Phenological synchrony between a weed (Dioscorea bulbifera) and a biocontrol agent (Lilioceris cheni) in the introduced range, Florida: implication in biological control

Authors: Rayamajhi, Min; ROHRIG, ERIC - Florida Department Of Agriculture And Consumer Services; Lake, Ellen; Smith, Melissa; Pratt, Paul; Dray, F Allen; Halbritter, Dale; Leidi, Jorge

Submitted to: Biocontrol Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/31/2021
Publication Date: 2/19/2021
Citation: Rayamajhi, M.B., Rohrig, E., Lake, E.C., Smith, M., Pratt, P.D., Dray Jr, F.A., Halbritter, D.A., Leidi, J.G. 2021. Phenological synchrony between a weed (Dioscorea bulbifera) and a biocontrol agent (Lilioceris cheni) in the introduced range, Florida: implication in biological control. Biocontrol Science and Technology. 31(8):797–816. https://doi.org/10.1080/09583157.2021.1885627.
DOI: https://doi.org/10.1080/09583157.2021.1885627

Interpretive Summary: A viny weed known as air potato plant was introduced into Florida around 1905. Since then, it has invaded, smothered, and disrupted native plant communities. Every year, vines senescence during fall and overwinter as underground tubers and aerial bulbils which sprout in spring and repeat the growth cycle. A beetle that feeds only on air potato vines was discovered in Asia and introduced in Florida. During winter the adult beetles become dormant and hide in the folds of dead air potato leaves, duff layers and emerges with the new vines in spring. It has established and dispersed throughout air potato invaded places in Florida. The emergence and growth of air potato vine has to closely match with the beetle emerging time, and a favorable local weather condition is a must for vine growth and beetle population increase. Such a good match provides plenty of food for rapid development of beetles and substantial damage of vines which in turn ensures the removal of smothering impact on native plants and reduction in the bubil production and hence recruitment of new vines and invasion of new areas. We conducted a study to understand how air potato vines behaves in outdoor conditions followed by a 5 years long field study on beetle impacts on its natural infestations by releasing beetles in four sites. We gathered monthly data on air potato vines and beetles and assessed possible synchronies between their life stages and with local weather variables. Air temperature and total rainfall showed positive correlation with timing of air potato vine emergence/senescence, vine coverage, adult beetle emergence from diapause, and their life stages (egg clutches, larvae, and adults) populations. Vines sprouting and beetle emergence in two southern sites began in February and April, and in remaining two northern sites in March and May, respectively. Vine sprouting and beetle emergence initiated at 15 and 20oC, respectively. All sites achieved maximum vine coverage in July. Bulbil development, egg laying by overwintering adults, vine damage by adult and larval feeding began in June. These sequences of events indicated phenological synchrony of the beetle and air potato life stages in Florida.

Technical Abstract: Dioscorea bulbifera, a viny weed introduced into Florida around 1905, has invaded, smothered, and disrupted ecological functions of native plant communities. Vines senesce in late fall, then overwinter as tubers and aerial bulbils which sprout in spring and repeat the growth cycle. A biocontrol insect Lilioceris cheni, introduced from Asia as a biocontrol agent has established throughout D. bulbifera’s range in Florida. Synchronies among the growth phenology of weed, life stages of biocontrol agent and weather conditions, are considered essential for successful suppression of an introduced weed. We conducted a common garden study that encompassed pre-biocontrol release attributes of D. bulbifera followed by a 5-yr post-L. cheni release impacts on its natural infestations in four sites. We gathered monthly data on both organisms’ and assessed possible synchronies between D. bulbifera and L. cheni life stages and with local weather variables. Air temperature and total rainfall showed positive correlation with timing of D. bulbifera vine emergence/senescence, vine coverage, adult beetle emergence from diapause, and their life stages (egg clutches, larvae, and adults) populations. Vines sprouting and beetle emergence in two southern sites began in February and April, and in remaining two northern sites in March and May, respectively. Vine sprouting and beetle emergence initiated at 15 and 20oC, respectively. All sites achieved maximum vine coverage in July. Bulbil development, oviposition by overwintering adults, vine damage by adult and larval feeding began in June. These sequences of events indicated phenological synchrony of the beetle and air potato life stages in Florida.