Overwintering of the Citrus Leafminer, Phyllocnistis citrella (Lepidoptera: Gracillariidae), without Diapause in Florida

Un Taek Lim, Marjorie A. Hoy

Abstract


The citrus leafminer, Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae), is an important pest of citrus that has spread around the world. The citrus leafminer invaded Florida in 1993 and rapidly colonized all citrus-growing areas. Despite the fact that the citrus leafminer has been studied extensively, gaps in our knowledge of its biology remain. One issue is how the citrus leafminer overwinters. Citrus leafminers have been observed to overwinter in many countries, but their capacity to diapause has not been confirmed. To investigate whether P. citrella overwinters in diapause, we evaluated the ability of eggs to develop to adulthood on potted citrus trees when reared in both outdoor and growth chamber conditions. No pupae were found to be in diapause in the outdoor assessment in which three populations of citrus leafminer were reared in a shade house in Gainesville, Florida beginning on Oct 15, Nov 11, or Nov 22. Larval and pupal mortality significantly increased in the population set out on Nov 22 compared to the other populations. Adult longevity significantly increased in the last two populations compared to the Oct population. However, similar degree days were accumulated during the adult lifespan among the three populations. In the growth chamber assessments, citrus leafminers showed no arrestment in development during the pupal stage by short-day treatments. Development (days) from egg to adult was not different between short- and long-day conditions in both sexes. No signs of reproductive diapause were found from dissections of adult females reared under short- or long-day conditions. We concluded that P. citrella may overwinter on the few small flushes available during winter in mid and central Florida, and the relevance of these results for citrus IPM programs is discussed.

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