Seasonal incidence of major insect pests of bamboo like leaf roller, Pyrausta coclesalis

Introduction

Bamboo is one of the most versatile and rapidly renewable plant resources in the world. Although it belongs to the grass family Poaceae, its woody culms, height and long service life enable it to perform many ecological and economic functions commonly associated with timber trees. More than 1,400 bamboo species occur across tropical, subtropical and temperate regions, where they support construction, furniture, paper and pulp industries, handicrafts, food production and rural livelihoods (Soderstrom and Calderon, 1979; Banik, 2015; Shende et al., 2021) [7,3,11] . Bamboo also contributes to soil and water conservation, carbon sequestration, biodiversity protection and the rehabilitation of degraded land. These attributes have increased its importance in afforestation and agroforestry programmes. Across Asia, bamboo's presence is ubiquitous. It flourishes in nations including Japan, China, India, Bangladesh, Pakistan, Sri Lanka, Cambodia, Vietnam, Laos, Myanmar, Korea, and Indonesia (Verma and Sajeev, 2012; Annon., 2016) [13,1] India is a major centre of bamboo diversity and production. Bamboo is especially important to rural and tribal communities because it provides household material, employment and marketable products within a relatively short production cycle. Although the north-eastern states are traditionally associated with bamboo resources, large bamboo-bearing areas also occur in central India, including Madhya Pradesh and Maharashtra (Naithani, 1993; Verma and Sajeev, 2012) [7,13] . In Maharashtra, bamboo cultivation is being promoted through plantations, agroforestry systems and institutional programmes intended to improve farm income and supply raw material to bamboo-based industries. The productivity and sustainability of these expanding plantations, however, depend upon effective protection from biotic stresses.

Bamboo is attacked by a diverse complex of insects from the nursery stage to harvested and stored products. The pest complex includes defoliators, leaf rollers, sap feeders, shoot and culm borers, termites and post-harvest beetles. Approximately 170 insect species have been reported in association with bamboo in India and neighbouring countries, although information on their field abundance, seasonal activity and economic impact remains limited (Singh et al., 1990) [10] . Among these groups, defoliators are particularly important because repeated loss of foliage directly reduces photosynthetic area, weakens clumps, retards culm and shoot development and may reduce the quality and quantity of usable bamboo. Pest outbreaks are often more conspicuous in nurseries and intensively managed plantations than in natural stands because of concentrated host plants and favourable microclimatic conditions (Tewari, 1992; Pal et al., 1996) [12,8] . The bamboo leaf roller, Algedonia coclesalis (Walker), reported in past literature under Crypsiptya coclesalis or Pyrausta coclesalis, is considered a major defoliator in central India. The lesser bamboo leaf roller, Pyrausta bambucivora Moore, is also of regional importance. Earlyinstar larvae initially scrape or feed on tender leaf tissues and subsequently roll or fold leaves, within which they continue feeding. Heavy infestation results in extensive leaf rolling and defoliation, reduced plant vigour and, in severe cases, drying or mortality of young culms. Leaf rollers have been recorded on several commercially important bamboo species, including Bambusa vulgaris, B. nutans, B. tulda, Dendrocalamus asper, D. longispathus and D. strictus (Pal et al., 1996; Joshi et al., 2005) [8,5] . Joshi and Meshram (1989) [4] reported that bamboo defoliators belong to order Lepidoptera, Coleoptera and the most important Leaf roller belongs to Lepidoptera i.e. Pyrausta bambucivora. Wang et al. (1998) [14] authored "Insect Pests of Bamboo in Asia: An Illustrated Manual," published by INBAR, Beijing. This comprehensive manual provides extensive documentation of the diverse insect pests attacking bamboo species across Asia.

Materials and Methods

The present study was carried out on "Seasonal incidence of major insect pest of bamboo like leaf roller, Pyrausta coclesalis" at AICRP on Agroforestry, College of Agriculture, Nagpur, during 2025 to 2026. The material required for the study of incidence include, a hand lens for immediate close-up field observation, permanent marker and labels a camera or mobile phone for photographing insects under field conditions, and a field notebook or logbook for recording collection data such as location, date and conditions, sample labels and record book of plantation of bamboo, polyethene bags, aluminum foil paper, ice packs and thermal insulated box for collection , preservation and transportation of samples. The observations were recorded on bamboo spp. Bambusa vulgaris for incidence of major insect pest like leaf roller infestation. Total number of leaves and leaves damage by leaf roller was counted from 3 randomly selected clumps on Bambusa vulgaris species for computation of percent damage infestation.

Results and Discussion

The seasonal abundance of bamboo leaf roller was recorded on bamboo species Bambusa vulgaris which was planted in year 2020. The data presented in Table 1 revealed that the population of bamboo leaf roller on Bambusa vulgaris was recorded from the 29th Standard Meteorological Week (SMW), corresponding to the third week of July, 2025, and continued till the 40th SMW, corresponding to the first week of October, 2025. Leaf damage due to the pest showed a progressive increase from 13.1 percent at the onset of observation, 29th SMW corresponding to the third week of July, 2025 and attained a peak of 23.4 percent during the 36th SMW, i.e., the first week of September, following which a decline in infestation was evident.

Correlation of bamboo leaf roller infestation with weather parameters

The data presented in Table 2 revealed that the correlation coefficients between bamboo leaf roller-induced leaf damage on B. vulgaris and various weather parameters recorded during 2025-2026, against a critical r-value of 0.632 at 5 percent level of significance, Morning relative humidity (RHM) exhibited a significant positive correlation with leaf damage (r = 0.758). Maximum temperature (Tmax) (r = -0.636) and evaporation (Evapo) (r = -0.679) each showed a significant negative correlation. Wind speed (WS) (r = -0.595), although negative, did not attain statistical significance, being marginally below the critical value. Rainfall (RF) (r = -0.357), rainy days (RD) (r = 0.090), minimum temperature (Tmin) (r = -0.312), evening relative humidity (RHE) (r = 0.246), and bright sunshine hours (BSH) (r = -0.189) were all non-significantly correlated with leaf damage. The present findings indicated that bamboo leaf roller infestation on B. vulgaris was initiated with the onset of the monsoon season in July, increased progressively, and reached its peak in first week of September 2025 and declined afterwards. During this period greeny texture with sufficient foliage on bamboo with maximum relative humidity. This pattern was in general agreement with Joshi et al. (2005) [5] , who reported that larval populations of leaf rollers generally appeared with the onset of rains at the end of June, coinciding with the leaf-flush season in bamboo when sufficient foliage was available for larval feeding, and that population build-up reached a peak during August and September under monsoon conditions. The peak infestation recorded in the present study during the 36th SMW (early September) closely corresponded with this reported peak period. Similarly, Pal et al. (1996) [8] reported that outbreaks of Crypsiptya coclesalis on bamboo were observed during July, August, and September, which is consistent with the period of active infestation and peak buildup recorded in the present study. The findings also agreed with those of Kumar et al. (2021) [6] , who reported that infestation of Algedonia coclesalis on bamboo species in Ranchi, Jharkhand, initiated in July and persisted till Octobera period that closely matches the July-to-early-October observation window of the present study. However, the present findings were only partially in agreement with those of Ashad-Uz-Jaman Kazi et al. (2021) [2] , who monitored the pest on a monthly basis throughout the year at a silviculture nursery and was reported that 20 percent and 22 percent infestation of leaf roller during August and November 2021 and it was declined upto 2 percent during March to June. It was declined upto 2 percent. While both studies concurred, that larval activity increased sharply from July onward and remained minimal during the early months of the year. The present study neither conducted on silviculture nor extended observations beyond the first week of October and therefore could not confirm whether infestation continued to rise toward a later peak, as reported by Kazi et al. (2021) [2] for December. This discrepancy may be attributable to differences in geographic location, prevailing climatic conditions, or possibly to species-specific or site-specific or stage/age of plant variation in pest phenology, and does not necessarily indicate a contradiction between the two studies.

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