Texas citrus mite, a new pest of San Joaquin Valley citrus
Texas citrus mite, a new mite pest of San Joaquin Valley citrus, has recently been identified from widespread regions in Kern County. High densities of this pest have been associated with leaf drop, and uncertainties regarding the severity of this pest have led to fall miticide applications in some of Kern County's blocks of citrus.
Description and Distribution
This year in Kern County, growers have found high numbers of this pest in the Edison/Bena Road area, General Beale area, and in the Maricopa flats area along Highway 166. It has also been observed farther to the north in the Belridge area, where one PCA noted that this is the third year that he has seen this pest. In previous years the numbers so few that pesticide controls were never needed.
Life Cycle and Critical periods
In general, defoliation in October and November in the San Joaquin Valley has not occurred until mite densities have reached 3 to 4 times the spring threshold for Florida. This fall in Kern County, trees have been identified with mite densities exceeding 150 mites per leaf on some individual leaves. In all cases with mites averaging over 35-50 per leaf, some leaf drop was present. In most cases, the first leaves to drop are those of the fall flush that are expendable, will freeze, or will be pruned off anyway.
Spider mites, including the Texas citrus mite, do well under dry, dusty conditions. Border trees near dirt roads commonly have the highest mite densities, and the most leaf drop. Watering roads, or driving more slowly on them, will help.
Texas citrus and other mites also reproduce more quickly on water-stressed trees. It is worth mentioning that the worst incidences of this pest this year were in mid- to late-October in blocks of early-maturing varieties in Kern County. This is the period when growers typically deficit irrigate their trees in an effort to bring up fruit sugars. It was also the period in 2003 that had warmer-than-normal temperatures. A combination of warm weather, deficit irrigation, and dust likely greatly influenced some of the worst outbreaks of this pest.
Most beneficial insects that feed on citrus red mite will also feed on Texas citrus mite. This includes lady beetles, lacewing larvae, and sixspotted thrips. It is unclear if predaceous mites, such as Euseius tularensis will also feed on this pest.
Several growers have sprayed blocks over the past month to avoid continued defoliation. Pyridaben (Nexter), dicofol (Kelthane), and fenbutatin oxide (Vendex,applied before cool weather set in) have all been effective. In addition to these products, literature from other states suggests that wettable sulfur and propargite (Omite) would also be effective. In the case where spring applications become warranted, oil applications or abamectin (Agri-Mek) used as a thrips spray may also be effective.