many of which died during the course of the trials. 'Reed' was consistently highly susceptible. In many cases superior tree health was associated with increased tree height and trunk girth. The trials also clearly demonstrate the negative impact of Phytophthora root rot on establishment of new avocado production blocks, and the importance of identifying and selecting avocado rootstock material that can withstand high P. cinnamomi disease pressure.

The safety record of weed biocontrol was questioned recently when examples of damage to nontarget plants were reported overseas Until now systematic investigations of nontarget feeding have not been performed in New Zealand Results of surveys looking for evidence of nontarget damage caused by 20 biological control agents released against weeds in New Zealand are presented Most agents (16) are apparently hostspecific However two species (Tyria jacobaeae and Phytomyza vitalbae) were recorded attacking native plants although their attack was very minor and predictable from hostrange testing performed prior to release For two other species Bruchidius villosus and Cydia succedana nontarget attack was not predicted from hostrange testing Larval feeding by these species was confined to mainly weedy exotic plants that are closely related to their target plants The reliability of hostspecificity testing and overall safety record of weed biological control in New Zealand are discussed

No abstract

No abstract

No abstract

Experiments were conducted to determine the effect of time of planting, plant size, and nursery-growing environment on the performance of bare-rooted ‘Festival’ strawberry plants (Fragaria ×ananassa) at Nambour in southeastern Queensland, Australia, over 3 years. Yields were best with a planting in mid-March (1013 g/plant), with lower yields with a planting in early March (711 g/plant), late March/early April (765 g/plant), mid-April (671 g/plant), or late April/early May (542 g/plant). Plants obtained from Stanthorpe in southern Queensland, a warm-growing environment, were just as productive (695 g/plant) as those from Toolangi in Victoria (710 g/plant) or Kempton in Tasmania (701 g/plant), two cool-growing environments. In contrast, large plants from these nurseries with crown diameters ranging from 10 to 17 mm had 17% higher yields than small plants with crown diameters ranging from 6 to 10 mm (751 vs. 642 g/plant). These results suggest that planting in mid-March is optimal for ‘Festival’ in this environment. Lower yields with an earlier planting reflected the small size of the plants, whereas lower yields with later plantings reflected the shorter growing seasons. It can also be concluded that plant size is more important than nursery-growing environment in determining the productivity of strawberry fields in southeastern Queensland.

No abstract