Integrated Pest Management: Preventing Bugs From Destroying Plants

Bugs on plants are more than a nuisance. They damage plants by sucking out sap, destroying leaves and transmitting diseases. I’m all for a balanced ecosystem, and I realize bugs gotta eat too, but there’s a point at which I have to choose between the bug and being able to eat the cucumbers I have spent time and precious water nurturing from seed. I might not be smarter, but I’m bigger and I have tools and creativity.

For many years in the past, home gardeners like us relied on chemicals to kill a bug at the first sign of trouble, and I’m so glad that the concept of integrated pest management, or IPM, has replaced that approach for so many people who care about the food they eat, the environment and preserving beneficial insects.

cucumber beetle
Cucumber beetles like any yellow flower, including the ones on this honeydew melon. This is the last known photo of this particular beetle…

Let’s break down a rather fancy term into the basics: start with the least harmful control. It’s really the same as prevention in medicine. Ward off a disease as your first choice instead of having to go through treatment. Here are the basic steps:

1. Start with healthy plants and good cultural management. This is the most important step to try to prevent insects in any yard or garden. First and foremost, plant native plants. I’ll never stop repeating this mantra. When you include plants adapted to your environment, they’re less likely to get stressed. There’s lots of research on the plant stress hypothesis because I guess some people disagree with it. But prevailing thought seems to be that plants stressed by drought or other conditions are more vulnerable to bug infestations and damage. It makes sense, and it’s still better to keep plants healthy anyway for flower or fruit production. Be sure to rotate crops, plant a variety of plants, and place plants in the right conditions based on shade or sun requirements, for example.

healthy tomato in container
This grape tomato plant is healthy and happy. It’s in a container with rich soil. I think it’s a little easier to control pests with containers.

2. Keep bugs away by weeding as much as possible and cleaning up debris to prevent hiding places. And cover seedlings with tunnels and row covers (with no holes) to keep bugs off while the plants are young and more vulnerable. Make sure plants are not too close together so they have airflow and can dry out as needed. Use mulch to cool roots and hold in water and compost to enrich soil. If one plant gets a disease, remove it from your garden and throw it out. Don’t lay it near the garden or compost it.

Covered seedlings
These lettuce seedlings have green beans for shade and cloth to keep bugs out until they get a little larger.

3. Hand pick bugs that appear if you can. This is not always easy, but if I can touch bugs, anyone can. Home gardeners who visit their garden regularly to water, deadhead flowers and check or harvest vegetables should inspect for bugs, especially in the morning. A major advantage of handpicking is that you can pick just the bad insects, causing no harm to beneficial bugs on your plants, who are there helping in your cause. See my Resources page for a few links to articles or photos that help identify beneficial insects. And here’s what I do when I pick off the little bug – throw it in a container of dish soap and water. I like to reuse a plastic container with a flip lid each year for easy, one-handed entry. Last year, it was an empty sanitary wipe jar. This year, I had used nearly all of my taco spice mix from Costco. I put the rest in a plastic zipped bag and had an instant bug bath. A blister bug infestation at our community garden one year had Tim and I doing a “swipe and boot stomp” method because those monsters bite and because of pure numbers. Our neighbor finally had to vacuum the potato plants.

dish soap and water for handpicking bugs in the garden
The little beetle featured in the photo above got a spicy ending courtesy of my handmade holding cell. All that’s inside is environmentally friendly dish soap (because that’s what I had), some water, and taco seasoning residue. The top snaps open.

4. When all else fails and you must use a pesticide, there are several organic choices. It’s also important to know that although an insecticide is organic, it still can be harmful, especially to bees and other beneficial insects. The three we keep on hand are insecticidal soap, Neem oil and Diatomaceous earth. Still, it’s recommended only to use these products once you have identified the pest or really have to do so. For example, I can spray a plant with water first to stop aphids before resorting to soap. I encourage reading labels carefully for time from use to harvest for any edibles, for specific pests they destroy and for any cautions about other insects, pets or warnings.

diatomaceous earth on ant hill in garden
This poor pepper has been attacked already by a gopher (and poor watering because it all floods down the hole the critter left behind). Now the stressed plant has an ant hill below. I am trying diatomaceous earth to stop them from doing more damage.
natural pesticide choices
Diatomaceous earth stops crawlers, and soap and oil can stop flying insects.

Further, you can’t be perfect at IPM cultural practices, as hard as you try. For example, I’m pretty sure tomatoes are not native to my region. But I want a vegetable garden. I have to work harder to keep tomatoes healthy than I do the ornamentals (and weeds!) native to New Mexico. I also can’t control the weather. I’m certain many of our bug (and snail!) trouble occurred during frequent night rains and cool, cloudy days. Our plants aren’t adapted to that. Finally, we spend most of our time on weeds – mowing, pulling and preventing. But we can’t control all of the weeds, nor can we control what our neighbors do with weeds or chemicals.

Thinning Might Hurt You, But it Helps Your Crops

Your garden is prepped and you plant a row of carrot seeds or several cucumber seeds, just to be safe.You’re thrilled when you get a nearly 100 percent germination rate. Wow, you must be good! Or in my case, lucky. As I beam with pride, I know that the next step is to thin the seedlings. But sometimes, I fail to heed my own advice or that of horticulturalists. This year, I am trying to do a better job of thinning some of my vegetables. Baby steps…

romaine lettuce thinned
This head lettuce is lined up nicely, but it’s still a little closer together than recommended. Of course, I can cut and enjoy it anytime — before the plants get too close.

First, let’s look at the reasons why thinning helps your crops and yield, and even improves the health of flowers you start as seeds in your garden:

  • A plant can only provide so much energy to the leaves, stems and fruit. If your aim is to get as many health, juicy tomatoes as possible, then most expert gardeners recommend pruning suckers from indeterminate, or vining, tomatoes. We often trim a few lower branches too, especially if they’re touching the ground.
  • The same goes for some fruit trees, though I’ve seen some advice that says not to bother too much with thinning unless it’s obvious that a small branch can’t handle the number of budding apples or pears. And clearly, a home gardener is probably safer letting nature and birds take care of thinning out fruit from upper branches! We chose not to thin our cherry tree and it handled the fruit just fine. The birds helped out more than I would have liked, but there were several bunches of six or more cherries on one spur and most of the tree’s fruit ripened fine.
sour cherries on tree
These cherries were nearly ready to pick and growing fine in a large bunch.
  • With vegetables planted in groups or rows, such as carrots or lettuce, thinning is more to avoid overcrowding. The plants’ roots need space to grow underground – especially true of root vegetables. If crowded, the roots might not support full, healthy growth. And above ground, the leaves need air circulation and sun. Crowded plants hide bugs and hold water on their leaves. It’s like being squashed up in bleachers at a baseball game. Aren’t you more comfortable sitting out on the grass (or in one of those chairs with a cupholder), with the wind blowing through your hair?
carrots in container
I had to do a second thinning on the carrots in this container. They are way too crowded.
Thinning carrots in container
OK, still closer than the recommended two inches in a few spots, but closer. I’ll add a few of the tiny ones pulled up to my next salad.
  • I’ll add another reason to thin that I can more easily relate to. If I feel like pulling up seedlings that made it is wasteful, I have to look at continually watering seedlings I eventually have to thin out – or even worse, plants that grow to nearly mature height and then need pulling up because of a disease or just provide a low yield – as wasting water. It’s not right to let that plant continue soaking up water that could be put to better use.
green bean seedlings
These green bean seedlings are just about right. They can be four to six inches apart, since most of the growth — and the beans — vine up above the plant.

So, what can you do with seedlings so that you don’t feel like you’re wasting a viable plant, small as it may be? The little survivor, that broke through the soil and bore leaves? If the flower or vegetable is one that transplants well, you can move it to another spot, or try it in a container. Lettuce seedlings and carrot seedlings from a second thinning are often large enough to eat, even if they’re mostly garnish on your salad.

Of course, you can also compost the plants you thin and leaves or suckers you prune. When thinning, take care not to pull up the root of an adjacent plant. It helps to thin when the soil is damp and to avoid procrastinating until plants are large and closer together.

Don’t Be Afraid To Prune Perennials

One of my favorite spring chores is pruning ornamental bushes and shrubs to get them ready for vigorous spring growth. I’ll throw in the caveat that pruning wild rose bushes is not a favorite chore. Even with special gloves made for rose pruning, I manage to stab myself around my upper arm, legs and shoulders. These are some pretty big bushes!

My husband and I have different philosophies on how to prune. He tends to cut a lot of the plant, but does a great job of shaping trees. I tend to underprune and some of the bushes look leggy, with too little growth on the lower portions of the branches. So we try to temper each others’ approaches.

spring blooms in xeric garden
Spring means the apple tree along the river (background) blooms big. It also means time to prune. The green plant in the left foreground was almost as tall as the red bud to the right only a few weeks before.

The best approach, especially in xeric gardens, is to follow the plant’s natural growth pattern. This means avoiding the “haircut” prune, or cutting a plant straight across the top. It’s like topping trees; it makes me crazy. A haircut prune on a bush forces new growth only along the top of the plant.

For deciduous shrubs (those that lose leaves in winter and come back in spring), pruning should include thinning to make sure sun reaches bottom branches and to prevent crossing or rubbing of branches. Gradual renewal pruning involves removing dead and old branches just above ground level each year. You also can trim to shape long branches.

Rejuvenate old plants by cutting up to one-third of the oldest and tallest branches just at or above ground level before new growth starts. Here’s the thing, though: Although experts generally warn against pruning an entire plant all the way to the ground, I have done that for several established woody plants that get long and leggy and have few flowers. I’ll even do it annually with great success.

For example, I trim Russian sages (Perovskia atriplicifolia) to just a few inches above the ground, or just above new growth, each spring and they love it. We had a hibiscus (I’m not sure of the variety, but see below) that we pruned to the ground each fall to help it winter over in Albuquerque. It came back in the spring, with huge, maroon-colored blooms that would cause people to stop on their walks and comment.

hibiscus-pruned-nm-landscape
We trimmed this hibiscus, the plant with the large, deep read blooms, to the ground in the fall to protect it from frost and to produce foliage and blooms.
hibiscus-flower
The hibiscus blooms were beautiful and continuous from mid-summer to early fall.

 

Finally, I trimmed an old and overgrown butterfly bush (Buddleia davidii) to just above the ground last year, and by the end of summer, it was more than six feet tall and full of deep purple blooms, butterflies and hummingbirds.

Butterfly bush trimmed back
Butterfly bush (the woody plant in the back of the first bed) cut back last year nearly to the gtound.

 

Butterfly bush after hard pruning
Here’s the same bush in September from the other side. It’s happy, and so are the hummingbirds and butterflies.

Every plant differs in just how much to prune and when to prune it. For example, most of our xeric plants enjoy a cut in early spring. I wait until I see a little new growth appearing and then bring out my pruning shears. But we have a few forsythia bushes, which bloom early, but should be pruned after they bloom. And most evergreen shrubs need only some thinning.

Be sure to use clean bypass pruners and loppers on your plants, and clean after each use, especially if you cut any diseased branches.