|French, J - TEXAS A&M UNIV KINGSVILLE|
|Garza Zuniga, Aurora - UNIV AUTONOMA NUEVO LEON|
|Legaspi, JR., Benjamin - TEXAS A&M UNIVERISTY|
Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 22, 2000
Publication Date: May 1, 2001
Citation: Legaspi, J.C., French, J.V., Garza Zuniga, A., Legaspi, Jr., B.C. 2001. Population dynamics of the citrus leafminer, Phyllocnistis citrella (Lepidoptera: Gracillariidae), and its natural enemies in Texas and Mexico. Biological Control. 21(1):84-90. Interpretive Summary: The citrus leafminer (CLM), Phyllocnistis citrella is a major insect pest of citrus in southeast Asia, Australia, the Middle East and parts of Africa. Since 1993 CLM has been reported in Florida, Alabama, Louisiana, Texas and California. In Mexico, P. citrella was reported in 1994 in the state of Tamaulipas, with subsequent reports in Veracruz, Hidalgo, Nuevo Leon and Colima. The CLM feeds on the leaves, stems and fruit of all varieties of citrus and several ornamentals. In 1997 a collaborative effort between U.S. and Mexico scientists was initiated to determine and compare the populations of CLM and their parasites and predators in both countries. From 1997-1999 we surveyed the numbers and different stages of CLM and monitored the species of parasites and predators attacking the CLM throughout the citrus growing seasons. We randomly collected infested leaves from sites in Montemorelos, and General Teran, Mexico and in 2 counties in the Lower Rio Grande Valley of Texas. Parasites of CLM collected were sent to local taxonomists for identification. Over the 3- year period from 1997-1999 CLM populations increased in the sample sites in Mexico with Zagrammosoma multilineatum, as the most abundant parasite of CLM. Major predators of CLM in Mexico were the green lacewing, minute pirate bug and the convergent ladybeetle. In Texas Z. multilineatum was also the dominant parasite of CLM, followed by the Pnigalio, Horismenus and Closterocerus spp. CLM populations in Texas declined from 1997-1998. The differences in populations of CLM may be due to a hotter, drier climate in Texas compared with Mexico. Although CLM is not a serious pest in south Texas, migration from Mexico remains a risk. Furthermore, other citrus- growing areas of the U.S. are still vulnerable to the citrus leafminer.
Technical Abstract: The citrus leafminer, Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae), was unreported in the western hemisphere until May 1993 when it was discovered in citrus nurseries in Florida. In Mexico, P. citrella was reported in 1994 in the state of Tamaulipas. A bi-national collaborative research project was initiated in 1997 to define and compare the status of P. citrella and levels of biological control between the two countries. In general, P. citrella populations increased in Mexico over the 3-year period from 1997-1999. In 1997, P. citrella peaked at APPROX. 0.4 immatures/leaf in mid-October. In 1999 the pest began to increase in April, reaching peaks of approx. 1.0 larvae/leaf in early July. In both years over all parasitism averaged approx. 20%. The dominant parasitoid in Mexico was Zagrammosoma multilineatum (Ashmead), which comprised >30% of the parasitoid complex. Predators recovered were Chrysoperla spp., Orius insidiosus (Say), and Hippodamia convergens Guerin-Meneville. In contrast, P. citrella generally declined in Texas over the same period. In 1997, the pest peaked at 0.8 immatures/leaf in August and did not exceed 0.4 immatures/leaf in 1998. The decline of P. citrella in south Texas is more evident when compared to a 1995 survey when pest densities exceeded 6.0 immatures/leaf. Monthly parasitism of P. citrella in Texas increased from <1% in May, to approx. 10% in November 1997. In contrast parasitism in 1998 fluctuated from 0-20%. Numbers of parasites were always <0.05 individuals/leaf and often zero. Similar to Mexico, the dominant parasitoid was Z. multilineatum, which comprised 46.2% (128 of 277) of the parasitoids sampled. Differences in P. citrella populations and those of its parasitoid complexes may be partially attributed to a hotter, drier climate in Texas.