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Title: Expression of feeding symptons from pink hibiscus mealybug (Hemiptera: Pseudococcidae) by commerically important cultivars of hibiscus

item Zhang, Aijun

Submitted to: Florida Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/13/2009
Publication Date: 6/15/2009
Citation: Vitullo, J., Zhang, A., Mannion, C., Bergh, C., Smith, Jr, A. 2009. Expression of feeding symptons from pink hibiscus mealybug (Hemiptera: Pseudococcidae) by commerically important cultivars of hibiscus. Florida Entomologist. 92(2):248-254.

Interpretive Summary: The pink hibiscus mealybug (PHM) is an invasive insect pest in Florida. It not only infests hibiscus, but also damages numerous fruits, vegetables, and ornamentals. As it feeds, PHM injects toxic saliva into plants. Heavy infestations can lead to defoliation and death up 100% of the host plants. Because of the historical importance of hibiscus to ornamental production in south Florida, we studied the PHM feeding response of several commercially significant hibiscus cultivars. We found that one feeding symptom, “bunchy top”, is not a reliable indicator of the presence of PHM infestation or level of infestation on all hibiscus cultivars. PHM can reproduce on some hibiscus cultivars that do not express “bunchy top”. This knowledge of how PHM infestation affects different hosts will be used by scientists and growers to understand the biology of this pest. This knowledge will also be utilized by regulatory agency, such as APHIS, to aid in creating aesthetic injury thresholds, facilitate early detection of new infestations, and assure timely management measures.

Technical Abstract: 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 has 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.