Functional response of temperature tolerant and control strain of Aenasius arizonensis against different densities of Phenacoccus solenopsis Tinsley
摘要
The abiotic factors particularly temperature known to affect the proliferation and distribution of parasitoids in the crop ecosystem and the functional response offers valuable insights into assessing the effectiveness of parasitoids. The parasitoid, Aenasius arizonensis Girault (Hymenoptera: Encyrtidae) is an important natural enemy of the cotton mealybug, Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae). The current experiment evaluated the performance of temperature-tolerant (36ºC) and control strain (27ºC) of A. arizonensis against varying densities (2, 4, 8, 16, 32, and 64) of the third instar P. solenopsis nymphs in the laboratory conditions of respective temperatures, 65 ± 5% RH and 12L: 12D photoperiod. Results indicated a type II functional response in A. arizonensis at both temperatures. According to Holling's disc equation, the control strain exhibited a searching efficiency (à) of 1.29 ± 0.11 h⁻1 and a handling time (Th) of 0.11 ± 0.00 days, while the temperature-tolerant strain showed a slightly lower searching efficiency of 1.18 ± 0.15 h⁻1 and a handling time of 0.12 ± 0.01 days with higher maximum parasitization rate of 8.76 for control strain and 8.03 for tolerant strain. Roger’s random attack equation reported higher searching efficiencies of 2.35 ± 0.81 h⁻1 and 2.89 ± 0.95 h⁻1, and lower handling times of (Th) 0.12 ± 0.01 and 0.14 ± 0.01 days for control and temperature-tolerant strains, respectively. It results in maximum parasitization rate of 8.25 nymphs/day for control strain and 7.06 for the tolerant strain. Despite minor variations, both strains demonstrated effective control potential. Thus, the temperature-tolerant strain of A. arizonensis is equally viable for augmentative biological control of P. solenopsis, especially in regions experiencing rising temperatures during the cotton-growing season.