Margaret Lauterbach

Midsummer gardening roundup: Dealing with leaf miners, blight and different levels of growth

Leaf miner damage is pretty easy to spot.
Leaf miner damage is pretty easy to spot. AP file

You’ve probably noticed light-colored trails on the leaves of Aquilegia (Columbine), beets, Swiss chard, lambsquarter, pigweed, orach or even grapevines. Those trails are made by leaf miners, consuming chlorophyll between the top and bottom surfaces of leaves, not eating completely through a leaf. Often you can even see the larva (worm) inside part of a trail. A spray can’t reach it there, but you can certainly pinch it to death with fingers.

In our area there are several generations of these miners each growing season. Small flies lay tiny eggs in neat little rows on the backs of leaves, the whole cluster so small it looks like a white spot at a glance. Look closer. You can rub off the eggs with a thumb or spray them with an egg destroyer such as Neem. The destruction is mainly cosmetic, but leaf appearance is so unpleasant you really don’t want to eat the unmined part of the leaf. With beets it usually doesn’t affect the size of the bulb, unless the infestation is so severe the leaves can’t make food for the bulbous root.

To get to eat Swiss chard, you can sow it so early the flies aren’t out yet or later pull off damaged leaves, leaving the center growing point intact. By the time those leaves are large enough to harvest they’ll probably have eggs laid on them, but just wash or rub them off and cook and enjoy the leaves. I’ve tried using a screened dome over spinach, but leaf miner parent flies are persistent and very determined. They’ll wiggle their way under.

▪  Our unusually wet spring has brought an unwelcome visitor to my house: fire blight on a pear tree. It may be an Anjou pear, but I’m not sure. I just bought it when I saw it was in bloom when my Seckel pear tree was in bloom, and planted it nearby. The Seckel is said to be very resistant to fire blight, but we shall see. It’s an American variety, having been a mutation on a Pennsylvania farm owned by a man named Seckel in the early 19th century. I’ve been told there were two specimens of this variety growing in England that both succumbed to fire blight. I’m unable to reach brown-leafed branches, so had garden helper prune them out, sterilizing pruners after each cut with Lysol spray, and making sure there was a green ring left inside the bark instead of reddish brown, that would indicate the disease was still in the tree. I think we got this sufficiently early that we may save the tree. Had we waited days or a few weeks, the brown leaves would have been black, as if burned, hence the name “fire blight.”

▪  Sweet potato vines from last year’s home-grown potatoes are especially vigorous this year, escaping my raised beds. I will cut them back a bit, and could use the leaves in stir-fry. Spaghetti squash, planted next to a mint-loaded path, is pumping out large fruits like crazy, but I’ve yet to see any female blossoms on the heirloom butternut squash planted in the same bed. On the summer squash front, Zapallito del Tronco squash is producing much more rapidly than in previous years. Those plants aren’t far from the mint, but so far I’ve been able to scrape off all squash bug eggs and smashed two small clusters of hatching eggs and nymphs.

▪  Determinate tomatoes such as Mountain Princess, Taxi and Early Wonder set fruit early, but it’s not ripening, probably due to high temperatures. They will ripen in their own time. The indeterminate tomatoes set some fruit early, but they’re a little light on foliage to prevent sunburn. When the weather cools a bit, I’ll fertilize them. As usual, no tomato hornworms.

▪  I’m growing a lot of bean varieties for dry bean use: eight varieties of pole or semi-runner beans, and 15 varieties of bush beans. I intended the semi-runner beans to climb on short pole setups, but mistakenly planted bush beans in front of one trellis and semi-runners where bush beans were to be. I’m also growing three varieties of snap beans: Roma, Slenderette and Calima. The latter is new to us, the beans slenderer than Slenderette. We’ve always liked Roma snap beans and Slenderettes are fine fresh or frozen.

The problem with Slenderettes is that they’re very hard to germinate. I planted bean seeds three times to get them to fill out a 10-foot row. I complained about that poor germination online to friends, one of whom (in Ireland) said she was having the same problem with Slenderette beans. I don’t know whether the variety is just petering out, whether it’s smallish white bean reluctance to germinate, or just this variety. Next year I think I’ll start them in pots in the greenhouse and transplant after June 1. Roma snap beans are larger and fatter than Slenderettes, but they have good flavor, different from Slenderettes. They are both heavy producers.

Send garden questions to or Gardening, The Statesman, P.O. Box 40, Boise, ID 83707.