So why are organic farmers allowed to use chemicals?
Organic food is a whole system approach to growing food – from the farm to the product you find on the shelf.
Certain chemicals are permitted, but regulations require these are kept to a minimum, and aren't used to support badly managed systems. Instead the emphasis should be on a 'closed input' approach since it's recognised that even acceptable inputs have the potential to add some form of contamination if used carelessly.
Organic farming management of pests in crops is not about wiping out the insect population with a pesticide. Pest management is also about planting crops with bio-diversity in mind, to support the attraction and populating of pest predators, parasitoids and crop pollinators. The idea is to reduce insect pests while having minimal impact on beneficial insects.
Some requirements for organic inputs include:
- Consideration of environmental safety and ecological protection
- Consideration of animal and human welfare
- A half-life of 5 days, breaking down easily in sunlight or soil
- No residue remaining in the food
- No synthetic chemicals or xenobiotics
- Not suspected of having mutagenic or carcinogenic properties
- All inputs recorded in a log book for auditing purposes.
About specific organic pesticides
Bt (Bacillus thuringiensis)
Both conventional and organic farmers often use Bt (Bacillus thuringiensis) products on grains and other crops against most species of leaf eating caterpillars. It's a naturally-occurring soil bacteria that breaks down in sunlight, thus leaving no trace within days of being applied.
While Bt is not considered mutagenic, carcinogenic or teratogenic, it has been shown to cause skin and mucous membrane irritation.
Applied Bt is not substantially equivalent to a Bt corn or Bt cotton which have been genetically engineered to contain the Bt virus, effectively making the crop into the pesticide. Thus the pesticide remains in the crop once it is harvested and processed.
NPV (Nuclear Polyhedrosis Virus)
A viral disease of caterpillars that occurs naturally in the Australian environment, NPV is used on some fruits and vegetables, as well as crops such as sorghum, chickpeas and maize.
NPV specifically targets the Heliothis armigera and Heltiothis punctigeracan species of moths while being safe for other moths. It persists for years in the soil, but is rapidly killed by exposure to sunlight and high temperatures, and thus will no longer be present by the time crops are harvested.
The virus is unable to affect humans in the way it affects insects as it needs to be broken down by the alkaline digestive system of the insect in order to be released.
While it can enter human cells, there is no evidence of negative affects on farmers' health.
Pyrethrum, pyrethrins and pyrethroids
Organic farmers may use pyrethrins as an insecticide for fruit and vegetable crops. It's not commonly used in cereal grain crops. However it may be used by many home gardeners so it's worth knowing the difference between these often confused substances.
Pyrethrins are the active ingredients derived from the natural insecticide pyrethrum, also known as the chysanthemum daisy.
Pyrethroids are synthetic or manufactured versions of pyrethrins. While they have a similar mode of action, they are more toxic than natural pyrethrins and persist for a longer time in the environment. Low-level exposures to the pyrethroid pesticides such as deltamethrin may negatively affect the neurocognitive development of children by age six.
Natural pyrethrins are permitted in organic agriculture because they are degraded, by sunlight and changes in pH, into non-toxic byproducts that are immobile in soil. Once in the soil they are metabolised by microbes which means the product does not bioaccumulate. When applied appropriately, by the time of harvest they will have broken down, leaving no residue.
Pyrethrum and pyrethrins are toxic to most insects, including beneficial pollinators, as well as being toxic to fish and amphibians.
Exposure to high-levels of pyrethrum, which is the unrefined form of the pesticide, can cause toxic effects such as respiratory stress, asthma, allergic reactions and long-term immune problems.
However, pyrethrins, the extracts of pyrethrum, are less toxic to humans and there is no evidence that they're stored in the body after exposure, as mammals quickly metabolise and excrete them.
When pyrethrins are mixed with piperonyl butoxide (PBO) to make a pesticide more potent they are not allowed in organic agriculture.
Because synthetic pyrethroids are more toxic, combining pyrethrin and pyrethroids in products such as insecticides and pet shampoos will increase their effectiveness. But this also increases the likelihood of toxicity for humans.
If you are buying household or pet pesticides that claim to contain 'natural pyrethrum', double-check the additives to ensure it's not a pyrethroid or doesn't contain PBO.
As a natural substance found in the roots and stems of a small number of subtropical plants (Derris elliptica), rotenone, or derris dust, has been considered appropriate for organic use. It also breaks down quickly in sunlight. It's used on leafy vegetables not cereal grains, but there has been some controversy about it so it's worth mentioning the current status of Rotenone use in certified organic produce.
Recently, a study showed exposure to rotenone caused Parkinson's Disease-like symptoms in rats.
Consequently, since 2013 rotenone is listed as a prohibited input in accordance with the Australian Certified Organic Standard 2013, Annex I.
Chemicals used for storing grains
Insecticides allowed in the conventional milling industry to control insects in stored grain include:
- phostoxin (a Phosphine based gas),
- organophosphate dichlorvos (which has been associated with reproductive effects, neurotoxicity, kidney/liver damage, and is a possible carcinogen. Several dichlorvos based products have been phased out for use on grain crops.)
- organophosphate chlorpyriphos-methyl (still commonly used in Australia despite links to reproductive effects, neurotoxicity and birth defects.)
Certified organic status means that at Kialla we don't use these toxic insecticides.
Instead we use CO2 (carbon dioxide) gas, aeration systems and good plant hygiene – none of which leave any residue in the grain.