The greenhouse whitefly is a one-millimeter-long insect with four nymphal instars which are flat, oval, and transparent. Fifth instar nymphs move around as crawlers searching for a preferred feeding site on the leaf.

Laboratory analysis is critical to determine if the plant malady is present. Growers can provide samples to UCCE or county agricultural commissioner’s office for no-charge testing. Samples can also be sent to commercial labs.

Heather Scheck, plant pathologist with the Santa Maria agricultural commissioner’s office, received nearly 20 suspect samples for testing. One sample tested positive for pallidosis.

Unknown is the amount of pallidosis in California strawberry-growing regions. Pallidosis disease was first reported in California in 1975.

Dara recommends these methods to help limit the disease:

  • Utilize good agricultural practices, including regular monitoring, communication, and collaboration between growers and PCAs, to limit the spread of the vector and the pathogens.
  • Use clean transplants;
  • Rotate chemical insecticides with different modes of action for vector control;
  • Alternate with botanical or biopesticides;
  • Conserve natural enemies;
  • Timely control of pest infestations especially in upwind fields;
  • Timely diagnosis of the pest and disease; and a
  • Host-free period to break the disease transmission.

Several web pages with information on the disease can be found online, including the UC IPM pest management page at www.ipm.ucdavis.edu/PMG/r734101211.html. Dara has several online articles available at http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=10523and

http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=10824.

California strawberry growers produce almost 90 percent of the nation’s crop, according to the California Department of Food and Agriculture. Strawberries are the state’s 14thlargest exported crop with export values of about $336 million.

The leading strawberry counties include Monterey, Ventura, Santa Barbara, Santa Cruz, and San Luis Obispo, respectively.

cblake@farmpress.com

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