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Pesticide Use

Despite all of our efforts to keep our collections clean, tidy, and pest-free, there simply will come a time when we’re forced to pull out the “big guns” in our arsenal of commercial pesticides. Your stewardship of their use is an important aspect of orchid culture.

While I am not intending to list specific products, I would like to share some general pesticide use guidelines.

  • READ THE LABEL, and read it completely, including not only the application instructions, but be especially careful to read – and heed – the safety warnings and recommended protective gear.
  • Preventive treatment with pesticides is a mistake. As there is no way to totally kill all critters with a single treatment, that’s how resistant strains are developed. Use pesticides as a curative measure only.  Insect Growth Regulators (IGR’s, such as Enstar II) are less of an issue in this regard, as they kill all development stages of insects and prevent them from reproducing, which precludes the possibility of passing on the resistant genes.
  • Rotate your pesticides. Different classes of chemicals have different modes of action on the pests. At one end of the spectrum are those that suffocate the insect (oils) or simply remove protective coatings (soaps) and make them vulnerable to the environment around them, while at the other end are those that disrupt biological processes in one or more of several different ways. Varying the mode of action between bouts of infestation is the best way to ensure maximum effectiveness and prevent the development of resistance.   Here is a chart of the control mechanisms of many commercial insecticides, so you can choose wisely.
  • Follow the label directions explicitly in terms of the concentration to use, the frequency of application, and the period between those applications.

    Note: If orchids are not listed on the label, it is often acceptable to use the dosage intended for roses.

    One of the most common issues that folks have with pesticide use is that of improper treatment:
    • Too weak of a concentration seems obvious, in that it simply won’t kill the pests.
    • Too strong of a mix concentration can also be bad, as not only might it be damaging to the plants, in some cases it will negatively affect the solubility of the active ingredient, rendering it less effective.
    • Most pesticides do not kill insects in all stages of their maturity – egg, larva, pupa, adult – so while a single treatment might kill all of the adults present, there are more critters waiting to mature and take their places devouring our plants. Insecticide labels recommend repeating the treatment – I recommend three times at one-week intervals – so be sure to do just that.
    • Be thorough in your treatments! Wet all exposed plant surfaces and drench the medium, as some critters can live on the roots system, as well as on the foliage.
    • The time period between treatments is dependent on both the pesticide and the life cycle of the pest. If the chemical has extended residual action, the time period between treatments may be longer. If it doesn’t, such as is the case with home remedies concocted from soaps and alcohols, more frequent treatments will be necessary.  Likewise, pests with short life cycles will need more frequent treatments to avoid missing the maturation and reproduction of an entire generation. Generally, I stick to a “3@7” regimen – three thorough treatments at 7-day intervals, and find it is quite effective.
    • Do not rotate pesticides during one treatment cycle, but if, a few weeks after such a thorough regimen, you find that your pest population has returned, repeat the “3@7” regimen, using a pesticide having a different Mode of Action (MOA)

Failure to comply with any of these guidelines can fail to control the pests and may lead to the development of resistant strains that are even harder to eradicate.

Here’s another tip I find handy: Many pesticides have extensive labels that contain safety information as well as usage guidelines, and they are often glued loosely on the package. Get a manila document-storage folder or box and place the labels in it after reading them completely. Then, document the effective dosage on the front for quick reference.