It’s not the hot, dry weather that’s responsible for the brown blotches on chard. The spots are caused by beet leaf miners and about all you can do about it now is remove the infected parts of the plants.
In the Garden
Q: There are large brown blotches on the leaves of my chard. Was this caused by our unusually hot spring?
A: Those translucent blotches that look like they were scorched by the sun are caused by beet leaf miners, tiny black and yellow flies that lay their eggs on the leaves of spinach, beets and chard. The eggs hatch into pale green maggots that feed inside the leaves, resulting in hollowed-out, translucent beige blotches filled with frass (polite word for bug poop).
The insect won’t kill your plant, and you can eat any unaffected parts, but you obviously won’t want to eat any of the blotched sections of the leaves.
‘Grow Fresh Produce Year Round’ at Windmill Gardens:
10 a.m., Saturday, Aug. 1. Master Gardener Larry Davis offers tips for late planting of vegetables that grow well in the Northwest fall to winter climate. Free, but RSVP for a seat. 16009 60th St. E., Sumner. Phone: 253-863-5843.
‘The Mad Propagationist with Justin Galicic,’ sponsored by Northwest Horticulture:
10 a.m., Saturday, Aug. 1. In this hands-on class, you will learn two easy-to-master techniques: air layering and stem cuttings. Cost: $35, $25 for NHS members. Space is limited, register in advance. Location: Normandy Park.
The Garden Conservancy’s Olympia Area Open Days Tour:
10 a.m. to 4 p.m. (or 3 p.m. for the Chase Garden), Saturday, Aug. 1. Self-guided tour of two private gardens in Olympia, plus the Chase Garden in Orting. Cost: $7 per person, per garden ($8 for Chase), cash or check, children 12 and under are free (discounted tickets available in advance). No reservations required. Phone: 888-842-2442.
After a couple of weeks of feeding in the leaves, the maggots drop to the ground and form tiny pupae that resemble brown grains of rice. The adult soon emerges from the pupae to lay more eggs, and there are several generations per year, so once you have the problem, if you don’t take steps to prevent it, it will only get worse. Once the larvae are inside the leaf they are protected from sprays, so about all that can be done is to remove infected leaves to reduce their numbers. New leaves will grow back, but they will be reinfected unless they’re protected from egg-laying adults.
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Safer-brand Bioneem, available at some nurseries, and online, is an organic, plant-based spray that repels leaf minors and is safe for use on vegetables. Unfortunately, to be effective it must be applied at seven- to 10-days intervals for the rest of the season.
Save yourself a lot of work next spring by covering your chard, beets and spinach with row-crop cover, a polypropylene fabric that transmits air and light, while preventing the flies from reaching the plants to lay their eggs. Secure the edges of the cloth to prevent the flies from access, and make sure to rotate the location where you plant your beet family crops. Be careful: If the adults emerge inside the cover, you’ll be left with a very unappetizing crop of chard.
Q: I was excited because my tomatoes ripened earlier than ever this year, but now the bottom of almost every fruit has turned black and leathery. What’s going on?
A: A condition known as blossom end rot is causing the bottom of your tomatoes to turn black. It’s not a disease; rather it’s a physiological problem caused by a lack of calcium uptake during fruit development.
To prevent this problem from occurring next year, send a sample of your soil into a lab for testing. Begin with King Conservation District (kingcd.org/pro_far_soi.htm) and use their “additional resources” links if you don’t live in the boundary. A soil test will determine exactly how much lime is needed to make sure there is adequate calcium in your soil.
In lieu of a soil test, adding one pound of agricultural lime per 10 square feet, or working a half-handful of fish bone meal into the planting hole usually will provide enough calcium to solve the problem.
Even if there is adequate calcium available, however, tomato plants can absorb the nutrient only if there is adequate moisture, so mulch around your tomatoes, and water regularly to maintain evenly moist soil. Also avoid using high-nitrogen fertilizers that can exacerbate the problem.
It’s too late to add lime or bone meal to solve the problem now, but there is one treatment that done soon might help. Insert a couple of antacid tablets such as Tums at the base of each affected plant. Antacid tablets are high in calcium, and watered in well, will dissolve within a few hours. The increased calcium will be picked up by the roots and if all goes well any tomatoes that form afterward should be blossom end rot (and heartburn) free the rest of the summer.