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Posts Tagged ‘Insecticidal soap’

The first of the aphids showed up in November, a small herd of them clustered on the soft, succulent tips of the hibiscus plant overwintering in the sunny window of the back room. My spouse was concerned, but I pooh-poohed this, saying I’d pick up some insecticidal soap to get rid of the sucking pests.  “A couple of spritzes and they’re out of here,” I said.

Mother Nature loves overconfidence, especially in gardeners who routinely try to bend her to their will. She clearly loved the challenge I threw down, because the aphids she sent to worry my plant are imbued with a resilience and will to conquer that would please any conqueror of yore.

As soft bodied insects, aphids are vulnerable to soaps; it disrupts their exoskeleton and causes catastrophic water loss. In order for it to work, the soap has to coat the body of the bug, so spraying the entire colony is a must to ensure control of the pests.

If you miss any aphids, they’re bound to bounce back quickly. Aphids are parthenogenetic; they can produce offspring without fertilization of eggs.  They’re also viviparous, hatching eggs within the mother’s body and birthing live young.  The young are almost always daughters, who, at the time of their birth, are already maturing their own eggs for offspring.

They’re all girls, nearly all the time, and are born pregnant, which is why their numbers increase alarmingly fast. Nymphs are mature enough to produce their own daughters in an average of 10 days, under good conditions such as a warm place with no predators.

This is exactly the condition in our back room, something that in my overconfidence I failed to take into consideration. Casually, I sprayed the colonies at the tips of the plant.  A few weeks later my spouse asked when I was going to get the soap to spray the aphids, and, puzzled, I said I’d already done this.

“Really? It didn’t work,” he said, calling me to the back room to behold colonies covering both tips and budding flowers.  I sprayed again, to the same results: the soap knocked back some of the aphids, but the colonies returned with greater vigor in a few days.  Muttering and calling the beasts unpublishable names, I attacked again, and again, employing soap and hand swipes to rub the bugs away.

The battle seemed lost, until one day a sight stopped me as I raised the soap bottle. A ladybug, perched atop the uppermost growing tip, snacking on aphids as if they were cookies.  We welcomed this beetle like an honored guest, the two of us hovering and watching her feed.  “Will she get all of them?” My spouse asked, eyeing a bud with a particularly large number of aphids.

She got through quite a few of them, but she didn’t stick around; after her snack she seems to have settled back into the mulch in the pot to continue her off-season rest. We look for her daily, and considered purchasing more to help her out.

But ladybugs come in bags of hundreds and our house is too small to host them; my imagination had them raiding our meals once the aphids were gone in a manner much like the zombie hoards on TV. Other biocontrol options are even less appealing, such as releasing parasitic wasps.  Although they’re helpful in reducing aphids, swarms of wasps aren’t exactly a welcome mat to visitors.

The aphids are still there, but fewer in number; my routine of spritzing them with soap are keeping them at bay until the ladybug reappears. This balance is a good one, and we wait for warm spring days when the ladybug reappears to help out.

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Photo courtesy of Alison O'Connor

Several years ago a friend gave me hops plants, encouraging me to grow them, not because I love beer, but because I love bugs.  Each year, she assured me, her bines are crawling with ladybugs and lacewings feasting on the aphids that load the leaves. 

 The prospect of such a scenario won me over, and the hops have a home in the garden.  I’ve watched and waited for the insects, but the outbreak of historic proportions never arrived.  Until now.

Cleaning up and trellising the overgrown mass, I got up close and personal with more aphids than was comfortable.  True, they’re soft bodied and not aggressive, but the sheer numbers on the hops is alarming and the longer I worked with the bines, the more aphids I had crawling on me. 

Eventually I had to get the hoard off of me, and the stamping legs, shaking arms, and head flipping made my spouse think my iPod must be playing a rocking tune.  But soon he noticed the moving mass of pale green slowly engulfing me, the fence, and everything else in their path, and rescued me with a series of well aimed thwacks from his gloves. 

We fled the area, telling ourselves that the ladybugs have it under control, but in truth those plants are on their own.  A quick poll of gardeners this season shows many are fighting the same battle against that pear-shaped menace, which are rapidly turning our gardens into the Year of the Aphid.

Aphids are small, soft bodied, sap-sucking pests, and Colorado has several hundred species in a variety of sizes and colors, from green to black, purple, and red.  They feed by treating plants as their own personal big gulp, sucking the sap and reducing the plant’s vigor.  Aphids are born pregnant, and reproduce so quickly they rapidly build up on the plant. 

 But being soft bodied they’re easy to control.  Grab the hose and attach a nozzle that can direct a strong jet of water onto the plant.  The stream rips aphids from the stems.  If they aren’t crushed by water pressure, at least they’re flung to the ground, and due to very poor eyesight, can’t find their way back. 

 Insecticidal soap is excellent, provided the formula is made for the plant it’s sprayed upon.  Always read the label of any spray to see if your plant is listed.  Your plant must be mentioned on the label or chances are something about the spray will harm the plant.

Leaf curl aphids pose a different problem by stimulating the leaf to form a protective tent around the aphid colony.  This is a common problem on ash, plums and viburnums. Within the leaf, the colony is protected from water sprays and insecticidal soap, but there are a few beneficial insects can wriggle in and wreak havoc on leaf curl aphids. 

If you’re brave enough, grab one of the leaf curls and unroll it, ignoring the sticky sap and crushed insects that coat your hands.  Look for lady bug and lacewing larvae, or young syrphid flies, which are maggots.  Not all beneficial insects look cuddly like the ladybug, and learning to recognize pest predators is a must for savvy gardeners.  Check out the photos and information on Colorado State University Extension’s fact sheet .  To encourage beneficials, avoid spraying broad-spectrum insecticides that kill both good and bad bugs.

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