Learning to Love Natural Enemies

Learning to Love Natural Enemies

One of the beautiful things about conducting "NO SPRAY" plant trials is seeing just how resilient landscapes can be if you give them a chance. We are all familiar with "helicopter parents", those fussy fearful folks who hover over their children to protect them from every possible physical and emotional risk of harm. Well, I think there are way too many helicopter gardeners- hovering over their plants with a spray bottle in one hand and a granulated fungicide in the other!

The truth is that you have to allow a certain amount of what may be harmful in order to establish a balanced system that can take care of itself. This is hard. We don't like the occasional brown leaf or aphid sighting. But if we respond to the first sign of trouble with the nuclear option like a broad-spectrum insecticide or fungicide, we kill off our friends along with our enemies. If we can take the wait-and-see approach, we will usually find that our allies will show up in time and restore a balance we can live with. We don't need a perfect landscape, we just need a healthy one.

This became really obvious to me again this spring in our Stockton trial plots of the American Rose Trials for Sustainability at the San Joaquin County Agricultural Center. The first two years after converting grass lawns into rose trial plots we were plagued with some pretty heavy aphid and thrips damage. Because this is a NO SPRAY trial, we simply observed and recorded what we saw, which was still pretty good performance despite some leaf scarring.

These are 2-year trials, so the roses planted in 2018 are finished, the roses planted in 2019 are in their second year, and the roses planted late this winter in 2020 are just getting established. We have had roses here long enough now for that healthy balance to take hold. Once again this spring, as is pretty common everywhere, there was a flush of aphids that appeared as the plants were filling in with spring leaves. In mid April, I recorded the presence of these critters, though they had yet to cause any real damage.

Two weeks later when I went back to take end of the month ratings, I spotted in all the plots at least 4 different natural enemies working diligently to clean up our pests! These included lady bugs, syrphid flies, tachinid flies and green lacewings. Was there some early leaf and flower bud damage? A bit. But with the hands-off approach, the plants have since outgrown early munching and show no significant signs of the earlier infestation.

This is a model that I have seen succeed again and again. It requires patience and patience is something we may have to teach our clients, our supervisors, and our public agencies. From a labor and financial perspective, this is the most feasible course of action. From an ecosystem perspective, it is the healthiest, most sustainable way we can show our respect for the resilient world we all share.


By Karrie Reid
Author - Environmental Horticulture Advisor

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