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Key to the Most Common Species of Thrips Found in Early-Season Blueberry Fields in Florida and Southern Georgia1
H. A. Arevalo, A. B. Fraulo, and O. E. Liburd2Flower thrips are some of the most important pests of early-season blueberries. In 1998, 40% of the losses in blueberry production in Georgia were attributed to flower thrips (USDA 1999). Thrips damage blueberries by oviposition and feeding. Females lay their eggs inside the ovary of the flowers and as the larvae emerge, they leave scars on the ovaries. Mobile stages feed on the flower damaging the cells of superficial layers. This damage is magnified when the ovaries increase their size to form fruits. Scars become more evident during fruit formation, therefore diminishing fruit quality. Under extremely high thrips pressure, the damage to the flowers is so severe that flower abortion may occur (Arevalo and Liburd unpublished data). We have identified six species of flower thrips that were collected in early-season blueberries in Florida and southern Georgia during the flowering period of 2004, 2005 and 2006. Samples were collected by three methods: 1) white sticky boards deployed inside the bush canopy, 2) white sticky boards located 30 cm above the canopy of the bushes, and 3) thrips collected from flower-clusters of the blueberry bushes. Samples were collected in Florida from Sebring, Haines City, Inverness, and two farms in Gainesville. In Georgia, samples were collected from two farms in Alma in Bacon Co.
At each site we randomly selected 100 specimens per week, for four weeks in each year, during the flowering period of blueberries. We observed approximately 7,000 specimens. Using the information published (Mound and Marullo 1996, Moritz et al. 2001, Moritz et al. 2004, Edwards Unpublished data) and from personal observations we identified the species assemblage. Based on these identification keys and personal experiences, we have compiled a dichotomus key to aid in the identification of flower thrips in early-season blueberries in Florida and southern Georgia. To use this key, it is necessary to slide-mount the thrips specimens for observation under a compound microscope. For slide mounting we used CMC-10 media (Masters Chemical Company, Inc. Elk Grove, IL). This identification key incorporates illustrations of specific morphological features that will facilitate their recognition. The first couplet serves to differentiate the two genera found on early-season blueberry fields, Frankliniella and Thrips.
This species assemblage is dynamic, therefore, the Small Fruit and Vegetable IPM Laboratory at the University of Florida will be glad to assist you with your identification if you find unusual flower thrips species in your blueberries.
Identification Key to the Flower Thrips of Blueberries in Florida and Georgia
1. Four or five pairs of elongated pronotal setae (Figure 1). Abdominal sternite VII has no discal setae. The first-vein setal-row in the forewing is complete and the setae are uniformly spaced (Figure 2) . . . . . . . . . . . . . . . . . . . . . . (Frankliniella spp.) 2
Figure 1.
Figure 2. 1'. Three or fewer pairs of elongated pronotal setae. Abdominal sternite VII has discal setae. The first-vein setal-row in the forewing is incomplete (Figure 3) . . . . . . . . . . . . . . . . (Thrips spp.) 5
Figure 3. 2. The postero-marginal comb of microtrichia is complete in the middle. The microtrichia are long and irregular and their bases are broadly tirangular (Figure 4). Major post-ocular seta is more than 1/2 of the length of ocellar seta III, and usually extending clearly to the outside of the head (Figure 5) . . . . . . . . . . . . . . . . . . F. occidentalis
Figure 4.
Figure 5. 2'. With a different combination of characters from the ones described above . . . . . . . . . . . . . . 3
3. Base of the first antennomere restricted (Figure 6). The reticulation on the metanotum media area is equiangular. No post-ocular seta I. Wings might be absent in the adult stage . . . . . . . . . F. fusca
Figure 6. 3'. Base of the first antennomere is swollen (Figures 7 and 8). The metanotum has no equiangular reticulations, but irregular longitudinal ones. Post-ocular seta I is present and adults always have wings . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Base of the first antennomere is swollen and the edges are more or less sharp (Figure 7). It presents two well developed and sclerotised setae in the second antennal segment. This species is the most abundant in Florida, and very rarely found in Georgia . . . . . . . . . . . . . . . . . . . . . . F. bispinosa
Figure 7. 4'. Base of the first antennomere is swollen but the edges are not sharp. Setae are less developed and less sclerotized on antennal segment II than in F. bipinosa (Figure 8). This species is very common in blueberry plantings in Georgia . . . . . . . . . . F. tritici
Figure 8. 5. Seven or eight antennal segments. The postero-marginal microtrichia are short and irregular in length, they appeared to have their bases fused or more than one microtrichia per base (Figure 9). Sternite V has between 10 and 13 discal setae (Figure 10). Has no equiangular reticulation on the metanotum median area . . . . . . . . . . . T. hawaiiensis
Figure 9.
Figure 10. 5'. Always with eight antennal segments. The postero-marginal microtrichia are long slender and irregular. Their bases are broad and clearly separated at the base (Figure 11). Sternite V has between 3 and 9 discal setae (Figure 12). The metanotum median area presents some equiangular reticulation . . . . . . . . . . . . . . . . . . . . . . . . T. pini
Figure 11.
Figure 12. Acknowledgements
We thank Drs. Joe Funderburk, Howard Frank, and Marc Branham from the Entomology and Nematology Department at the University of Florida, for critically reviewing an earlier version of this manuscript. This research was supported by projects EPA X8-96424405-0 and SARE GS05-045.References
Edwards, G. B. unpublished data. Thripidae (Thysanoptera: Terebrantia) of Canada and United States, pp. 18. Department of Plant Industry, FL.Moritz, G., D. C. Morris, and L. A. Mound. 2001. Thrips ID pest of the world. An interactive identification and information system. CSIRO Publishing. Collingwood, Australia.
Moritz, G., L. A. Mound, D. C. Morris, and A. Goldarazena. 2004. Pest thrips of the world. Visual and molecular identification of pests thrips. An identification and information system using molecular and microscopical methods. Lucid-CSIRO publishing, Collingwood, Australia.
Mound, L. A. and R. Marullo. 1996. The thrips of Central and South America: an introduction (Insecta: Thysanoptera), pp. 40-185, Memoirs on Entomology, international. Associated Publishers, Gainesville, FL.
USDA. 1999. Crop profile for blueberries in Georgia. NSF Center for Integrated Pest Management, North Carolina State University, Raleigh, NC.
Footnotes
1. This document is fact sheet ENY-836 (IN679), one of a series of the Department of Entomology and Nematology, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Publication Date: October 2006. Please visit the EDIS Website at http://edis.ifas.ufl.edu.2. H. A. Arevalo and A. B. Fraulo, research associates and O. E. Liburd, associate professor, Department of Entomology and Nematology, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611.
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