The current investigation entitled, “Unified Pest Management in Ladies’ Finger Species (Abelmoschus esculentus L.)” was undertaken during recent years. At present, schedule based application of various insecticides are recommended for the management of different insect pests. But, the injudicious use of synthetic chemicals to manage these pests is fraught with the tribulations of resistance, resurgence, secondary infestation, phyto-toxicity, toxicity to beneficial organisms, residues in food beyond the tolerance limits posing unwarranted health hazards to the consumers.
Introduction
Lady’s finger (Abelmoschus esculentus (L.), frequently known as bhendi or Okra belonging to family Malvaceae, is an important warm season vegetable crop cultivated comprehensively in tropical and sub-tropical regions of the world. Okra is native to Ethiopia (Vavilov, 1951). It is a short duration crop propagated through seeds, cherished for its tender and scrumptious green fruits used in curries, soups or in canned, dehydrated or frozen forms for off-season consumption (Neeraja et al., 2004). Okra is more remunerative than the leafy vegetables. The roots and stems are useful for clearing cane juice from which gur or jaggery is prepared (Chauhan, 1972). Its ripe seeds are roasted, ground and used as a substitute for coffee in Turkey. Fruits have high nutritive value containing proteins, calcium, phosphorus, iron, carotene and vitamins A, B and C (Singh, 1970) which are very useful against genito-urinary disorders, spermatorrhoea and chronic dysentery. Okra has occupied a prominent position among the export oriented vegetables in India because of its high nutritive value, palatability and good post- harvest life. It has an enormous potential as one of the foreign exchange earner crops and accounts for 70 per cent of the export of fresh vegetables. At present, it is being exported to the neighbouring countries in the Gulf and South- East Asia, particularly Singapore, Mauritius, Malaysia, Sri Lanka and Bangladesh. In India, okra is cultivated in an area of 0.37 million hectare with an annual production of 3.53 million tons (Anonymous, 2004b). In Himachal Pradesh, the crop is grown during summer and rainy seasons in low and mid hills occupying an area of 357 hectare with an annual production of 4114 tons which is much lower than that of many other states. One of the major rationales for low yield is the wide array of insect-pests that sabotage this crop right from germination till harvesting.
Scientific classification Ladies’ finger
Kingdom: Plantae
Clade: Angiosperms
Clade: Eudicots
Clade: Rosids
Order: Malvales
Family: Malvaceae
Genus: Abelmoschus
Species: A. esculentus
Research Methods
Raising of the crop
ladies' finger (Abelmoschus esculentus) was raised in the fields at the two sites under different experiments following all agronomic practices as recommended for the crop in the package of practices (Anonymous, 2005b). The crop was sown in the first week of April at Kachhiari during both the years and first week of June and last week of May and at Rajasthan during recent years, respectively, with a row to row and plant to plant spacing of 60 x 15 cm.
Surveillance and monitoring of insect-pests associated with ladies' finger (Abelmoschus esculentus)
In order to understand the insect-pests associated in ladies' finger (Abelmoschus esculentus) and also to study their extent of incidence, the crop was grown in 10 plots of size 3m x 3m and observations were taken on 10 randomly selected plants per plot (100 plants in total) under natural infestation conditions. Observations were taken on Pusa Sawani variety because of the fact that it is still one of the most popular varieties grown in the mid-hills of Himachal Pradesh and also reported to be susceptible to insect-pest attack.
The sampling of insects infesting the crop was carried out at weekly intervals throughout the cropping season. The percent plant infestation on each sampling was recorded by observing 100 randomly selected plants. The broad criteria for classifying the insects were according to Wilson (1994) as follows:
Minor pests: 5 to 10 per cent plants affected.
Major pests: More than 10 per cent plants affected.
Seasonal incidence/ population-build up of insect- pests on cotton and ladies’ finger
For studying population build-up of insect-pests, cotton and ladies’ finger variety- Pusa Sawani was raised at Palampur and Kachhiari as per the recommended package of practices. No insecticide was sprayed. Observations were recorded for different groups of insect-pests viz. sucking pests, shoot/fruit borers and foliage/flower pests at both the locations on 100 randomly selected plants at weekly intervals throughout the crop growth period as follows:
Result & Discussion
Insect-pests associated with ladies' finger (Abelmoschus esculentus) crop
Surveillance studies conducted recent years at Rajasthan revealed that 18 different pest species were associated with ladies' finger (Abelmoschus esculentus) crop (Table 1). Among these, 4 were observed to cause plant damage of more than 10 per cent and thus classified as major pests during both the years. These included cotton jassid, Amrasca biguttula biguttula (Ishida), cotton aphid, Aphis gossypii Glover, blister beetle, Mylabris pustulata Thunbergo and cotton leafroller, Sylepta derogata (Fabricius). The remaining insects were rated as minor pests of the crop as they caused 5 to 10 per cent damage.
At Rajasthan, the surveillance studies carried out recent years revealed 19 different pest species associated with and ladies' finger (Abelmoschus esculentus) crop (Table 2). Among these, 5 were rated as major pests of ladies' finger (Abelmoschus esculentus) (plant damage of more than 10%). which included cotton jassid, A. biguttula biguttula; cotton aphid, A. gossypii; shoot and fruit borer, Earias vittella (Fabricius); blister beetle, M. pustulata and cotton leafroller, S. derogata. The rest of the insects were categorized as minor pests because of their lower numbers and plant damage of 5 to 10 per cent.
For evolving an effective pest management strategy, it is imperative to know the insect-pest complex attacking a crop in a particular agro-climatic zone. Surveillance studies conducted on cotton and ladies’ finger at Rajasthan revealed 18 different pests’ species belonging to 6 orders and 12 families associated with A. esculentus (var. Pusa Sawani) from June to September. At Rajasthan, 19 different pests’ species belon ging to 6 orders and 12 families were associated with ladies’ finger crop from May to September. At rajasthan, the locations, Nodostoma spp. and Popillia spp. were identified as new insects of ladies’ finger from the state. Nodostoma spp. were found to attack both foliage and flowers whereas Popillia spp. attacked flowers only although both these insects were rated as minor pests.
Earlier Butani and Verma (1976) had reported as many as 30 insect and non-insect pests attacking ladies’ finger crop. They have listed 13 pests attacking ladies’ finger at various stages of crop growth at Gwalior in Madhya Pradesh. Eight species of insects were reported to feed on cotton and ladies’ finger at 182 Raipur (Chhattisgarh).
During the present investigation, the severity of pests was noticed from June to September at the Rajasthan . A number of workers have also observed that the pests of ladies’ finger are more serious from June to August i.e. during warm and rainy season. The present research revealed that out of 18 pest species recorded on cotton and ladies’ finger at Palampur, 4 were observed to cause major damage to crop. These included jassid, A. biguttula biguttula, aphid, A. gossypii, blister beetle, M. pustulata and leafroller, S. derogata. At Kachhiari, in addition to these pests, shoot and fruit borer, E. vittella was also observed as the major pest of cotton and ladies’ finger.
A. gossypii has previously been reported to cause considerable damage to cotton and ladies’ finger crop in different parts of the country.
Seasonal incidence/ population build up of major insect- pests on ladies' finger (Abelmoschus esculentus) crop
Studies on the seasonal incidence/ population build up of major insect-pests on cotton ladies' finger (Abelmoschus esculentus) crop were conducted at the two locations viz. Rajasthan during the crop seasons.
Cotton jassid, A. biguttula biguttula Population count (nymphs + adults)
Data on the population build up of jassids at Palampur presented in Table 4.3 revealed that the jassids were active on ladies' finger (Abelmoschus esculentus) crop from 1st week of July to last week of September during crop season. The pest was first noticed on the crop on July 3, with a total population of 2.63 jassids (1.01 nymphs + 1.62 adults/3 leaves) which showed a variable trend till the final harvesting. The peak infestation of the pest was recorded during last week of August with utmost population count of 46.20 (35.57 nymphs+ 10.63 adults) per 3 leaves. The corresponding means of maximum temperature, minimum temperature, relative humidity, bright sunshine when the maximum population of the pest was recorded were 27.4 ˚C, 18.8˚C, 79 per cent, 5.9 hours with a total of 64.4 mm rainfall. Subsequently, the population declined rapidly. However, the pest population did not cease completely and remained on the crop till final harvesting i.e. till last week of September.
Table 1 Population build-up of A. biguttula biguttula on ladies' finger (Abelmoschus esculentus) at Rajasthan
Sampling Population count#/3 leaves Per cent Infestation
date plant index
Nymphs Adults Total
infestation
3 July 1.01 1.62 2.63 8 0.21
10 July 5.20 2.10 7.30 14 1.02
17 July 3.70 1.70 5.40 14 0.78
24 July 12.93 2.75 15.68 22 3.45
31 July 16.79 4.10 20.89 33 6.89
7 Aug. 19.23 7.78 27.01 46 12.42
14 Aug. 29.15 8.93 38.08 58 22.09
21 Aug. 18.69 5.93 24.62 46 11.33
28 Aug. 35.57 10.63 46.20 72 33.26
4 Sept. 23.56 6.57 30.13 53 15.97
11 Sept. 14.76 3.21 17.97 37 6.65
18 Sept. 2.24 1.27 3.51 12 0.42
25 Sept. 2.95 1.25 4.20 9 0.37
During crop season also, the pest commenced its activity in 1st week of July when a total population of 2.25 i.e. 0.50 nymphs + 1.75 adults per 3 leaves was observed (Table 4.3) which again showed an irregular pattern. Highest population (45.86/3 leaves) of the pest was recorded during 3rd week of August coinciding with mean meteorological conditions of 28.5˚C (maximum temperature), 20.2˚C (minimum temperature), 79 per cent (relative humidity), 7.5 hours (bright sunshine) and 80.5 mm (total rainfall). Thereafter, the jassid population showed a speedy decline but remained on crop till 2nd week of September. At Kachhiari, the activity of A. biguttula biguttula initiated during 4th week of May, 2005 when a total population of 0.71 i.e. 0.46 nymphs + 0.25 adults per 3 leaves (Table2) was observed. The pest population remained low till 3rd week of June due to higher temperature after which it gained impetus and illustrated an increasing trend subsequently till August 2, when peak population (51.02/3 leaves) of the pest was recorded concurring with weather parameters of 29.7°C (maximum temperature), 25.3˚C (minimum temperature), 75 per cent (relative humidity) and 75.7 mm (total rainfall). Consequently, the population showed a retreating tendency during 2nd week of August but amplified in the following week after which it declined
Table 2 Population build-up of Amrasca biguttula biguttula on cotton (Gossypium arboreum L.) and ladies' finger (Abelmoschus esculentus) at Kachhiari (Kangra)
Sampling Population count#/3 Per cent Infestation
date Leaves plant Index
infestation
Nymphs Adults Total
24 May 0.46 0.25 0.71 8 0.06
31 May 0.70 0.33 1.03 12 0.12
7 June 0.97 0.50 1.47 14 0.21
14 June 1.00 0.54 1.54 16 0.25
21 June 0.81 0.43 1.24 17 0.21
28 June 2.85 1.50 4.35 22 0.96
5 July 4.20 1.97 6.17 27 1.67
12 July 8.60 2.18 10.78 35 3.77
19 July 10.74 3.78 14.52 42 6.39
26 July 20.58 8.01 30.59 63 19.27
2 Aug. 37.54 13.48 51.02 77 39.29
9 Aug. 26.30 10.70 37.00 54 19.98
16 Aug. 30.12 11.84 41.96 58 24.34
23 Aug. 11.18 5.17 16.35 25 4.09
30 Aug. 3.10 2.53 5.63 16 0.90
Conclusion
The surveillance studies revealed that 18 different pest species were associated with Ladies’ finger A. esculentus at Rajasthan while 19 different pest species were associated with okra at Rajasthan Out of these pests, some identified as the major pests. These included cotton jassid, A. biguttula biguttula, cotton aphid, A. gossypii, blister beetle, M. pustulata and cotton leafroller, S. derogata. At Kachhiari, in addition to these 4 pests, shoot and fruit borer, E. vittella was also observed to cause major damage to the crop.