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Copper on Apples
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Copper on Apples
I was told recently that many organic apple growers are currently using alarmingly high amounts of copper to control the pests that may threaten the success of their crops. Apparently the levels of copper in some apples are so high that it has become more of a health hazard to eat them than it would be to eat regular apples that have been treated with conventional chemical sprays. Please let me know what the story is regarding these claims.
Geoff

Dear Geoff
Copper use in organic fruit production is the most common criticism that is thrown at organic growers by some conventional growers and misinformed people. I work with the organic pipfruit growers in Hawkes Bay (approx 40 growers who produce 8% of the Hawkes Bay pipfruit crop). All organic pipfruit growers that export fruit are certified by Bio-Gro.

One of the key difficulties of growing pipfruit organically is the fungus 'black spot'. Conventional growers use a range of fungicides to eradicate the risk of this disease. Organic growers use lime Sulphur, Sulphur, and copper at low rates as prevention methods, and cultural practices (grazing sheep in winter to eat the leaf litter which breaks the disease cycle, increasing soil organic matter and increasing worm activity to also increase the breakdown of the leaf litter). Without some protectant spraying we have observed black spot infestations on fruit of up to 80% - this of course makes production unviable. Naturally, consumers will not buy (and should not) apples with black spot on them. Most growers base their disease management programme around lime Sulphur use.

Annually we collect the spray diaries and information on the cultural practices employed by the growers to analyse the success of organic pest and disease management.

Copper is a restricted product under Bio-Gro certification. Bio-Gro allow a maximum of 3kg of active ingredient copper per hectare per year (based on the IFOAM international standards). Bio-Gro have strict requirements such as growers must show that they are reducing the use of restricted products. Analysis of the Hawkes Bay pipfruit growers spray diaries shows average use during 1999/2000 was 1.4 kg of copper per hectare per year.

It is worth noting that conventional growers use more copper than the Bio-Gro annual allowance in one winter 'clean up' application. Many organic growers are now growing organic pipfruit without the use of copper (and using lime Sulphur or Sulphur as protectants) because of the public perception around the use of copper. Many of the growers are also trialing disease resistant varieties (the problem is that the new varieties do not have the market characteristics that a Royal Gala or Braeburn have), using new technologies for assessing their disease risk, and enhancing their soil health to build up tree health.

Additionally, the Hawkes Bay growers have requested that Bio-Gro randomly sample apples from each orchard and do a multi residue test (which tests for 180 different chemicals). This is an additional check requested and paid for by the growers to assist with maintaining the integrity of organic production. Copper levels have never been detected as an issue (or any other residues).

I hope that answers your question.

Kind Regards
Heidi Stiefel
Horticulture Consultant.

 

 





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