Eight years ago Arizona citrus growers primarily had to deal with one
major pest, citrus thrips, Scirtothrips citri, ( The woolly whitefly, Aleurothrixus floccosus, ( When the citrus
leafminer, Phyllocnistis citrella, appeared in Florida in 1993,
it spread through that state, Louisiana, and Texas in less than one year
causing a great deal of damage. When this pest appeared in Yuma in the
spring or 1999, we were very concerned. Although the citrus leafminer
can be easily found during the fall and winter in Yuma, it has not spread
to central Arizona, nor has it reached economically damaging levels. The
primary reason the citrus leafminer has not reached "severe"
pest status in Arizona is the presence of biological control agents. Parasitoids
that prey on the endemic pest, the citrus
peelminer, Marmara gulgosa, a close relative of the leafminer,
crossed over and attacked the citrus leafminer. In addition to these parasitoids,
the previous mentioned mites have been observed preying on citrus leafminers
as well. In a study during the fall and winter of 2002, 66% of citrus
leafminer larvae were killed via predation and parasitism. Another difficult to control pest is the cottony-cushion scale. This
pest occurs throughout Arizona, but infrequently reaches damaging levels.
In almost all instances of the occurrence of cottony-cushion scale, the
vedalia beetle, Rodolia cardinalis ( A lot of the insect problems we encounter in the summer can have their origins traced to what we did for thrips control in the spring. When whiteflies, scales, or mealybugs are present in the spring, insecticides choice for thrips control has important long-term implications. If products such as Carzol, Dimethoate, Danitol, or Baythroid are heavily used, the natural enemy complex can be devastated leaving the secondary pests with little or no natural control. Unfortunately we do not have a large number of selective insecticides to use for thrips control. Presently, Success is the only product available that fits this niche although there are several experimental insecticides that have promise. Predaceous mites, (Tydeus and Yuma spider mite) can effective suppress citrus thrips populations. In 2003, in experimental plots where these mites were not killed by insecticides, only one application of Success was required for season-long thrips management, whereas where the mites were eliminated, two to three insecticide applications were required. As the citrus pest complex continues to change in Arizona, it is evident
that biological control has and will become to be more heavily relied
upon. We should be cognizant of the implications non-selective insecticide
use has, not only on the target pest, but also on the potential impact
on natural enemies and subsequent relationship to outbreaks of secondary
pest such as whiteflies and mealybugs. Issued in furtherance of Cooperative Extension work, acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, James A. Christenson, Director Cooperative Extension, College of Agriculture and Life Sciences, The University of Arizona. The University of Arizona is an equal opportunity, affirmative action institution. The University does not discriminate on the basis of race, color, religion, sex, national origin, age, disability, veteran status, or sexual orientation in its programs and activities. Any products, services, or organizations that are
mentioned, shown, or indirectly implied in this web document do not imply
endorsement by The University of Arizona. Information provided by: Barry Bequette, plantdoc@ag.arizona.edu Extension Agent, Urban Horticulture Barry Tickes, btickes@ag.arizona.edu Extension Agent, Yuma County Mohammed Zerkoune, zerkoune@ag.arizona.edu Extension Agent, Agriculture University of Arizona, Tucson, Arizona. Material written September 2003. |
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