We all dread one word when it comes to our garden and plants. Drum roll please.. PESTS it is!! Whiteflies are ranked right up there in the annoying and hard-to-control pest list. Read more to learn about this.
This article will deal with the detailed description, identification and life cycle of this pesky creature, and enlighten us with several ways to treat infected plants.
Whiteflies are small hemipterans that typically feed on the undersides of plant leaves. They are tiny, sap-sucking insects that are frequently abundant in vegetable and ornamental plantings.
Whiteflies feed by tapping into the phloem (tissue that carries nutrients) of plants causing decreased vigour and growth. Whiteflies may also transmit plant diseases depending on the species.
Whiteflies excrete sticky honeydew that attracts aphids and other pests and cause yellowing or death of leaves. Outbreaks often occur when the natural biological control is disrupted. Management of outbreaks is tremendously difficult.
Just as the name implies, whiteflies are small, fly-like insects with white colored wings. Whitefly numbers grow dramatically in the heat and due to overuse of pesticides; many strains have become resistant to them.
More than 250 ornamental and vegetable plants are prone to whitefly attacks. Citrus, squash, potato, cucumber, grape, tomato, and hibiscus are commonly infested.
Mostly, all whiteflies tend to look alike, but there are two major types – greenhouse whitefly and silverleaf whitefly.
Adult greenhouse whiteflies 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 whiteflies are slightly smaller than the greenhouse whitefly and have a yellowish hue.
Whiteflies normally lay their tiny, oblong eggs on the undersides of leaves. The eggs hatch, and the young whiteflies gradually increase in size through four nymph stages called instars. The first nymph stage (crawler) is barely visible even with a hand lens. Later nymph stages are oval and flattened like small scale insects. The legs and antennae are greatly reduced, and older nymphs do not move.
The winged adult emerges from the last nymphal stage. All stages feed by sucking plant juices from leaves and excreting excess liquid as drops of honeydew as they feed.
Adults are minute sucking insects with powdery white wings; whiteflies fly out in clouds when disturbed. Larvae are flattened, legless, translucent, 1/30-inch scales on leaf undersides. Eggs are gray or yellow cones the size of a pinpoint and are commonly found in greenhouses.
Females lay eggs on undersides of leaves, which hatch in about 2 days into tiny, mobile scales. These scales feed on plant juices and molt to a legless stage in a few days. After progressing through 4 major growth stages, the nymphs rest in a pupal-like stage, before emerging as adults. Most whitefly species require 20 to 30 days for a complete life cycle at room temperature, fewer in summer.
Controlling Whiteflies Organically
1. Remove infected parts: Immediately remove severely diseased leaves and branches (without handicapping the plant). Make sure to seal it properly in a bag for disposal or burn the diseased leaves and stems to avoid spreading of diseases and whiteflies.
2. Organic Insecticidal Soap: Spray wash your plants with a soapy solution, especially the underside of the leaves where the insects live. This method kills adult insects by suffocating them with a coat of soap.
3. Yellow Sticky Pads: Yellow sticky pads are a wonderful control and monitoring method. Whiteflies are attracted to the color yellow and will turn up to investigate, only to find themselves glued to their doom. Hang a yellow cardboard or yellow piece of wood with a very sticky substance applied to it. These sticky traps can be purchased from garden stores too.
4. Beneficial Insects: Several predators and parasitoids may be effective in controlling whitefly infestations, including green lacewings, ladybirds, minute pirate bugs, big-eyed bugs, and damsel bugs. Attract these insects by planting several flowering plants in your garden.
5. Companion Plants: A number of plants can be intercropped with vegetables and ornamental plants, in a garden setting, to serve as companion plants to protect against whiteflies. Nasturtiums are thought to provide a defense to gooseberries and tomatoes owing to particular root chemicals that deter whiteflies. Zinnias help by attracting predators that consume whiteflies, including predatory wasps and flies. Hummingbird bush, pineapple sage and bee balm are other such plants that help attract predators in addition to concealing the scent of nearby susceptible plants.
6. Neem Oil Insecticide: Neem oil has several complex active ingredients, azadirachtin being the most potent and well-studied. These ingredients disrupt the proper functioning of the natural hormones of insects and unsettle their feeding, mating and egg laying activities. If eggs are produced they don’t hatch, or the larvae don’t molt. The population eventually plummets, and they disappear. Neem oil has some systemic (absorbed by the plant) benefits when applied as a foliar spray, but seems to work best as a systemic when applied as a soil drench, absorbed by the plant roots. Dilute 2-5 ml of neem oil in a liter of water and spray it on your plants, every fortnight.
7. Earthworm castings: Spray earthworm castings at the base of the plant. Reports show that vermi-compost helps repel pests.
8. Homemade repellant: Try this homemade mixture to control and deter whiteflies from attacking your plants. In a spray bottle, mix 2 parts rubbing alcohol, 5 parts water, and 1 tablespoon biodegradable liquid soap. Spray the mixture on the foliage of garden plants that are susceptible to these pests.
9. Reflective mulches: Aluminum foil or reflective plastic mulches can repel whiteflies by reflecting sunlight onto them, thus hindering their ability to seek out their favorite plants.
10. Seaweed extract: Use a seaweed spray to mist the leaves of your plants. It serves a dual purpose: benefits plants by providing nutrition and makes sprayed parts undesirable for whiteflies to reproduce on.
Start your mission and make your garden whitefly free. Share your experiences with us and don’t forget to spread the word.