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Protect Your Greenhouse Plants from Whiteflies

Whiteflies can wreak havoc in your greenhouse. These little soft-bodied greenhouse pests multiply so quickly they can take over your greenhouse before you know it. They suck the juices from your plants causing leaves to turn yellow or fall off the plant. White flies secrete honeydew, leaving a sticky coating on the leaves of your plants. It is important to monitor your greenhouse carefully to control these garden pests. Once you have in infestation, you have to act quickly to save your plants.

A useful way to monitor the whitefly population is to use yellow sticky traps. White flies are attracted to the color yellow. The traps can be made by using yellow poster board and applying a sticky substance such as axle grease. Punch a hole in the poster board and hang the traps with string near the infested plants in your greenhouse. Re-apply the grease when the traps loose their stickiness. The traps alone won’t be enough to control a white fly infestation, but it will help you to realize when their population is multiplying.

One effective and all natural way to combat whitefly greenhouse pests is to apply insecticidal soap. You can make a homemade insecticidal soap concoction or purchase a commercial spray such as Flower Pharm insecticidal soap to eliminate the bugs.

Try making your own insecticidal soap with a recipe of one gallon water, 2 t baking soda, 2 t dish detergent, and 2 t white vinegar. Spray the pest treatment under the leaves of your plants where the white fly eggs, scale and adults reside. This can be time consuming as the bugs will die only when they come in direct contact with the spray. Each leaf needs to be sprayed. You must be diligent and apply the spray every 3 to 5 days to maintain control over the white files. Use soaps when plants are not drought-stressed and when temperatures are under 80°F to prevent possible damage to plants. Test the insecticidal soap first on your plants to make sure it will not burn the leaves. Spray the soap on a few leaves and wait two days to see if there is any burning. If burning occurs, try diluting the spray with more water and test again. Insecticidal soap is very effective on controlling white flies and many other greenhouse pests. The drawbacks are it can also kill the good bugs and it is generally a big time commitment.

An alternative to the time commitment of spraying insecticidal soap is to use beneficial bugs as in your greenhouse. A very effective beneficial insect for eliminating white flies in the greenhouse is Encarsia formosa. This tiny parasitic wasps sting the whitefly scale and deposit there eggs inside the whitefly. As the wasp offspring develop, they eat the white fly from the inside out. The Encarsia need warm temperatures of 65 to 80 degrees so you may be limited to using Encarsia only during late spring and summer. Green lacewings and ladybugs also feed on whitefly and other bad bugs. You can order both of these bugs through mail order programs. It is best to set up a program to receive the bugs in regular intervals for a couple months to get a handle on any infestation. Avoid using sticky traps and insecticidal soaps when releasing beneficial bugs so you don’t kill off your investment.

As a final note, make sure to wash off any sticky honeydew residue left behind on the leaves of your plants to prevent disease.

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