Spider mites, also known as two-spotted mites, become a particular problem for the gardener through the winter. Normally, they hibernate in ground litter or under the bark of trees or shrubs. However, if they stowaway onto a plant being brought indoors, the artificial lights, and warm, dry, conditions of most heated homes will allow them to keep infecting plants.
The spider mite, Tetranychus urticae, is a tiny, 8-legged pest related to the spider & tick. Adults are normally green or yellow but turn red when the day lengths shorten in the autumn. They attack plants by stabbing the underside of the leaves and sucking out the sap. This damage causes a distinctive stippling effect due to the loss of chlorophyll. As their numbers increase, the number of white speckles on the leaf increases and the leaf eventually dies. Once the spider mites begin reproduction, a distinctive “webbing” forms, usually under the leaf and then at the growing tip of the plant.
What makes this pest truly difficult to control is its rate of reproduction. Each female will lay up to 12 eggs per day. Mating is not required for egg production. At 21ºC, these eggs will hatch in as few as 3 days and will develop into adults in only 14 days. If left unchecked, 10 spider mites in May will become 100,000 by July!
Spider mites have been found in greenhouses across North America and Europe and are known to attack over 200 species of plants including azalea, camellia, citrus, evergreens, hollies, ligustrum, pittosporum, pyracantha, rose, and viburnum; fruit crops such as blackberries, blueberries and strawberries; vegetables including tomatoes, squash, eggplant, cucumber; and trees such as maple, elm, ash, black locust, and poplar.
The Predatory Mite
Unlike the spider mite, the predatory mite, Phytoseiulus persimilis, is a welcome insect in the garden & greenhouse. It is a fast moving insect with an orange teardrop-shaped body. The species is a specialized predator the two-spotted spider mite and feeds on all stages of its prey, from egg to adult.
The adult P. persimilis is a voracious eater, eating between 5-20 prey per day. It uses its sense of smell to find plants infected by spider mites. As soon as it comes into contact with spider mite webbing, it will intensify its search.
P. persimilis can be purchased from many biological control companies. Often it is shipped in a glass vial or on trays of bean leaves. The easiest method of application is to sprinkle about 20 adults on each plant. These predatory mites prefer to work their way up a plant, searching for food so try to introduce them as low down as you can. In addition, if many of your plants are infected, keep them close together with their leaves touching so that these predators will be able to easily move from one plant to another.
Unlike the spider mite, P. persimilis prefers humid conditions and misting will not only help it multiply, but will keep down the numbers of the spider mite. A relative humidity of 70% is ideal for P. persimilis. Once its food supply is exhausted, the numbers of P. persimilis will decline.
Other cultural controls
As previously mentioned, misting plants at least twice a day will keep spider mite numbers down. Mite populations can also be reduced by spraying the underside of the leaves with a jet of water to break up the webs and wash the mites off.
Soap sprays are also very effective at controlling spider mites. The active ingredient, potassium or sodium salts of fatty acids, is not toxic and can safely be used indoors. A homemade spray can also be prepared using ordinary dishwashing detergent. Mix 5 tablespoons of detergent in 1 gallon of water and spray the plants, especially the underside of the leaves.
Resources
Terra Viva Organics – a source of P. persimilis
University of Florida Dept of Entomology – life cycle of the spider mite
Cornell University Biological Control – A guide to P. persimilis, the predatory mite
Arzeena Hamir is an agronomist and President of Terra Viva Organics. When she’s not planting peas or picking zucchini, she answers questions about organic gardening at: advice@tvorganics.com. You can also read her gardening articles on Vegetable Gardening at http://www.suite101.com/join.cfm/47083
Did you know that 80 % of the plants that were available at the turn of the century are no longer available to us?
As a child I remember sitting with my grandfather on the back porch eating tomato sandwiches. The tomatoes were huge and the air was filled with a tangy, tart smell that tickled your taste buds long before your first bite. As an adult I remember ordering a BLT, in a charming restaurant in Charleston, SC. When my sandwich arrived I gawked at the tomato that was the size of a slice of bread and as I inhaled I could almost hear my grandfather laughing as that tangy, tart smell reached my nostrils. I looked at the waiter and said “These tomatoes . . .” He replied, “Oh, yes ma’am we only use heirloom vegetables and herbs here.” And just like that, a whole new world of gardening opened up for me.
To be considered an heirloom, the plant itself (be it vegetable, fruit, herb etc . . .) must be open-pollinated, or able to produce seeds that will come back true year after year. You will find as you delve deeper into the world of heirloom gardening that many heirloom plants come with humorous names and usually a touch of folklore such as the “Mortgage Lifter” tomato or the beautiful flower named “Kiss Me Over the Garden Gate”.
There are 4 different classifications of heirlooms:
Family heirlooms – the most common and well known. These are seeds that have been passed down from generation to generation.
Commercial heirlooms – the open pollinated varieties that were offered commercially until approximately the 1940’s.
Created heirlooms – the result of the deliberate crossing of 2 known hybrids or an heirloom and a hybrid.
Mystery heirlooms – result of the natural crossing between 2 heirlooms where only 1 parent is known.
The past few years we have seen a renewed interest in the plants that our ancestors held so dear, and rightly so, but why? There are several different theories. The first being that the resurgence of gourmet foods and restaurants have been able to bring a new appreciation to the strong flavors and wide array of colors and textures available in these older varieties.
The second theory, the new millennium evoked such a mistrust towards future food supply within the public as a whole, more and more interest came to the plants that could provide seed that would come up true year after year, without interference from us or commercial nurseries etc.
The third theory, after many years of dealing with mass crops of corn, soybeans, potatoes being wiped out by a single blight or bacteria, we have finally begun to understand the importance of genetic diversity. Jennifer Heer, a good friend of mine, is a Genetic Research Assistant at North Carolina State University. I posed the question to her as to why she felt so strongly towards maintaining heirloom plants, and this was her response:
Anytime I think about heirloom ANYTHING, I think about genetic diversity (of course). There are all these genes in a plant, and some you like and some you don’t and some you have no idea what they do because they are “quietly” important. Important in ways we don’t know. If we let some herbs “fall out of favor” and push them to the side or even go EXTINCT, we are losing something that we can’t find again and LATER it might be important, medicinally, for drought tolerance, for pest tolerance, etc. It’s like fighting to save the world’s endangered species, only it’s not species, it’s GENES and we can’t even describe them yet so that makes it even harder.
I, on the other hand, sadly, am not that complex. My reasoning for getting so involved in heirloom gardening is the simple reason that I cannot imagine not having these plants in this world. I want my children to be able to experience what it is like to go into the garden and find a delightful “Moon and Stars” watermelon, painstakingly gather the seed after delighting in the sweet taste, and saving those seed to plant next year.
My grandfather grew luffa for years. I remember walking with him on the cold days of October and November and checking the luffa to see if they were dry enough to harvest yet and then watching in absolute amazement when he peeled the skin back and there was a sponge! I thought that these seed had died with him. As I was chatting with a neighbor of mine I mentioned this story and he replied, “Oh, your granddaddy gave me some of those about 10 years ago. I still grow them, want some?” He went out into his garage and came back with a dried luffa just ready for me to collect the seed and replant! Wonderful.
Whatever your reasons may be to want to save these plants, whether it is maintaining genetic diversity, bringing a touch of nostalgia into your garden, or to be able to pass part of your garden on to others, you will be greatly rewarded with the outcome.
Resources
Seed Savers Exchange: a great organization that is assisting in the cultivation of heirloom plants by growing some of them themselves but also teaching others about the importance as well as the how-to’s of heirlooming.
Natural Land: wonderful website containing much information on organic growing and the beauty of heirlooming.
Elizabeth Harwick is an avid gardener specializing in the historical, medicinal, and therapeutic properties of herbs and other little known “wayside” plants. “To maintain a garden you must also maintain a sense of humor.” All questions or comments are welcome : epharwick@coastalnet.com
Gardeners practiced the concept of the three R’s: Reduce, Reuse, Recycle, long before it became trendy. People who grow things have a special relationship with the land and they naturally take steps to take care of it. Take composting for example, they have always known that recycled plant material was beneficial to the soil. Nothing from my grandmother’s garden or kitchen was ever wasted. Using manure in the garden was an accepted fact. These are just some of the recycling practices which have been around for a long time.
Reducing has also been widely practiced among the garden folk. Mulching to conserve water and reduce watering has been standard practice among many. Water caught in a rain barrel was and is a good way to get water for the garden taking the strain off the household water supply. Using that compost so carefully acquired reduces the chemicals that have to be added to the soil.
But, I don’t think that any other group shows as much imagination when it come to reusing. All of our modern conveniences have created a wealth of discarded materials that have challenged the gardener. What self-respecting gardener has not found some use for clear plastic pop bottles? From plant covers to scoops to bird feeders, these containers have been a gardener’s friend. Panty hose quickly became a staple to tomato growers for holding up their tender stalks.
All kinds of containers have been used for starting seeds most notably: foam cups or egg cartons, either foam or fibre. The rigid plastic packs that baked goods come in make great mini greenhouses for starting plants. Even plastic bags are useful to cover a pot of cuttings or a tray of seeds.
Popsicle sticks are useful in any household but to a gardener they become plant markers or even small stakes for seedlings that have become leggy. Pill bottles or film canisters make excellent storage containers for seeds.
It is a great temptation for a true gardener to put a plant or two in any discarded container. Tea pots, wash tubs, cooking pots, old boots, buckets, any empty container that can hold some soil is likely to become a planter or a liner for a planter. And a plastic bucket, especially if it has a lid, is a real find.
Ask any gardener what makes the best tomato stakes. Broken hockey sticks are the number one choice. But any long stick will do so don’t leave any scrap pieces of wood where any gardeners can get their hands on it.
A patch of fruit is not complete without a few foil plates strung up to scare away the birds. And what better use for old clothes than to clothe the distinguished friend of the garden: the scarecrow.
Old sheets, blankets, towels or any good sized piece of fabric should never be thrown out – they all come out to adorn the gardenscape on nights when frost threatens. On those nights the garden takes on an eerie appearance all decked out in colourful garb.
See what happens when an inventive group of people takes advantage of the discards of our modern living. I am proud to associate myself with this illustrious group of caring and imaginative people. You all deserve a big thank you and a hearty ‘bravo’.
Elaine is a horticulturist, landscape designer and free lance writer mailto:evdesign@vianet.ca
