An assessment of damage to citrus leaves by the Texas citrus mite was conducted. Damage was quantified by estimating the density of feeding stipples per cm2 on the upper leaf surface. Damage to the naked eye generally appeared light, moderate or heavy at densities of 400, 1000, or 1800 stipples per cm2. A variable ‘mite-days’ [average number of mites per leaf times days of infestation] was used to investigate the relationship between increases in damage and mite infestations. Increases in number of stipples per cm2 per leaf (Y) across different mite-day values (X) were described by the equation Y=44.08 + 0.59X (r2=0.57). Three cohorts of 100 leaves were monitored for mites and damage. Damage was permitted, then mites were controlled. The final mean density of stipples on leaves for the cohorts averaged 327, 134 and 873 per cm2. Leaf life from the date of full expansion until abscission averaged 442, 386 and 379 days for the cohorts, respectively, with a maximum leaf life of 20, 19 and 18 months, respectively. The longevity of the leaves was generally shorter than observed in California citrus but, in spite of mite damage, probably typical of leaves in Florida. No significant relationship was found between leaf longevity and damage over all three cohorts nor for two cohorts individually. Possibly due to a freeze event, leaf longevity within one cohort decreased as damage increased but, ironically, the average life of these leaves was longer than the life of leaves of the other two cohorts. The study indicated that damage by the mite to ‘Valencia’ leaves may promote little premature leaf abscission, at least in irrigated trees when growing conditions are reasonably good and in the absence of extreme environmental events.
Species 1: Acari Tetranychidae Eutetranychus banksi (Texas citrus mite)
Keywords: predicting damage, leaf longevity
The ESA 2001 Annual Meeting - 2001: An Entomological Odyssey of ESA