Grow Good Brassicas Using Non-toxic Methods
Brassicas, including broccoli, broccoli raab, kale, cauliflower, cabbage, Napa cabbage, pak choi, Brussels sprouts, and other mustard family crops, have their share of pests. They attract aphids and whitefly, flea beetles, harlequin bugs, and several leaf-eating caterpillars. You can grow then successfully without resorting to harmful chemicals. Here are some techniques that every home gardener should know:
How to Grow Healthy Brassicas
Rotate your Brassicas. Not only will this prevent soil nutrients from being depleted, it will also break the cycles of pests and diseases that persist in the soil.
Use floating row covers. These are particularly helpful for preventing caterpillar damage, as they can prevent cabbage moths from laying their eggs on your crops.
Use biological control products, such as Bt (Bacillus thuringiensis), to control caterpillars when necessary.
Plant lots of flowers and herbs. Sweet alyssum, dill, cosmos, phacelia, and coneflowers are among the many flowers that attract insects that will help keep brassica pests under control.
Plant a diverse garden. Mix it up! Rather than plant a large block of kale, plant just a few plants, intercropped with other, non-related plants. This will help promote a well-balanced biological community.
Attend to your soil. SARE (Sustainable Agriculture Research and Education) reports: “when plants are healthy and thriving they are better able to defend themselves from attack.” This means that ensuring good drainage, fortifying your soil with compost, and using mulch, cover cropping, and other soil building techniques will also help deter pests!
Prevent Pest Damage
Cabbage worms often hide in plain sight.
Cabbage worms are not all one species. There are several kinds, including the Imported Cabbageworm, the Cabbage Looper, the Diamondback moth larva, and the Cross-striped Cabbageworm. The controls are the same, no matter which caterpillar is chewing holes in your brassicas.
Bt is a naturally occurring soil bacterium that can be sprayed on the leaves of kale, cabbage, and other susceptible crops. When caterpillars consume the leaves they will stop feeding and then shrivel and die. Bt is nontoxic to humans and animals, and will not harm wasp parasitoids.
Encourage wasp parasitoids, which will help control cabbage worms of all types, if you let them. Learn to recognize the wasp pupae, and leave them alone! In a home garden, they can often be relied on to keep cabbage worms mostly in check. For more information, visit this UF Extension website.
Cover your brassicas with floating row covers.
Crucifer and striped flea beetles chew tiny shot holes in brassicas of all kinds, but are especially problematic with pac choi, and very young mustard and kale greens.
Tiny wasps lay eggs in cabbage worms. Adult wasps emerge from the pupae, shown above.
Timing helps. Flea beetles are less numerous in fall, so this is an opportune time to grow a quick crop of pac choi. In spring, get brassicas started early so that they will be less susceptible to damage once the weather warms and the beetles emerge.
Crop rotation is especially important for flea beetle control, as they lay their eggs in the soil.
Floating row covers act to exclude the beetles. Edges need to be tightly sealed.
Gray-green cabbage aphids multiply in late summer and fall, especially on crinkly leaved cabbage and kale varieties.
The good news is that aphid numbers fluctuate from year to year so if you have a particularly bad year, the next will likely be better!
Check your plants early and often and remove infested leaves or plants as you find them. Cabbage aphids are difficult to control late in the season, so the sooner you take action, the better.
Plant flowers to attract wasp parasitoids, lady beetles, and syrphid flies, all of which are aphid predators.
Insecticidal soap sprays can set back aphid infestations, but keep in mind that these organic sprays will also harm lady beetle larvae and other soft- bodied predators.
Dispose of infested plant debris. Cabbage aphids can overwinter in plant debris, or in plants left standing over the winter.
Consider planting a fall or a spring crop of aphid-susceptible brassicas, but not both. This will give aphid populations less time to build.
Harlequin bugs pierce the stems and leaves of brassicas and other plants, and suck out the juices. They can be especially damaging to Brussels sprouts.
Hand picking harlequin bugs is fairly easy, as they stand out. Eggs are equally photogenic. Toss bugs and eggs in a bucket of soapy water.
Dispose of plant debris at the end of the season, as the bugs overwinter in garden debris and weeds.
Use floating row cover to exclude harlequin bugs.
