Lupines (Lupinus spp.) are members of the enormous Fabacae, or pea, family. Because they are available in a dizzying array of sizes and colors, gardeners may choose from miniatures to shrubs, yellow to pink to purple lupines to suit any area of the garden. Lupines adapt to almost any setting, from woodland plantings to traditional English cottage gardens. Blue lupine and yellow bush lupine are two readily available species native to California. U.S. Department of Agriculture plant hardiness zones vary depending on the species or cultivar, but many types of lupines grow well in zones 4 through 8, but also grow in higher zones with moderate summer and winter temperatures. Whiteflies are a troublesome pest of lupines.
Description of the Pest
Whiteflies are white, winged insects that lay eggs on the undersides of the lupine plant's leaves. Adults are only 1/16 inch long, and the eggs are almost too tiny to see with the naked eye. Their entire life cycle only lasts a month, but when the weather is warm, the insects reproduce prolifically. Whiteflies and their larvae, or crawlers, feed on the vital juices of the lupine's leaves. The insects tend to stay almost stationary, but it is easy to determine if the lupine is infested. Simply shake the foliage and watch for a small cloud of annoyed adult whiteflies to rise from the leaves. The whiteflies quickly return to the plant.
As whiteflies suck the sap from the lupine, the leaves may turn yellow, become deformed, or turn dry-looking and wilted. Whiteflies also excrete a sticky substance called honeydew that is a delicacy to ants. To keep the honeydew flowing, ants protect the whiteflies from predatory insects. Honeydew can promote the growth of sooty mold, a fungus that can spread and block out sunlight, interfering with photosynthesis. If whitefly numbers are low and the lupines are healthy, damage to the plants is generally minimal. In warm climates, whiteflies may breed year around, and infestations can quickly become serious.
Biological and Organic Treatment
Whiteflies are difficult to control. Several beneficial insects feed on whiteflies, and can keep the population low enough to prevent damage to the lupines. Beneficial predatory insects include small lady beetle species, minute pirate bugs, lacewings and bigeyed bugs.Try washing whiteflies off the lupines with a hard spray from the garden hose, paying close attention to the undersides of the foliage, every two or three days. This also washes honeydew off the leaves. Remove infested leaves and destroy them to kill eggs and pupae. A handheld vacuum can suck up large numbers of adult whiteflies. Place the bag or vacuum inside a sealable plastic bag and place in the freezer overnight to kill the insects. A mulch made of aluminum foil or reflective plastic may repel whiteflies.The mulch can be used around the base of shrub lupines. Eliminate weeds around the lupines to decrease the places where whiteflies can hide.
If biological and organic methods fail to control a heavy infestation of whiteflies, try spraying the lupines with horticultural oils, neem oil, or insecticidal soap. These are the least toxic pesticides available, and will smother and kill any whiteflies on the plants. Be sure to spray the undersides of the leaves thoroughly for maximum effect. Although these products also kill beneficial insects, they have no residual effect. Whiteflies might return, but so will the predatory insects that feed on them.
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