Thursday 16 July 2009

More crawlies: aphids? spider mites? and some recipes

I feel like I've experienced just about every pest going in my garden: wireworm, crane fly larvae, cutworms, tent caterpillars, slugs and snails, cabbageworm, spinach leaf miner, and sugar ants.

I took a picture of the specks of dirt on the backs of some troubled tomato leaves, which I thought were just water-stressed. When I blew the images up, the specks turn out to have legs,



and I'm guessing spider mites or else aphids. Apparently the spider mite larvae are six legged, while the spiders have eight. They can be carried by wind, and my tomato pots sit at the top of a windy driveway just waiting for pestilence to reach them. Aphids can apparently cause leaf curl. Whichever one it is, the remedies seem to be the same.

Spray the leaves top and bottom with:
  • water: water critters off the leaves and then mist to keep the leaves moist (spider mites prefer dry, arid conditions whereas their natural predators prefer damp, moist conditions)
  • a liquid seaweed solution
  • a solution of food-grade diatomaceous earth (kills larvae and spiders but not the eggs)
  • a spray made with rhubarb leaves (the oxalic acid kills aphids and mites)
  • a spray made with soap solution (a classic solution for aphids too, though in the hottest part of the season this can burn the leaves)
  • a spray made with olive oil or neem oil (the oil smothers the aphids, mites and eggs; neem has fungicidal properties as well); can combine the oil and soap
  • dormant oil (the sulfur combats both aphids/mites and mildew)
  • compost tea (or combinations of water, compost tea, molasses, liquid seaweed and apple cider
Or introduce predators such as ladybugs, pirate bugs, predatory thrips, and predatory mites; but if you're also spraying even with organic solutions (except plain water) you risk doing these guys in too.

I don't know how spider mites feel about baking soda but if the plant is also afflicted with a fungal disease such as early blight, black spot or powdery mildew, here's a recipe for a spray to treat all of that:

Baking soda spray
Mix four teaspoons baking soda with one teaspoon of vegetable oil or horticultural oil into one gallon of water.

And a whole list of organic remedies from the Dirt Doctor.

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