The Spring Pest Edition (April 25 2021)

From Linda Gilkeson:

Realizing that many new subscribers will not have seen some of these notes in previous years, here is a roundup on common pests at this time of year and what to do about them:

If you are growing currants or gooseberries, there are two pests to watch for:

  1. Currant Sawfly/Imported Currantworm (same critter, 2 names). The sawfly larvae look like green caterpillars with black heads. They chew up a lot of leaf area, often leaving just the large veins behind. Right now female sawflies are laying eggs on the veins on the underside of the leaves, looking like tiny stitches of dental floss along the veins: See: Linda Gilkeson | West Coast Gardening | West Coast Gardening: Natural Insect, Weed and Disease Control Generally the eggs are laid on just a few leaves, down in the bottom part of the bush, from mid-April to mid-May. All you have to do is check every few days and pick off any leaves with eggs and destroy them. That’s it for the season since there is only one generation per year. If you don’t catch them at the egg stage, you will find groups of tiny green larvae feeding together on leaves in a few weeks. Catching them early will still prevent a lot of leaf damage later.

  2. Currant Fruit Fly: Females lay eggs in the developing berries. The tiny white maggots feed on the seeds inside, leaving gunky black blotches in the fruit. These also only have one generation per year so by covering bushes with insect netting for a month during the egg-laying period you can entirely prevent damage. The flies are beginning to emerge about now and will start laying eggs after the flowers have opened and set fruit. For see what egg scars look like on developing fruit: Linda Gilkeson | West Coast Gardening | West Coast Gardening: Natural Insect, Weed and Disease Control Starting in early May, cover each bush with sturdy insect netting, such as ProtekNet, BugOut, Enviromesh, or similar insect netting products. Gather the netting at the base of the plant and tie it into the trunk so insects can’t get under the bottom edge and leave the bushes covered to mid-June. For this purpose, it is possible to get away with using sheer curtain material (often found at thrift shops) for covers, if you limit the time the plant is covered to 3 weeks. Despite appearances the fabric doesn’t let in sufficient light for growth so plants start to suffer if covered for longer than that.

Other usual suspects:

Wireworms: They are narrow golden brown or yellowish-tan larvae with a very tough skin. Check the photos at Linda Gilkeson | West Coast Gardening | West Coast Gardening: Natural Insect, Weed and Disease Control so you can distinguish them from other soil-dwelling creatures, such as millipedes and centipedes. If you see something the same size and shape as a wireworm, but it is creamy white instead of distinctly brownish colour shown in the photos, it is a predator of wireworms called a stiletto fly (be sure to spare their lives!). Wireworms bore into root crops, tubers of flowers, and also into big seeds, such as corn. Before planting a bed, comb through the surface couple of inches soil and pick out the wireworms (they are easy to see). Then use chunks of potato to lure more wireworms out of the soil. Cut a spud into 1 to 2 inch cubes, skewer each on a small stick and then bury the potato chunk an inch or two deep, leaving the skewer sticking up so you can find the trap again. After a couple of days, pull up the traps and deal with any wireworms that have burrowed into the potato. You can keep re-using the traps for quite a while. To break the cycle of wireworms in the garden (it takes 4 years for them to mature from egg to adult), weed the garden well, right now, so there are no grasses and other weeds present because that is where the beetle will shortly start to lay eggs that will become the next crop of wireworms. This is also why it is not a good idea to use fall rye cover crops (which are turned under in the spring) for a vegetable garden because that attracts more click beetles to lay eggs the become another 4 years of wireworms.

Slugs: The safe slug baits, containing iron/ferric phosphate, are very effective. Where slug numbers are high, use these baits in combination with manually catching slugs coming out in the evening or hiding under boards in the morning. The iron slug baits act slowly (when they eat the iron in the bait, slugs can’t make slime and therefore die) so don’t put a ring of bait around plants you want to protect. Slugs attracted to eat the pasta pellets have plenty of time to finish off your plants before they feel the effects. A good way to use the bait is to use small amounts, sprinkled widely over a garden bed before you plant seeds, continuing periodically, while seedlings are small and need the most protection. Replace the bait often, especially after rain, because it quickly disintegrates.

Birds: Purple and House Finches eat flowers of fruit trees to get at the nectar, also Pine Siskins do it as well and with their numbers high this year, more people are noticing bird damage to fruit flowers this year. On a mature tree with lots of flowers, birds are not likely to significantly reduce the crop, but for small or young trees with few flowers, you might need to put bird netting over the tree or use bird scaring devices, such as dangly foil strips, streamers, tin cans on strings, etc. to protect the flowers. Since pollinators have to reach flowers, bird netting should have at least 1 cm (1/2 inch) holes to allow them in. I made a couple of cardboard cutouts shaped like large owls with huge googly scare eyes drawn on them and mounted one on my orchard fence and the other on a tall pole in the much-persecuted cherry tree.
Other birds, such as robins, are ferocious predators of peas, broadbeans and beans, digging deeply to find the fat seed at the base of seedlings. Cover seedbeds and seedlings with bird netting, chicken wire, wire screening or other barriers until the plants are well established. Quail and other birds also peck leaves of young plants, taking V-shaped, beaky bites out the margins of leaves, breaking stems of small plants or pulling up onion seedlings (apparently just to see what’s under there…) [……am I sounding fairly annoyed with birdies this year!?#!]

Cabbage root maggots, Carrot rust fly: The first generation of these root flies will be laying eggs at the base of plants soon. Protect large cabbage family plants, such as broccoli, cauliflower, cabbage, with a barrier fitting closely to the stem, lying flat on the surface of the soil. These discourage flies from laying eggs right where the stem and soil meet. Barriers can be made of any water resistant, soft, flexible material: cut them out of compost or potting soil bags, feed bags, heavy freezer paper, etc., but not cardboard, which is too stiff and will injure the stems of the tiny plants when you try to slip the barrier in place. Barriers should be about 15 cm/6 inches square, with a slit cut to the centre. I cut a tiny X at the centre end of the slit to accommodate the stem to make a tight fit. For small cabbage family plants (radishes, leafy greens, Chinese cabbage) and for carrots to protect them from a similar insect, cover the whole bed with insect netting or floating row cover before the seedlings emerge to prevent the flies from laying egg on the plants. See: Linda Gilkeson | West Coast Gardening | West Coast Gardening: Natural Insect, Weed and Disease Control Leave the netting in place until harvest because there are several generations of root flies that continue to lay eggs over the season.

Republished with permission from Linda Gilkeson’s Gardening Tips. See Linda’s website to sign up for her newsletter, purchase books, access free presentations and identify pests and diseases which may affect West Coast gardens.


Just read this post…Once again thank you Linda for the great information! Greatly appreciated.

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