Phenological synchrony between a weed (Dioscorea bulbifera) and a biocontrol agent (Lilioceris cheni) in the introduced range, Florida: implications for biological control.
Dioscorea bulbifera has invaded, smothered, and disrupted ecological functions of native plant communities in Florida. Vines senesce in late fall, then overwinter as tubers and aerial bulbils which sprout in spring and repeat the growth cycle. A foliage-feeding beetle Lilioceris cheni, introduced from Asia as a biocontrol agent has established throughout D. bulbifera's range in Florida. Synchronies among the growth phenology of the weed, life stages of biocontrol agents and weather conditions, are considered essential for the 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 study on its natural infestations in four sites. We gathered monthly data on D. bulbifera and L. cheni and assessed possible synchronies between their life stages and with local weather variables. Air and soil temperatures 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). Vine sprouting and beetle emergence in two southern sites began in February and April, and in the remaining two northern sites in March and May, respectively. Vine sprouting and beetle emergence was initiated at 15 and 20°C, respectively. All sites achieved maximum vine coverage in July. Bulbil development, oviposition by overwintering adults, and 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.