Last Planting, Powdery Mildew and Rats

Well, so that summer went by in a blur…and here we are at the last planting window of the season.

What to plant: If you sow this week, you should still be able to grow nice-sized plants of hardy winter lettuce and arugula before winter. It is expected to be pretty hot this week, so cover seed beds with burlap or other covers to cool the soil enough to allow seeds to germinate. Now is the right time to scatter corn salad seeds under tomatoes, squash and other plants that won’t continue in cold weather. Corn salad may not germinate until the soil cools down, so don’t worry if they don’t come up immediately; it is the hardiest salad green I know of and will continue to grow (slowly) during the winter. If you will be growing winter greens in a coldframe, plastic tunnel or unheated greenhouse, you could also sow Chinese cabbages, leaf mustard and other hardy greens now, because the protected environments provide a little more growing time.

If you can find seedlings of spinach, chard, lettuce and other leafy greens you can still plant them now and expect to have a harvest this winter (on Salt Spring, Chorus Frog Farm stand still has these available). Do be generous with nitrogen-rich amendments when you plant and keep the plants well-watered and shaded during hot weather to make sure they don’t slow down. It is too late to plant seedlings of cauliflower, cabbage, broccoli and Brussels sprouts as there isn’t enough growing season left for them. Days are substantially shorter now and the lower sun at this time of year casts more shade from trees and buildings at both ends of the day, further reducing the hours of sunlight.

Check on thinning: Time for a last check of winter roots crops to make sure they are weeded and thinned for this last good growth month. I always have to have another go at my winter carrots no matter how well I thought I thinned them in July. I am often asked whether carrot rust flies will dive in and lay eggs on carrots when you take off the insect netting or row covers—but not to worry: the adult flies lay their eggs in the evening. As long as you uncover carrots during the day, do the thinning and replace covers immediately, you won’t be risking attack. Right now, there are high numbers of adult rust flies around so you do have to replace the insect barrier and leave it on until the end of October.

Powdery mildews: With the dry weather of late summer, powdery mildew fungi are showing up on a variety of plants as a white, dusty coating or chalky blotches on leaves. This year there were many reports of powdery mildew on tomatoes, which is not as common as powdery mildews on squash family plants. New leaves resist infection, therefore keep plants growing as vigorously as possible with plenty of water and weekly boosts of liquid fertilizer (e.g., fish fertilizer). Growing new leaves allows an infected squash to carry on ripening fruit even though old leaves are covered with fungus. Picking off infected leaves won’t do anything to control the disease since spores are everywhere. Leaves that are green under the fungal coating are still providing some benefit to the plant, but yellow or brown leaves can be cut off to improve appearance if desired (it is fine to put them on the compost pile). Overhead irrigation or daily syringing of leaves with water can slow the spread of mildew on squash and cucumbers, but don’t try this on tomatoes as that invites late blight. Once again, I am finding that a zucchini seeded on June 20 is working out really well for late summer, producing lots of fruit and so far, with no sign of powdery mildew.

Rats! Quite a few inquiries have come my way lately about critters nibbling tomatoes, fruit, beans, corn and other tasty crops. The way you know it is a rat, and not a racoon, is that racoons take off with whole pieces of fruit and ears of corn; they also often break branches while they are marauding. If a racoon family is involved they can strip a fruit or nut tree in a night or two of hard work (the nuts I can understand, but I wonder what they think will happen to their stockpile of fresh fruit?). Rats work away at one fruit at a time, but usually can’t eat the whole thing in one night so the next morning you see half-eaten pieces of fruit or hollowed out tomatoes hanging on the plant. Rats eat through the side of corn ears, and typically, rat-chewed things show small tooth marks or have a shredded appearance. Squirrels will also gnaw on the same things that rats like, but squirrels tend to drop small chips of the woodier parts of whatever they were eating (bean pods, fruit skins). Rats will also gnaw on potatoes pushing up out of the ground or close to the surface, which is a reminder to keep potatoes well buried. Rats can be kept out of grape bunches, figs, tomatoes by bagging each fruit or by covering whole plants with insect netting (bird netting doesn’t work, because they can climb it and eat fruit through the holes). Organza gift bags, which you can buy from wholesalers, so far have worked fine for keeping rats out of my figs and corn, though they would never stand up to racoons. Rats tend to go back to the same piece of fruit or corn cob they were working on the night before, so leaving the half-eaten food on the plant diverts them from starting on a new piece of fruit. When plums and tomatoes are ripe enough to attract rats, they are also ripe enough to be picked and allowed to ripen fully indoors away from the mayhem.

If you have rat problems this year, try to get them under control well before harvest time next year. You can use snap traps, but outdoors they are a hazard for birds. Locked bait boxes with fast-acting baits present less of a risk of secondary poisoning to animals that might catch a poisoned rat than the old warfarin baits did. You may want to get help from a pest control service to set out bait boxes or traps and monitor monthly. Killer cats and rat terriers, of course, work for some people. For fruit trees, one of the most effective critter prevention devices is a wide sheet of metal wrapped around the trunk. At least 18 inches, but the wider the better, the slippery metal prevents animals from climbing the trunk. Lumber yards (e.g., Windsor Plywood) have sheet metal in a variety of widths, sold by the foot, and they will sell you just the amount you need. This strategy won’t work if the tree’s branches droop low enough to allow animals to jump up or where branches are touching fences, trees or other objects that animals can use as a route into the tree. Squirrels can jump quite a distance, so barriers on trunks only squirrel-proof trees that are set well away from other objects.

September 4, 2017 5:52 PM

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