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Beneficial & Harmful Insects in Your Garden
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You decide to plant a vegetable garden and it seems like that was an invitation to all the insects you never wanted to see: cabbage beetles, harlequin beetles, tomato hornworm, nematodes, flea beetles, aphids…. And that’s just a few of them!
What to do?
In years past, you might have received recommendations to spray the heck out of everything. The problem with that approach is it kills beneficial insects as well as bad insects. Plus, the sprays are bad for people, water, soil, and the friendly insects. We like to take a different approach. Here are some safe and natural remedies for insect problems.
First, let’s look at some of the beneficial insects.
The first group is pollinators. Bees, butterflies, and flies are in this category. They go from flower to flower and help pollinate. Whatever we are doing with the plants, we want to make sure that nothing interferes with our honey bees and butterflies.
Beneficial insects will improve the productivity of your garden dramatically. It is well worth encouraging beneficial insects.
One of the best things you can do is to plant flowers which attract pollinators. Mix some flowers in among your vegetables to help bring these friends to your garden.
Perennial Pollinator Attractors
Bee Balm (Monarda), Beardtongue (Penstemon), Threadleaf (Coreopsis), Sedum (also known as Stonecrop, Crassulaceae), Yarrow (Achillea millefolium), Coneflower (Echinacea), Cardinal Flower (Lobelia cardinalis), Black Eyed Susan (Rudbeckia).
Most of these are perennials in zones 4-9, very hardy, and produce lots of flowers. Tuck some around the edges of your garden to encourage pollinators.
Hardy annuals are also great for attracting the insects that gobble up the harmful bugs that damage your plants. Annuals are nectar-rich and can offer early blooms before your vegetable plants are in flowers. Small clusters of flowers are great for your beneficial insects, as they have tiny mouths.
Some annuals which we like for our native pollinators:
Bachelor buttons (Centaurea cyanus)
Pot Marigold (Calendula)
Ammi (Ammi majus)
Dill and Cilantro (yes, the herbs. Let some of each planting go to seed to attract your beneficials.)
These flowers can be planted around your vegetables, in the midst of them, or alternating with vegetable plants. The flowers themselves are edible as well, so it’s an easy way to level up your meals by adding some flowers to the plate or bowl.
The second group of beneficials is insect eaters. Insect eaters can also help with pollination, but we value their services as insectivores. These are:
lady bugs (or lady beetles)
green lacewings (or aphid assassins)
assassin bugs (eat beetles, caterpillars, and can bite people)
praying mantis (but they eat all bugs, including ladybugs, honey bees, and butterflies; you don’t want very many)
minute pirate bugs (very tiny but they can eat aphids, mites, and thrips)
ground beetles (metallic green sheen)
Syrphid flies (kind of look like a bee, but no stinger)
Lady bugs and green lacewings are our two favorites.
You can order beneficial insects online and release them into your garden. Any source that has a variety is good. Be sure the company guarantees live delivery. We primarily use Arbico Organics to add to our beneficial insect numbers. You can see that this can be a pricy solution, so building a habitat to attract your beneficials is a solid long-term solution.
We are always looking out for our beneficials and we make sure the habitat is friendly for them. However, we always order beneficials at certain times of the year because certain crops can use the boost. Consider what your particular garden needs.
Plants that attract beneficial insects include Butterfly weed (Asclepias tuberosa), cilantro, dill, parsley, Tickseed (Coreopsis), and Yarrow. Be sure to include some of these in your flower or herb garden to make a hospitable habitat for your friends.
Notice that many herbs are attractive to beneficial insects. It is well worth having a perennial herb garden and adding some of the annual herbs. Herbs are great for cooking in addition to encouraging our friendly insects.
Now, Insects You Do NOT Want
This list can go on forever, but we will touch on the most common.
Keep in mind, the insect pressure is lower in the early part of the season. You will most often see problems in the second half of the growing season. The hotter it is, the more the insects like it.
Stink bugs, Squash bugs, cabbage beetles, flea beetles, harlequin beetles, Japanese beetles, squash vine borers, fruitworms (damaging to tomatoes and corn.) You can see that most beetles are not the gardener’s friend.
Strategies for how to treat:
Anything which kills an insect is considered an insecticide, even if it is plain soap. Read any label carefully to make sure it is safe for people. Even organic sprays or treatments can be harmful to beneficial insects or pets or people. Also, check the “PHI” or Preharvest Interval. This is the amount of time you must wait between applying the spray and harvest. We have an organic mint spray which has a 3-day PHI. Spray on Friday, wait until Monday to harvest.
Remove by hand, dispose. Disposal can be squishing or drop into a soapy liquid in a bucket. It’s important to be sure the insect is dead, as these are the ultimate survivors. You don’t want them to revive and survive.
Plant decoy plants and plants that help deter. Nasturtiums, arugula, and marigolds will attract some bugs, which then leave your vegetable plants alone enough so that the vegetables can mature.
Plants that help repel harmful insects include: basil, borage, calendula, catmint, chives, dill, garlic, hyssop, mint, onions/scallions, oregano, radishes, rosemary, sage, thyme, artemisia (aka wormwood), chrysanthemums. You can plant in the middle of the vegetables or around the border. The herbs work best when the leaves are crushed to release the aroma. Artemisia is a pretty, silver-leafed plant with an unpleasant odor. It seems to deter a lot of pests, including ants, cabbage maggots, carrot flies, and flea beetles. Plant at the corners of your garden bed as a sentinel! You do not have to plant all of these—choose the ones that you enjoy having around.
Check the undersides of the plant leaves. If you see tiny eggs, wipe them off and squish the eggs. You may not see a lot of adults at this point, and you want to keep it that way.
There are traps and lures which you can hang in the garden to capture the insects. They look like a liter bottle with an alluring scent. The insects can get in but then cannot get out. Each trap tends to be for a specific insect, so make sure you match up your problem bug with the correct trap.
Sprays and Dusts
Sprays should be a last resort. They can damage the plant, the soil, and the water system if applied incorrectly. This is not something to be done in a hurry.
You want to apply any spray very early or very late in the day when your beneficial insects are not active. We choose to spray early evening. Our honeybees, ladybugs, and butterflies go to bed early. Many beneficial insects will sleep in the center of flowers. Always check to make sure you are not disturbing any visitors.
Make sure that what you are spraying is appropriate for the crop. The good news is that most organic sprays are useful for nearly all vegetables. Check the label carefully! There is a lot of information on the label.
When you spray, the trick is to get to the stem and the underside of the leaves, where the bugs are hiding out. You may need to move leaves around in order to hit the areas correctly. Many sprays are contact sprays, meaning you have to make contact with the insect in order to get rid of it.
Some spray options:
Soap: a combination of liquid soap and water in a 1:10 ratio. Spray directly on the insects and on the undersides of leaves. Re-apply after rain. Be sure to wash your vegetables before eating. You can harvest within one day of application.
Neem oil: This is an oil which works on a lot of different insects and a lot of different vegetables and flowers. This is approved for organic growing. Depending on the concentration you get, you will mix with water and spray on the leaves and stems of the plant. For a 70% concentration, you mix 2 tablespoons of Neem oil with 1 gallon of water. Re-apply after rain. You can harvest within one day of application.
Dusts include pyrethrin, copper, sulfur, and diatomaceous earth. You can get combinations of these for different effectiveness. They come as a powder, which you can dust directly onto the plants or mix with water and spray. There are some which are already mixed. Sulfur is good as a fungicide (helping to kill fungus and mold).
These dusts are more potent than the Neem or soap sprays and have a longer PHI as a result. You could need 7 days or longer before harvest. Read the label carefully! Although these are natural minerals or made from plants, the concentrated form of them is harsh for people.
Any spray or dust which kills the harmful insects also has the potential to disrupt or kill your beneficial insects. Use them as a last resort.
These are fabric covers which allow light and water through to the plants, but are densely woven so that bugs or pest stay out. Row covers are about the only thing that works to keep flea beetles off your broccoli, kale, and collard greens. Flea beetle damage shows as tiny holes in the leaves. The leaf does not turn brown or decay, but it can be pretty holey. Leave the row cover over your plants until you are ready to harvest.
Another option is to do nothing! We often choose this option and put up with some holey leaves rather than worrying about sprays or dusts. Often the bugs go away after a few weeks. Even organic treatments have consequences for our beneficial insects, the soil, and the underground water resources.
If you go the do-nothing route, make sure you are supporting your plant in other ways. Mulching around your plants is an easy way to do this. In addition to conserving water and suppressing weeds, mulch provides a moist environment for friendly bugs, frogs, and toads.
Non-organic treatments always have consequences, so it is best to use those sparingly. We choose not to use those, because of the long-term issues for the soil. Many pesticides will stay in the soil for years.
An easy-to-read book with lots of pictures is Good Bug, Bad Bug, by Jessica Waller. This can help you identify all the different friends you have in your garden. She has great non-toxic suggestions for dealing with the unfriendlies.
These are just a few ideas to help you keep your garden healthy and growing well. These are strategies which we use here at Highland Orchards. My family has been farming here for 190 years, and we have lots of tricks that we have learned over the years.
Happy growing and happy eating!