Okra (
Bio-fumigation is very important agronomic practice of using volatile chemicals (allelochemicals) released from plant tissues after the decomposition to suppress pests (Kumar and Mishra, 2014). The term bio-fumigation was coined by different scientists to describe the suppression of soil-borne pathogens by releasing different compounds by brassica species (Motisi et al., 2010). Bio-fumigation has been widely researched by many countries, namely Australia, Italy, South Africa, New Zealand, the Netherlands and the USA. Asian countries like Cambodia, China, India, Thailand, and Philippines have also been involved in bio-fumigation trials (Kumar, 2005). Bio-fumigation has a lot of potential in Asian countries because cruciferous crops are widely grown and consumed. This strategy is an alternative to the environmentally damaging chemical fumigants and sterilants (Gouws, 2004). Therefore, bio-fumigation techniques are developing worldwide. It has been shown that there is a potential to use bio-fumigation as an alternative to methyl bromide in horticulture and broad agriculture to manage pests (Ghoname et al., 2015). Majority of the studies on bio-fumigation have been conducted in laboratory and greenhouse conditions. Keeping all the facts in mind, this study was performed to evaluate the efficacy of cruciferous bio-fumigants against root-knot nematode,
The experiment was conducted in years 2017 to 2018 and 2018 to 2019 in research area, Department of Nematology, CCSHAU Hisar, Haryana, India (Latitude: 29°10´N, Longitude: 75°46´E, and Altitude: 215.2 m), which has subtropical and tropical climate with an annual average temperature of 25.1°C and an average annual rainfall of 459 mm.
Root-knot nematode inoculum was obtained from okra infested field of Hisar, Haryana, India. It was maintained and cultured on tomato variety ‘Hisar arun’ and species identified by using the perineal pattern (Netscher and Taylor, 1974). The field trial was conducted at the CCS Haryana Agricultural University research area, Department of Nematology. Soil type was a sandy loam having sand 89.7%, silt 4.5%, clay 5.8%, organic matter 1%, and pH 7.2. Before conducting this experiment, the field was sterilized with formalin followed by soil solarization. Then nematode infestation was maintained for seven years by growing different susceptible crops like okra (
The plants were observed regularly, and watering, hoeing, etc., were done whenever required. Fertilizers were applied according to the recommended dosage for okra.
The effect of two cruciferous species, namely cauliflower (
Management of root-knot nematode in okra by bio-fumigation (2017-2018).
Sr. No. | Treatments | INP/200 cc soil before addition of leaves | INP/200 cc soil after addition of leaves | FNP/200 cc soil at harvest | Okra yield (kg/plot) | % increase in yield/over check | Root-knot index at harvest |
---|---|---|---|---|---|---|---|
1 | Cabbage leaves @ 25 t/ha | 224.0 | 197.0 | 258.0b,c | 8.6b,c | 8.9 | 3.8a,b |
2 | Cabbage leaves @ 50 t/ha | 224.0 | 185.0 | 215.7d,e | 9.9a | 25.3 | 3.3a |
3 | Cauliflower leaves @ 25 t/ha | 224.0 | 203.0 | 268.0b | 8.2c,d | 3.8 | 4.0a,b |
4 | Cauliflower leaves 50 t/ha | 224.0 | 200.0 | 231.0d | 9.2a,b | 16.4 | 3.5a |
5 | Carbofuran @ 1.0 kg a.i./ha | 224.0 | 153.0 | 188.0f | 8.4c,d | 6.3 | 3.5a |
6 | Untreated check | 224.0 | 215.0 | 340.6a | 7.9c,d | − | 5.0c |
7 | CD @ 5% | − | − | 19.8 | 0.8 | − | 0.83 |
Management of root-knot nematode in okra by bio-fumigation (2018-2019).
Sr. No. | Treatments | INP/200 cc soil before addition of leaves | INP/200 cc soil after addition of leaves | FNP/200 cc soil at harvest | Okra yield (q/ha | % increase in yield/over check | Root-knot index at harvest |
---|---|---|---|---|---|---|---|
1 | Cabbage leaves @ 25 t/ha | 256 | 225 | 274e (15.60) | 65.5c | 14.0 | 2.8a,b |
2 | Cabbage leaves @ 50 t/ha | 256 | 151 | 226f (15.05) | 78.2a | 36.2 | 2.5a |
3 | Cauliflower leaves @ 25 t/ha | 256 | 242 | 290c (17.06) | 63.2c,d | 11.2 | 3.3a,b |
4 | Cauliflower leaves 50 t/ha | 256 | 181 | 268d (16.40) | 71.8b | 25.0 | 3.0a,b |
5 | Carbofuran @ 1.0 kg a.i./ha | 256 | 194 | 250a (20.83) | 63.4c,d | 11.2 | 3.5b |
6 | Untreated check | 256 | 265 | 417b (20.43) | 57.1e | − | 4.8c |
7 | CD @ 5% | − | − | (0.13) | 5.1 | 0.89 |
Data were calculated for okra yield expressed as q per ha and nematode reproduction parameters (INP/200 cc soil before the addition of cabbage/cauliflower leaves, INP/200 cc soil at the time of sowing of okra, final nematode population/200 cc soil, root-knot index at harvest). The percentage increase and decrease in the yield over the control were calculated by the following formula:
Roots from these plants were indexed for galling and egg mass presence on a scale from 1 to 5 where 1.0 = no galls or egg masses, 2.0 = 1-10 galls or egg masses, 3.0 = 11-30, 4.0 = 31-100 galls or egg masses, and 5.0 = more than 100 galls or egg masses (Heald et al., 1989). For the estimation of nematode populations, soil was processed as per the sieving method of Cobb’s sieving and decanting technique (Cobb, 1918) followed by the Modified Baermann’s funnel technique (Viglierchio and Schmitt, 1983). The extracted second-stage
The data were subjected to RBD using OPSTAT program available online at CCSHAU Hisar University website (
The multiplication of
Relationship between number of galls and percentage increase in okra yield over check (2017-2018).
After the incorporation of cruciferous bio-fumigants, the highest decrease in nematode juvenile population was observed in cabbage leaves @ 50 t/ha (151 J2/200 cc soil) followed by cauliflower leaves @ 50 t/ha (181 J2/200 cc soil). A highest reduction in the gall index of okra roots was obtained from field plots incorporated with cruciferous bio-fumigants but not in untreated check (Table 2). The carbofuran-treated plots also had significantly lower galling compared with untreated check. Gall indices were detected 2.5 and 3.0 for roots of okra in plots treated with cabbage leaves @ 50 t/ha and cauliflower leaves @ 50 t/ha, respectively. Positive effect of cabbage leaves @ 50 t/ha was increased 36.2% in yield over check followed by 25.0% in cauliflower leaves @ 50 t/ha. Okra yields obtained from the plots treated with cruciferous bio-fumigants and the carbofuran were all significantly higher than that of untreated check (Table 2). The final nematode population in the soil was lowest in cabbage leaves @ 50 t/ha (226) followed by carbofuran @ 1.0 kg a.i./ha (250). The regression studies showed (Fig. 2) negative and significant relationship between number of galls and percentage increase in okra yield over check (
Relationship between number of galls and percentage increase in okra yield over check (2018-2019).
In recent years, bio-fumigation has emerged as an effective non-chemical alternative to manage nematode pests. However, these results aim to be only indicative of the potential use of cruciferous bio-fumigants for nematode management and need to be validated by future trials in farmers field conditions, as well as different combinations of bio-agents with cruciferous bio-fumigants should also be tested to verify a potential synergism among different practices. The experimental study indicated that cruciferous bio-fumigants have provided a satisfactory nematode suppression, confirming previous findings of some researchers (Haroutunian, 2013). In cruciferous bio-fumigants, the enzyme (myrosinase)-catalyzed hydrolysis of sulphur-containing substrate (glucosinolate) initially involves cleavage of the thioglucoside linkage, yielding D-glucose and an unstable thiohydroximate-O-sulphonate, which spontaneously rearranges to produce sulphate and a number of reaction products (Zhou et al., 2012). The end products are generally isothiocynate, thiocyanate, nitrile, epithionitrile, or oxazolidine-thione, depending on substrate, pH, or ferrous ions available (Zhou et al., 2012; Avato et al., 2013). In field environment, both fresh chopped cruciferous bio-fumigants had significantly inhibited the galling of
Most used nematicides banned from world markets and trends toward natural farming and sustainable agriculture continue to escalate; more research and outreach effort are necessitated towards developing and disseminating information on alternative PPN management strategies. One such strategy is the use of cruciferous bio-fumigants against root-knot nematode. Although a plethora of research have been conducted on using these crops for root-knot nematode management, agricultural stakeholders remain to be convinced to integrate bio-fumigation into their INM practices. Indeed, it is unlikely that bio-fumigation as a standalone technique will eliminate target PPNs in soil, but this technique can easily be integrated with other strategies such as soil solarization, minimal use of nematicides, use of resistant varieties, bio-control agents, etc., in a cost-effective manner to provide acceptable levels of nematode management.