Japanese Beetles On A Grape Leaf
Japanese beetles only became a pest in my garden four years ago. When they first appeared their numbers were so overwhelming that I pretty much had no choice but to let them go unchecked. They nearly defoliated my raspberries, but I still got an okay harvest. They loved the asparagus fronds, but they did not seem to be doing severe damage there. Their favorite food was the leaves of the wild grapes that grow all over my property, especially along the fence lines. Many grape leaves were skeletonized, but the vines survived the onslaught.
Three years ago, I saw that the beetles also were doing damage to the raspberry fruit. I decided to fight back. I knew that hand-picking against some insects can be effective, and since, as an organic grower, I either had to hand pick, cover the crops (very unlikely with the berries or the asparagus); or use inoculants like a Bt or milky spore. I read that inoculants, as well as traps, were of limited success, so I decided killing the little buggers with my bare hands would be the best approach.
I’ve been able to do an effective control for asparagus beetles by hand picking. I’ve also been able to keep potato beetles in check and kill off squash vine borers. Hand picking doesn’t work for everything, though. I’ve had no good luck with cabbage moths and their cabbage looper caterpillar. I now totally cover my cole crops with ag fabric to keep the moths off. Cucumber beetles and squash bugs are very difficult to control, as well.
Beetles on An Asparagus Frond
The Japanese beetle is easy to see and slow. Its usual defense is to just let go of whatever it is hanging onto and drop down. The typical hand picking methods cited in gardening literature are to grab the bug with your fingers and squash it, or drop it into a dish of soapy water, where the surfactant properties of the soap drown the bug very quickly; or hold the dish under the beetle(s) and let them drop to their deaths in the soapy water.
I was employing both the pick and squash method and the drop into soapy water method with only limited success. In trying to grab the beetles, they often drop before you can get to them. They react to even a shadow of movement, or, if it’s quite warm, they just fly away. Like houseflies and many other insects, the beetles have much better reflexes when its hot. They are difficult to pick in the heat of the day. That’s why I wait until the sun is no longer overhead and heating up their wings before I do most of my picking. The morning is not good as the plants are usually still wet with dew.
While the drop-into-soapy-water method was delivering a higher success rate than direct picking, it was extremely difficult to use in the asparagus. Trying to slide a bowl, or even a yogurt cup of water under a beetle in the dense fronds was almost impossible. Very often the fronds would fall into the water and a half dozen not-yet-drowned beetles would be clinging to them when I pulled the cup back. I’m not sure what turned on the light, but I realized there had to be a better way, and there was.
I now give the beetles a funnel ride to their deaths with a very simple, cheap, and extremely effective home made device. My material list is a plastic funnel – I’m using one that is about 7″ across the top and with about a half inch opening at the bottom, a gallon plastic juice jug with a screw on top – I’m sure a milk jug would work, and masking tape.
Funnel Taped to Screw-on Cap
When I first put the contraption together, I just taped the funnel to the top of the jug, but I’ve since drilled a 1 1/4″ hole into the screw top and pushed the funnel firmly into the hole and taped it up tightly. This allows me to unscrew the funnel to clean out the bugs rather than having to un-tape the funnel every time the bottle needs to be cleaned out. It also makes the funnel much more stable. I’ve had no problem with it working loose.
Several Days Kill
To say this thing works well is an understatement. My kill ratio versus the hand pick and soapy water methods, has way more than doubled. It is easier and faster. In most instances I just position the funnel under the enemy, wave my hand above the beetle and let it fall. I’ll still hand pick them when they don’t want to let go. But then it’s just a matter of coaxing them to their final ride. I could put some soapy water in the jug, but I don’t. The bugs have never flown back out. I’ll run a little water into the jug when I’m ready to clean it out. I dump the mass of dead bodies into the compost pile and give the jug a good rinsing.
I’m not saying I’ve solved the Japanese beetle problem, but I know I’ve reduced their populations significantly in both the asparagus and the raspberries, as well in my domestic grapes. Those are my only crops where they do damage. The beetles swarm, and if you leave them alone they develop huge masses and will clean the leaves bare. You have to pick just about daily to prevent the swarming from occurring. I don’t know how long the season will last. I’m still picking the plants clean each day, but the funnel trap certainly has made the job a lot easier.