Diversity of insect pests infesting Maize (Zea mays L.) in the high-altitude ecosystem of Gurez Valley, A retrospective analysis

Introduction

Maize (Zea mays L.) is among the major cereal crops cultivated across diverse agro-ecological regions of the world and ranks as the third most important grain crop globally. It is commonly referred to as the "Queen of Cereals" because of its broad adaptability, remarkable genetic variability, and high yield potential. The extensive genetic diversity of maize enables its cultivation under a wide range of environmental and agro-climatic conditions. In Jammu and Kashmir, maize occupies a prominent position among food crops and ranks third after rice and wheat. Nutritionally, maize is an important source of carbohydrates, proteins, minerals, vitamins, iron and other essential nutrients, with an energy value of approximately 365 Cal per 100 g. Its utility extends beyond direct human consumption, as it is extensively used as feed for livestock and poultry. Maize also serves as an important raw material for various industrial processes, particularly for the extraction of starch and oil. From an Indian agricultural perspective, maize is an economically important crop whose production and demand have shown a steady upward trend. The rate of increase in maize production has been reported to be approximately three times that of wheat and twice that of rice [10] . In high-altitude areas such as Gurez Valley, maize assumes additional importance because of its contribution to household food requirements and livestock and poultry production. Its nutritional richness, combined with its adaptability, makes it an important component of the traditional subsistence farming system practiced in the valley. Agriculture in Gurez is shaped by its distinctive high-altitude environment, characterized by a relatively short crop-growing period, low temperatures and unique agro-climatic conditions. Under such circumstances, successful maize production is both challenging and essential for rural livelihoods. The crop contributes to household food requirements, feed and fodder resources, and local economic activities. Farmers, therefore, depend on maize for multiple aspects of their farming system. Nevertheless, its productivity is affected by several biotic and abiotic constraints, among which insect pest infestation represents a major production challenge. Pest attack at different stages of crop development can cause considerable damage to various plant parts and ultimately reduce attainable yield. Although maize cultivation forms a major component of agriculture in developed countries such as the USA, its productivity in India remains comparatively low. The considerable difference between achievable yield and actual productivity highlights the potential for improving crop production and protection technologies [18] . The ecological characteristics of Gurez, together with ongoing changes in climatic conditions, may influence the occurrence, abundance and distribution of insect pests associated with maize. Consequently, understanding the constraints affecting maize production in this high-altitude ecosystem is important for developing location-specific crop protection strategies. Documentation of the existing pest complex can provide essential baseline information for designing integrated pest management approaches, thereby supporting sustainable maize production and strengthening food security in the valley. Maize is susceptible to attack by a diverse range of insect pests throughout its growing period, beginning from seedling establishment and continuing until crop maturity and storage. Different insect species may feed on or damage almost every major plant structure, including roots, stems, leaves, tassels, silks and grains. Approximately 140 insect species have been reported to infest maize and cause varying levels of damage, although only a relatively small proportion are considered economically important [14] . Among these, nearly ten species have been reported to inflict substantial damage from crop establishment through the post-harvest storage phase [3] . The pest complex associated with maize is not static, however, and its composition and distribution may change in response to environmental and climatic factors. Alterations in global climatic patterns can modify pest development, host association, geographic distribution and seasonal incidence. Consequently, insect species that were previously uncommon or not reported as pests of maize have increasingly been observed utilizing the crop, while shifts in the geographical distribution of several insect pests have also been documented [7] . In view of the increasing cultivation of maize in newer and relatively unexplored areas, along with the potential influence of changing climatic conditions on insect pest dynamics, systematic documentation of the pest complex has become important. The present investigation was therefore undertaken to assess the diversity and occurrence of insect pests associated with maize in Gurez Valley. Information on pest incidence and distribution is essential for identifying potentially damaging species and developing appropriate, timely and environmentally compatible management interventions. Such knowledge can contribute to minimizing pest-induced yield losses and improving the productivity and sustainability of maize cultivation in the high-altitude agroecosystem of Gurez Valley.

Materials and Methods

Study Area

The present investigation was carried out at Gurez Valley, located in the high Himalayas of north Kashmir, at an altitude of about 8,000 feet (2,400 meters) above sea level. It is characterized by a short growing season where maize and other temperate crops are cultivated. The high altitude and cool climate influence crop diversity, productivity, and pest dynamics in the region. The crop was observed under natural infestation conditions in the field.

Methodology

Weekly visual observations were taken from maize plants in addition to catches from yellow sticky traps. The crop observations for infestation by insect pests were taken on the basis of presence of dead hearts, presence of damaged plant parts, number of insect pests per plant in case of bugs, beetles, etc., and number per centimetre square of leaf or cob sheath in case of aphids [13] . For soil-borne insects such as cutworm, the status was ascertained by digging a soil pit in dimensions of 20 × 20 × 10 cm [6] , and for white grubs and wireworms, soil was excavated in dimensions of 20 × 20 × 21 cm [17] .

Results and Discussion

The data presented in Table 1 indicate the occurrence of nine insect pest species associated with maize at different phenological stages in Gurez Valley. These pests belonged to three insect orders, namely Lepidoptera, Coleoptera and Hemiptera, and were distributed among seven families. In addition to the phytophagous insects, three groups of beneficial natural enemies-ladybird beetles, green lacewings and robber flies-were also observed in the maize ecosystem. Previous investigations on the ecology and population fluctuations of maize insect pests have primarily focused on economically important species such as Chilo partellus, Mythimna separata, Agrotis ipsilon, Helicoverpa armigera, Rhopalosiphum maidis, Corizus spp., Dolycoris baccarum and Cletus punctiger. The increasing cultivation of maize in new geographical areas, together with changing climatic conditions, may alter the abundance, distribution and damaging potential of these insect pests. In the present investigation, Chilo partellus and Mythimna separata emerged as the most prominent pests under field conditions. Differences in pest abundance among observations may be associated with variations in maize genotype, local environmental conditions and other agro-climatic factors. Although nearly 250 species of insects and mites have been reported in association with maize, only a limited number attain sufficient abundance to cause economically significant damage [16] . Important pests include the maize stem borer (Chilo partellus Swinhoe), pink stem borer (Sesamia inferens Walker), two species of shoot flies, armyworm (Mythimna separata Walker), maize cob borer (Helicoverpa armigera) and maize aphid (Rhopalosiphum maidis Fitch). Depending on the season and geographical region, these pests can inflict substantial losses in maize production across the country [11] . The observations obtained in the present study are comparable with those reported by Yogesh et al. [19] , who documented the occurrence of several insect pests during different developmental phases of maize. Their study recorded pink stem borer (Sesamia inferens), green stink bug (Nezara viridula), leafhoppers (Cicadulina spp.), black aphids (Rhopalosiphum maidis) and cob borer (Helicoverpa armigera) during the vegetative, tasselling and cob-forming stages of the crop. The diversity recorded in the present investigation is also broadly consistent with earlier reports. Painter [12] documented 14 insect species associated with maize, while Boupha et al. [5] reported 22 species. Deole et al. [8] identified three lepidopteran species functioning as maize borers, whereas Erhan et al. [9] and Fischer et al. [10] recorded nine and 11 species, respectively. Patra et al. [13] reported a considerably higher diversity comprising 24 insect pest species, while Sekhar et al. [15] documented three beetle species associated with maize. Similarly, Beres [4] reported seven aphid species, whereas Ahad et al. [1,2] recorded five and 17 insect pest species, respectively, from maize ecosystems. The differences in pest diversity among these studies may reflect variations in geographical location, climatic conditions, maize genotype, cropping practices, sampling intensity and the stage of crop development at which observations were made.

Conclusion

It can be concluded that a larger number of insect pests infests maize crop in Gurez valley revealed diverse pest complex. Their activity at various stages leads to stunted growth, reduced grain yield and quality. These findings suggest the timely monitoring and effective integrated pest management strategies to increase maize productivity in this region.

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