Someone asked me the other day what it means to be an "organic gardener", and that's a good question. I would say that you must first recognize that most destructive or invasive insects can be controlled by beneficial insects or, as in the case with Japanese Beetles, by methods that kill off or divert the JBs from their target food, such as roses. In other words, going organic means making a commitment to stop using insecticides, in order to stop killing-off the beneficial insects that then kill-off the destructive insects you are targeting. A simple example is having an infestation of aphids and believing (correctly) that you can squirt them off the plants with a sharp stream of water a few times, while awaiting the arrival of lady beetles which will take them out permanently. However, if you succumb to the knee-jerk reaction of spraying insecticidal soap or something stronger like carbaryl (Sevin), you will kill off both the lady beetles and the aphids, which will surely return and have no natural predators to hold them down. With Sevin you will also have killed off the bees and other pollinators, which begins a downward spiral toward creating a toxic waste site, which, unfortunately, many pretty rose gardens already are.
The only exception I can think of is the use of a miticide to eliminate eriophyid mite infestations. Spider mites can usually be held down with regular water washings, but the hundreds of different eriophyid mites, including phyllocoptes fructiphilus, which carries the rose rosette virus, are far more difficult to control without a miticide like Abamectin (Avid). Miticides are different than other insecticides, however, in that they do not kill off most beneficial insects (except naturally occurring beneficial mites which can be reintroduced after the miticide is finished). In this regard, please read my most important blog post "The Pesticide-Free Rose Garden":
And now, here is our new American Rose article on organic control of JBs... a good place to begin an organic gardening journey:
Organic Japanese Beetle Control
By Jack Falker “The Minnesota Rose Gardener” and Paul Zimmerman “Paul Zimmerman Roses”
JBs mating on Earth Song
Using insecticides to control Japanese Beetles (JBs) destroys beneficial insects (like lady beetles) and pollinators (like bees and wasps) and accomplishes virtually nothing in controlling JBs, other than killing off the current cloud of invading critters.
To control JBs organically, you must know your enemy. First, understand that most of the JBs invading your garden come from amazing distances, up to five miles away, where they pupate in the rich turf of golf courses, cemeteries, parks, pretty neighborhood lawns etc. In other words, the vast majority of JBs you see during the four or five weeks they invade your garden do not originate in your garden or lawn. So, you can spray them with insecticides but you can’t stop them from coming; and you can treat your lawn with a grub control like the milky spore bacteria to control the JB grubs for next year, but unless everyone within a five-mile radius does the same thing, you can’t stop them from coming and coming and coming.
The first step in organic JB control is pretty simple: once in the morning and once in the evening, knock them off the buds and leaves of your roses into a can of soapy water. Skin-tight surgical or milking gloves help, if you’re squeamish about touching the JBs. You’ll soon realize that JBs have a dropping instinct, which makes them easy to drown. They’re harder to catch in the hot sun of mid-day, when they quickly fly away. You’ll find that JBs are very docile and don’t sting or bite, leaving only a little stain in your hand of what we’ll call “beetle juice”. Using a few drops of dishwashing detergent in the water creates surface tension and impedes them from making an emergency takeoff. Here’s how that looks:
Drowning JBs in Soapy Water
This is important: Don’t be tempted to squish JBs! When you squish a female JB, her sex- pheromone is spewed out and brings in every male in the neighborhood! This is also why JB traps are not a good idea, at least in your own garden. Here’s a quote from the University of Minnesota on JB traps:
“Pheromone traps contain the sex pheromone of the JB female. The pheromone is very powerful and will call in beetles from a few thousand feet. Research demonstrated that more beetles fly toward traps than are caught, resulting in surplus beetles that feed on your plants. Think twice before purchasing and installing a pheromone trap.”
JBs are amazingly canny critters and it's useful to observe what they do as they approach your garden. When a JB arrives in the garden, it hovers, like a helicopter, looking for a suitable place to land. Almost always, it will land on a flower or leaf that has one or more JBs already on it, or on a flower or leaf that has been previously chewed by other JBs; obviously attracted to the sexual pheromone of other JBs. Therefore, it's important to get rid of tainted leaves and flowers, whenever possible. It’s hard to pluck a brand-new bud that has two JBs imbedded in it but it's necessary, in order to stop it from attracting incoming beetles. Using the old-fashioned, thumb and forefinger method of dead-heading, while drowning JBs, is very effective in encouraging rapid growth on roses, which is indicative of the positive multiplier-effect that organic gardening always has.
Nowhere is this more evident than in the mid-south, where the infestation of JBs is huge. In 2016, an organic rose-gardener in Virginia was ready to succumb to commercial spraying of the pyrethroid Demand CS to remedy a seemingly uncontrollable infestation of JBs. Here is the classic organic-gardening advice she received from rose-gardener extraordinaire, Paul Zimmerman, who gardens in South Carolina:
“As organic gardeners, we don't use insecticides. We build a host environment for beneficials and let them take care of it. That works for native pests but, of course, JBs are not native so they have no enemy.
“Around here the JBs appear in early June, which is after our spring flush. When the JBs are out in full force, we clean up the gardens from the spring flush and get them ready for fall. We trim the roses back, do a thorough deadheading and clean out dead and weak wood. Essentially, we’re cleaning out a lot of the parts of the roses the JBs like, during normal maintenance. As the beetles start to wind down, the roses wake back up again.
“We’ve also added perennials amongst the roses. This was for aesthetics but more so to help create a host environment for beneficials. The JBs seem to flock to the perennials and, while there is some damage, it's not as noticeable as on the roses. Essentially, we work with the JBs that way, using their arrival as part of normal summer cleanup, and plant other plants they find more attractive.”
An Ultra-Beneficial Lady Beetle on a Companion-planting Echinacea in my rose garden
As in South Carolina, we use companion plantings in and around our Minnesota organic rose gardens, for both insectary and aesthetic purposes. We have beds of zinnias where the JBs gather and we now drown more JBs on the zinnias than on the roses; lots of chewed leaves but they’re very fast-growing and keep ahead of the JBs. We also have big shrub-roses in our tomato/insectary garden, away from the main rose gardens, that attract clusters of JBs, which we drown, eight and ten at a time. The shrub they really like is Dr. David Zlesak's amazing "Above and Beyond" and, since it's done blooming for the year, we cut it back, making it far less attractive.
JBs love Zinnias more than Roses (so plant zinnias)
The key element in organic gardening is PATIENCE! Remember that JBs only last about four weeks and, if you work hard to deter them organically, they ultimately go away, leaving you with lots of beneficials and pollinators, as well as fully fertilized and dead-headed rose gardens for the rest of the growing season. Remember that every JB you drown is a monster-bug that can't breed more monster-bugs next year. It’s particularly enjoyable taking them down when they’re atop one another, stopping the breeding cycle.
For more information, see these “Minnesota Rose Gardener” blog posts: