Bad Bugs, Good Bugs

As I brushed against the beautiful blue flowering Salvia guaranitica I saw a burst of movement out of the corner of my eye. I would have loved to ignore it and just keep on pruning, but I’m an old and wily gardener, and I know it’s best to investigate anything unusual I see in my garden immediately. Sure enough, when I brushed the salvia again, there was a burst of action. Tiny white insects swarmed for a moment and then settled back onto the undersides of the leaves. Oh no. Whitefly.

Whitefly is an insect, which, like aphid or scale, lives by sucking the sap of plants. They can form big colonies if undisturbed, and they can be a terrible bother both from the unpleasant cloud of whiteflies that emerges every time an affected plant is touched, and from the “sooty mold” which darkens the leaves of the affected plants, leaving them looking sticky and dirty. A whitefly infestation can also weaken your plants and transmit disease.

Whitefly on iris leaves at GFE.

A quick chat with my neighbor over the fence revealed that she had whitefly too, although she didn’t know what to do. “I guess I better spray” she said. “Let’s see” I answered. We agreed to start by finding the plant which seemed to be the whitefly headquarters and removing it. It turned out to be a honey bush (Melianthus major) in her yard. She wanted more space for her dog anyway, so it wasn’t that difficult to sacrifice the whitefly mothership. She dug it out, cut it up, and bagged it so the whiteflies couldn’t just keep hatching out and moving to other plants.

This was a great first step, but several weeks later my salvia still had clouds of whitefly hanging around. So I started inspecting other nearby plants, and found a secondary whitefly colony on my nasturtiums, which were wandering through the flower bed and climbing into my blooming shrubs. Not only were the winged whitefly adults resting under the leaves, but the immature whitefly crawlers were living and growing up under there. So I sacrificed the cheerful orange and yellow flowers and the nasturtiums went into the green bin.

I love a wildish look in my garden, and I tend to let plants clamber over one another creating a bit of a jungle. But now was no time to be squeamish. All these shrubs had to be pruned hard to open up space around each plant. Insect infestations in healthy gardens don’t last long once they are exposed to the spiders, birds, and predatory insects which thrive in an organic, biodiverse garden.

Over the next several weeks I checked on my salvia frequently. At first there were still whiteflies, but they were fewer each day, and by the end of several weeks I only saw a few tiny wasps patrolling the area, looking for any extra whiteflies they might have missed on previous raids. There was really not much left to chomp on. The all-you-can-eat whitefly bar was closed, and the dragonflies, hummingbirds, and ladybugs would have to look elsewhere for dinner.

This was a relatively quick turnaround for whitefly, which can be an extremely frustrating and persistent infestation. I was lucky to have a cooperative neighbor, willing to try other methods and not spray right away. I was also fortunate to have a garden so richly populated in beneficial bugs and birds.

I’ve always loved the hummingbirds and butterflies that visit my flowers, so I’ve planted especially to attract them. Luckily for me, the same plants also attract other beneficial insects, like the hover flies and predatory wasps which were probably the best whitefly warriors. These are the “good bugs” which every organic gardener loves to see buzzing around.

Butterflies and many other beneficial insects favor plants which have a large flat flower which makes a good “landing pad.” If it is made up of multiple tiny flowers, with many opportunities to sip nectar, so much the better. So my yarrows and verbenas, besides being beautiful and bringing butterflies into my garden, were also protecting my other plants from “bad bugs,” as the whiteflies found out the hard way. Here is a picture of an anise swallowtail butterfly on a Verbena bonariensis. We might not get to see this beautiful sight, if we had jumped the gun and sprayed our “bad bugs” before we tried to solve the problem without chemicals.

Anise swallowtail butterfly on Verbena bonariensis flowers.

If you want to learn more about managing insect pests and diseases in your garden without spraying toxic chemicals, come to a workshop at Garden for the Environment or just drop by and chat. We’d love to see you in the garden Wednesdays and Saturdays from 10am-3pm.