P90612‘Cide’ as a suffix that designates something to be killed. ‘Insecticide’ kills insects. ‘Miticide’ kills mites. ‘Molluscicide’ kills molluscs such as snails and slugs. ‘Herbicide’ kills herbaceous plants, which are presumably weeds. These examples and other chemicals that kill things that are considered to be pests are collectively known as ‘pesticides’. Many are potentially useful in the garden, since that is where so many familiar pests are problematic.
Most modern pesticides are designed for physiological characteristics that are unique to the targeted pest. They therefore kill only very specific pests, but are generally harmless to other organisms. For example, horticultural oil, which is one of the simplest of all insecticides and miticides, kills insects and mites by obstructing the exoskeletal pores through which they respire. It is harmless to those of us who conduct respiration by means of lungs.
In fact, most (although not all) commonly available pesticides, if used properly, are relatively safe for those who are not the targeted pests. (Rodenticides that remain toxic to predators who eat afflicted rodents are some of the exceptions, but that is a topic for later.) That is why I have no compunction about using such pesticides. When necessary, I would use them on the farm, in the landscapes that I so often work in, or in the home garden.
However, such pesticides are almost never necessary. Seriously. I would not refrain from using them, but the need for such use almost never presents itself. Insecticides and, to a much lesser extent, miticides are sometimes applied on the farm (although I have not been there to apply any in a few years). I applied a minor fungicide for rust on English daisies in a landscape more than a year ago. Otherwise, pesticides are almost never necessary.
It is not that there are no pests. There most certainly are. Roses get aphid. Rhododendrons get thrip. Snapdragons get rust. We just deal with such pests without much pesticides.
There are so many alternative horticultural techniques to use instead. We prune roses so aggressively in winter that they regenerate faster in spring than the aphid can keep up with. We prune rhododendrons to eliminate much of the congested and sheltered inner growth where thrip tend to proliferate. Snapdragons are so susceptible to rust that we probably will not grow them again. Pests are not eradicated, but are reasonably controlled.
All too often, the problem with pests is not the pests at all, but improper horticulture.

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14 thoughts on “Horridculture – Pesticides

    1. Yes. People think that we must be either for or against pesticide use. I am not at all against it. However, I know that there are much better options, and that excessive use of pesticides is an indication that something is being done wrong!

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  1. Great post, Tony! There are so many better and safer methods to try first. I very rarely – if ever – use pesticides, but our next door neighbor does, to keep her lawn perfect. After our dear kitty developed bone cancer last year, I couldn’t help but wonder if that’s where he got it. I hear it’s a rather common disease for outdoor cats.

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    1. Pesticides are so much more safer than they were decades ago, and even safer than they were in the 1980s. Yet, they are chemicals, and they are designed to be toxic is some way or another. My issue is that so few of them would be used if people just gardened properly.

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  2. A fellow who manages nine properties for the Nature Conservancy spoke at our native plant society meeting last Monday, and he made the same point you make here: that a properly balanced ecosystem has almost no need for pesticides. I still remember the first time I saw the theory in action. Out on a prairie, some lady beetles were happily munching on aphids that covered a milkweed plant. When I came back to the same plant about three hours later, the lady beetles were gone — and so were the aphids. The plant looked fine.

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    1. Prior to my formal education in horticulture, I learned form great grandparents who were gardening during the depression, when they could not afford pesticides, and the produce from their gardens was very important.

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  3. Hear, Hear Tony. Through my hort career I’ve worked with many herbicides. Despite studying weed science (actually mostly herbicide science)and working as a weed spray contractor I’ve concluded that herbicides are mainly detrimental – they’re only useful if you can clean out a troublesome plant (e.g. couch \ Elytrigia) and replace it (not so easy at all tho’). Chemicals are like having slaves, but eventually there is a payback time.

    A certain common herbicide disrupts most life forms through disruption of common enzyme pathways as as I work to understand this more I find more and more effects like this.

    The right plant in the right place is key.

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    1. Proper horticulture is also important. So many plants have been too extensively bred to be ignored. In that sense, there is no ‘right place’ for plants that are dependent on the intervention of others. Roses are a classic example. They are so much more susceptible to fungal pathogens than they would be naturally. That is why it is important to keep them vigorous with aggressive pruning, and to clean up the fallen infested foliage that pathogens complete their life cycles in. Exotic plants certainly need attention. They just do not need all the chemicals that so-called ‘professionals’ like to sell.

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  4. GREAT POST and I agree. I don’t have much of an insect problem unless I bring a plant home with the problem already. I planted several planters for a friend and yesterday I noticed leaves falling off of what was a beautiful Sedum ‘Rock ‘N Roll’. At first I thought it was because he was watering too much. As I removed the leaves that had fallen off, I noticed a lot of very tiny inch worms on the underside of the leaves. I have never seen such tiny inch worms. The worms weren’t eating the leaves, but they are still there leaving tiny marks where I asume ​they punctured the leaves. I am not sure if the plants ​problem is too much water or the worms but I feel the need to get rid of the worms and tell him to stop watering. Possibly Neem Oil will get rid of the worms. What do you think?

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    1. It sounds like a sawfly larvae, which work something like cabbage maggots, but above the soil. Drier conditions wold likely make things more difficult for them. Unfortunately, the upper portions of the affected plants may already be ruined. Even if the upper growth survives, new growth will likely emerge from the roots to replace it.

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