Groundnut (
Arachis hypogaea L.) belongs to family Fabaceae and having rank 2nd in oilseed crop in India. It is the most important food and cash crop of our country having high quality edible oil (45-50%), easily digestible protein (26-28%), 13 essential vitamins and 7 crucial minerals necessary for normal human growth and maintenance, it produces high quality fodder for animals. Groundnut is cultivated on about 4.81 mha in India, with an average annual production of 6.69 million tonnes (
Anonymous, 2019). The average yield in India is over 1393 kg/ha. In Rajasthan, total area under groundnut is 0.67 million hectare with total production of 1.38 million tonnes (
Anonymous, 2019). White grub
Holotrichia consanguinea existing as soil-inhabiting polyphagous pest, grub feeding on roots and is pre dominant species in Rajasthan, Gujarat, Haryana, Punjab, Bihar and Uttar Pradesh followed by
M. insanabilis. The scarabaeids have become difficult insect to control as both the adult and immature have different habitats. The grubs sometimes go deep into the soil and become more difficult to control (
Khagta, 2006). To combat this pest, usually insecticides are recommended but management of the grubs is often ineffectual because of the difficulty of insecticides to reach the insect and insecticides have deleterious effects on the environment. Therefore, there is urgent need to search and explore, alternate ecofriendly and economically realistic strategy for the control of white grub. Several isolates of fungi
, Beauveria bassiana, Beauveria brongniartii,
Metarhizium anisopliae, Paecilomyces fumusoroseus and
Verticillium lecanii have been applied in a number of countries
(Rath et al., 1995). The entomopathogens against white grub,
Holotrichia serrata (
Supekar and Mohite, 2015),
Leucopholis lepidophora (
Bharathi and Mohite, 2015) and
Phyllognathus dionysius (
Rathour et al., 2015) reported high infection rates in the grub population. The use of nematodes as biological pest control agents has increased exponentially over the past few decades. Nematodes that parasitize insects have been described from 27 nematode families but most significant families,
Heterorhabditidae and
Steinernematidae also called as entomopathogenic nematodes have received the most attention because of their potential as inundatively applied biological control agents (
Kaya and Gaugler, 1993;
Grewal et al., 2005; Koppenhofer, 2007).
The experiment was conducted for two consecutive seasons during
kharif 2018 and 2019 at Research Farm, Rajasthan Agricultural Research Institute, Durgapura, Jaipur. The RG-510 variety was sown in field at 30 cm distance from row to row and 10 cm plant to plant apart in plot size of 5 x 4 m and treatments were replicated thrice with randomized block design (RBD). Groundnut crop was raised following standard recommended package of practices for the zone IA except for soil insect management. Bioagents treatments were applied in furrow at sowing time.
Details of treatments are as follows: 7 treatments
T
1:
Metarhizium anisopliae @ 5 kg per hectare at sowing (1´1012 CFU/ gm)
T
2:
Beauveria bassiana @ 5 kg per hectare at sowing (1´1012 CFU/ gm).
T
3:
Heterorhabditis indica @ 5000 galleria per hectare (2 lakh IJs/galleria).
T
4:
Heterorhabditis indica powder @ 5 kg/hectare at sowing.
T
5:
Steinernema glaseri @ 5000 galleria per hectare (2 lakh IJs/galleria).
T
6:
Steinernema glaseri powder @ 5 kg/hectare at sowing.
T
7: Control.
Observation recorded
Observations on initial plant population just after the germination and plant mortalities due to white grub infestation at 20, 40, 60 and 80 days after sowing were taken. The data on groundnut pod yield were also recorded treatment wise at the time of harvest and collected data were subjected to statistical analysis to draw the conclusion.
Crop yield and economics
Groundnut crop was harvested when the pods mature and their weight from each treatment was expressed as pod yield q ha
-1. The yield was subjected to analysis of variance. The increase yield of groundnut over the control was calculated for each treatment separately by the formula given by
Pradhan (1964).
The incremental cost benefit ratios of different treatments were also worked out by given following formula.
The data presented in the Table 1 and (Appendix1) on efficacy of
M. anisopliae, B. bassiana, H. indica galleria
, H. indica powder,
Steinernema glaseri galleria and
Steinernema glaseri powder indicated that all the bio-agent treatments were significantly superior over untreated control in reducing the per cent plant mortality due to white grub,
H. consanguinea in groundnut crop. During both the seasons per cent plant mortality was observed at 20, 40, 60 and 80 days after sowing and minimum (28%) per cent plant mortality on 80th day after sowing observed in the plots treated with
B. bassiana @ 5 kg (1×10
12 CFU/ gm) per hectare followed by
M. anisopliae (29.33%) @ 5 kg (1×10
12 CFU/ gm) per hectare and
H. indica galleria (31.77%) @ 5000 galleria (2 lakh IJs per galleria) per hectare at the time of sowing in comparison to 87.28 per cent in untreated control. The treatment of
S. glaseri powder proved to be the least effective (37.11%) followed by
H. indica powder (35.69%) and
S. glaseri galleria (33.75%).
The results bare that yield of pod in all the treatments of bio-control agents was significantly superior in comparison to untreated control of 0.5 q/ha. The maximum pod yield of 12.82 q/ha was recorded with treatment of
B. bassiana @ 5 kg (1 × 10
12 CFU/gm) per hectare which was at par with the treatment of
M. anisopliae @ 5 kg (1 × 10
12 CFU/gm) per hectare (11.53 q/ha),
H. indica galleria @ 5000 galleria/ha (10.78 q/ha) and
S. glaseri galleria @ 5000 galleria/ha (10.17 q/ha). The maximum incremental cost benefit ratio of 1:31.05 was obtained in the treatment of
B. bassiana @ 5 kg per hectare at the time of sowing followed by the treatment
M. anisopliae @ 5 kg (1 × 10
12 CFU/gm) per hectare (1:27.82),
H. indica powder (1:9.64),
S. glaseri powder (1:9.00),
H. indica galleria (1:4.60) and
S. glaseri galleria (1:4.33). The present studies indicated that the furrow application of
B. bassiana @ 5 kg per hectare or
M. anisopliae @ 5 kg per hectare at the sowing time is the most active than others used in reducing the percent plant mortality due to white grub,
H. consanguinea and increasing the pod yield in groundnut crop.
The results are in agreement with work of
Bhagat et al., (2003), Chirame et al., (2003), Hajeri (2003),
Channakeshava (2006),
Manisegaran et al., (2011), Prabhu et al., (2011) Visalakshi et al., (2015), Vinayaka and Patil (2018) and
Kumbhar et al., (2019) who evaluated
Beauveria bassiana and
Metarhizium anisopliae and found that
M.
anisopliae was most effective in reduction of plant mortality and increase of yield in sugarcane followed by applied in FYM enriched field.
Patil et al., (2016) evaluated efficacy of
Steinernema abbasi and
Heterorhabditis indica against white grub,
H. consanguinea and found that
H. indica at a dose of 2.5×10
9 IJs ha
-1 significantly reduce the grub population of
H. consanguinea then followed by
S. abbasi.
Mohan et al., (2017) reported an average reduction of 69.1 per cent in the white grub population by use of
H. indica infected galleria and an average increase of 60.49 q /acre in sugarcane yield over untreated control
. Sharmila et al., (2019) recorded the highest grub mortality (58.32%) with
S. glaseri @ 5×10
9 IJs/ha and increase in yield by 15.78 t/ha.
