Seasonal Development, Cumulative Growing Degree-Days, and Population Density of Spotted Lanternfly (Hemiptera:...

Seasonal development, cumulative growing degree-days (CUMDD10), and population density of Lycorma delicatula (White) were studied through weekly sampling of 30 plants (5 plants/species, 3 common plus 3 site-specific species per site) at six sites in Pennsylvania in 2019. In total, 24,159 L. delicatula (1,987 egg masses, 1,068 first instars, 239 second instars, 153 third instars, 410 fourth instars, and 20,302 adults) were recorded in 28 wk. Seasonal development followed similar pattern at all sites despite differences in starting, peaking, and ending time for specific life stages. The average CUMDD10 requirement for the onset of the first instars, second instars, third instars, fourth instars, adults, and eggs was 270, 465, 645, 825, 1,112, and 1,825, respectively. Population density ranged from 0 to 207.4, 0-298.9, and 0-9.6/m2 for nymphs, adults, and egg masses, respectively. Significant difference in population density was found between sites, hosts/substrates, and sampling weeks. Favored oviposition substrates included tree-of-heaven and black birch despite egg masses being laid on many other surfaces. Nymphs fed on different hosts in early stages but preferred American beech, tree-of-heaven, black birch, and multiflora rose. Adults were predominately found on tree-of-heaven with preoviposition surge on black birch and red maple. Sizable nymph and adult populations persisted on summer grape throughout the season. Tree-of-heaven played an irreplaceable role in the seasonal development and life history of L. delicatula in the field. Survey and detection activities should focus on tree-of-heaven with management efforts directed to aggregating adults for maximum efficacy.