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In the fall of 1984 excessive flower drop was observed in lime Citrus aurantifolia (Christm.) Swingle trees in the vicinity of Homestead, Dade Co., Florida. In a preliminary survey, two lime groves were sampled on the 13th and 25th of October 1984. Sampling consisted of randomly selected collections of floral clusters from 20 trees on each date. Prodiplosis longifila (Gagne) larvae were collected for the first time from lime flowers. Larvae were observed feeding on the style, ovary and filaments. After larval injury, the flowers bore symptoms of fungal infection characterized by necrosis of the ovary and calyx. P. longifila has been reported feeding on wild cotton Gossypium hirsutum L. in Florida (Rainwater 1934) as Cantarinia gossypii (Felt), and is also known to attack alfalfa Medicago sativa L., beans Phaseolus vulgaris L., tomatoes Lycopersicon esculentum L. and potatoes Solanum tuberosum L. in Peru (Gagne 1986). A survey of arthropods associated with lime flowers was conducted on March 20 and March 27, 1985 to establish whether a relationship exists between P. longifila infestation and flower damage. Lime flowers were obtained from commercial lime groves in Dade County, Florida. Clusters of flowers were randomly selected, picked, and transported to the laboratory for examination, where the flowers were opened and examined for the presence of arthropods. Eighty-five percent of 270 lime flowers analyzed contained P. longifila larvae (Chisquare: X2 o5[4] = 9.48) and 11% contained Polyphagotarsonemus latus Banks (Acarina:Tarsonemidae). Species of Hymenoptera were present in 2% of the flowers and Homoptera and Thysanoptera were present in 1% of the flowers. C. sinensis (L) Osb., C. aurantifolia, C. limon (L.)., C. volkaneriana (Ten. & Pasq.) and C. grandis (L.) were sampled for P. longifila March 20, and March 27, 1985 in the 1.37 ha Citrus germplasm collection of the University of Florida Tropical Research and Education Center. Sampling consisted of randomly selected floral clusters from 2 trees for each Citrus species and date. From 20 inflorescences collected for each Citrus species, more C. aurantifolia (1250%) flowers were infested with P. longifila larvae than were C. sinensis, var. Valencia (7%), C. grandis (0%), and C. volkaneriana (0%). Sixty lime flowers infested with P. longifila larvae were dissected and the stamens, ovary, and petals were separated. The petals, stamens and ovary were dipped in Tween 20R (1 drop/50 cc), rinsed in running water for 20 min, disinfected with 95% ethanol for 5 seconds, aseptically cut and then plated out on pH 5.6 potato dextrose agar (PDA). These plates were examined for evidence of fruiting structures after 10 days. Three different isolates were obtained: Cladosporium herbarum LK. ex Fr. var. citricola Farl., Colletotrichum gloesporoides Penz and Penicillium sp.. Infection of Citrus flowers by all or any one of these fungi can cause premature fruit drop. Feeding by P. longifila causes wounding which may play an important role in fungal infection of blossoms and subsequent development of flower rot. Similar type of disease induction with cotton flowers has been previously correlated with feeding by another Cecidomyiidae, Cantarinia gossipii in South America (Jimenez & Ramirez 1984). Symptoms of Colletotrichum infection on the ovary and stamens, where P. longifila feeding occurs differs from other bloom infections |
