Tobacco (Nicotiana tabacum), is an annual or perennial herb. This plant is the most extensively grown non-food cash crop because it is playing a vital role in economy worldwide1. Tobaccos has contributed towards poverty alleviation in many rural areas in China and above 4 million Chinese households are dependent on tobacco for their livelihood, either as tobacco farmers, cigarette industry employees or cigarette retailers2.
During tobacco production, insects and diseases attack on plant therefore, the output and quality of tobacco leaves get affected. Myzus persicae (Sulzer) is the major pest of tobacco and cause huge economical losses. To avoid any side effects including pollution, scientists are switching to biological control of pests e.g. natural enemy Aphidius gifuensis is being used to control tobacco aphids3,4. Aphidius gifuensis belonging to Aphidiidae family of Hymentoptera, is widely distributed in Hawaii and eastern Asia, including China, Japan and North Korea5,4. It is reported that A. gifuensis has been used profitably to manage aphid population in tobacco fields. Moreover, in China, mass rearing and release techniques for A. gifuensis have been developed and applied on a large scale to manage the major pest Myzus persicae (Sulzer) in tobacco fields6,7. Shicai Shen and team conducted a study to explore the impacts of A. gifuensis on species composition, species richness, importance value, diversity indices and evenness index. For which, insect samples were collected via field surveys and malaise trap collection in Yunnan Province.
In this experiment, 39 insect species and 1 spider (including 20 pests, 14 natural enemies and 6 others), chiefly belonging to 40 families and 13 orders in tobacco fields of Yunnan were recognized. M. persicae, Empoasca flavescens and Drosophila melanogaster were the dominant species among collected insects and Spodoptera litura, one unidentified species, Sphex haemorrhoidalis, Vespa veutinaauraris, Aedes albopictus, A. gifuensis and Liriomyza huidobrensis were the subdominant species. Scientists noted that the relative density of A. gifuensis steadily amplified from June to August. While alongside, the total relative density of other natural enemies showed a minor turn down in July and marked increase in August. The relative density of M. persicae considerably accelerated in July and then declined sharply in August. Furthermore, the values of Simpson index, Shannon-Wiener index and Pielou index were greater than 0.50, 1.50 and 0.50, respectively, representing high insect diversity.
Researchers concluded that beneficial insects, including biocontrol agents are relatively copious in tobacco fields of Yunnan Province. These facts indicate the improvement in the local insect community diversity after a long term discharge of the biocontrol agent A. gifuensis and reducing the relative density of M. persicae. These outcomes will help to understand ecological efficacy of A. gifuensis release which will ulitimately set up multi-evaluation systems for ecological effectiveness and large-scale extension of A. gifuensis release.
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17 November, 2019