Tag Archives: integrated pest management

Ethephon, the ‘good guy’ organophosphate?

14 Mar
Ball-and-stick model of the ethephon molecule,...

Ball-and-stick model of the ethephon molecule, the most widely used plant growth regulator. Colour code (click to show) : Black: Carbon, C : White: Hydrogen, H : Red: Oxygen, O : Orange: Phosphorus, P : Green: Chlorine, Cl (Photo credit: Wikipedia)

Have you ever tried putting an unripe pear in a paper bag with a ripe banana to ripen the pear more quickly? Go ahead! It works. The reason this works is because many ripe fruits give off ethylene, a gaseous growth hormone, when they are ripe, and ethylene triggers the generation of more ethylene, in a cascading, snowball effect within these ‘climacteric’ fruits. Ethylene also triggers stems and leaves to senesce, or turn yellow and mobilize their valuable photosynthesis machinery to other parts of the plant. In the original example, if you put a head of broccoli in the paper bag with the ripe banana, the broccoli will yellow and then brown. Pest managers have learned that you can use this hormone to good advantage in an integrated pest management plan by hastening the ripening of fruits to avoid late-season pest pressures such as walnut husk fly in walnuts. But how can you target the application of a gas like ethylene to the fruits of a tree in an orchard at high enough concentrations to ripen the husk (fruit) of the walnut tree? The answer might surprise you: spray an organophosphate pesticide such as ethephon that breaks down into ethylene and phosphonic acid. This stuff is now only registered in the USA as a plant growth hormone, but in fact it was originally registered in the 1970’s as a pesticide and has pesticidal properties, acting upon the nervous systems of insects, crustaceans and humans. It is a lousy pesticide, since it is not very toxic to insects and breaks down quickly in the environment, so nobody uses it as a pesticide on purpose any more. Instead, it is used exclusively as a growth regulator. http://1.usa.gov/16w8BO7

Avoidance by changing the timing of harvest is a wonderful strategy for preventing the need for ‘real’ pesticides which have serious insecticidal properties in the late season. I think it is important, however, to be aware that this stuff is actually an organophosphate pesticide as well, and to take proper precautions when applying and storing it, just as you would if you were spraying diazinon or chlorpyrifos or any other major organophosphate pesticide, which everyone knows are neurotoxins by means of inhibiting the enzyme cholinesterase in the brain. We can toy with the idea that we are using a safer material, but safer is a relative term.
Also, please note that ethephon acts upon plants as a growth regulator and upon insects and mammals as a neurotoxin, so let that be a lesson to ya not to assume, as I did, that plant growth regulators are as safe as water for human handling and for beneficial insects.
In my amateur opinion, then, ethephon is an undercover organophosphate playing the ‘good guy’ in today’s orchard crops because of the small concentrations and low toxicities applied and because these applications allow farmers to avoid rather than treat late-season pests through early ripening, but it is important to remember that this stuff is still a neurotoxin and to take proper precautions when handling it.


Pest management for your sweetie: Cacao Pesticide Public Relations poster–Thoughts?

22 Mar
A Russell Stovers box of milk chocolates.

A Russell Stovers box of milk chocolates. (Photo credit: Wikipedia)


An industry poster (above) shows a picture of a heart-shaped box of chocolates with all but one of the chocolates missing, a vivid depiction of the impact of pests, particularly a fungus commonly known as black pod disease, has on this tropical crop where no pest control is applied. The poster advocates for “modern agricultural approaches”, implying that the chemical industry should be thanked for the rest of the box of chocolates in the image, the chocolate harvest to which we have become accustomed (example at right).

I researched the pest management options available to cacao growers and found that black pod disease is one of the primary pests in cacao, resistant varieties of the crop are not resistant enough to ward off the disease, beneficial fungi such as Trichoderma give about 50% control of the pest, but fungicides like Kocide give almost complete control of the pest.

1. What is this fungicide, Kocide? Copper Hydroxide.

2. Who makes it and what kinds of precautions should be taken when using this material? This is a basic salt of copper and it is most hazardous if you inhale it, causing lung and kidney problems. It is also very hazardous to inhale as a gas if it were exposed to fire. Handlers should wear long sleeves and protection against breathing the wettable powder or the spray.

3. Does it harm nontarget species? How long does it stick around? Copper hydroxide is very toxic to aquatic invertebrates like daphnia, the classic ‘canary in the coal mine’ of water bugs. This substance should not get into waterways, and empty containers need to be disposed of as hazardous waste because it is a heavy metal and is regulated as hazardous waste. Copper binds tightly to the soil and may reside there for a long time in a not-very available form, but repeated use of this pesticide might result in buildup of this naturally occurring metal in the soil.

OP-ED: What are the implications for chocolate growers around the world?
Deberdt’s article mentions that most farmers in Cameroon, a cacao growing country, cannot afford the chemical fungicide and may experience up to 100% loss of their crop, validating the poster’s depiction of the losses that the untreated disease can cause. Copper hydroxide is a real option for improving yields and livelihoods of these farmers and they probably would use it if they could afford it. Biological controls like beneficial fungi might be a good compromise because they have some carry-over effects to the following year, so farmers can buy them every few years and get some relief from the black pod disease. I actually do agree with this industry poster and feel that this particular fungicide, if used away from waterways and if care is taken to prevent inhaling this product, can make a big difference in the lives of growers and I will still eat cacao!