Whiteflies are usually considered a minor pest on strawberries, but greenhouse whitefly, Trialeurodes vaporariorum has become an important pest with regular and high infestations in the recent years. Due to the increased concern, I spoke at my recent Extension meetings and wrote an article about whiteflies to inform the strawberry industry about potential risks and management options.
Infestations in different fields in the Santa Maria area varied widely from a few whiteflies here and there to as many as 50-60 per leaflet on many plants in large areas. Heavy infestations of whiteflies cause direct damage to strawberries through their feeding and indirectly through sooty mold development on honeydew secretions. Additionally, whiteflies transmit Strawberry pallidosis associated virus (SPaV) or Beet pseudo yellows virus (BPYV) that contributed to the pallidosis-related decline of strawberries in association with non-whitefly transmitted viruses. Both SPaV or BPYV and other viruses transmitted by aphids, nematodes, or pollen are necessary to cause the pallidosis-related decline of strawberries.
A few fields in the Santa Maria area (cultivar San Andreas) seem to have a problem with dying plants. Stunted plant growth, purple or reddish foliage, and brittle roots which are typical symptoms of pallidosis-related decline of strawberries are seen in the affected fields. These fields also suffered from high whitefly infestations. Preliminary testing of samples at the ARS laboratory in Salinas revealed the presence of SPaV. Additional testing is underway at another ARS laboratory in Corvallis to detect non-whitefly transmitted viruses. Although whitefly history, disease symptoms, and the presence of SPaV suggest pallidosis-related decline, it is necessary to confirm the presence of other viruses.
These incidents emphasize the importance of certain pests especially when they are also vectors of some diseases. Growers should exercise caution in regularly monitoring fields and taking appropriate management decisions to control whiteflies. Suspected plant samples can be sent to our office in San Luis Obispo or to the Ag Commissioner’s offices in Santa Barbara County.
Additional information can be found at:
http://cesantabarbara.ucanr.edu/files/163916.pdf (Handout in English and Spanish)
For more from Surendra Dara on Western Farm Press, see: