Silverleaf Whitefly - Ecological Impact

Ecological Impact

The silverleaf whitefly is considered an invasive species in all areas it inhabits in the United States as well as Australia and several European countries. It was classified as an agricultural pest in Greece around 1889 and had a significant impact on tobacco crops there. The first whitefly found in the United States dates back to 1897, and was found on a crop of sweet potatoes.

This tiny insect wreaks havoc in two simple ways. First, the silverleaf whitefly, a parasite, feeds off of its host plants by piercing the phloem or lower leaf surfaces with its mouth and removing nutrients. Affected areas of the plant may develop chlorotic spots, whither, or lose leaves. Whiteflies also produce a sticky substance called honeydew, which is left behind on the host. Honeydew can induce the growth of sooty molds, which can then reduce the plants ability to absorb light. This results in less growth, lower yield, and poor quality plants. It also requires that crops be thoroughly washed after harvesting, which raises processing costs for the grower.

The second problem with the silverleaf whitefly is its notorious status as a vector for plant disease. It has been transmitting gemniviruses such as lettuce infectious yellows virus, tomato yellow leaf curl virus, and African cassava mosaic virus for years and over many continents and is now a vector for cassava brown streak virus disease.

Bemisia tabacia became a serious issue in crops across the southwestern United States and Mexico in the 1980s. Scientists speculate that this pest was introduced via infested ornamental plants brought into the United States at this time. Florida’s poinsettia greenhouses were crippled by the pest beginning in 1986, and by 1991, the whitefly infestation had spread through Georgia, Louisiana, Texas, New Mexico, and Arizona to plague crop growers in California. California, the state that produces approximately 90% of the United States’ winter vegetable crop, has incurred an estimated $500 million in crop damage due to silverleaf whitefly populations. Across the plant industry, this is thought to cost the state $774 million in private sector plant sales, 12,540 jobs, and $112.5 million in personal income. On a national scale, the United States has suffered crop and ornamental plant damages in excess of $1 billion.

In particular, the whitefly is a devastating pest simply because it feeds on over 500 hosts. Included in its host domain are agricultural crops such as tomatoes, squash, broccoli, cauliflower, cabbage, melons, cotton, carrots, sweet potato, cucumber, and pumpkin, and ornamental plants such as poinsettia, crepe myrtle, garden roses, lantana, and lilies. It can cause specific damage to certain host plants, like "silverleaf" on squash, irregular ripening of tomatoes, whitestalk in broccoli and cauliflower, white stem in poinsettia, and light root in carrots.

The whitefly has many natural predators including parasitoids and various arthropods. More on this subject can be found below in the section titled natural enemies.