The Australian Pesticides and Veterinary Medicines Authority (APVMA) have placed new restrictions on arsenic-treated timber.
From this Sunday, July 1st 2012, timber treated with copper, chromium and arsenic (CCA timber) will be declared a restricted chemical product, and further restrictions will be placed on its use that will protect children, in particular.
See APVMA’s media release
There are hundreds of types of fungi that cause ‘rust’ on plants but each type has a limited number of host plants so that your whole garden is not likely to be overrun by rust.
Rust can occur in various seasons but it does need moisture to grow. It typically causes yellow or brown markings on upper surface of leaves, and small yellow or brown powdery growths on the underside of leaves. The powdery substance consists of fungal spores that can be blown about by wind, infecting other plants that are susceptible to that type of rust fungus.
Below, on the left, are pictures of rust on the underside if a frangipani leaf and typical signs of rust on grasses. Some leaf markings can be confused with fungal diseases. On the right are pictures of hail damage on a cycad and spores on the underside of a fern frond – which is how ferns reproduce.
Basically, rust diseases are a sign of malnutrition that produces an unsuitable pH on the leaf surface. Plants, like humans and animals, are more prone to diseases when they have a poor diet, and rust diseases can be avoided by keeping plants growing vigorously – but this is not always possible in extreme weather conditions. Sulphur or copper are the usual treatments for rust. Both of these are nutritional elements that can be supplied by various fertilisers, including seaweed extracts. Seaweed also contains plenty of potassium that strengthens cell walls, sulphur, and trace elements (including copper) that boost plants’ immune systems.
For mild cases of rust, remove damaged parts of the affected plant and burn these, or dispose of them in a sealed plastic bag. Don’t ever compost them, as the spores may not be killed. Then give the plant a foliar feed of seaweed extract tea and water some into the ground over the root area. Improve your fertilising program using a complete organic fertiliser.
For deciduous plants, rake up and dispose of dropped leaves to avoid reinfecting the plant. Apply the seaweed tea at bud swell.
For more severe cases, after removing damaged foliage, plants can be dusted with elemental sulphur (flowers of sulphur. However, as the spores are under leaves and the dust can be difficult to apply, affected plants can be sprayed with wettable sulphur in cool weather only, as sulphur will damage plants when temperatures are over 24 degrees Celcius. Be aware too, that sulphur will also kill pest predators. If these are present on affected plants, apply chamomile tea (one tea bag to 500 ml water) instead.
I am concerned to hear that CCA treated timber has been used to construct garden beds and other structures in some school gardens, so it might be a good time to remind readers that the uses of these timbers have been restricted.
Since the end of March 2006, timber treated with copper, chromium and arsenic as a preservative (CCA timber) is not permitted to be used for garden furniture, picnic tables, exterior seating, children’s play equipment, patio and domestic decking, or handrails.
Problems with CCA treated timber
The restrictions on use were implemented by the Australian Pesticides and Veterinary Medicines Authority (APVMA) because they were “not satisfied that the continuing use of CCA for timber used in structures with which the public (and particularly children) are likely to come into frequent and intimate contact is safe“.
Common sense would dictate that the APVMA restrictions would also apply to garden beds (as they do to sand pits) because this timber can leach arsenic (a known carcinogen) into compost and soil for up to 20 years, and some species of food crops can absorb high levels of arsenic.
As young children have a tendency to put their fingers in their mouths, and tend to be less careful about washing their hands, they can ingest significant amounts of leached arsenic, a known carcinogen, from CCA treated timber. Children are, of course, more vulnerable to all pesticides because their organs are still developing and young children eat more food per kilogram of body weight than adults do.
The APVMA’s decision follows the phase-out for domestic uses of CCA treated timber in the US, EU, Canada, Indonesia and Vietnam, and restrictions to its use in Japan.
The regulations allow the use of CCA treated timber for ‘structural timbers’ and the timber industry has included retaining walls in that description. However, the APVMA Review (page 11) clearly states, structural timbers “where frequent contact is unlikely, and the level of exposure and risk, is low“.
Once installed ……..
Research by the US EPA (in 2005) found that penetrating sealants can reduce, but not eliminate, arsenic migrating from the treated wood. The data show sealants that can penetrate wood surfaces are preferable to products such as paint, because paints and other film-formers can chip or flake, requiring scraping or sanding for removal, which can increase exposure to arsenic.
More recent US research has found that arsenic levels on CCA-treated wood remained high for 20 years, and that timber had to be re-coated every 6 months, making the maintenance of this timber to reduce students’ exposure a tedious and expensive process. The only safe solution is to replace the CCA treated timber with one of the safer alternatives that are now available.