Influence of silicon and growth regulator on leaf, whorl and cob damage of maize fall armyworm in vivo

doi:10.21203/rs.3.rs-2693103/v1

Microplot field experiment was conducted to study the effect of silicon sources and growth regulator against maize fall armyworm, Spodoptera frugiperda at Thoppur village of Virudhunagar district during Rabi, 2021-22. Basal application of different doses of calcium silicate and foliar application of silicic acid and potassium silicate were carried out. The results revealed that basal application of 150 kg of calcium silicate/ha + 0.2% silicic acid @ 15 DAS + 50 ppm GA @ 30 DAS was found to be effective in reducing leaf damage (42.88% per plant), whorl damage (36.05% per plot ) and cob damage (26.92% per plot) followed by treatment with 75 kg of calcium silicate/ha + 0.2% silicic acid @ 15 DAS + 50 ppm GA @ 30 DAS with leaf, whorl and cob damage of 44.74 per cent/plant, 39.24 per cent/plot and 26.92 per cent/plot respectively. Regarding yield, maximum yield of 7, 287 kgs/ha was recorded in the treatment with basal application of 150 kg of calcium silicate/ha + 0.2% SA @ 15 DAS + 50 ppm GA @ 30 DAS followed by treatment with 75 kg of calcium silicate + 0.2% SA @ 15 DAS + 50 ppm GA @ 30 DAS (7, 092 kg/ha). Hence in the present study, the basal application of calcium silicate 150 kg/ha combined with foliar application of silicic acid (0.2%) and gibberellic acid (50 ppm) at 15 and 30 DAS reduced the leaf, whorl and cob damage level of fall armyworm on maize at field condition.

Spodoptera frugiperda

silicon

gibberellic acid

leaf

whorl and cob damage

Maize (Zea mays L.) is the most important cereal crop being cultivated in an area of 180.63 m ha in 165 countries across the world with a production of 1,134 million tonnes [1]. Fall armyworm, Spodoptera frugiperda (J E Smith) is emerging as the most destructive pest of maize in India since its report during May 2018. Fall armyworm is predicted to cause 21 to 53 per cent loss in annual maize production in the absence of control measures [2]. Farmers solely rely on synthetic insecticides for the management which aggravates residue, resistance and resurgence problems. Various eco-friendly management strategies need to be developed for its management. One of the areas which could be employed for fall armyworm management in India is induced host plant resistance approach.

Insect pest damage can be reduced through the proper management of nutrient requirements of the crop and modification with the availability of mineral nutrients such as silicon. Silicon confers induced resistance to herbivores via three descried mechanisms viz., biophysical, biochemical and Herbivore induced plant volatiles (HIPVs) [3]. Reduction in digestibility and increase in hardness and roughness of plant tissue have been observed because of deposition of silica as opaline phytoliths in numerous tissues [4]. Si induced defense mechanism also includes alternations in the trichome [5].

Many farmers are not aware of the role of silicon for better crops with increased insect stress and improved resistance. Silicon (Si) is recognized as an agronomically essential element for sustainable crop production [5]. Therefore, exogenous application of silicon in silicon depleted agricultural land provides a viable component of integrated management of insect pests and also it leaves no residues in food or the environment and it can be easily integrated with other pest management practices, including biological control.

Microplot field experiment was conducted at Thoppur village, Kariyapatti block, Viruthunagar district. To evaluate the effects of foliar application of silicon fertilizers and growth regulators on FAW. The experiment was laid out in a Randomized block design with three replications and sixteen treatment combinations with spacing of 60 \(\times\) 25 cm and plot size of 60 m². The treatments comprised of T₁- Soil application of calcium silicate @ 150 kg/ ha, T₂ - Soil application of calcium silicate @ 300 kg/ ha, T₃- ½ dose of T₁ + 0.2 silicic acid (SA) @ 15 DAS + 50 ppm gibberellic acid (GA₃) @ 30 DAS, T₄- ½ dose of T₂ + 0.2 SA @ 15 DAS + 50 ppm GA @ 30 DAS, T₅- ¼ dose of T₁ + 0.4 SA @ 15 DAS + 100 ppm GA @ 30 DAS, T₆- ¼ dose of T₂ + 0.4 SA @ 15 DAS + 100 ppm GA @ 30 DAS, T₇- ½ dose of T₁ + 0.5 potassium silicate @ 15 and 30 DAS, T₈- ½ dose of T₂ + 1 potassium silicate @ 15 and 30 DAS, T₉- ¼ dose of T₁ + 0.5 potassium silicate @ 15 & 30 DAS, T₁₀- ¼ dose of T₂ + 1 potassium silicate @ 15 & 30 DAS, T₁₁-Foliar spray 0.2 SA @ 15 and 45 DAS + 50 ppm GA @ 30 and 60 DAS, T₁₂ - Foliar spray 0.4 SA @ 15 and 45 DAS + 100 ppm GA @ 30 and 60 DAS, T₁₃ - Foliar spray 0.5 potassium silicate @ 15, 30, 45 and 60 DAS, T₁₄ - Foliar spray 1 potassium silicate @ 15, 30, 45 and 60 DAS, T₁₅ - Standard check (Neem cake 250 kg/ha and need based application of insecticide) and T₁₆- Untreated check. Foliar spray was done at 15, 30, 45 and 60 days after sowing. All foliar sprays were applied by a 10 L volume knapsack sprayer. Foliar application of silicic acid and potassium silicate was done at 15 and 30 DAS and gibberellic acid at 45 and 60 DAS. For the cultivation of maize, all of the agronomical practices recommended by the crop production guide were followed (CPG, 2021). In all plots except the untreated control, silicon nutrients were foliar sprayed at their respective doses. FAW leaf damage (%) = No. of FAW damaged leaves/total number of leaves × 100. Whorl damage (%) = No. of FAW larva damaged whorl/total no. of whorls× 100, Cob damage (%) = No. of FAW larva damaged cob/total no. of cobs × 100. The count was taken from ten randomly selected plants per all the treatments in each plot.

2.1 Statistical analysis

Data collected in the microplot field experiment were statistically analyzed. The data on leaf, whorl and cob damage per cent were subjected to arc sign transformation and yield data was subjected to square root transformation and analyzed by SPSS (version 22) (IBM Corp Released in 2013) software to identify the most effective treatments and means were compared with Tukey’s test at p < 0.05 [6].

3.1 Leaf damage per cent

After first spray (15 days after sowing), the mean leaf damage per cent/plant ranged from 37.30 to 62.26 among the treatments. The treatment with basal application of 150 kg of calcium silicate/ha + 0.2% SA @ 15 DAS + 50 ppm GA @ 30 DAS (T₄) was found to be significantly superior over other treatments with minimum mean leaf damage per cent of 37.3/plant followed by 75 kg of calcium silicate + 0.2% SA @ 15 DAS + 50 ppm GA @ 30 DAS (T₃) (39.11/plant). The treatment with ¼ dose of T₂ + 1% potassium silicate @ 15 & 30 DAS (T₁₀) (51.7% /plant) was on par with ¼ dose of T₁ + 0.5% potassium silicate @ 15 & 30 DAS (T₉) (52.85% /plant). The treatment with foliar spray of 0.4% SA @ 15 & 45 DAS + 100 ppm GA @ 30 & 60 DAS (T₁₂) (53.66% /plant) was on par with foliar spray of 0.2% SA @ 15 & 45 DAS + 50 ppm GA @ 30 & 60 DAS (T₁₁) (55.77%/plant). The treatment with foliar spray of 1% potassium silicate @ 15, 30, 45 & 60 DAS (T₁₄) (56.98% /plant) followed by foliar spray of 0.5% potassium silicate @ 15, 30, 45 & 60 DAS (T₁₃) (58.11 per cent/plant). Soil application of calcium silicate @ 300 kg/ ha (T₂) recorded mean leaf damage per cent of 53.10/plant followed by soil application of calcium silicate @ 150 kg/ ha (57.23% /plant). The mean leaf damage per cent recorded in untreated check (T₁₆) was 62.26 /plant (Table.1).

After second spray (30 days after sowing), the results revealed that the treatment ½ dose of T₂ + 0.2% SA @ 15 DAS + 50 ppm GA @ 30 DAS (T₄) was found to be effective in reducing leaf damage per cent/plant (42.88) as against (74.41% /plant) in the untreated check (T₁₆).

After third spray (45 days after sowing), the treatment with ½ dose of T₂ + 0.2% SA @ 15 DAS + 50 ppm GA @ 30 DAS (T₄) was found to be most effective and significantly superior over all other treatments by recording lowest mean leaf damage per cent of 33.20/plant followed by the treatment with ½ dose of T₁ + 0.2% SA @ 15 DAS + 50 ppm GA @ 30 DAS (T₃) (35.56% /plant). Application of¼ dose of T₂ + 0.4% SA @ 15 DAS + 100 ppm GA @ 30 DAS (T₆) (38.04% /plant) was on par with¼ dose of T₁ + 0.4% SA @ 15 DAS + 100 ppm GA @ 30 DAS (T₅) (40.69% /plant). The application of ½ dose of T₂ + 1% potassium silicate @ 15 & 30 DAS (T₈) (41.49% /plant) was significantly inferior among treatments but performed better over untreated check (T₁₆) (67.02% /plant).

After fourth spray (60 days after sowing), the mean leaf damage per cent/plant ranged from 26.85 to 60.19 in all the treatments. The lowest mean leaf damage per cent/plant was recorded in ½ dose of T₂ + 0.2% SA @ 15 DAS + 50 ppm GA @ 30 DAS (T₄) (26.85% /plant) while highest in untreated check (T₁₆) (60.19 leaf damage per cent/plant). The next best treatment was ½ dose of T₁ + 0.2% SA @ 15 DAS + 50 ppm GA @ 30 DAS (T₃) (30.19 leaf damage per cent/plant). Application of¼ dose of T₂ + 0.4% SA @ 15 DAS + 100 ppm GA @ 30 DAS (T₆) (33.42 leaf damage per cent /plant) followed by ¼ dose of T₁ + 0.4% SA @ 15 DAS + 100 ppm GA @ 30 DAS (T₅) (36.19 leaf damage per cent/plant).

3.2 Whorl damage per cent

After first spray (15 days after sowing), the mean whorl damage per cent/plot ranged from 31.21 to 80.69 among the treatments. The treatment with basal application of 150 kg of calcium silicate/ ha + 0.2% SA @ 15 DAS + 50 ppm GA @ 30 DAS (T₄) was found to be significantly superior over other treatments with minimum mean whorl damage per cent of 31.21 /plot followed by 75 kg of calcium silicate + 0.2% SA @ 15 DAS + 50 ppm GA @ 30 DAS (T₃) (35.57%). The treatment with ¼ dose of T₂ + 1% potassium silicate @ 15 & 30 DAS (T₁₀) recorded 55.16 per cent of whorl damage/plot followed by ¼ dose of T₁ + 0.5% potassium silicate @ 15 & 30 DAS (T₉) (57.46%). The treatment with foliar spray of 0.4% SA @ 15 & 45 DAS + 100 ppm GA @ 30 & 60 DAS (T₁₂) recorded 59.91 per cent of whorl damage/plot followed by foliar spray of 0.2% SA @ 15 & 45 DAS + 50 ppm GA @ 30 & 60 DAS (T₁₁) (63.37%). The treatment with foliar spray of 1% potassium silicate @ 15, 30, 45 & 60 DAS (T₁₄) recorded 65.72 per cent of whorl damage/plot followed by foliar spray of 0.5% potassium silicate @ 15, 30, 45 & 60 DAS (T₁₃) with 70.84 per cent of whorl damage/plot. Soil application of calcium silicate @ 300 kg/ ha (T₂) recorded mean whorl damage per cent of 61.69 per cent of whorl damage/plot followed by soil application of calcium silicate @ 150 kg/ ha (71.94%). The mean per cent whorl damage/plot recorded in the untreated check (T₁₆) was 80.69 /plot (Table.2).

After second spray (30 days after sowing), the results revealed that the treatment ½ dose of T₂ + 0.2% SA @ 15 DAS + 50 ppm GA @ 30 DAS (T₄) was found to be effective in reducing whorl damage per cent/plot (36.05%) as against (82.63 per cent of whorl damage/plot) in the untreated check (T₁₆).

3.3 Cob damage per cent

After third spray (45 days after sowing), the treatment with basal application of 150 kg of calcium silicate/ ha + 0.2% SA @ 15 DAS + 50 ppm GA @ 30 DAS (T₄) was found to be most effective and significantly superior over all other treatments by recording lowest mean cob damage per cent/plot of (26.92%) followed by the treatment with ½ dose of T₁ + 0.2% SA @ 15 DAS + 50 ppm GA @ 30 DAS (T₃) (32.03%). Application of T₂ + 0.4% SA @ 15 DAS + 100 ppm GA @ 30 DAS (T₆) recorded 36.97 per cent of cob damage /plot followed by ¼ dose of T₁ + 0.4% SA @ 15 DAS + 100 ppm GA @ 30 DAS (T₅) (41.55%). The mean cob damage per cent/plot recorded in the untreated check (T₁₆) was 73.00.(Table 2).

After fourth spray (60 days after sowing), the mean per cent of cob damage /plant ranged from 19.45 to 51.56 in all the treatments. The lowest mean per cent of cob damage was recorded in ½ dose of T₂ + 0.2% SA @ 15 DAS + 50 ppm GA @ 30 DAS (T₄) (19.45%) while highest in untreated check (T₁₆) (51.56%). The next best treatment was ¼ dose of T₂ + 0.4% SA @ 15 DAS + 100 ppm GA @ 30 DAS (T₆) (25.37%) followed by ¼ dose of T₁ + 0.4% SA @ 15 DAS + 100 ppm GA @ 30 DAS (T₅) (28.77%). The mean cob damage per cent/plot recorded in the untreated check (T₁₆) was 51.56.

3.4 Yield and BC ratio

The maize grain yield recorded was significantly different among various treatments. It was significantly high the in treatment with basal application of 150 kg of calcium silicate/ha + 0.2% SA @ 15 DAS + 50 ppm GA @ 30 DAS (7, 287 kg/ha) followed by 75 kg of calcium silicate + 0.2% SA @ 15 DAS + 50 ppm GA @ 30 DAS (7, 092 kg/ha) and 75 kg of calcium silicate + 0.4% SA @ 15 DAS + 100 ppm GA @ 30 DAS (6, 928 kg/ha). The yield recorded in the untreated check was (4, 104 kg/ha). While considering benefit cost ratio, the highest BC ratio was observed in basal application of 75 kg of calcium silicate + 0.2% SA @ 15 DAS + 50 ppm GA @ 30 DAS (2.70) followed by the treatment with ½ dose of T₂ + 0.2% SA @ 15 DAS + 50 ppm GA @ 30 DAS (2.64). (Table.3).

The results of microplot field experiment revealed that the per cent leaf, whorl and cob damage of fall armyworm was significantly less in plants treated with silicon sources and growth regulator compared to untreated check (Fig. 1). Basal application of 150 kg of calcium silicate/ha + 0.2% SA @ 15 DAS + 50 ppm GA @ 30 DAS (T₄) followed by the treatment with 75 kg of calcium silicate/ha + 0.2% SA @ 15 DAS + 50 ppm GA @ 30 DAS (T₃) were found effective in reducing leaf damage 42.88 per cent /plot followed by treatment with 75 kg of calcium silicate/ha + 0.2% silicic acid @ 15 DAS + 50 ppm GA @ 30 DAS (44.74 per cent/plant). Basal application of 150 kg of calcium silicate/ha + 0.2% silicic acid @ 15 DAS + 50 ppm GA @ 30 DAS was found to be effective in reducing whorl damage 36.05 per cent /plot followed by treatment with 75 kg of calcium silicate/ha + 0.2% silicic acid @ 15 DAS + 50 ppm GA @ 30 DAS (39.24 per cent/plot) in maize field condition (Fig. 2). This work was confirmed by Liu et al. [7] who found that maize crops treated with silica significantly showed negative impact of Si on immature stages of Spodoptera frugiperda. Hence, Si application may diminished S. frugiperda colonization and initial damage in maize due to decreased fecundity and significantly increased the mortality of newly emerging larvae.

The present study is in line with findings of Jeer et al. [8] who showed that stem borer damage was significantly reduced (66% over control) in wheat plots treated with K and Si when compared with untreated control (T₁) and insecticidal check (T₆). Both, K and Si treated plots recorded lower pink stem borer damage than control, while soil applied Si had significant influence in reducing plant stem borer damage. Similar study was carried out by Nagaratna et al. [9] who observed a substantial effect of Si and plant growth regulators on larval survival, with the foliar Si application and gibberellic acid resulting in the lowest (70%) larval survival. Perdomo et al. [10] reported that soil fertilization with Si increased Si leaf or stock content in maize and promoted plant resistance against attack by FAW under field conditions. Si doses from 600 to 1,200 kg∙ha-1 reduced FAW defoliation without affecting maize yield. Ganapathy et al. [11] confirmed that highest per cent reduction of pod borer of green gram in potassium silicate @ 0.5% + gibberellic acid @ 50 ppm (54.87%) followed by potassium silicate @ 1% + gibberellic acid @ 100 ppm (51.79%) and silicic acid @ 0.2% + gibberellic acid @ 100 ppm (49.35%). Similarly, NuamboteYobila et al. [12] revealed that Si treated plants disturbed the larval growth of FAW larvae only from the corn strain but not from the rice strain. Tarikul Islam et al. [13] reported that the lower integument resistance of larvae when fed on Si supplemented plants could contribute to their vulnerability to natural enemies and high polyphenol oxidase activity in the haemolymph led to delayed development.

There is increasing evidence that Si treatment alters the accumulation of various defensive compounds, including phytoalexins, phenolics and chlorogenic acid [14,15]. Silicon applications significantly decreased the population of immature whiteflies and tomato leaf miner on tomato crop in the greenhouse; Si-foliar spraying was more effective in reducing the population density of these key pests compared to Si- soil drench application [16]. Similar confirmatory results were obtained by Pereira et al. [17] who demonstrated the larval mortality of S. frugiperda on Si supplemented plants. After 48 h of being fed, they observed that larval mortality was about six times higher on plants receiving Si applications than plants with no Si. Nagaratna et al. [9] observed various biological parameters of S. frugiperda such as larval weight and larval survival were negatively impacted by Si application. Si supplementation to the soil increases absorption by plants and the subsequent ability of plants to resist infestation with chewing insects [18]. Nikpay and Laane [19] found that the effectiveness of silicic acid treatment on the damage of yellow mite of two commercial of sugarcane varieties. Application of calcium silicate @ 1000 kg/ha reduced the incidence of sucking pests and lepidopteran borers of sugarcane [5]. Hall et al. [20] indicated that Si acted as a direct defensive mechanism against herbivores having chewing mouth part through enhancing the mechanical plant resistances.

Interestingly, the larval mortality of true armyworm Pseudaletia unipuncta was increased when allowed to feed maize leaves treated with silicon compared with leaves without silicon [21]. Jeer et al. [22] observed lower damage from the caterpillar Scirpophaga incertulas (Walker) in vegetative and reproductive stages of rice plants fertilized with Si. Moreover, caterpillar mandibles that were collected from Si-fertilized plants were damaged and the gut mesentery of these insects showed ruptured perithrophic membranes. Alvarenga et al. [23] revealed that gibberellic acid can alter the vegetative characteristics and silicon uptake of corn plants, leading to a reduction in the consumption by S. frugiperda larvae and a decrease the oviposition.

Moreover, Melo et al. [24] revealed that foliar application of 1% silicic acid solution (SiO₂. xH₂O) reduced the numbers of whitefly eggs and nymphs in chrysanthemum plants. Arivuselvi [25] confirmed that the incidence stem borer, Scirpophaga incertulas damage was significantly less in the basal application of calcium silicate 2 t/ha with foliar spray of 1% sodium metasilicate sprayed during the critical stages of rice crop. According to Swedhapriya [26] the basal application of calcium silicate 200 kg/ha with foliar spray of 0.25% sodium metasilicate significantly reduced the damage incidence of stem borer and leaf folder in rice. This is again in consonance with the findings of Santos et al. [4] who found that T. absoluta reared on tomato plants accumulating silicon showed decrease in larvae and pupae survival and male and female weight. Reduced fecundity in Bactrocera cucurbitae (Coquillett) and S. frugiperda, when fed on plants treated with gibberellic acid [27, 28].

Basal application of calcium silicate 150 kg/ha combined with foliar application of silicic acid 0.2% at 15 DAS + gibberellic acid 50 ppm at 30 DAS reduced larval damages on leaf, whorl and cob and maintained a low per cent of damage level. In organic farming, the use of silicon-based products opens a new gate in the era of Integrated Pest Management (IPM) and growth regulator like various analogues of gibberellic acid is widely accepted. Therefore, exogenous application of silicon and growth regulator is considered an ecofriendly strategy as the population of maize fall armyworm was reduced to a greater extent without having residues.

Acknowledgements All authors are thankful to Agriculture College and Research Institute, Madurai. Tamil Nadu Agricultural University, India for the facilities provided to carry out the research and also thankful to Mr. Solaikumar for his assistance in the microplot field trial experiment.

Author Contributions Chinnadurai Srinivasan formulated the research project and with the help of Chandramani Periyakaman, Shanthi Mookiah, Mahendran Peyandi Paraman, Renuka Raman and Nalini Ramiah field experiments and written this article. All authors have read and approved the research article.

Funding Not applicable.

Data Availability and materials All relevant data and materials are within the research paper.

Ethics approval Not applicable.

Consent to Participate All authors were highly cooperative and involved in research activities and preparation of this article.

Consent for Publication All authors agreed to publish this research article.

Conflict of Interest The authors have declared that no competing interests exist.

Competing interests The authors declare that they have no competing of interest.

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Table 1 and 2 are available in the Supplementary Files section.

Table 3. Impact of silicon and growth regulator on the yield in maize

Treatments	Yield (Kgs/ha)	BC ratio


T₁	5002 (70.72)^ij	1.91
T₂	5158 (71.81)^ij	1.80
T₃	7092 (84.21)^ab	2.70
T₄	7287 (85.36)^a	2.64
T₅	6906 (83.10)^abc	2.55
T₆	6928 (83.23)^abc	2.50
T₇	6383 (79.89)^de	2.62
T₈	6698 (81.83)^bcd	2.60
T₉	6314 (79.46)^def	2.58
T₁₀	6534 (80.83)^cde	2.57
T₁₁	5935 (77.04)^fg	2.24
T₁₂	6097 (78.08)^efg	2.08
T₁₃	5322 (72.95)^hi	2.20
T₁₄	5714 (75.59)^gh	2.31
T₁₅	4908 (70.06)^j	2.05
T₁₆	4104 (64.06)^k	1.74
SE	0.758	-
P	0.000	-

* Mean values of three replications as mean ± standard deviation; Figures in the parentheses are square root transformed values; means followed by the same alphabets are not significantly different from each other, Tukey’s test (p ≤ 0.05); SEd: Standard Error of difference.

No competing interests reported.

Influence of silicon and growth regulator on leaf, whorl and cob damage of maize fall armyworm in vivo

Status:

Journal Publication

Version 1

Abstract

Figures

1 Introduction

2 Material And Methods

2.1 Statistical analysis

3 Results

3.1 Leaf damage per cent

3.2 Whorl damage per cent

3.3 Cob damage per cent

3.4 Yield and BC ratio

4 Discussion

5 Conclusion

Declarations

References

Tables

Additional Declarations

Supplementary Files

Status:

Journal Publication

Version 1