Certain garden pests must be treated long before the plants even grow. When you notice them on your plants it’s already too late. You can’t be rid of them this season, but you can dramatically lessen them.
About a week ago I noticed that my climbing beans and cucumbers had little holes their leaves. I was devastated to find the evil Striped Cucumber beetle and their savage sidekick the Japanese beetle feasting on my hard work.
Why are these two beetles a nuisance?
The Striped Cucumber beetle mainly targets cucurbit plants like cucumber, melon, and squash, though they will eat many other plants as well. They eat roots as a larvae and they eat the stem, leaf, and fruit as an adult. More annoying than damaged leaves and fruit is the bacteria these beetles carry in their digestive tract. They can spread bacterial wilt which hinders the flow of water and nutrients in a plant’s stem. Infected plants wilt and die off quickly. The Striped Cucumber beetle can also spread squash mosaic virus. This virus increases the chances for powdery mildew and black rot, stops plants from branching properly, and gives the mature fruit a mottled skin.
Japanese beetle larvae are called grubs. Grubs are well-known for destroying grass as they feed off the nutrients in the roots. These grubs mature into Japanese beetles. After they damage your lawn as a larvae, they will move on to destroy the leaves of your plants as adults. They are a gardener’s nightmare because they destroy vegetable, fruit, flower, and tree foliage.
2 ways to quickly lessen the impact of the Striped Cucumber beetle and Japanese beetles on your plants for this season
It’s too late to completely eradicate these two kinds of beetle for this growing season, but a garden can be managed with natural annoyances and a careful eye if you act fast.
In late-June to mid-July both beetles will emerge so be ready for them.
The Japanese beetles will scour your neighbourhood looking for great gardens to feast on. They will mark areas they like with an excreted scent. Their friends will soon follow this scent. Kill them as soon as you see them in case they are the first ones out on patrol. Killing the first Japanese beetles you see could be all it takes, but if you noticed them too late, there’s a strong chance they will be around all season.
The Striped Cucumber beetle could: be in your garden soil already, come from a neighbouring garden, or come in on a cucumber plant purchased at a nursery.
Ideally you want them all gone, but if you already have them, you will have to deal with them for the season. Both these pests can be organically managed now in the same way: spraying and killing.
1. Natural Pesticide Sprays
Only natural ingredients should be used in the spray for the obvious reason that the vegetable garden is a food supply.
Spray only the infested plants as there are many beneficial bugs that could also be harmed by the spray. Generously mist the leaves and flowers with this solution a couple of times week. Don’t forget to mist underneath the leaves as well and reapply after rain. The same rules apply as normal watering – not at the hottest part of the day. Early morning or evening is best.
Take a strong pure soap like Ivory, Murphy’s Oil, or any natural soap and dilute with tap water. Do not use detergents or any soap with a degreaser in it.
The recipes below are based on two cups of water because my spray bottle holds two cups. Feel free to multiply the recipe to suit the size of your spray bottle.
Ivory soap bar and water recipe
Mix an eighth of the Ivory bar into two cups of warm water. Crumble it into the water so it dissolves faster. Shake it often.
Murphy’s Oil liquid soap and water
Mix one teaspoon of the liquid soap into two cups of warm water. Give it a light shake. It will cloud the water as soon as you shake it.
Vanilla and water
(I am telling you about this one as many people use it but I find it to be the more expensive of the homemade options, and I prefer to save my vanilla for baking!)
Mix 1 tablespoon of pure vanilla extract with 1 liter of tap water.
Photo from Home Depot’s website.
Neem oil is effective for both Striped Cucumber beetle and the Japanese beetle.
Neem oil repels bugs, and damages their reproductive system and ability to eat.
It’s naturally derived from a neem tree. There are no reported links to any health risk to animals or humans who consume plants exposed to neem oil.
For neem oil to work, the insect has to eat the leaves. Merely landing on the leaf or eating from the flower will not spread the poison. This makes it safe for insects like bees and butterflies. Like any oil, it will harm good bugs too if they are spayed with it directly. Try to spray at the times of day when good bugs are not active, like early morning or evening.
You can buy neem oil at most garden centers.
2. Good ol’Fashioned Squishing
My high-tech squish tool. Patent pending.
It doesn’t matter how you do it – just do it. Squish as many as you can as often as you can.
They are slow and clumsy but they fly so move fast.
If squishing them is out of the question then knock them into a cup of hot soapy water.
How to naturally eradicate Striped Cucumber beetle and Japanese beetle from your property
This process could take a couple of years, but eventually your soil will be larvae-free.
The beetle larvae will winter in your soil and emerge late-June until mid-July. Once they mature in your soil it’s too late once again so you need to get to work right away.
Don’t give up the fight this season though because the more you kill now, the fewer larvae you have to fight later.
6 Steps for beetle-free gardens
1. Destroy their winter home and food
The larvae will survive the winter by feeding on the nutrients in the soil so don’t leave any plant matter in the garden beds. When you clean the garden out for the season don’t toss the plants into the compost pile. Throw them into a hot bonfire to burn up any larvae and the bacteria they carry.
2. Apply nematodes
Nematodes are microscopic worm-like organisms that live in soil and feed on larvae. They are naturally occurring so they pose no threat to people or animals. They can be purchased at your local nursery or garden center. All you do is mix them with water and apply them to your lawn and garden soil. Read the manufacturer’s packaging for more specific instructions. The nematodes will help rid you of both beetles.
3. Apply Milky Spore (bacterium Paenibacillus popillae)
This powdered bacteria called Paenibacillus popillae is lethal to Japanese beetles. It’s applied to the grass to kill the grubs before they can become beetles. The powdered spore will leach into the soil when watered. The grubs will consume the organic matter infected by the spore, which kills them by turning their blood milky. To apply milky spore you place one teaspoon of the powder every four feet in a grid pattern, then water it for about 15 minutes. The best time to apply it is mid-July to early August. Read the manufacturer’s packaging for more specific instructions.
4. Keep soap spraying
Use the soap spray in late-June through to mid-July as this is when they emerge from the soil. They may not emerge from your soil but a neighbouring garden so do all you can to keep them from staying.
5. Keep squishing
A dead beetle won’t reproduce or keep eating your leaves.
6. Talk to your neighbours
Spread your knowledge of natural pesticides to your neighbours as well so they don’t unknowingly reinfect your property with their beetles. Japanese beetles will travel kilometres to find their favourite leaves. Good neighbours are made by great fences and a shared love of dead beetles!