Friday, August 13, 2010

Whiteflies in the Landscape

Lately, we have been receiving many calls at the office about tiny, whitish, flying insects on veggie garden plants and around trees. These insects are probably whiteflies, a sap sucker that can be a pest of ornamental or agricultural plants.

People who have them are noticing a wet feeling when they stand under trees where the bugs are present. This is probably their honeydew. These guys are sap suckers, and in order to get enough nutrients, they have to get rid of the extra water they suck up. What they "pee" out is honeydew. The honeydew can encourage ants to come to feed and can also cause sooty mold to grow. In most cases, sooty mold is just ugly, its not a problem for the plant.

Whiteflies seem to thrive in tomatoes and sweet potatoes in our area. If you have those plants, and they are infested with whiteflies, there are a few things you can try. Cultural control measures include:

  • Prevent over watering, which can encourage whiteflies

  • Avoid planting new plants when populations are high (they will just spread!)

  • Use covers to keep populations stuck on one plant and prevent spread

  • Avoid planting plants that attract whiteflies (tomatoes, sweet potatoes)

  • Control weeds (adults use these to rest)

If you feel the need to treat, make sure they are actually causing some damage. On ornamentals, trees and shrubs, they seem to just be a nuisance when you walk past the plant than they are actually doing damage. There are some products you can try: insecticidal soaps and oils which will give you a short-lived knock down. Only use soaps and oils when you see whiteflies present, otherwise you won't kill anything. Remember, there is no residual with those. Other products that contain the active ingredients acephate, bifenthrin or cyfluthrin can be effective as well. Be sure the product you use is labeled for the plant you will be spraying it on (for example, don't use a tree and shrub spray on your veggies).

I don't have a good reason why they seem to have exploded this month, but they certainly have. People who have never had whiteflies before are seeing them. As you start your new fall gardens, be sure you remove and destroy all old plants that may be providning harborage for your whiteflies. And remember, destroying doesn't just mean pulling it up and throwing it across the fence; remove them completely from the area!

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