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Waterways And Pesticides Don’T Mix

Despite careful use, farm chemicals can and do on occasions enter our waterways.

By Department of Primary Industries - 14th May 2003 - Back to News

Despite careful use, farm chemicals can and do on occasions enter our waterways. Although some chemicals are registered specifically for use in or near water eg. for aquatic weed or algae control, others may move off-target and find their way in to streams, lakes, dams or groundwater. Fortunately there are few recorded incidents of pesticide contamination in water in Victoria. This is not necessarily the case elsewhere, with a number of fish kills recorded in the cotton growing areas of NSW and Queensland. Internationally, there are concerns with the salmon breeding streams of the Western USA and with repeated fish kills in the potato growing region of Prince Edward Island, Canada.

As mentioned, some chemicals are registered for use in or near water and, if used according to label directions, should present minimal risk to the aquatic environment. Others may have product label restrictions, such as "no mixing/loading within 20 m of any well, sink hole, intermittent or perennial stream"; "no application within 60 metres of natural or impounded lakes or dams". Specific label statements such as "DO NOT irrigate to the point of runoff for at least two days after application" are enforceable under State law.

Certain chemicals may have particular training or licensing requirements due to risks involved with their use. Atrazine was declared a restricted use chemical because of its mobility in surface and ground water. Its use requires the applicator to hold an Agricultural Chemical User Permit or Commercial Operator Licence.

Pollution of waterways is an offence listed under the Environment Protection Act. The Act, however, provides for certain circumstances and levels at which contaminants may be acceptable. Levels are established under the National Water Quality Management Strategy. Guidelines for Pesticides can be found in the Australian Drinking Water Guidelines website www.health.gov.au

There are a number of things that we can do to manage the risk of pesticides unintentionally entering our waterways:

· Consider alternatives to chemical use, in particular on stream banks.

· Use pesticides in an Integrated Weed and Pest Management program.

· Avoid using products that are mobile, volatile, persistent or of high aquatic toxicity.

· Follow label directions carefully.

· Provide contractors with adequate and accurate information to enable risks to be identified

· Locate mixing, washdown and storage sites well away from streams, drains and bores.

· Take precautions to avoid spillage.

· Avoid back-syphoning from the spray tank when filling from a water body.

· Avoid overspray or spray drift to water.

· Avoid over-irrigation or spraying when rain is likely.

· Avoid application to waterlogged soils.

· Cultivate on the contour wherever possible.

· Maintain vegetative ground cover in pasture and row crops.

· Utilise grassed buffer areas between cultivated areas and waterways.

· Establish barriers of suitable trees and shrubs to reduce spray drift.

· Dispose of chemicals, excess spray mix, washdown water and containers appropriately.

Overseas markets are beginning to look for substantiation of good environmental practice from exporting countries. Australian producers pride themselves on their "clean and green" reputation. Keeping farm chemicals out of our waterways is essential if we are justify that claim.

BEWARE OF ACUTE BOVINE LIVER DISEASE (ABLD) IN CATTLE

DPI District Veterinary Officer, Piotr Fabijanski, recently investigated a severe outbreak of Acute Bovine Liver Disease (ABLD) at Neerim South. He reports that 32 cattle out of the milking herd of 69 became affected, 23 of which died rapidly, in what appeared to be a severe case of Facial Eczema.

Facial eczema is caused by the fungus Pithomyces chartarum, which grows in dead grass litter that is always present at the base of the pasture. The spores of the fungus contain a toxin called sporidesmin which, when eaten by stock, causes damage to the liver. Liver damage is responsible for decreased production and photosensitization (sunburn).

Other cattle in the herd became clinically ill, dropping in milk production by 95%, showing symptoms of staggering, lack of appetite, and photosensitization. Some cows became lame and had visible swelling of the vulvae and on legs.

The most striking post mortem picture was internal bleeding, mostly in the body muscles and in the abdominal cavity. Blood samples were collected from six animals showing varying degrees of clinical illness for liver damage assessment. Grass samples from three suspect paddocks were submitted for Facial Eczema spore counts and three liver samples from cows found dead were collected for histopathological examination.

Blood examination revealed severe liver damage in five out of six cows. Spore counts for two out of three paddocks were nil. The third sample recorded a low spore count. This result is rather inconclusive, as the spore count at the time of exposure might have been higher.

Piotr said that the most interesting result was the histopathological examination of liver samples.

"The changes indicated that although facial eczema was probably responsible for some of the liver damage, other characteristic lesions were fairly unique for diagnosis of Acute Bovine Liver Disease (ABLD)".

"This is a relatively newly-recognized disease restricted to both beef and dairy cattle on pasture in cool, higher rainfall areas of southern Australia, with majority of reported cases either in SE South Australia or in Victoria’s East Gippsland," Piotr said.

"The causes for ABLD are poorly understood, but mycotoxins are thought to be involved in association with rough dogstail grass (Cynosurus echinatus). It is unknown whether a plant toxin per se or a plant-associated mycotoxin is responsible. Kikuyu grass and blue green algal toxins have also been suspected to play a part."

The outbreaks are characterised by severe photosensitivity, coupled with immediate drop in milk production up to 50% or more in individual cows and over 10% for the herd. Animals become severely depressed and uncomfortable. Other symptoms include kicking, foot stamping, limping and tail flicking which can make it dangerous to milk them. Many animals may die very quickly. Survivors may display jaundice and photosensitization with thickening of unpigmented areas and swelling of the vulva and lower legs. Prolonged and severe liver damage and illthrift may result in more animals being culled from herds.

Source: http://gippsland.com/

Published by: news@gippsland.com

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