Evaluation of net house and mulching effect on Cucurbit fruit fly (Bactrocera cucurbitae Coquillett) on cucumber (Cucumis sativus L.)

Cucurbit fruit fly (Bactrocera cucurbitae Coquillett) is a pest of cucurbits, such as summer squash (Cucurbita moschata Duchesne), cucumber (Cucumis sativus L.), pumpkin (Cucurbita pepo L.) and bittergourd (Momordica charantia L.). Yield as well as quality of crop is significantly reduced by B. cucurbitae damage in cucurbit fields. This study was conducted to evaluate the effect of net house and mulching on the incidence of B. cucurbitae on cucumber production from June to August 2017 in Rampur, Chitwan, Nepal. The experiment was carried out in a completely randomized block design (RCBD) with four replications and five treatments such as i) untreated (no plastic mulch ​+ ​no net house ​+ ​no insecticide spray), ii) black plastic mulch ​+ ​no net ​+ ​deltamethrin 1% EC ​+ ​triazophos 35% EC at a rate of 2 ​ml/L spray, iii) reflective plastic mulch only, iv) black plastic mulch only, and v) net house ​+ ​black mulch ​+ ​no insecticide spray. The net house with black mulching treatment totally restricted the adult cucurbit fruit fly to enter in the cucumber field. The lowest cucurbit fruit fly population was recorded in deltamethrin 1% EC ​+ ​trizophos 35% EC at a rate of 2 ​ml/L treated plot along with black mulch, however there was no significant effect either of black or reflective plastic mulch only. The highest fruit fly damage (15.50%), ovary damage (8.44%), post-set damage (7.86%), harvest damage (14.35%) were recorded in untreated plot. The highest marketable yield was recorded inside the net house with black plastic mulch (59.08 ​mt ​ha⁻¹) followed by reflective plastic mulch (42.95 mt ha⁻¹) and the lowest in untreated plot (28.35 mt ha⁻¹). Fruit fly damage was not recorded in net house with black mulch (0.00%) followed by black mulch with deltamethrin ​+ ​triazophos plot (3.46%). Economic analysis showed the benefit cost ratio of 1.43 in net house. The cost of net house construction is expensive, however higher yield and quality production without use of insecticides can be achieved in net house production system, which in the long run is beneficial to the farmers and the environment.