Growing organic prawns - in inland saline waters

This report details the results of research into organic production of prawns in Australia. This has involved activities and experiments over two years at several sites and using a multidisciplinary approach. This includes farm trials at an inland demonstration prawn farm which solely utilises saline bore water, sample collection from two commercial prawn farms in coastal regions of south-eastern Queensland, replicated feed trials at one of DPI&F’s aquaculture research stations, specified feed manufacture at the laboratories of University of Queensland, and packaging and product storage trials and food analyses at two of DPI&F’s food technology laboratories. This work was designed to investigate and assist in the possible adoption of organic procedures by the Australian prawn farming industry. The import from Asia of cheaply produced prawns has forced all Australian prawn farmers to review their marketing procedures. Additionally investors are becoming increasingly concerned at the prospects for the expansion of this industry in Australia. Since the competition of seafood products in the marketplace is increasing on a global basis, alternate products are being investigated by those wishing to maintain and/or grow their market share. The premium paid for organic food products would hopefully provide an economic incentive for farmers to convert to organic production systems, with an added advantage that the standards that apply have beneficial implications also for the social and environmental practices of industry.

Introduction, establishment, and potential geographic range of Carmenta sp. nr ithacae (Lepidoptera: Sesiidae), a biological control agent for Parthenium hysterophorus (Asteraceae) in Australia

Parthenium (Parthenium hysterophorus L.), a major weed causing economic, environmental, and human and animal health problems in Australia and several countries in Asia, Africa, and the Pacific, has been a target for biological control in Australia since the mid-1970s. Nine species of insects and two rust fungi have been introduced as biological control agents into Australia. These include Carmenta sp. nr ithacae, a root feeding agent from Mexico. The larvae of C. sp. nr ithacae bore through the stem-base into the root where they feed on the cortical tissue of the taproot. During 1998-2002, 2,816 larval-infested plants and 387 adults were released at 31 sites across Queensland, Australia. Evidence of field establishment was first observed in two of the release sites in central Queensland in 2004. Annual surveys at these sites and nonrelease sites during 2006-2011 showed wide variations in the incidence and abundance of C. sp. nr ithacae between years and sites. Surveys at three of the nine release sites in northern Queensland and 16 of the 22 release sites in central Queensland confirmed the field establishment of C. sp. nr ithacae in four release sites and four nonrelease sites, all in central Queensland. No field establishment was evident in the inland region or in northern Queensland. A CLIMEX model based on the native range distribution of C. sp. nr ithacae predicts that areas east of the dividing range along the coast are more suitable for field establishment than inland areas. Future efforts to redistribute this agent should be restricted to areas identified as climatically favorable by the CLIMEX model.

Postharvest handling practices and irradiation increase lenticel discolouration in ‘B74’ mango fruit

ABSTRACT 'B74' mango is a recently commercialised cultivar in Australia, with an appealing skin colour and firm fibreless flesh. However, fruit can develop lenticel discolouration (LD) after harvest, with loss of commercial value, especially after γ-irradiation as a disinfestation treatment. We hypothesised that postharvest practices could increase fruit sensitivity to LD and tested that by sequentially sampling fruit between the orchard and the end of the packing line over two seasons, followed by ripening without and with irradiation treatment. Exposure of 441-610 Gy γ-irradiation significantly increased the severity of LD by 6.8-fold in commercially picked and packed ripe fruit, reducing the proportion of marketable fruit from 98% to 2%, compared to irradiated fruit harvested directly from the trees and not exposed to de-sapping solution and packing operations. Also, LD increased progressively as the fruit passed through the harvesting and packing processes, and exposure to only bore water increased LD severity compared with no water contact. Results suggest that the typical de-sapping process used during harvesting is a major contributor to skin sensitivity to LD in 'B74' mango fruit, and that other packing operations involving wetting of the fruit have an additive effect on it. These effects are exacerbated if fruit is irradiated.