The warm temperatures of the summer bring on a rush of new foliage growth, attracting a wide variety of pests. Whitefly, one of the most difficult pests to control, pose a special challenge to gardeners. Whitefly numbers grow dramatically in the heat, most strains are resistant to pesticides, and the pests infect a huge range of hosts including bedding plants, strawberries, tomatoes, and poinsettias.
Just as the name implies, whitefly are small, fly-like insects with white coloured wings. They hide on the underside of leaves where they multiply rapidly. Whitefly feed on plant juices and, in large numbers, can consume a considerable amount of nutrients, causing plants to pale in colour. Like aphids, they also excrete honeydew, attracting black sooty mold fungus. Recently, these pests have been found to spread viruses.
Although all whitefly tend to look alike, there are two major types – greenhouse whitefly and silverleaf whitefly (formerly sweetpotato whitefly). The greenhouse whitefly has been recorded on over 250 plants while the silverleaf whitefly attacks over 500 hosts. Adult greenhouse whitefly are slightly less than 1/8 inch long. They have a white, waxy coating and hold their wings parallel to the leaf surface. Adult silverleaf whitefly are slightly smaller than the greenhouse whitefly and have a yellowish hue. They hold their narrow wings at a 45-degree angle to the leaf surface.
Although not as prevalent, other whitefly types include the bandedwing whitefly; the spiraling whitefly which attacks star apple and ornamental banana; the cloudywinged whitefly which can infest citrus, gardenia and Ficus; and the citrus whitefly which occurs on citrus and gardenia.
Whitefly eggs are spindle-shaped and stand vertically on the leaf surface. For many species, eggs are white when first laid and turn dark grey (greenhouse whitefly) or amber-brown (silverleaf whitefly) with time. Eggs are deposited on the underside of leaves, sometimes in a circle or crescent-shaped patterns. After hatching, the “crawler” stage moves about on the plant looking for a feeding site. At temperatures between 65 and 75F, it takes less than 40 days to develop from egg to adult. Mating is not necessary for egg production and a female may lay up to 200 eggs.
Thankfully, there are a number cultural techniques and organic sprays to help keep whitefly from over-running your plants. A combination of these control techniques is the best method to keeping whitefly numbers down.
When purchasing new plants, inspect both the upper & lower surfaces. Preventing whitefly infection this way saves headaches in the long term. Floating row cover, placed over plants, will also prevent them from becoming infected.
If you do find whitefly, don’t panic! A cylinder vacuum can bring numbers down considerably. Since the adult moths can fly easily from one plant to another, do not place infested plant material next to clean plants.
Whitefly are attracted to the yellow colour of sticky traps. For best results, hang or place the cards close to the top of the plant. Doors, vents and other openings where whiteflies can enter greenhouses are other good sites to hang yellow sticky cards.
Whitefly began showing resistance to synthetic insecticides in the 1980s. Sprays containing pyrethrum or neem give the best control for organic growers. Both the surface & the underside of the leaf need to be covered and during the summer, a spray regime every 5 days is required.
Biological Control Agents
Encarsia formosa, a small wasp, parasitizes to up to 100 immature greenhouse whitefly each. Encarsia populations prefer temperatures above 70 degrees F for development. The best time to use Encarsia is between mid-March and mid-September.
Delphastus pusillus, a small black ladybird beetle, will control both greenhouse and silverleaf whitefly. The larvae will consume up to 1000 whitefly eggs in its lifetime but will also feed on nymphs. Like Encarsia, the beetles perform best at temperatures between above 65F.
For more information on whitefly, look to the following websites:
USDA’s Whitefly Knowledgebase
Information on silverleaf whitefly from the University of Florida
Whitefly research at the University of Arizona
Arzeena Hamir is an agronomist and garden writer based in Vancouver, BC. When she’s not planting peas or harvesting zucchini, she runs Terra Viva Organics – http://www.tvorganics.com/
What do you imagine when you hear the word Lavender? Romance? Smell? Herb? Sachets? Food?
Lavender (Lavandula). It belongs in the mint (lamiaceae) family. Lavender reaches the height of 24″ and the width of 18.” Its flowers are either lavender, purple or white. The whole plant from blooms to leaves is highly aromatic. It blooms in midsummer. It is a perennial and is hardy in zones 5-9.
Native to the Mediterranean area, lavender likes hot, dry summers and cold winters. There are some types of lavender that are not hardy including French lavender (only hardy to Zone 9-10) and Spanish lavender (Zone 7-9). Lavender prefers well-drained and full sun. This plant is so versatile that it can be grown indoors as a potted plant or in the garden.
In the spring, either cut back last year’s growth or start lavender from seed indoors. The seed will need 5-6 weeks cold stratification and can sometimes take two weeks to a month for the seeds to germinate. Fall is when you can divide lavender for extra plants.
Lavender is an herb. It not only smells wonderful, but it tastes just as good as it smells. What better way to say romance than with lavender and strawberries? Or, have a nice cool glass of lavender lemonade on a hot sunny afternoon in the garden.
To dry lavender, cut stems to about a foot in length and tie with a string. Twist the string around the stems to form a lavender bunch. Hang to dry in a warm, ventilated area. When they are dried, you can hang the lavender bunches from pegs in your kitchen or any place you want the wonderful smell around you. I keep a bunch sitting by my computer.
It is a known fact that lavender helps relieve stress and headaches. At the end of a day, enjoy a bath by adding drops of lavender oil and bath salts to the water. Use a lavender sleep pillow to help you fall asleep. In Victorian times, lavender oil was used to perfume the body and the house, to wash the floors and clean furniture, perfume the linens, make potpourri and soap. We still use lavender for all these purposes.
Culinary–pick flowers/stems just as the flowers open. You can pick leaves the anytime. Dry the lavender stems/flowers by hanging in small bundles. You then can add flowers/stems or leaves to vinegars, stews or jams.
Household–dry the flowers to put into sachets. You can then use it to scent drawers. Make a pin of the flowers and attach it to your clothes to repel flies.
Cosmetic–lavender water can be used against acne. Add into soaps, or as an oil for muscle aches.
Medicinal — both dried lavender (used as a tea) and lavender oil (one drop on the temple) are used for headaches. It is known to be a painkiller for insect bites.
I urge you to consider having this wonderful plant in your garden. Even if you don’t use it within your household, the smell of it in your garden will be worth it.
Vinegar This solution will kill broadleaf plants as well as grass plants so be careful of where you spray it. Mix together 3 parts vinegar to one part dishwashing liquid. Spray the mixture in a narrow stream on the weed’s leaves and the base of the plant.
Boiling Water Boiling water will kill any plant and seed it touches. Just pour it on the plant, being careful not to splash on any desirable plants.
Alcohol Mix 1 tablespoon rubbing alcohol with 1 litre of water. Spray the mixture on the weeds thoroughly but lightly. This will kill all plants, so be careful of where you spray it. For tougher weeds, you may need to increase the amount of alcohol you use.
Prevention Minimize the number of dandelions your lawn has by not letting the flowers go to seed. Mow your lawn often to keep the flowers from maturing. Dandelions thrive in acidic, compacted soil. Check the pH of your soil with a home testing kit and adjust the pH if necessary. In gardens, use a deep organic mulch to reduce the dandelion population.
Physical Control Hand dig out the plant, removing as much root as possible. Spot treat the hole with boiling water. Spread grass seed on the bare spot to prevent weeds from returning.
Prevention Quackgrass thrives in compacted soil with low organic matter. Make your lawn inhospitable to the weed by aerating at least
once a year and by adding organic matter such as compost to your soil.
If quackgrass is a prevalent problem in your gardens, consider smothering the with a cover crop. To do this, remove all desirable plants from the problem area. Till the soil and broadcast buckwheat seed over the entire area. Just before the buckwheat flowers, till it under and reseed the area with buckwheat. Repeat the till and seed process before the second growth blossoms. In the fall, till the third stand of buckwheat in and replant heavily with crimson clover. The next year, allow the clover to flower and till it under. The area is now ready to plant again.
Physical Control Keep pulling it out. Make sure to get all of the root as small pieces can sprout new quack grass. If mowed regularly, the quackgrass population will decline.
Prevention The presence of chickweed in your garden indicates frequent tillage and high fertility. Reduce the frequency with which you turn your soil and hold off on adding more organic material.
Prevention The best way to prevent thistles is to use a heavy duty mulch around gardens. Corrugated cardboard works well. Cover the cardboard with a more decorative mulch if you are concerned about the appearance of your garden.
Borax Borax works well on creeping charlie. Note: it may cause yellowing of nearby grasses. If yellowing occurs, mow the grass frequently and it should clear up within 6 weeks.
Mix together 5 teaspoons borax and 1 litre of water. (measure the borax exactly- too little won’t work and too much can kill your lawn) Spray to cover a 25-square-foot area. Fertilize and water the grass afterwards so it rapidly fills in the space left by the weeds.
Even though these weed control methods are natural, it is important to remember that some of them can still be harmful to pets and children. Store all mixtures out of reach of children and keep animals and kids away from areas that have been treated with a potent mixture
Dill is not only a pretty foliage plant; it’s fragrance is a “comfort smell” for many people. I barely touch it’s feathery leaves and the smell of homemade dill pickles, crisp and savory, rubs off on my hands. At the same time, dill is an herb that is often passed over as just a pickle spice and is not truly appreciated.
Dill can easily be grown from seed in full sun, and can even tolerate a slightly sandy soil. However, when first planting you should keep the soil moist until established. Do not move your dill; instead plant where you will be growing it. Thin the seedlings to 10 inches apart; they will grow about 3 feet high. Use the seedlings that you pull up; they are tender and delicious! Be sure to let one of the plants remain with it’s seeds after the season is finished, so it will reseed itself. These plants will be much sturdier and hardier. Throughout the summer you can plant dill in 2 week intervals also, to maintain a supply of fresh leaves.
Dill leaf can be clipped and used in cottage cheese, potato salad, cream cheese, tomato soup and salads. You may also sprinkle chopped young dill on broiling lamb, pork chops or steak during the last five minutes of cooking. The seeds that form on dill can be sprinkled on small pieces of toast or crackers with salmon that has been mixed with mayonnaise. Both the seed and leaf can be used in fish sauces. The fresh leaves can be frozen in small resealable bags and used in dishes. When the leaves are dried, they are referred to as dill weed in recipes. The seeds can be kept in a closed container and used as needed.
Cucumber and Sour Cream Dressing
1/2 cucumber, peeled, seeded and grated (1/2 cup)
1/4 tsp. salt
2 tsp. Dijon-style mustard
1 tablespoon vinegar or fresh lemon juice
pepper to taste
1/2 cup sour cream
1/4 cup plain yogurt
1 tablespoon snipped fresh dill
In a small sieve set over a bowl, toss the cucumber with the salt and let drain for ten minutes. In a blender blend the mustard, vinegar, pepper and salt to taste. Add the sour cream, yogurt and the dill. Blend the mixture, scraping down the sides until it is smooth. Add the cucumber and blend until combined. Makes 1 1/2 cups.
Brenda Hyde is a wife, mom, freelance writer and editor at seedsofknowledge.com For more herb tips and recipes sign up for Herbs ‘N Spices, a free newsletter, by sending any email to firstname.lastname@example.org