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Comparative Demographic Parameters of the Coconut Scale Insect, Aspidiotus rigidus (Reyne) (Hemiptera: Diaspididae) on Four Different Host
Dissertation Abstract:
The suitability of different plants—namely, banana, mangosteen, and taro as host of Aspidiotus rigidus (Reyne) was quantified. This was done by comparing demographic parameters such as development rate, survivorship, and reproductive potential of A. rigidus on coconut with those observed on test plants. The study insect was collected from an outbreak area in Basilan, Mindanao, and the experiment was carried out in the University of the Philippines Los Baños (UPLB) under laboratory condition with temperature ranging from 25°C to 34°C.
This study showed that the development time of immature stages, adult longevity, survival, growth, and fecundity of the scale insect were significantly different among the host plants tested. A. rigidus completed its life cycle on the leaves of all test plants except on taro. Total immature development time of both male and female scale insects on banana and mangosteen were significantly longer as compared to coconut; 34.77 ± 4.32 and 32.18 ± 4.10 days on banana, 39.35 ± 6.30 and 39.20 ± 7.82 days on mangosteen, while only 29.03 ± 2.65 and 28.46 ± 3.69 days long on coconut, for male and female, respectively.
Settling rate of the crawlers was also considerably lower on banana and mangosteen, i.e., only 57.46 percent and 56.62 percent on banana and mangosteen, while 87.18 percent of settling was observed on coconut. Regardless of the host plant, the lowest survival rate was observed in the first instar nymph. The highest survivorship was always observed on coconut, followed by banana and mangosteen, and the lowest was on taro. Summing up, 56 percent of original cohort survived on coconut, 33 percent on banana, and only 10 percent on mangosteen.
The data showed that A. rigidus female on coconut had the earliest age of reproductive activity (16.23 ± 1.63 days), followed by banana (17.34 ± 2.28 days), and the latest activity was observed on mangosteen (20.56 ± 5.00 days). Significant variability was also found on total fecundity among the hosts wherein 27.86 ± 6.39 eggs laid on banana, 17.11 ± 9.12 eggs on mangosteen, while 45.83 ± 9.01 eggs were laid on coconut.
