Appraisal of nut yield reduction in East Coast Tall (ECT) variety of coconut palms with exotic and invasive rugose spiraling whitefly (RSW) infestation @ low (<10 spirals per leaflet), medium (10 – 20 spirals per leaflet) and high (> 20 spirals per leaflet) incidence was studied out at two experimental locations viz., Horticultural Research Station (HRS), Ambajipeta and Kalavalapalli. The per cent (%) yield loss was estimated to be 6.61 and 22.45 per cent in ECT palms with low and medium RSW incidence, while comparatively greater yield loss of 27.59 per cent was recorded in palms with high incidence at HRS, Ambajipeta. Likewise, at Kalavalapalli village, the per cent (%) yield loss in ECT palms with low, medium and high RSW incidence was recorded to be 6.49, 25.65 and 30.38 per cent respectively. Further, declining trend of button setting was noticed for last 2 years (2019 to 2021) at HRS, Ambajipeta with 45.04 per cent during 2018 (highest before RSW infestation), while the least setting was recorded in the year 2021 with 28.39 per cent. The button setting during the years 2019 and 2020 was 33.41 and 31.19 per cent.
Research Article
Yield loss in coconut variety East Coast Tall (ECT) owing to rugose spiraling whitefly (RSW), Aleurodicus rugioperculetus M. infestation
https://doi.org/10.21203/rs.3.rs-2486144/v1
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Journal Publication
published 12 Jul, 2023
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Coconut
yield loss
button setting
East Coast Tall (ECT)
Coconut, Cocos nucifera L., belongs to family Arecaceae regarded as "Tree of Life", "Kalpavriksha" and “Tree of Abundance” providing livelihood to billions of people across the world (Ahuja et al. 2014). It is grown for oil, coconut meat, coconut water and raw ingredients for the coir industry. In India it is grown in 2.18 million ha area, with production and productivity of 21,206.74 million nuts and 9,687 nuts/ha in 2020-21 (Nair and Pramod, 2021). In the present scenario of climatic change this valuable palm is devastated by incidence of several pests and diseases that not only deteriorate the quality of nuts but also reduced the vigour and yield of palms (Chowdappa et al. 2018 and Neeraja et al. 2020).
In this modern era, damage of coconut palms can be identified with invasion of exotic insect pests, particularly whiteflies. Among different invasive whiteflies, rugose spiraling whitefly (RSW), Aleurodicus rugioperculetus Martin has been reported from India in Tamil Nadu (Sundararaj and Selvaraj, 2017) and Andhra Pradesh (Chalapathi Rao et al. 2018). The invasive RSW feeds and reproduces prolifically on under surface of coconut palm leaves and as a result secretes honey dew. This honeydew secretion facilitates the growth of sooty mould on leaves, which further degrades photosynthetic activity and vigour, resulting yield loss in coconut palms. Though literature pertaining to yield loss particulars in East Coast Tall (ECT) coconut palms due to RSW is meagre, the similar study by Kalidas (2019) in oil palm revealed that fresh fruit bunch (FFB) yield losses were in the range of 20 - 45 per cent in farmer’s fields at village level and 30 - 42 per cent at mandal levels after one year of the RSW incidence. Selvaraj et al. (2019) also reported that there was a reduction in bunch yield of oil palm by 20 – 25 per cent due to RSW infestation. Previous investigations of Chandrika et al. (2010) estimated nut yield reduction by 45.4 per cent from Opisinia arenosella W. infested coconut palms. Later in the year 2011, Rajan et al. reported that slug caterpillar (Macroplecta nararia M.) inflicts higher yield losses up to 90-95 per cent. Nut yield reduction must be estimated so as to plan realistically for research and development policies. As a result, the study was undertaken to evaluate yield loss in terms of nut production of ECT palms due to A. rugioperculatus infestation at different intensities.
Estimation of yield loss (%) in RSW infested East Coast Tall (ECT) variety
Estimation of yield loss (%) studies in RSW infested coconut palms of local East Coast Tall (ECT) variety (25 years and 20 years) under low (<10 spirals per leaflet), medium (10 – 20 spirals per leaflet) and high (> 20 spirals per leaflet) incidence were carried out at Horticultural Research Station (HRS), Ambajipeta (16°59’38” NL and 81°95’36” EL) and Kalavalapalli plantations (16°94’82” NL and 81°63’98” EL) of Andhra Pradesh, India. The data pertaining to number of harvested nuts per palm were recorded at monthly intervals during the year 2020-21 at HRS, Ambajipeta and Kalavalapalli village. Additional observations were also recorded on button setting (%) in ECT palms selected for hybridization at HRS, Ambajipeta only.
The impact of RSW infestation on nut yield of ECT palms was validated at HRS, Ambajipeta and Kalavalapalli. Fifteen different palms carrying developing nuts after fertilization i.e., three months and above from each cultivar were identified and marked by using simple random sampling technique method. The data was recorded on number of harvested nuts per palm at monthly intervals during the year 2020-21.
Number of harvested nuts per palm
Data on number of harvested nuts per palm was noted as and when harvesting was carried out meticulously in each of the five selected palms of local East Coast Tall (ECT) variety under varied RSW intensities. The data on harvested nut yield of five selected palms in local East Coast Tall (ECT) variety for preceding three years (2018-20) was also obtained from yield record registers maintained in the research station as to compare the yield and to calculate the yield loss (%) at HRS, Ambajipeta and Kalavalapalli villages by using the following formula.
Button setting (%) in coconut palms
The data on button setting (%) was collected in 15 selected and marked East Coast Tall (ECT) variety palms meant for hybridization in 7 different blocks at HRS, Ambajipeta for 4 consecutive years (2018 to 2021). The means are tabulated and finally expressed as mean button setting (%) per year.
Statistical analysis
The statistical analysis used to compare mean nut yield per palm during the year 2018 with 2019, 2020 and 2021 in ECT palms was paired t-test using SPSS 17.0 version pioneered by W. S. Gosset (1908) and later on developed and extended by Prof. R. A. Fisher.
An average nut yield of 121.00 nuts was recorded in 2018 and this was reduced by 6.61 per cent in the year 2021 in ECT palms with low incidence (< 10 spirals per leaflet) (Table 1). The results given in Table 2, depicted that there was a reduction in nut yield by 22.45 per cent with medium incidence (10–20 spirals per leaflet) in ECT palms, while comparatively higher yield loss of 27.59 per cent was observed in ECT palms with high RSW incidence (> 20 spirals per leaflet) at HRS, Ambajipeta (Table 3).
The per cent (%) yield loss was recorded to be comparatively less with 6.49 per cent in ECT palms with low RSW incidence (< 10 spirals per leaflet) (Table 4), whereas in medium (10–20 spirals per leaflet) and high incidence of RSW (> 20 spirals per leaflet) the nut yield reduction by 25.65 and 30.38 per cent respectively was noticed at Kalavalapalli (Tables 5 and 6).
The mean nut yield per palm differed significantly at HRS, Ambajipeta and Kalavapalli between the years 2018 and 2019 as per the paired t-statistical value (t cal = 6.78* and 7.71*) depicted in the Table 7. Similarly, the observations presented in Table 8 also reveal the significance in nut yield between 2018 and 2020 according to paired t-statistical value (t cal = 7.62* and 7.89*) at both of the experimental locations. The data in Table 9, also indicated that there is existence of significant difference mean nut yield per palm in the year 2018 to that of year 2021 as per the paired t-statistical value (t cal = 7.79* and 7.66*) at HRS, Ambajipeta and Kalavapalli coconut plantations.
| Palm number | Nut yield / palm | Yield loss (%) | |||
|---|---|---|---|---|---|
| Before RSW infestation | During RSW infestation | ||||
| 2018 | 2019 | 2020 | 2021 | ||
| 1 | 116 | 114 | 112 | 110 | 5.17 |
| 2 | 126 | 123 | 121 | 119 | 5.55 |
| 3 | 116 | 113 | 110 | 107 | 7.76 |
| 4 | 130 | 127 | 124 | 120 | 7.69 |
| 5 | 117 | 113 | 110 | 108 | 6.89 |
| Yield loss (%) due to RSW infestation | 6.61 ± 0.54 | ||||
| Palm number | Nut yield / palm | Yield loss (%) | |||
|---|---|---|---|---|---|
| Before RSW infestation | During RSW infestation | ||||
| 2018 | 2019 | 2020 | 2021 | ||
| 1 | 124 | 110 | 105 | 98 | 20.97 |
| 2 | 129 | 114 | 108 | 100 | 22.48 |
| 3 | 130 | 119 | 113 | 104 | 20.00 |
| 4 | 123 | 110 | 104 | 92 | 25.20 |
| 5 | 127 | 118 | 107 | 97 | 23.62 |
| Yield loss (%) due to RSW infestation | 22.45 ± 0.93 | ||||
| Palm number | Nut yield / palm | Yield loss (%) | |||
|---|---|---|---|---|---|
| Before RSW infestation | During RSW infestation | ||||
| 2018 | 2019 | 2020 | 2021 | ||
| 1 | 123 | 114 | 102 | 91 | 26.02 |
| 2 | 129 | 112 | 100 | 94 | 27.13 |
| 3 | 124 | 118 | 101 | 90 | 27.42 |
| 4 | 124 | 115 | 102 | 88 | 29.03 |
| 5 | 127 | 116 | 103 | 91 | 28.35 |
| Yield loss (%) due to RSW infestation | 27.59 ± 0.52 | ||||
| Palm number | Nut yield / palm | Yield loss (%) | |||
|---|---|---|---|---|---|
| Before RSW infestation | During RSW infestation | ||||
| 2018 | 2019 | 2020 | 2021 | ||
| 1 | 138 | 135 | 133 | 131 | 5.07 |
| 2 | 126 | 123 | 120 | 118 | 6.34 |
| 3 | 125 | 121 | 119 | 116 | 7.20 |
| 4 | 136 | 134 | 132 | 130 | 4.41 |
| 5 | 127 | 123 | 119 | 115 | 9.45 |
| Yield loss (%) due to RSW infestation | 6.49 ± 0.88 | ||||
| Palm number | Nut yield / palm | Yield loss (%) | |||
|---|---|---|---|---|---|
| Before RSW infestation | During RSW infestation | ||||
| 2018 | 2019 | 2020 | 2021 | ||
| 1 | 113 | 106 | 94 | 82 | 27.43 |
| 2 | 118 | 110 | 101 | 88 | 25.42 |
| 3 | 121 | 112 | 102 | 92 | 23.97 |
| 4 | 125 | 114 | 103 | 94 | 24.80 |
| 5 | 124 | 112 | 104 | 91 | 26.61 |
| Yield loss (%) due to RSW infestation | 25.65 ± 0.62 | ||||
| Palm number | Nut yield / palm | Yield loss (%) | |||
|---|---|---|---|---|---|
| Before RSW infestation | During RSW infestation | ||||
| 2018 | 2019 | 2020 | 2021 | ||
| 1 | 127 | 118 | 109 | 87 | 31.49 |
| 2 | 123 | 119 | 112 | 85 | 30.89 |
| 3 | 124 | 115 | 107 | 88 | 29.03 |
| 4 | 106 | 102 | 93 | 76 | 28.30 |
| 5 | 115 | 105 | 90 | 78 | 32.17 |
| Yield loss (%) due to RSW infestation | 30.38 ± 0.74 | ||||
| Years | Mean nut yield at HRS, Ambajipeta | Mean nut yield at Kalavalapalli |
|---|---|---|
| 2018 (Before RSW infestation) | 124.33 ± 1.24 | 123.20 ± 2.10 |
| 2019 (After RSW infestation) | 115.73 ± 1.11 | 116.60 ± 2.49 |
| t cal. value | 6.78* | 7.71* |
| t tab. value | 1.76 | |
| P value (P > 0.05) | 2.14 | |
| Years | Mean nut yield at HRS, Ambajipeta | Mean nut yield at Kalavalapalli |
|---|---|---|
| 2018 (Before RSW infestation) | 124.33 ± 1.24 | 123.20 ± 2.10 |
| 2020 (After RSW infestation) | 108.13 ± 1.84 | 109.20 ± 3.42 |
| t cal. value | 7.62* | 7.89* |
| t tab. value | 1.76 | |
| P value (P > 0.05) | 2.14 | |
| Years | Mean nut yield at HRS, Ambajipeta | Mean nut yield at Kalavalapalli |
|---|---|---|
| 2018 (Before RSW infestation) | 124.33 ± 1.24 | 123.20 ± 2.10 |
| 2021 (After RSW infestation) | 100.60 ± 2.68 | 98.07 ± 4.81 |
| t cal. value | 7.79* | 7.66* |
| t tab. value | 1.76 | |
| P value (P > 0.05) | 2.14 | |
The reduction in harvested nut yield was least in ECT palms with low RSW incidence in comparison to that of medium and high incidence ECT palms. The RSW incidence was ascertained initially on ECT palms in the year 2018 and its continuous incidence all through the years up to 2021 resulted in significant nut yield reduction at HRS, Ambajipeta and Kalavalapalli.
Despite of literature unavailability on yield loss studies in coconut palms in relation to RSW infestation at different intensities, similar study conducted by Kalidas (2019) in oil palm revealed that fresh fruit bunch (FFB) yield losses was in the range of 20–45 per cent in farmer’s fields at village level and 30–42 per cent at mandal levels after one year of the RSW incidence. In the same year, Selvaraj et al. also estimated bunch yield reduction of oil palm by 20–25 per cent due to RSW infestation.
The yield loss (%) was recorded to be high in Kalavalapalli plantations than that of HRS, Ambajipeta as the pest intensity at Kalavalapalli was high which could be due to presence of highly suitable multi cropping system of coconut and oil palm plantation in which both the host crops being highly attractive to RSW. Similar observations on combined high incidence of RSW on coconut and oil palm in West Godavari district was also reported by Kalidas, 2019.
The current yield loss estimation studies are contrary to Chandrika et al. (2017) and Subramanian et al. (2018) who reported that heavy RSW incidence may not result any economic crop loss in coconut. However, in the present study it was observed that only under low incidence of RSW there may not be any economic crop loss in coconut. The yield loss studies undertaken in coconut due to various insect pests are deliberated to substantiate the present findings. Taylor (1937) recorded the mean reduction in coconut production by 50 per cent with Fiji coconut hispid, Promecotheca coeruleipennis infestation. Voegele (1989) estimated 50–70 per cent nut yield loss due to the coconut hispid beetle, Brontispa longissima at Samoa. Perera (1993) reported 40 per cent damage to the coconut leaves during O. arenosella outbreak.
Studies of Chandrika et al. (2010) recorded yield loss of 45.4 per cent from O. arenosella infested coconut palms in the succeeding year of severe pest incidence. In the year 2011, Rajan et al. reported that slug caterpillar (Macroplecta nararia) inflicts higher yield losses (90–95 per cent) of coconut palms in severely infested gardens. Subramanian et al. (2018) reported that red palm weevil (RPW) causing loss to an extent of 1–3 per cent in young coconut plantations.
RSW infestation on button setting (%) in ECT palms meant for hybridization
The mean button setting (%) was calculated from seven different blocks replicated with 15 hybridized ECT palms per each block at HRS, Ambajipeta for four consecutive years (2018 to 2021). The results in the Table 10 and Fig. 1 revealed that a declining trend of setting was noticed for the last two years (2019 to 2021). There was 45.04 per cent during 2018 (highest before RSW infestation), while the least setting was recorded in the year 2021 with 28.39 per cent. The button setting during the year 2019 and 2020 was 33.41 and 31.19 per cent respectively.
The mean button setting (%) in ECT hybridization palms was calculated and tabulated at HRS, Ambajipeta for four consecutive years (2018 to 2021). During 2018, there was a 45.04 per cent setting (before RSW infestation) which is in agreement with Niral et al. 2009 contrarily a low setting of only 28.39 per cent was recorded in the year 2021 (Table 10). The button setting during the years 2019 and 2020 was also on a lower scale i.e., 33.41 and 31.19 per cent respectively and can be attributed to RSW infestation alone as all these palms are under standard package of practices.
| Years | Before RSW infestation | During RSW infestation | ||
|---|---|---|---|---|
| 2018 | 2019 | 2020 | 2021 | |
| Block - I | 37.99 | 26.22 | 23.36 | 22.41 |
| Block - II | 49.09 | 27.77 | 26.42 | 25.84 |
| Block - III | 43.80 | 31.45 | 29.69 | 32.50 |
| Block - IV | 45.25 | 37.54 | 33.45 | 29.84 |
| Block - V | 44.50 | 36.90 | 33.90 | 30.50 |
| Block - VI | 48.33 | 35.76 | 32.50 | 33.19 |
| Block – VII | 46.35 | 38.25 | 27.16 | 24.47 |
| Mean ± S.E | 45.04 ± 1.38 | 33.41 ± 1.86 | 31.19 ± 2.05 | 28.39 ± 1.57 |
| Range | 11.10 | 12.03 | 6.74 | 10.78 |
The study revealed that yield loss (%) was minimal in RSW infested ECT palms with low incidence (< 10 spirals per leaflet) (6.61 and 6.49 per cent), whereas greater loss was estimated in palms with those of medium (10 – 20 spirals per leaflet) (22.45 and 25.65 per cent) and high RSW incidence (> 20 spirals per leaflet) (27.59 and 30.38 per cent) at both experimental locations. There was a highest button setting per cent in ECT hybridized palms during 2018 (before RSW infestation), while the least setting was recorded in the year 2021 (after RSW infestation). The declining trend of button setting was noticed for last 2 years (2019 to 2021) at HRS, Ambajipeta.
RSW: Rugose spiraling whitefly; ECT: East Coast Tall; FFB: Fresh Fruit Bunches; HRS: Horticultural Research Station, DRYSRHU: Dr. Y.S.R. Horticultural University, RPW: Red Palm Weevil
Acknowledgements The author would like to express deepest gratitude to scientific and non-scientific staff of Horticultural Research Station (HRS), Ambajipeta for providing all necessary facilities during this investigation.
Author’s contribution The experiments were conducted and undertaken by PVRT at both of experimental locations. NBVCR was the chairman and participated in monitoring of experiment and refining the manuscript. EP and AK also reviewed the manuscript. KU extended all possible help for statistical designing of experiment. All the authors read and approved the manuscript.
Competing interests On behalf of all authors, the corresponding author states that there is no conflict of interest.
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No competing interests reported.