| Summary: | 博士 === 國立屏東科技大學 === 熱帶農業暨國際合作系 === 101 === Eggplant (Solanum melongena L.) production and cultivation in Taiwan is severely affected by Thrips palmi karny, resulting poor fruit quality, low yield, and loss of income of the farmers. This thrips causes cosmetic scars on and deforms fruits, thus lowering their market value. For the purpose of effective pest management module, construction of temperature-dependent life table, development, survivorship, effective sampling technique to estimate population, economic threshold for timely application of insecticide, and farmer’s level knowledge and response for pest management were studied and appealed.
The life history of Thrips palmi Karny on eggplant leaves was studied based on the age-stage, two sex-life tables at 16, 19, 22, 25, 28 and 31 oC. The intrinsic rate of increase (r) at these temperatures was 0.0427, 0.0566, 0.0979, 0.1738, 0.1797, and 0.2237 d-1, respectively. The mean generation time was 47.52, 38.33, 29.52, 19.81, 17.30, and 13.88 d, respectively. The developments of pre-adult and adult stages were faster in males than females. The means of developmental periods for each developmental stage decreased with increases of temperature. The maximum life span of female adult was noted 56.67 d whereas that of male was 50.66 d at 16 oC. The highest female fecundity (64.18 eggs /female) was recorded at 25 oC and the lowest (23.38 eggs /female) at 16 oC. The developmental threshold temperature (C) estimated for egg-to-adult was 11.25 oC, with a thermal constant (K) of 196.1 DD. The optimal developmental temperature for T. palmi in eggplant was determined to be 25 oC.
To investigate the relationship between the density of thrips and the resulting damage, experimental plots with initial release densities of 0, 20, 40, 70, and 100 adults’ thrips per plot were established under greenhouse conditions. Thrips density (for flower sampling = x1; for sticky trap = x2) was found to be directly related to the proportion of damaged-fruits (y) and the reduction in fruit yield: significant relationships were found for the flower samples (y = 1.2261x1 - 0.6232, r2 = 0.8582) and for the trap catches (y = 11.667 ln(x2) - 9.5, r2 = 0.8896). The proportion of damaged fruits that could be tolerated from an economic perspective, based on the cost of controlling the thrips population chemically and the market value of the fruit, was 6.67–11.76 %; this translated into economic thresholds (ET) of 1.05–1.50 adults and/or larvae of T. palmi per flower or 4.91–10.17 adults T. palmi per four-day sticky card count.
Farmers’ knowledge, perceptions, and practices of T. palmi management were evaluated by interviewing farmers of problematic area of southern Taiwan, and data collected using questionnaire interviews was analyzed. Results showed flowering and fruiting stage was recognized more serious for degrading the fruit quality and growers mostly (35%) prefer spraying of chemical insecticides twice per week for thrips pest management. The price differences between healthy and damaged fruit due to T. palmi were TWD 30–34 per kg fruit. Considering 49.88% of scarred and deformed fruit production, the total loss will be TWD $538,508.00 per hectare per year.
To find efficacy of chemical insecticide for developing integrated control, 5 insecticides namely carbosulfan 48.34% soluble powder (SP), spinosad 2.5% soluble concentrate (SC), fipronil 4.95 % SC, imidacloprid 9.6% solution (SL), chlorfenapyr 10% SC were sprayed at the rate of 0.83, 0.25, 0.5, 0.67, and 1.00 milliliter (ml) per liter of water on section leaves (3 × 3 cm) in petri dish (9 cm diameter), containing larvae and adult of T. palmi. The number of died and alive insects were recorded after 24 hour of spray. Spinosad 2.5% SC showed most effective for controlling of larva (99.13%) and adult (100%) population. Chlorfenapyr 10% SC and carbosulfan 48.34% SP reduced more than 90% of adult population of T. palmi; however their effect was less than 85% for control of larvae.
The field experiment was conducted from September 2012 to March 2013 at Ruiguang road, Pingtung city to develop sustainable pest management for T. palmi in field condition with seven treatments and 3 replications. The treatments were chemical insecticide (spinosad 2.5% SC and chlorfenapyr 10% SC), alternate spraying of spinosad and chlorfenapyr with cultural control (use of black plastic mulch/ pruning of older leaves and branches), mass trapping with blue sticky trap, farmer practice of management (imidacloprid 9.6% SC), and control. The treatments decision for spraying spinosad and chlorfenapyr were made based on monitoring with flower sampling or blue sticky trap and economic threshold of T. palmi (1.05–1.5 thrips per flower or 4.91–10.17 adults per sticky trap). Spraying spinosad or alternate spraying of spinosad and chlorfenapyr with mulching black plastic were observed most effective to minimize pest population at or below ET, more number of flower and fruits (27.3–27.9/plant), the largest yield (4.13–4.25 kilogram/plant), and the least fruit damage (2.77–3.13 fruit/plant). The farmer practice was observed with 18.67 scarring and deforming fruits/plant whereas that of chlorfenapyr treated plot was recorded 12.67. The thrips density monitored with flower, leaves, and sticky traps showed that scarring and deforming fruit production in eggplant could not be reduced if spraying decision would be made with number of thrips on leaves sampling. In conclusion, integration of cultural practice such as pruning and destroying of older leaves, use of plastic mulch or soil cover to suppress pupal development of thrips in soil, capturing of thrips by blue sticky trap, and spraying spinosad based on economic threshold of T. palmi could be useful for managing this pest.
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