Burrowing times and proportions of Mesodesma donacium

Data archives with raw data of burrowing times and proportions of succesfully burrowed clams.

Beyond chemical dependency for managing plant-parasitic nematodes: Examples from the banana, pineapple and vegetable industries of tropical and subtropical Australia

Plant-parasitic nematodes are important pests of horticultural crops grown in tropical and subtropical regions of Australia. Burrowing nematode (Radopholus similis) is a major impediment to banana production and root-knot nematodes (predominantly Meloidogyne javanica and M. incognita) cause problems on pineapple and a range of annual vegetables, including tomato, capsicum, zucchini, watermelon, rockmelon, potato and sweet potato. In the early 1990s, nematode control in these industries was largely achieved with chemicals, with methyl bromide widely used on some subtropical vegetable crops, ethylene dibromide applied routinely to pineapples and non-volatile nematicides such as fenamiphos applied up to four times a year in banana plantations. This paper discusses the research and extension work done over the last 15 years to introduce an integrated pest management approach to nematode control in tropical and subtropical horticulture. It then discusses various components of current integrated pest management programs, including crop rotation, nematode monitoring, clean planting material, organic amendments, farming systems to enhance biological suppression of nematodes and judicious use of nematicides. Finally, options for improving current management practices are considered.

Chemical containment and eradication of screw− worm incursions in Australia

Screwworms are obligate, invasive parasites of warm-blooded animals. The female flies lay batches of eggs at the edge of wounds or other lesions. These eggs hatch to larvae or screw-worms which feed on affected animals for 6-7 days, burrowing deeply into subcutaneous tissues and causing severe trauma to animals, production loss and potentially death. Susceptible sites include wounds resulting from management practices such as castration, de-horning and ear tagging and lesions caused by the activities of other parasites such as buffalo flies and ticks. The navels of the new born and the vulval region of their mothers following parturition are highly susceptible and body orifices such as nose and ears are also frequent targets for ovipositing screwworm flies. The Old World screw-worm, Chrysomya bezziana (OWS) is considered one of the most serious exotic insect pest threatening Australia's livestock industries and is endemic in a number of our closest neighbouring countries. New World screwworm (NWS), Cochliomyia hominivorax, endemic to South America, has also entered Australia on at least 2 occasions. Many tropical and subtropical areas of Australia are suitable for the establishment of OWS and the potential range is expected to increase with climate change. The Australian screwworm preparedness strategy indicates a program of containment with chemical treatments followed by eradication of OWS using sterile male release and parasiticides. However, there is no longer an operational OWS sterile insect screw-worm facility anywhere in the world and establishing a large scale production facility would most optimistically take at least 2 years. In the interim, containment would be almost totally dependent on the availability of effective chemical controls. A review of chemical formulations available for potential use against OWS in Australia found that currently only one chemical, ivermectin administered by subcutaneous injection (s.c.) is registered for use against OWS and that many of the chemicals previously shown to be effective against OWS were no longer registered for animal use in Australia.18 From this review a number of Australian-registered chemicals were recommended as a priority for testing against OWS. The Australian Pesticides and Veterinary Medicines Authority (APVMA) can issue an emergency use permit for use of pesticides if they are registered in Australia for other animal uses and shown to be effective against OWS. This project tested the therapeutic and prophylactic efficacy of chemicals with potential for use in the treatment and control of OWS.

Morphological and functional characterisation of the burrow systems of six earthworm species (Lumbricidae)

Earthworm burrow systems are generally described based on postulated behaviours associated with the three ecological types. In this study, we used X-ray tomography to obtain 3D information on the burrowing behaviour of six very common anecic (Aporrectodea nocturna and Lumbricus terrestris) and endogeic (Aporrectodea rosea, Allolobophora chlorotica, Aporrectodea caliginosa, Aporrectodea icterica) earthworm species, introduced into repacked soil cores for 6 weeks. A simple water infiltration test, the Beerkan method, was also used to assess some functional properties of these burrow systems. Endogeic worms make larger burrow systems, which are more highly branched, less continuous and of smaller diameter, than those of anecic worms. Among the anecic species, L. terrestris burrow systems are shorter (9.2 vs 21.2 m) with a higher number (14.5 vs 23.5) of less branched burrows (12.2 vs 20.2 branches m(-1)), which are also wider (7.78 vs 5.16 mm) than those of A. nocturna. In comparison, the burrow systems made by endogeic species appeared similar to each other. However, A. rosea burrows were short and narrow, whereas A. icterica had a longer burrow system (15.7 m), more intense bioturbation intensity (refilled macropores or soil lateral compaction around them) and thus a greater number of burrows. Regarding water infiltration, anecic burrow systems were far more efficient due to open burrows linking the top and bottom of the cores. For endogeic species, we observed a linear relationship between burrow length and the water infiltration rate (R (2) = 0.49, p < 0.01). Overall, the three main characteristics significantly influencing water infiltration were burrow length, burrow number and bioturbation volume. This last characteristic highlighted the effect of burrow refilling by casts.

Effects of the Maryland hydraulic clam dredge on populations of the soft-shell clam, Mya arenaria: final contract report

Final report on a three year study designed to investigate the effects of the Maryland hydraulic escalator clam dredge on populations and recruitment of the soft-shell clam, Mya arenaria. Experimental plots were established in the Potomac river, Maryland, and were dredged ina commerical manner by removing only legal size clams. quarterly samples were taken in the experimental and control plots by means of a van Veen grab for juvenile clams and the hydraulic dredge for older, deeper burrowing clams. Sediment samples were taken at selected periods for organic carbon and grain size analysis. Clams were separated into two size-groups. (PDF contains 38 pages)