The bacterial biocontrol agent, Serratia entomophila, and the insecticide diazinon, were applied as separate granular formulations with ryegrass seed and compared with a seed-only control treatment on three pastures of different ages and composition on the North Island volcanic plateau. In the first 2 years, diazinon and S. entomophila significantly reduced healthy grass grub populations compared with the control. However, by the third year populations in the diazinon treatments had recovered and were significantly higher than in S. entomophila or control plots. Grass grub populations were reduced by disease outbreaks after S. entomophila was applied, which infected >40% of grass grub larvae in the treated plots in year two. Bacterial extraction from soil a year after application confirmed establishment and persistence of S. entomophila in treated plots. Visual positive pasture growth responses were noted in both the S. entomophila-and diazinon-treated plots.
The effect of diploid and tetraploid ryegrass on clover establishment in new pasture following maize, turnips or grass was investigated in Northland and Waikato in autumn 2004. White clover seedling establishment at 4 weeks was 12-20% higher with tetraploid ryegrass compared to diploid ryegrass, and lowest clover seedling numbers were in the ex-grass paddocks. Production data from the Northland site showed that in December 2004, the ex-maize and exturnip paddocks, respectively, had 54% and 79% more pasture than ex-grass paddocks. Keywords: clover establishment, break crops, tetraploid ryegrass
Outbreaks of insect pests can cause major losses in pasture productivity, but farmers are often poorly equipped to evaluate risk factors, predict pest impacts and determine appropriate control actions. Decision tools are described for pasture pest management using three case studies. For grass grub, "at risk" paddocks are identified based on factors such as time since sowing, soil type and larval damage the previous autumn/ winter. Targeted populations measurements can then be taken and a decision to control grass grub made using this objective measurement and/or an assessment of the pasture value, termed the insurance approach. For manuka beetle, pesticide application decisions are based on damage scores of individual paddocks and the correlation between these scores and larval densities. With porina, information on moth flight times, larval populations and pasture damage are used to make key control decisions. For all pests, decisions to control should be made in conjunction with other farm systems information, including the costs of lost forage production and long-term impacts on pasture persistence. Keywords: grass grub (Costelytra zealandica), porina (Wiseana spp.), manuka beetle (Pyronota spp.), farmer decision-making
This essay contains personal observations and interpretations by the author on the persistence of pastures in the northern North Island. Key pasture stress factors are identified as the increase of farming intensity over the past two decades, the impact of pasture renewal techniques and the role of pasture species on insect pest (particularly black beetle and clover root weevil) interactions. Keywords: insect pests, soil fertility, pasture renewal, cultivars, endophyte
Including forage cropping as part of the pasture renewal process can be beneficial; however, too often farmers achieve unsatisfactory results in terms of both crop yield and the re-establishment of new perennial pasture. To be successful with this approach the farmer needs to have a wide range of information on pest and weed control and cropping techniques. Keywords: pasture renewal, cropping, glyphosate, perennial weeds, endophyte, clover establishment
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