Seasonal abundance of stem fly on soybean and correlation with weather parameters

Introduction

Soybean (Glycine max) is one of the most important leguminous crop belonging to family Leguminosae syn. Fabaceae. Though, soybean is a legume crop, yet it is widely used as oilseed. Major soybean growing states in India are Madhya Pradesh, Maharashtra, Rajasthan, Andhra Pradesh and Karnataka. It provides 40% protein, well balanced essential amino acids, 6-7% total minerals, 20% oil, rich in poly unsaturated fats specially Omega 6 and Omega 5 fatty acids, 17-19% carbohydrates, 5-6% crude fibre (Chauhan and Joshi, 2005). Stem fly and girdle beetle are the main borers appearing on soybean crop. The stem fly attacks the soybean crop throughout the growing season, but the most vulnerable period is within three to four weeks after germination. The maggot may tunnel upto 70 % of the stem length and may reduce the grain yield about 33 % (Singh and Singh, 1990).

Material and Methods

The field experiment was conducted during kharif 2024 to study the seasonal abundance of stem fly on soybean at Research Farm of Entomology Section, College of Agriculture Nagpur. A separate plot of 100 m 2 area was sown. Soybean variety JS 95-60 was used for sowing. The observation on seasonal abundance of stem fly was recorded from 8 th July (27 th SMW) to 23 th September 2024 (38 th SMW). Observations of stem fly infestation, total number of plants/seedlings and plants/seedlings damage by the stem fly were counted from one meter row length of 10 randomly selected spots at 7 days interval from 7 days after germination till the harvest of the crop and calculated per cent infestation. Plant height and length of stem tunnel was measured in 10 plants for calculating per cent stem tunnelling. Simultaneously, weather data were recorded and it was correlated with the pest population.

Results and Discussion

The infestation of stem fly was noticed from 29 th standard meteorological week (SMW) i.e. 22 nd July 2024 with 3.15 % plant infestation and 5.04% stem tunnelling and it was recorded No. 1). The peak infestation was observed during 38 th SMW i.e. 23 rd September 2024 with 25.20 % plant infestation and 45.11 % tunnelling. The correlation coefficient analysis data revealed that, the evening humidity (r=0.853) had significant positive correlation with infestation of stem fly at 1 % significant level and rainy days (r= -0.644) had significant negative correlation with infestation of stem fly at 5 % significant level. Morning humidity (r=-0.280), rainfall (r=-0.478), maximum temperature (r=-0.326), minimum temperature (r=-0.057), bright sunshine hours (r=-0.515) and wind speed (r=-0.483) had non-significant negative correlation with infestation of stem fly. However, evaporation (r=0.067) had non-significant positive correlation with infestation of stem fly. The evening humidity (r=0.751) had significant positive correlation with stem tunnelling by stem fly at 5 % significant level. While, rainfall (r=-0.257), rainy days (r=-0.490), maximum temperature (r=-0.310), morning humidity (r=-0.052), bright sunshine hours (r=-0.586), wind speed (r=-0.586) and evaporation (r=-0.055) had non-significant negative correlation with stem tunnelling by stem fly. However, minimum temperature (r = 0.101) had nonsignificant positive correlation with stem tunnelling by stem fly (Table No. 2). The data trend of present study is in agreement with findings of Ahirwar et al. (2013) [1] , who reported that the stem fly (Melanagromyza sojae) infestation was 4.4% on the 31 st SMW whereas, the highest percentage of infested plants was 67.7% in 37 th SMW. They reported one more peak with infestation of 54.4% on 39 th SMW and 69.9% on 41 st SMW which was moderately higher than the present trend. Similarly, Yeotikar et al. (2015) [7] observed 59.45% stem tunnelling by stem fly at physiological maturity. Comparatively higher infestation levels of stem fly than the present study was reported by Kumar et al. (2019) [4] who identified stem fly as significant soybean stem borer and reported that 18% of plants were infested with stem flies, and 1.35 % of stems showed tunnelling in August 2017 with infestations of 78% in September, with 48.40% of the stems tunnelling where almost 90 % of the affected plants showed tunnelling, which was caused by the stem fly maggot. Similar findings were reported by Chouhan et al. (2019) [3] who reported plant infestation upto 80 % in the last week of September with highest stem tunnelling (48.50 %). The stem fly infested almost every plant (90%) in the first week of October 2015. Whereas, comparatively lower infestation levels of stem fly than the present study was reported by Patidar et al. (2021) [5] who revealed that the incidence of stem fly began in the third week of August (34 th standard week) with a 1.2% stem tunnelling and peaked at first week of October (40 th standard week) with a 11% stem tunnelling.

Table 1: Seasonal abundance of stem fly on soybean and weather data

Date of observations

Meteorological week

Stem fly

References

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