Silverleaf Whitefly

Whiteflies are common greenhouse pests, but they can cause surprising problems in the garden, as well.

Silverleaf whiteflies (Scott Bauer, USDA Agricultural Research Service, Bugwood.org) CC BY 3.0 US

Silverleaf whiteflies (Bemisia argentifolli, also B. tabaci biotype B) feed on many garden plants. Alfalfa, beans, broccoli, cabbage, cantaloupe, citrus, eggplant, grapes, lettuce, melons, peppers, potatoes, squash, sweet potatoes, tomatoes, and watermelon are all plants that silverleaf whiteflies use as food.
 
These pests hide and feed on the underside of leaves.

 ​Silverleaf whitefly identification

Silverleaf whiteflies and greenhouse whiteflies are both 1/8” long and look like tiny white flies. There are some differences, however. Silverleaf whiteflies have a slight yellow tinge. They hold their wings more tightly to their body, but you can usually see a space between the wings exposing the yellow body. Greenhouse whiteflies are paler, and they hold their wings flat.

Silverleaf whitefly nymphs (Alton N. Sparks, Jr., University of Georgia, Bugwood.org) CC BY 3.0

Silverleaf whitefly damage

Whiteflies are sapsuckers. They have piercing mouthparts which they insert into leaves and fruit to suck out the sap. This feeding leaves a severe mottling or silvering on the leaves of many plants in the cabbage, squash, and nightshade families. This feeding creates points of entry for diseases such as squash vein yellowing. It also allows whiteflies to “plant” misinformation into their hosts, making life easier for these pests.

Whiteflies carry viruses that cause plants to defend themselves against the viruses rather than the whiteflies. As plants defend themselves against the viruses, they release chemicals that tell neighboring plants to protect themselves against the same viruses. This means the plants are too busy to protect themselves against the whiteflies.

Silverleaf symptoms on right squash leaf (Alton N. Sparks, Jr., University of Georgia, Bugwood.org) CC BY 3.0

Silverleaf whitefly damage on bean leaf (Alton N. Sparks, Jr., University of Georgia, Bugwood.org) CC BY 3.0 US

You will rarely see any feeding damage on the leaves of tomato plants. Instead, the fruit will look very strange. What starts out looking like tomato gray wall evolves into longitudinal green or yellow stripes that never ripen. If you cut the fruit open, you will see that this uneven ripening affects the entire tomato. Squash and other crops will look bleached.

Fruit from plants infested with silverleaf whiteflies (right) looks bleached (Alton N. Sparks, Jr., University of Georgia, Bugwood.org) CC BY 3.0

Silverleaf whitefly management

If you live in an area with cold winters, the weather should wipe out your silverleaf whitefly problem. Of course, they’ll be back in the spring. If whiteflies are in your garden, you can protect your plants by helping out natural enemies, such as big-eyed bugs, lacewing larvae, and ladybugs. You can also use row covers and crop rotation. Harvesting as soon as crops are ready and applying insecticidal soap or neem oil, as needed, will also help. Whiteflies are resistant to most insecticides.

Commercial tomato growers use trap crops to lure silverleaf whiteflies away from their tomato plants. It ends up that squash plants are the trap crop of choice, so you may want to keep your squash plants away from your tomato plants. Cantaloupe and cucumber are also used as trap crops. Another silverleaf whitefly control method is to use an LED-CC trap. Inexpensive LED-CC traps use a green LED light to attract whiteflies to the trap. [I may need to get one of those!]

Take a look at the underside of leaves to see if silverleaf and other types of whiteflies are lurking.