Expression of feeding symptoms from pink hibiscus mealybug (Hemiptera: Pseudococcidae) by commercially important cultivars of hibiscus
Bergh, J. Christopher
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The pink hibiscus mealybug, Maconellicoccus hirsutus (Green), is a highly polyphagous pest that invaded southern Florida in 2002 and is now widely established throughout most of the state. Although Hibiscus rosa-sinensis L. is a preferred and economically important host of M. hirsutus, the susceptibility and expression of feeding symptoms by different cultivars have not been evaluated. Cultivars of H. rosa-sinensis were infested with M. hirsutus and evaluated daily for 40 d for the onset and percentage of terminals expressing feeding symptoms. Under different initial densities of M. hirsutus, the cultivar 'President' showed no difference in the latency to expression of feeding symptoms, which occurred between 7 and 15 d after infestation, but did show significant differences between initial density and percentage of terminals expressing feeding symptoms from 10 d onward. When infested with 20 females, 80% of 'President' terminals exhibited symptoms 30 d after infestation. Four other cultivars initially infested with 10 female M. hirsutus showed significant differences in the onset and severity of feeding symptoms. All plants of the cultivars 'Florida Sunset' and 'Joanne' expressed damage symptoms at 12 +/- 2 SE d and 10 +/- 1 d, respectively, following infestation. Only a single plant of the cultivars 'Double Red' and 'Snow Queen' showed such symptoms at 19 and 30 d after infestation, respectively. Significant differences between cultivar and the percentage of terminals expressing feeding symptoms were observed from 20 d onward. Terminals sampled from all plants after 40 d revealed that egg, nymph, and adult female M. hirsutus were found on all plants, including those that did not exhibit feeding symptoms. These data have shown that hibiscus cultivars differ in their expression of M. hirsutus feeding symptoms, that M. hirsutus can reproduce on cultivars of hibiscus that do not express feeding symptoms, and that feeding symptoms are not a reliable indicator of infestation by M. hirsutus, highlighting the need for further investigation of the mechanisms underlying differences among cultivars.