Endophytic herbivorous insects living within plant tissues create galls like structures and mines that offer protection from predators and harsh environments while enabling selective feeding on nutrient-rich, low-defense tissues. However, leaf miners attract more parasitoid species than other insect groups due to their limited mobility, visible mines and minimal protection from the leaf epidermis
(Hawkins et al., 1997). The survey conducted during
Summer and
kharif, 2023 revealed the natural parasitization of leaf miner larvae was only by
Bracon sp. (Fig 1a) and while no significant parasitization by other parasitoids were recorded. The parasitized samples collected from the experimental fields were maintained under laboratory and were shrank and mummified (Fig 1b). The matured parasitoid grub (Fig 1c) pupated outside of the host body (Fig 1d) and the emerged parasitoids were identified as
Bracon sp. and confirmed by the presence of a single recurrent vein in the forewings (Fig 2) which is a distinct taxonomic character of the Braconidae family. On the contrary,
(Shekarappa et al., 1990) recorded 16 species of hymenopteran parasitoids on
A.
modicella during
Kharif, 1989. While,
Simithramma (1998) reported 41 species of hymenopteran parasitoids including
Bracon sp. attacking
A.
modicella. Survey on different locations on the parasitoid fauna of
A.
modicella revealed that GLM larvae were parasitized by 13 species of hymenopteran parasitoids including four species of braconids:
Chelonus blackburni Cameron,
Avga choaspes Nixon,
Apanteles spp. and
Bracon hebetor Say. The reduced number of parasitoid species in the present study may be due to the dynamic nature of parasitoid communities, with species composition and dominance fluctuating throughout the year. In the current study, the parasitization of the groundnut leaf miner correlated with the occurrence of
A.
modicella with parasitization rates rising in tandem with higher pest infestations. This may be attributed to the continuous and staggered cultivation of groundnut in rainfed conditions, which likely contributed to the elevated
A.
modicella infestations. Additionally, the non or minimal use of insecticides in rainfed areas resulted in higher GLM populations, subsequently leading to increased parasitization rates.
At the early stage of the crop during February, 2023 no parasitization was observed. However, in early March
i.
e., 12
th SMW, a minimum parasitization rate of 8.00 per cent by
Bracon sp. was recorded (Table 1). The parasitization rate by
Bracon sp. on leaf miner larvae declined and ceased during late
Summer and early
Kharif season. Following the onset of rainfall, parasitization rates began to increase and reached a moderate level of 18.00 per cent during 23
rd to 30
th SMW
i.
e., June-July and peaked at 26.00 per cent during 31st to 33
rd SMW
i.
e., July-August in the late kharif groundnut season (Table 1). The present results were supported by
Subba Rao and Sharma (1966) who also reported 10.1-44.2 per cent parasitism by
Bracon gelechiae under irrigated ecosystem. The other studies reported about 26% parasitism by
Chelonus sp. and larval parasitoid
Goniozus indicus, about 16.67% (
Muthiah and Kareem, 2000).
Among the two seasons the parasitization rates were more during
Kharif, 2023 when compared to
Summer, 2023 (Fig 3). This was in accordance with the findings of
Kothai (1974) who found that the extent of larval parasitism by parasitoids in groundnut leaf miner varied which was 30.00, 14.00, 20.00 and 23.50 per cent respectively for July, August, September and October months.
Murugasridevi et al., (2022) found three parasitoids
viz.,
Trissolcus.
japonicus (Ashmead),
Sympiesis sp. and
Tetrastichus sp. and they were most prevalent during the month of August, while the occurrence of
Chelonus sp. was more common during the month of September. The study also found that the parasitization of groundnut leaf miner was more during rainy season when compared to summer and post rainy season. This was in accordance with earlier investigations by
Yadav et al., (1987) in rainfed groundnut.
As the percentage of parasitoid adult emergence is a key indicator of success in augmentative biological control (
Elbehery, 2020), the parasitic effectiveness of
Bracon sp. can be evaluated against groundnut leaf miners and considered for inclusion in biological control programs.
Understanding the adaptations of natural enemies to the change in climate is crucial for effective pest management (
Thanavendan and Jeyarani, 2010). In the present study, correlation analysis of weather parameters revealed that the maximum temperature (r= 0.768*) and minimum temperature (r= 0.533*) had a significant positive correlation with
Bracon sp. parasitism on groundnut leaf miner. However, rainfall (r= 0.483) and wind velocity (r= 0.015) exhibited a non-significant positive correlation. The Relative humidity (RH) showed a non-significant negative correlation (r= -0.117) with GLM larval parasitism (Table 2). A study conducted at Kanpur, India found that both maximum and minimum temperatures played a significant positive role in parasitization, whereas the relative humidity, sunshine and rainfall had no consistent impact on
Campoletis chlorideae parasitizing
Helicoverpa armigera in a chickpea ecosystem
(Singh et al., 2015). Similarly, a study from Pantnagar observed a non-significant positive correlation between abiotic factors and parasitism by
Campoletis chlorideae on pod borer
H.
armigera in a chickpea sole crop. In contrast, in intercropping systems, there was a significant positive correlation with evening RH and rainfall (
Jaba and Agnihotri, 2018).
