การใช้ไส้เดือนฝอยก่อโรคแก่แมลงร่วมกับชีวภัณฑ์อื่นในการควบคุมแมลงวันแตง (Zeugodacus cucurbitae) (Coquillett)

Abstract

The melon fruit fly (Zeugodacus cucurbitae) (Coquillett) is a major economic insect pest of Cucurbitaceae crops that can cause immense damage to the quality and quantity of agricultural products. Practical insecticides have proven only slightly effective and also leave toxic residues in the environment. The use of natural enemies presents a suitable alternative method to their control; however, the determination of a species-specific to the host or prey and the rate of application must be investigated. The objective of this study, therefore, is to integrate the use of entomopathogenic nematodes (EPNs) and other bio-pesticides to control the developmental stages of the melon fruit fly under laboratory, net house, and field conditions. Results from the field survey revealed that the fruit fly population and fruit damage from the insecticide-based plots were higher than those of the non-insecticide-based plots. The results on the effects of different EPNs species on both last instar larvae and pupae indicated that S carpocapsae at 25,000 IJs/host presented the highest mortality rate among all species; last instar larvae (97.50%) and pupae (95%). In comparison, S. siamkayai, H. indica, and H. bacteriophora produced lower mortality rates in the last instar larvae at 90%, 67.50%, and 75% and in pupae at 90 %, 75%, and 42.50%, respectively. Metarhizium anisopliae PSUM02 at 1×108 spores/ml was able to kill the last instar larvae and pupae with mortality rates of 61.25% and 59.38%, respectively. After the application of 1×107, 1×106, 1×105 spores/ml., the last instar larvae and pupae mortality rates reduced to 45.63% and 23.75%, 8.13%, and 50%, and 37.50% and 18.75%, respectively. The combination of the EPNs and M. anisopliae PSUM02, as well as the EPNs alone, proved to be superior control methods against last instar larvae and pupae compared to that of the M. anisopliae PSUM02 alone. The mortality rates of last instar larvae and pupae reached up to 100% and 85%, respectively. Results on the efficacy of bio-pesticides on fruit fly oviposition under net house conditions showed that neem extract inhibits fruit fly oviposition and decreases the number of fruit scars compared to other treatments. The number of pupa per fruit post-spraying with neem extract at zero (immediate), three, and five days after spraying was 5.15, 3.50, and 2.70 pupae per fruit, versus the control treatment at 15.95, 14.05, and 9.60 pupae per fruit, and 14.55, 13.25, and 7.70 pupae per fruit via the M. anisopliae PSUM02, respectively. The field experiment produced results similar to those of the net house experiment. Notably, the integration of neem extract and EPNs produced the highest control rate. The number of fruit scars and number of adult fruit flies were 0.96 scars per fruit and 10.95 adults per 6 cm2, respectively, whereas the insecticide (1.46 scars per fruit and 18.53 adults per 6 cm2) and the control (1.6 scars per fruit and 28.73 adults per 6 cm2) showed the lowest control efficiency. The cost of pest management incorporating the integration of natural enemies was slightly high at 515 baht per 6 cm2 compared to the insecticide at 315 baht per 6 cm2; however, the rate of control and product safety, as well as farmer and consumer satisfaction are much higher.