Species Composition and Relative Abundance of Insect Pests on Intercropping System of Sesame and Groundnut Under Irrigated Conditions

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Published on International Journal of Agriculture & Agribusiness
Publication Date: April 4, 2019

Khin Myint Mar
Associate Professor, Department of Zoology
University of Magway
Myanmar

Journal Full Text PDF: Species Composition and Relative Abundance of Insect Pests on Intercropping System of Sesame and Groundnut Under Irrigated Conditions.

Abstract
This field study was conducted in Jokekone Village, Taungdwingyi Township, Magway Region during December 2012 to March 2013. The total of 15 species of pests belonging to 14 genera, 12 families under four orders were collected from sesame-groundnut intercropping field. The morphological study on the collected specimens was described. With respect to the percent composition, the highest percentage (33%) of species composition were found in Orders Lepidoptera and Coleoptera, the medium in Hemiptera (27%) and the least (7%) in Orthoptera. The highest relative abundance among the species studied was found in Aulacophora foveicollis (22.32%) while the lowest abundamce was found in Hypomeces squamosus (0.86%). Pod borers like Helicoverpa armigera and Spodoptera litura were found very low percent compared with other species collected in the present study. It was assumed that this low percentage of the two major pest species may be due to the intercropping system. In the present work, 40% of the studied species was high status of pests and 60% was low. The results in the present study were revealed that the destruction of pests on the sesame-groundnut intercropping field was not very high. Therefore, it gives baseline information of the effect of intercropping to local farmers in order to reduce the damage of these two pests.

Keywords: Sesame-groundnut intercropping, Helicoverpa armigera, Spodoptera litura, Relative abundance.

1. INTRODUCTION
The cultivation of two or more crops at the same time in the same field is known as intercropping. Various crops such as tomato-maize, maize-legume, maize-velvet bean, maize-cowpea in Africa and pigeon pea-maize, maize-potato in Asia can be cultivated intercropping. Generally there are four basic types of intercropping; namely mixed intercropping, row intercropping, strip intercropping and relay intercropping (Ramert et al., 2001). Intercropping system is an advantage if the different crops have different maturity dates and different times of peak demand for nutrients, water and sunlight, thereby reducing competition for resources. Different crops may have a different architecture, i.e. height and width of the plant. In designing an intercropping system, farmers should pay attention to differences in plant architecture between the crops in the mixture. Moreover, pests and disease are often less abundant in intercrops. If the pest or disease has a specific host, it not spread as easily through an intercrop as it does in a monocrop. Substances that one crop produce may drive pests away from the main other crops or natural enemies of insects may be attracted by one of the crops in the intercrop (Wolfswinkel, 2013).
Many different species of insect might be occurred in a crop but not all are pests. Other insects and spiders serve as natural enemies for pests and it is therefore very important to correctly identify insect species before attempting any control measures in a crop. Identification will enable to establish the pest status of the insects and the type of damage of the crop to be assessed. The knowledge of the extent of damage likely to be caused by the insect is important whether or not it would be profitable to attempt control. If the damage caused leads to a loss in yield or quality of the crop that results in a loss of profit by the farmer, an insect is considered to be a pest of economic importance. When there is a 5-10% loss in yield, most species reach economic pest status. However, a 10% loss of plants or leaf area in a crop does not necessarily mean a 10% loss in yield (Chanthy et al., 2010).
Oil crops play an important role in the rural economy of Myanmar being second only to rice (Favre and Kyaw Myint, 2009). Sesame and groundnut plantations are important oilseed crops in the middle region (the dry zone) of Myanmar, especially Magway Region is so called “Large Pot of Oil” in Myanmar. For ancient times, intercropping and crop rotations had been recommended in Myanmar. Intercropping is an important planting system in the studied area because it is the practice of producing multiple crops in a given space at the same growing .time. In the present study, the mixed intercropping type of sesame and groundnut was employed by local farmers.
Today, world production of sesame is estimated to be over 15 million acres (6.2 million hectares) and over 57% of the world production is in Asia. Most of the Asian production is in India, China, and Myanmar (Smith et al., 2000). This paper reviews the pests of sesame-groundnut intercrops prevalent in Myanmar and to add the information of the research gaps concerned with intercropping system.

1.1 Statement of the problem
The statement of the problem is a survey of major insect pests on the intercropping field of sesame-groundnut.

1.2 Objectives
The objectives of this study were:
a. to confirm the identification of the predominant pest species in the intercropping system of sesame-groundnut plantations and
b. to assess the species composition, relative abundance, and the pest status of the species studied.

2. REVIEW OF LITERATURE
In 1990, Kennedy el al. published the effect of intercropping on insect pests of groundnut and their natural enemies in which they revealed that it would be possible to reduce the insect pests of groundnut and increase the population of entomophagous insects by intercropping with pearl millet.
In 1999, Waterhouse described major arthropod pests and weeds of agriculture in Southeast Asia. In 2002, Rao et al. reviewed that the population of different insect pests was reduced in the intercropping if suitable intercrop was selected.
In 2006, Girma et al. estimated the abundance of insect pests and their effects on biomass yields of single vs. multi-species planted fallows. They described that multi-species fallows did not indicate any advantage over single species fallows in terms of either reduced pest incidence or increased biomass production.
Chanthy et al. 2010 described Insects of Upland crops in Combodia. A field guide to identifying insect pests and beneficial insects and spiders in the upland cropping systems of Cambodia.
NICRA team of Groundnut Pest Surveillance (2011) reported manual for groundnut pest surveillance. It was jointly published by National Centre for Integrated Pest Management, New Delhi, Central Research Institute for Dry land Agriculture.
In 2012, Soundararajan and Chitra reported the impact of intercrops on insect pests of Blackgram, Vigna mungo L. in which the incidence of insect pests; white fly Bemisia tabaci, leaf hopper Empoasca kerri, defoliater Madurasia obscurella and pod borer Maruca vitrata, were assessed on black gram intercropped with ground nut sorghum and pearl millet. Their results revealed that the sucking pest population was low in the intercropped blackgram compared with the sole crop.
In 2012, Rao et al. studied the intercropping for management of insect pests of castor, Ricinus communis, in the semi–arid tropics of India in which their results showed a buildup of natural enemies (Microplitis, coccinellids, and spiders) of the major pests of castor was also observed in the intercropping systems and resulted in the reduction of insect pests.

3. Materials and Methods
3.1 Study site
The study area was located in Jokekone Village, 3.90 Km Taungdwingyi Township, Magway Region (19 59’1.8 N latitude and 95 23 14.6 E longitude) (Fig. 1). The intercropping field of groundnut and sesame plants has the area of about (0.72 ha). The type of intercropping in the study area was mixed intercropping system. Study period was lasted from December 2012 to March 2013.

3.2 Species Identification
The specimens were collected randomly by hand picking and insect net. Then, the collected specimens were transferred in to the plastic containers and transported to Department of Zoology, University of Magway. The specimens were examined the size, antennae, coloration and the patterns on the wings. Then, the specimens were photographed, measured. The adult specimens of each species were carefully studied under microscope. The insect were separated into different species with the help of available keys. The identification was followed Borror and Delong, 1964 and Imms (1963) Nair, 1995 and Ghosh, (1940).

3.3 Killing and mounting methods
Collected insects were killed in a jar containing ethyl acetate following after Hopkins et al. (internet accessed Hopkins et al., 2012). Leaf beetles and bugs were pinned down and stored in insect box and moths were dried and mounted. Some of the insects collected at nymph or larval stages were reared in the laboratory until the adults emerged.
For preservation, the specimens collected were killed rapidly to prevent damage. Large specimens were killed in a jar with closely fitting lid using a volatile toxicant such as 70% alcohol or soapy water. Plastic vials were very useful in the field. Large moths and some other winged insects were mounted with wings neatly spread on a spreading board. Insects of average size were usually mounted on pins. Large beetles were pinned in the middle of their right wing cover, close to the front margin. Insect too small to be pinned safely were mounted on the cardboard points, glued to the point on their right side. The physical appearances of insects were noted down and photos were also taken immediately after capturing the insects. The collected specimens were mounted for further studies.

3.4 Data Analysis
Data obtained was analyzed using Microsoft Excel (2013). Descriptive statistics, the relative abundance and percent composition of species were presented. Relative abundance (dominance or relative density) was calculated following the formula of Fager (1957) and Wallwork (1976).