October 14, 2015
Organic pesticides can still be toxic
2013 California Crop Pesticide Use By Category (based on pounds active ingredient). Organic pesticides. Image courtesy Forbes.

What are organic pesticides? A chart of California crop pesticide use in 2013 by category. Image courtesy Forbes.

There are many misconceptions about pesticides and organic farming. Did you know for example organic pesticides  are also used by conventional farmers? Also that sulfur is an approved organic pesticide? On, a plant scientist Steve Savage shares some facts and infographics on organic pesticides and their use in the US state of California.

Even though sulfur has been used by farmers since ancient times, today it is the most heavily used pesticide (fungicide) in California — 27.6% of all pesticides in crop agriculture in 2013.

Other organic-approved pesticides include even copper. These fungicides were discovered in the late 1800s and saved the European grape industry from a disease introduced from the New World. Copper’s compounds are the most effective substances against downy mildew in organic farming according to the European Commission.

Copper sulphate is also widely used around the world as a pesticide and seed fungicide. Many cases of accidental intoxication with this substance have been reported among farm workers who have absorbed large amounts of it through the skin. It can be deadly if toxic amounts are absorbed. The African Journal of Emergency Medicine reported on a 29 year old woman who diluted and used copper sulphate to try to terminate her pregnancy – she later died in hospital.

The last major group, or class, of organic-approved pesticides are petroleum-based oils such as mineral and paraffinic oils. These materials are used to control insect pests, and powdery mildew and represent around 20.4% of use in 2013.

The last sobering thought we’ll leave you with is of a recent scientific study in the Journal of Insect Science that found potential acute toxicity and sub-lethal effects of botanical insecticides (organic) on honey bees  A. mellifera.

The study aimed to assess the effects of organic pesticides and found extreme caution should be used when controlling insect pests on crops. The researchers looked at andiroba oil, citronella oil, eucalyptus oil, garlic extract, neem oil and rotenone. These pesticides are often touted as environmentally friendly, especially to pollinators like bees.

Only andiroba oil showed no lethal impact on honey bee ‘adult workers’. But, andiroba oil, garlic extract and neem oil all had an acute toxicity on ‘bee larvae’.

Larvae fed with syrup containing the other insecticides led to lower-body mass development in adult workers, except for eucalyptus oil. And eucalyptus oil, garlic extract, neem oil and rotenone decreased the rate of walking activity in adult workers.

The original article the Role Of Organic Pesticides In California was published on by Steven Savage, a scientist and expert consultant on agricultural technologies with more than 30 years’ experience. Since 2009 he has written nearly 300 blog posts, driven by his passion for agriculture.



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