Seasonal incidence of major sucking pest of okra in relation to weather parameters in Konkan condition

Introduction

Okra (Abelmoschus esculentus (L.) Moench is one of the most important vegetable crops grown in India and commonly known as lady's finger or Bhindi belongs to family Malvaceae. India is the largest producer of okra in the world followed by Nigeria. In India, the okra crop is mainly cultivated in states of Maharashtra, West Bengal, Gujarat, Karnataka, Madhya Pradesh, Uttar Pradesh and Rajasthan (Shinde et al., 2007) [10] . India ranks first in Okra production with estimated area of 531 thousand ha. with a production of 6466 thousand metric ton. Maharashtra rank 13 th in production of okra with estimated area 13.06 thousand ha with a production of 140.88 thousand metric ton. (Source-htpp agricoop.nic.in 2024). As high as, 72 species of insects have been recorded on Okra (Srinivas Rao and Rajendran, 2003) [11] , of which, the sucking pests comprising of leafhopper, Amrasca biguttula biguttula (Ishida), whitefly, Bemisia tabaci (Gennadius) and mite, Tetranychus urticae (Boisduval) causes significant damage to the crop. Incidence of insect pests is one of the limiting factors in production of okra. According to (Rawat and Sahu 1973) [8] the aphid, A. gossypii (Glover) is a polyphagous sucking pest and also acts as a vector of virus and transmits mosaic and leaf curl diseases in okra. (Butani and Verma, 1976) [1] . The sucking pest complex consisting of aphids, leaf hoppers, whiteflies, thrips and mites are major pests and cause 17.46 percent yield loss in Okra (Sarkar et al., 1996) [9] . Aphids, jassid, whiteflies and shoot and fruits borer are the major pests among the different pests infesting Okra (Das et al., 2021) [4] . All efforts are needed to tackle these major sucking pests by knowing their peak period of infestation through studies on seasonal abundance it provides not only the information of initiation of the pest but also provides the peak activity of the pest. Biotic and abiotic parameters play a vital role in population build-up of insect pest. Correlation study helps in to provide either positive or negative association of pest population with biotic or abiotic factors.

Materials and Methods

A field experiment was conducted at Vegetable Improvement Scheme, Central Experiment Station, Wakawali running under Dr. Balasaheb Sawant Konkan Krishi Vidyapeeth Dapoli in Summer 2023-24 and 2024-25 to study the seasonal incidence of different sucking pests infesting Okra. The experiment plot was kept unsprayed till final harvesting of crop. The Okra Konkan Bhendi genotype was sown in the spacing of 45x30 cm. All the recommended agronomic practices viz. weeding, harrowing, application of fertilizer dose and irrigation were carried out timely and properly to raise good crop.

Method of recording observations

The observations were recorded for different pests starting from one week after germination till the final harvesting of the crop. The number of nymph and adults of major sucking pest were recorded at weekly interval from three leaves (from top, middle and bottom) of selected plant for taking observations. Twenty plants were selected randomly and marked permanently for recording the observations.

Statistical analysis

The average of pest population/three leaves/plant recorded on Okra were corelated with meteorological weather parameters in each standard meteorological week (SMW).

Results and Discussion

The data on seasonal incidence of major sucking pests of okra during Summer 2023-24, Summer 2024-2025 and pooled are presented in Table 1 and graphically depicted in Figures 1, 2 and3.

Aphid, (A. gossypii Glover) Summer 2023-24

In summer 2023-24 aphid's population ranging from 0.20 to 12.20 aphids/three leaves/plant. The pest incidence was first noticed in the 5 th SMW (29 th January to 04 th February) i.e. (0.20 aphid/three leaves/plant), then incidence increased continuously up to the 12 th SMW (19 th March to 25 th March) and then it showed declined trend but remained till maturity of the crop. The maximum pest incidence (12.20 aphids/three leaves/plant) was recorded in 12 th SMW (19 th March to 25 th March) and minimum pest incidence (0.20 aphids/three leaves/plant) was recorded in 5 th SMW (29 th January to 04 th February) and 18 th SMW (30 th April to 06 th May). The seasonal incidence of the aphid's population during Summer 2023-24 exhibited a distinct trend correlated with the crop growth stages.

Summer 2024-25

In Summer 2024-25 the incidence of aphid's population ranging from 0.15 to 13.50 aphids/three leaves/plant. The pest incidence was first noticed in the 5 th SMW (29 th January to 04 th February) i.e. (0.15 aphids/three leaves/plant) then incidence increased continuously up to the 10 th SMW (05 th March to 11 th March) and then it showed declined trend but remained till maturity of the crop. The maximum pest incidence (13.50 aphids/three leaves/plant) was recorded in 10 th SMW (05 th March to 11 th March) and minimum pest incidence (0.15 aphids/three leaves/plant) was recorded in 5 th SMW (29 th January to 04 th February).

Pooled data

The pooled data of both the years recorded that, the incidence of aphid's population was in the ranging from 0.10 to 12.33 per three leaves. The pest incidence started from 05 th SMW (29 th January to 04 th February) i.e. (0.18 aphids/three leaves/plant), then incidence increased continuously up to the 12 th SMW (19 th March to 25 th March) and then it showed declined trend but remained till maturity of the crop. The maximum pest incidence (12.33 aphids/three leaves/plant) was recorded in 12 th SMW (19 th March to 25 th March)) and minimum pest incidence (0.10 aphids/three leaves/plant) was recorded in 18 th SMW (30 th April to 06 th May). The results of above findings are discussed here with earlier research worker Chouhan et al. (2016) [2] revealed that the peak population of aphids observed on third week (11 th SMW) of March with mean population of 22.07 aphid/plant.

Jassid (Amrasca biguttula biguttula Ishida) Summer 2023-24

During Summer 2023-24 jassid population ranging from 0.80 to 15.95 jassids/three leaves/plant. The pest incidence was initiated from 06 th SMW (05 th February to 11 th February) i.e. (0.80 jassids/three leaves/plant), then incidence increased continuously up to the 15 th SMW (09 th April to 15 th April) and then it showed declined trend but remained till maturity of the crop. The maximum pest incidence (15.95 jassids/three leaves/plant) was recorded in 15 th SMW (09 th April to 15 th April) and minimum pest incidence (0.80 jassids/three leaves/plant) was recorded in 06 th SMW (05 th February to 11 th February).

Summer 2024-25

In Summer 2024-25 the incidence of jassid ranging between 0.30 to 18.20 jassids/three leaves/plant. The pest incidence initiated from the 7 th SMW (12 th February to 18 th February) with (0.30 jassids/three leaves/plant). Then incidence increased continuously up to the 15 th SMW (09 th April to 15 th April) and then it showed declined trend but remained till maturity of the crop. The maximum pest incidence (18.20 jassids/three leaves/plant) was recorded in 15 th SMW (09 th April to 15 th April) and minimum pest incidence (0.30 jassids/three leaves/plant) was recorded in 7 th SMW (12 th February to 18 th February).

Pooled

The pooled mean incidence of jassid population ranging from 0.40 to 17.08 jassids per three leaves/plant. The pest incidence was initiated from 06 th SMW (05 th February to 11 th February) i.e. (0.40 jassids/three leaves/plant), then incidence increased continuously up to the 15 th SMW (09 th April to 15 th April) and then it showed declined trend but remained till maturity of the crop. The maximum pest incidence (17.08 jassids/three leaves/plant) was recorded in 15 th SMW (09 th April to 15 th April) and minimum pest incidence (0.40 jassids/three leaves/plant) was recorded in 06 th SMW (05 th February to 11 th February). Present findings are in close agreement with Dhandge et al. (2018) [6] revealed that the peak population of aphids was observed at 17 th SMW (14.1 aphids/3 leaves) and 16 th SMW (17.3 aphids/3 leaves).

Whitefly (Bemisia tabaci Gennadius) Summer 2023-24

During Summer 2023-24, whitefly incidence ranging from 0.45 to 5.15 whiteflies/three leaves/plant. The pest incidence was initiated from 07 th SMW (12 th February to 18 th February) i.e. (0.45 whiteflies/three leaves/plant), then incidence increased continuously up to the 12 th SMW (19 th March to 25 th March) and then it showed declined trend but remained till maturity of the crop. The maximum pest incidence (5.15 whiteflies/three leaves/plant) was recorded in 12 th SMW (19 th March to 25 th March) and minimum pest incidence (0.45 whiteflies/three leaves/plant) was recorded in 07 th SMW (12 th February to 18 th February).

Summer 2024-25

During Summer 2024-25, whitefly incidence ranging from 0.25 to 4.25 whiteflies/three leaves/plant the pest incidence was initiated from 06 th SMW (05 th February to 11 th February) i.e. (0.25 whiteflies/three leaves/plant), then incidence increased continuously up to the 12 th SMW (19 th March to 25 th March) and then it showed declined trend but remained till maturity of the crop. The maximum pest incidence (4.25 whiteflies/three leaves/plant) was recorded in 12 th SMW (19 th March to 25 th March) and minimum pest incidence (0.25 whiteflies/three leaves/plant) was recorded in 06 th SMW (05 th February to 11 th February).

Pooled

Pooled data ranging from 0.13 to 4.70 whiteflies/three leaves/plant. The pest incidence was initiated from 06 th SMW (05 th February to 11 th February) i.e. (0.13 whiteflies/three leaves/plant), then incidence increased continuously up to the 12 th SMW (19 th March to 25 th March) and then it showed declined trend but remained till maturity of the crop. The maximum pest incidence (4.70 whiteflies/three leaves/plant) was recorded in 12 th SMW (19 th March to 25 th March) and minimum pest incidence (0.13 whiteflies/three leaves/plant) was recorded in 06 th SMW (05 th February to 11 th February).

Correlation Studies Correlation Studies between aphid incidence and weather parameters

The correlation analysis was performed to ascertain the relationship between the aphid population and various meteorological parameters presented in (Table 2).

During Summer 2023-24, the aphid population exhibited a significant positive correlation with maximum temperature (r = 0.534 * ). Minimum temperature (r = 0.327), morning relative humidity (r = 0.295), evening relative humidity (r = 0.202), wind speed (r = 0.427), bright sunshine hours (r = 0.328), evaporation (r = 0.344) and rainfall (r = 0.045) showed positive but non-significant correlations and during Summer 2024-25, the population dynamics showed a stronger relationship with weather parameters. The aphid population showed a significant positive correlation with maximum temperature (r = 0.585*), Conversely, a significant negative correlation was observed with evening relative humidity (r =-0.642*) while, minimum temperature (r =-0.067), morning relative humidity (r =-0.516), wind Speed (r =-0.237) and bright sunshine hours (r =-0.433) showed negative non-significant correlations while, evaporation (r = 0.324) showed a positive non-significant correlation. Pandey and Kosta (2017) [7] reported that aphid population had significant positive correlation with maximum temperature.

Conclusion

The overall results of the present study revealed that, pooled data on both the years in aphid's population was in the range of 0.10 to 12.33 aphids/three leaves/plant while, peak population was observed during 12 th SMW, jassid population was in the range of 0.40 to 17.08 jassids/three leaves/plant whereas, peak population was observed during 15 th SMW and whitefly population was in the ranges of 0.13 to 4.70 whiteflies/three leaves/plants whereas, peak population was observed during 12 th SMW. However, weather parameters play an important role in the incidence of sucking pest on okra crop. The population of jassid, aphid and whitefly were significantly positively influenced by the maximum and minimum temperature.

References

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