June 2016 note: We were so fortunate last summer. We had hot weather but not for an extended time, so no Bagradas. The word from hot San Diego community gardens is they are simply not allowed to plant any Brassicas.
The extended Santa Barbara area hot spell at the end of August 2014 brought Bagrada Bugs. Ugh. They were sighted on radish, broccoli and kale at Pilgrim Terrace Community Garden. Bagradas thrive at sustained temps 85 degrees and above. They are small, less than a 1/4 inch length, but deadly. Other than seeing them, the first sign is your plant leaves have whitened areas at the leaf edges and the leaf starts to wilt.
Per Wikipedia, Bagrada Bugs are native to much of eastern and southern Africa and parts of southern Europe and Asia. They made a sudden appearance in Los Angeles in June, 2008, its first sighting in the Western Hemisphere. It then moved into the cropland of the heavily agricultural Coachella and Imperial Valleys of California, doing damage to cole crops there, especially those grown organically. As of September 2014 it has reached as far north as San Mateo, Santa Cruz, Merced and Inyo counties, and all California counties to the south except Tulare County.
Although spiders and other general predators may feed on the Bagrada bug, it does not have specific natural enemies in the United States. Birds don’t eat these nasty stink bugs.
The only effective substance, so far, that kills them, is one you have to have a license to use.
Brassicas are their favorite food, and Brassicas, that’s broccoli, cauliflower, collards, kales, Brussels Sprouts, cabbages, are THE SoCal winter garden plant! Last year, late summer, they also infested our tomato and pepper plants.
- Per UC IPM, as an alternative to greenhouses, screened tunnels or floating row cover fabric can provide plant protection in gardens. The mesh of the screening material must be fine enough to exclude the Bagrada bug nymphs and should be elevated so that it does not touch the plants because the bugs can feed through these coverings. The edges of protective covers must also be buried to prevent the bugs from crawling underneath to the plants, and they must be applied before Bagrada bugs get into the crop and soil.
- If you are planting Brassicas from seed, immediately securely cover with a floating row cover or the baby plants will be eaten.
- Some gardeners plant mustard and radish as trap plants, the Bugs go there first. But, believe me, they quickly mow those and it’s on to your other Brassicas and more! The big CON of trap plants is they BRING Bagradas! The best course of action, to prevent egg laying and further infestation, this year and next, is to harvest, then remove any Cruciferous plants – mustard types, radish, all Brassicas, until the weather cools. Then, plant whatever you want!
Bagrada Bug infestation on Bell Peppers
Removing Bagradas from your plants just isn’t feasible. Not only do they move FAST and instantly drop to the ground when the plant is disturbed, but are fast growers and reproducers. They make virtual swarms, and when they suck juices from your plant, toxic disease producing stuff gets in your plant. In hot temps, I’ve seen a 1 1/2 foot tall plant go down in 1 to 3 days. White patches start on the leaves, they wilt and the plant dies.
PLEASE Remove infested or diseased plants immediately. You can’t even sneak up on Bagradas to cover the plant with a plastic bag. The moment the plant is disturbed, the bugs instantly drop to the ground, skittering off in the blink of an eye. Squish or stomp any bugs you see. DO NOT lay the leaves or trim of infested plants on the ground. Bagradas lay eggs both on your plant and in the ground. Eggs you might not see, hatch quickly, defeating your clipping. If possible, securely tie plant and bugs in a plastic bag so they can’t escape, and take them to the TRASH. Do not put them in compost or green waste.
Simply shaking Bagradas off doesn’t work. They also fly. When you try to remove them, they are expert at playing dead, and once you are gone, quite quickly climb back up on the plant. I’ve seen it. Stand very still and wait…sure enough, there they come. That’s your second chance to remove, euphemism for kill, them. But, like I say, better to immediately harvest anything you can, then remove the plant.
Don’t lay down mulch; do REMOVE mulch habitat from around infested or susceptible plants until the Bagrada season is OVER. They hide out in mulch, mate like crazy, lay eggs in the ground.
The sooner you remove infested diseased plants and mulch habitat, the fewer eggs will be laid in your soil, the fewer Bagrada Bugs you will have next year if we have another sustained period of high temps.
- I highly suggest biodiversity, interplanting – that’s mixing it up, even interplanting different varieties of the same plant (especially broccoli), rather than monoculturing – a row of a single kind of plant. With rows of a single plant, the pest or disease simply goes plant to plant and you lose the whole row. This also stops leafminers (typical on overwatered soft leaved chard & beets) from going plant to plant. Slows them way down.
- Plant so mature plant leaves don’t touch! Stop the ease of transmission. If you can’t help yourself, and go monoculture or plant too close, thin out plants as they mature, clip back, harvest the between leaves so they don’t touch. More is not always better. Dense plantings can literally starve plants that get root bound, that have less access to a healthy allotment of soil food and soil organisms that tickle their roots. Jammed together leaves are not able to get the sun power they need, so there are smaller leaves and less and smaller fruits. Slugs and snails successfully hide out. Mildew and leaf miners spread easily and can ruin the crop. There are so many reasons to give your plants ample space to live and breathe.
- Unfortunately, Brassicas don’t mingle with mycorrhizae fungi. With other plants the fungi network linking your plants is proven that when one plant gets a disease or pest, it warns the neighbor plant. That plant then boosts its own defenses! No such luck with Brassicas.
- Wait to plant your Brassicas from transplants in October when the weather has cooled.
Here is the link to some additional really excellent information at UC IPM (Integrated Pest Management) published Jan 2014. Read it very carefully.
You have choices!
- For now, plant what Bagradas don’t care for. Wait until the weather cools, plant Brassicas from transplants in October. Greens are super healthy ~ just don’t plant cruciferous plants (plants with four-petal flowers/cross) like Mizuna, mustard or turnips. Better not to get those mixed mesclun 6 packs at this time.
- Take a chance, mix it up! Plant a few Brassicas/mustard/radishes here and there now. If these plantings fail, plant another round when conditions have changed. Succession plantings are a wise gardener technique!
- Don’t plant over winter; rest your soil, or plant soil restoring cover crops!
Keep a good watch. Steady yourself. Make calm decisions. What you do is especially important if you have neighbor gardeners who have plants that may become infested.
9.1.2014 Post revised and updated from experience