Population Ecology of the Golden Cicada (Cryptotympana atrata) in Pear Orchard Agroecosystems: Density-Dependent Effects of Inoculation on Emergence Yield and Economic Returns

The nymph of the golden cicada, Cryptotympana atrata (Fabricius, 1775), is a highly valued edible and medicinal insect in China. However, wild populations have declined precipitously due to overharvesting and habitat degradation. Artificial breeding within orchard agroecosystems offers a promising pathway for sustainable production, yet the population dynamic principles governing inoculation density and emergence yield remain poorly quantified. We conducted a two-year field experiment in a pear orchard (Pyrus spp.) agroecosystem to evaluate the effects of four cicada egg inoculation densities—Control (0 g/tree), 0.5 g/tree (~1500 eggs), 1 g/tree (~3000 eggs), and 2 g/tree (~6000 eggs)—on nymphal emergence yield, estimated multi-year total emergence, and projected cumulative economic returns per mu (1 mu = 666.7 m2). Results revealed a strong density-dependent response: two-year emergence increased from 2.43 ± 0.42 individuals/tree in the Control to 65.76 ± 6.33 individuals/tree at 2 g/tree, representing a 27-fold increase. Estimated multi-year total emergence exhibited a similar pattern, ranging from 15.77 ± 4.21 to 199.09 ± 26.24 individuals/tree. A linear mixed-effects model with block as a random effect indicated a near-linear dose–response at the plot-replicate level (marginal R2 = 0.968), suggesting that within the tested egg-input range, pear root systems had not yet reached resource saturation for established nymphs. Projected cumulative gross revenues over the full emergence period (years 2–5) were $172.09–$2172.51 per mu, equivalent to an annual average of approximately $43–$543 per mu across four emergence years. Specifically, the 2 g/tree treatment yielded the highest absolute cumulative return, whereas the 1 g/tree treatment achieved the highest benefit–cost ratio. Notably, even the lowest tested inoculation density (0.5 g/tree) produced economically viable yields, indicating that pear orchard agroecosystems enable profitable cicada production with relatively modest egg inputs. Collectively, these findings provide the first quantitative evidence of density-dependent population dynamics in pear orchard–cicada agroecosystems and offer practical guidance for smallholder farmers to diversify orchard income, while also advancing research on insect population ecology in managed ecosystems.