Gardening with Xpress: Managing tiny but formidable flea beetles

Sunny smiles in the midst of a gloriously greening world! I’m back with talk of bugs and dirt this month. Also, I wanted to let you know that Wild Abundance, the Earth-based skills school that I work for in Weaverville, has a free online class available this month. It’s called “Top 10 Vegetables to Plant That Will Really Feed You.” In it, my friend and co-instructor, Natalie Bogwalker, and I share which vegetables will give the most bang for your buck when it comes to feeding yourself from the garden. Just go to the Wild Abundance homepage (www.wildabundance.net) and click on online classes in the top bar. Don’t forget to send in your gardening questions so I can answer them in next month’s feature. My email is gardening@mountainx.com. 

What to do about flea beetles? 

The living world always exists in dynamic balance. This beautifully complex process means that, as we rejoice with spring warmth, flowering trees and opening leaves, so do the bugs. Insects that have been wintering beneath the soil are emerging everywhere, and they’re hungry. One of the first garden pests that get going in the spring is the flea beetle (Chrysomelidae family, several genera). 

This tiny beetle can spring from leaf surfaces with impressive force, similar to how fleas move, hence the name. We’ve got a few kinds in the mountains here, most notably the Crucifer flea beetle (Phyllotreta cruciferae), which loves to eat plants in the Brassicaceae family (formerly Cruciferae, also known as cruciferous vegetables — botany can be a little confusing). Another significant flea beetle in our area is in the Epitrix genus. It loves to eat plants in the Solanaceae (nightshade) family, especially eggplant and potatoes. 

Since flea beetles are so small, the damage they inflict looks like teeny-tiny holes on leaf surfaces, sometimes just on the backs of leaves where you may not notice it until the problem has escalated. When they attack very small plants, it can seem as though the leaves have been munched into nothingness. On larger plants, leaves can take on a lacy look. In most cases, as you examine damaged leaves, you will find flea beetles careening off in every direction, which confirms who’s to blame. If you don’t see the beetles themselves but do notice the characteristic collection of tiny holes on susceptible plants (cabbage, arugula, mustards, collards, kale, broccoli, cauliflower, eggplants, potatoes, peppers) in the early to midspring, it’s very likely that flea beetles are to blame. 

In my experience, the most effective way to manage flea beetles is with a combination of cultural practices and physical barriers. Since early spring is so hectic, I usually lean more on the cultural practices (what to plant when and where), rather than the more resource-intensive barriers (clay and row cover). I’ve tried to kill flea beetles with various kinds of organic pesticides (neem oil and safer soap), with very disappointing results. There are other organic sprays and powders that claim to kill flea beetle adults and larvae, but I’m not very motivated to try them. In our area, the population of emerging flea beetles can be massive, and it tends to rain pretty regularly. Both of these factors would mean frequent spraying of a purchased input, which I personally don’t have the time or budget to manage. 

So, getting a little deeper into cultural practices, one thing I’ve noticed is that flea beetles only inflict lasting damage on small plants. They do turn the bottom leaves of larger plants into doilylike shadows of their juicy, verdant selves, but they won’t usually kill the whole plant if it’s big enough. These tiny, bouncy pests seem to stay close to the ground and won’t reach taller leaves once a plant is about a foot tall. One simple practice for mitigating flea beetle damage, therefore, is simply to transplant instead of directly sow susceptible plants. For best results, allow transplants to grow fairly large before putting them in the ground. This can mean feeding your transplants extra yummy fertilizer so that they really fill out their pots, and/or “transplanting up” (moving them to a bigger pot to grow even larger before putting them in the ground). In my garden, eggplants tend to be the hardest hit by flea beetles, so I transplant them up twice, eventually into quart-sized pots where they can get seriously big before setting them out. Fertilizing well once your plants are in the ground also will help them outgrow the inevitable damage done by flea beetles. 

Another cultural practice is simply choosing what to plant when. For example, many people in this area plant potatoes as soon as the ground can be worked. This is great because it means fresh potatoes earlier in the season. However, if you’ve got a heavy load of flea beetles, it can be a disappointing battle. Potatoes can do well planted as late as May or June, and by that time, flea beetles have calmed down a bit. Another example is mesclun mix, a yummy blend of tender greens that are mostly, if not all, in the flea-beetle-susceptible Brassicaceae family. This can be a real challenge in the early spring in our area, so I just choose not to grow it then. It’s a fabulous choice for fall planting, when flea beetles are a thing of the past, and cooler temperatures increase the sweetness in these sometimes-spicy leaves. 

Physical barriers, if you have the time and resources to manage them, can be very effective for mitigating flea beetle damage, too. Notice that I say “mitigating,” and not “preventing.” Flea beetles are here to stay, are tiny and will have some impact on your garden if you’ve got them. Organic gardening is about finding balance, not controlling nature for our benefit alone. Using floating row covers (also known by brand names Remay and Agribon) to cover young plants can protect them from flea beetles. For this to work, you’ll need to make sure that the row cover is quite snug, with little to no open space at the edges for flea beetles to enter. Using some dirt to hold down the row cover on either side of the hoops that support it can help with this. 

Another physical barrier is an organic product called Surround (kaolin clay). This fine clay can be mixed with water and either sprayed onto plants or used as a dunk for transplants before they go into the ground. It’s very effective but will need to be reapplied as new leaves emerge to protect them, too. 

I just moved into a new house and want to get a garden going, but the soil seems like pure red clay. What can I do?

Soil health is the foundation of a successful garden. I cannot stress this enough. It’s well worth the wait to focus on soil building now and planting vegetables later, rather than trying to grow a garden where the soil is not capable of supporting such abundant giving. If you’ve got red clay and want a garden now, the best thing to do is get a container garden going while you work on building up the native soil to support a garden in the coming seasons. 

Red clay actually is a great blessing in the garden, though too much of it can be problematic. Clay particles help with water retention and the movement of nutrients around the soil and into plant roots. Ideally, garden soil will be about 10%-20% clay particles, with the rest being equal parts sand and silt (larger-sized particles). Of the total volume of soil, about 2%-6% should be organic matter like compost, manure, decomposing plant roots, etc. These are all ideals. 

Some techniques for transforming clay into rich garden soil are adding mineral amendments, adding bulk materials and cover cropping. If you can swing it, a mix of all three of these approaches is best. Two mineral amendments that can help loosen clay soils on a chemical level are greensand and gypsum. Only small amounts of these are needed, but it’s most effective to till them in. They’re available at garden centers and will have instructions on their packages. Bulk materials that can help loosen clay include sand, compost, soil conditioner, manure and other bulk organic materials. Sand is only effective if you have the means to mix it into the soil, whereas the others can be mixed in or simply added atop the clay. Cover cropping is a practice of growing “green manure” crops to protect and feed the soil. Instead of harvesting these plants to eat yourself, you cut or crimp them and allow their roots to die back and nourish the soil. Different types of cover crop are appropriate at different times of year. Fifth Season Gardening Supply is a good local resource for bulk cover crop seeds. 

After a season or two of care, heavy clay can transform into gardenable soil. Even as you begin to grow vegetables, keep engaging in these soil-building practices and you’ll continue to improve the texture of your garden soil over time.