5 Simple Tricks for Preventing Pests & Disease
1) Mulch. We’ve said it before; we’ll say it again: mulch everything you can. Whether you opt for black plastic, paper mulch, fabric, straw, leaves or newspaper, mulching well can prevent a lot of problems in the garden. To expound on its benefits, mulch
- Decreases mobility for pests that transmit diseases like powdery mildew and bacterial wilt
- Saves water by reducing evaporation from the soil, which in turn may help prevent problems related to water uptake, like blossom end rot
- Smothers weeds that reduce air circulation, exacerbate fungal diseases, and can be hosts for pathogens
- Straw mulch adds organic matter to the soil, lightening heavy soils and improving friability of sandy ones, ultimately improving soil health, biodiversity and resilience
- Regulates soil temperature, black plastic warming the soil in the spring for heat-loving crops, while straw cools it, reducing heat stress that makes plants vulnerable to infection
If you are gardening in a wet area, mulching will make it take longer for the soil to dry out. Wait until the soil is sufficiently warm and dry for planting before applying mulch.
2) Space. When laying out the garden or succession planting, try to visualize what it will look like when all the plants are full-grown, and space accordingly. Prioritize the plants that need the most space first, and only plant as many as can actually fit according to our planting chart. You won’t get higher yields by crowding your plants—you’ll just get stressed, shrunken ones that each produce less than they should. And by stressing your plants, you’re inviting enemies into the garden - practically waving a sign that says “Diseases Land Here!”
Part of good spacing is maintaining that space—if you take a “set it and forget it” approach to gardening, nature will take her course and quickly turn your plot into a jungle. Clean up weeds and diseased and dead leaves, prune tomato suckers by pinching them back as they appear, and be flexible—if it turns out there’s not enough room for a full-sized kale plant after the spring radishes come out, plant short-season lettuce instead. Keep the soil covered at all times by utilizing the space that’s available, and only plant what actually fits in the space when fully grown.
3) Interplant. There’s a delicate balance between fully utilizing your space and crowding it. Basically, I advocate for a “vertical first” approach: plan your garden around the height of plants, filling in with the shortest (and fastest) ones at the end.
So for example, along the north side of a bed I’ll plant a row of trellised tomatoes, since they’ll get taller than everything else and I don’t want them to shade out other crops. I can simply walk along the back of the bed and weave the leaders through my trellis, pruning and harvesting tomatoes as they ripen. In front of the tomatoes I could plant a row of eggplants, peppers, or tall greens like kale. These don’t need much attention – just occasional harvesting – so it’s ok if they’re sandwiched in the middle of the bed. In the front of the bed I could plant carrots—they’ll need lots of weeding and attention throughout the season, so it’s good to ensure easy access. All around and throughout these “tall” crops, I can direct sow fast-growing crops like salad mix, radishes, dill and cilantro. If they get shaded by the taller plants, that’s ok—in summer it means a longer harvest, since they won’t bolt as quickly in the shade.
The whole bed is now filled, the soil completely covered (discouraging weeds), and because of the orientation with tallest plants on the north side, everybody gets the light they need. Air moves freely around the plants, since they’re not in tight rows of the same height, and the wide diversity of plant families in just this one bed means that diseases will have a harder time spreading.
4) Trellis. Some people trellis cucumbers, squash, anything even slightly viney—but I have to draw the line at pumpkins and melons. Making little pantyhose hammocks for watermelons so they don’t slip off the vine? I’m just not going there. That being said, sturdy trellises are great for crops that really need them, like tomatoes and pole beans – you can check out my preferred trellising system here.
One of the biggest benefits of trellising is that it gets plant foliage off the ground, increasing air circulation and preventing fungal spores from taking hold. Trellises keep fruit off the ground too – which can be an advantage if you have poorly drained soil and find that melons or cukes tend to rot sitting on the ground. If you have a system that works for you, stick with it. But tomato cages and stakes never worked for me (and often collapsed, destroying magnificent plants). If you’re short on space and want to increase air circulation, growing vertically is the way to go—just invest in a system that is study enough to handle the weight.
5) Cover & Coat. Simple, affordable row covers can provide an impressive array benefits, and can be used over and over again if handled with care. Almost any crop that is susceptible to pest infestation (except potatoes) will benefit from being covered immediately after planting.
Row covers protect plants from frost, wind, hail and pests that carry diseases. Covering brassicas like broccoli and kale just after planting prevents infestations of flea beetles, cabbage worms, cabbage looper, and diamondback moth.
Covering cucurbits like cucumbers and squash until they begin flowering keeps out cucumber beetles and squash bugs. It can be used to keep plantings of peppers and eggplants warmer, helping them grow and produce faster. For pest prevention, it’s essential that all the edges of the row cover are completely buried – even a small opening is enough to allow an army of flea beetles in.
Where you can’t cover, you can coat. Cucumber beetles and squash bugs can be deterred by dipping seedlings in kaolin-clay solution – but it must be reapplied after heavy rains to continue protecting the plants. Likewise, you can coat cucurbit plants with baking soda or milk solution to control powdery mildew, and use immune-boosting compost tea to prevent blight on tomatoes. You can learn more about these coatings in our Disease ID article.