Effect of soil-applied silicon on the development, survival, and reproduction of Alabama argillacea (Lepidoptera: Noctuidae)

Efeito do silício aplicado ao solo no desenvolvimento, sobrevivência e reprodução de Alabama argillacea (Lepidoptera: Noctuidae)

Abstract

The cotton leafworm, Alabama argillacea (Hübner, 1818) (Lepidoptera: Noctuidae), is a major defoliating pest of cotton. Although Bt cotton technologies currently available in Brazil effectively control this species, it remains an important pest in structured refuge areas, organic production systems, and colored-fiber cotton crops, where alternative management strategies are required. This study evaluated the effects of silicon (Si) fertilization on the development, survival, and reproduction of A. argillacea. The experiment was conducted under greenhouse and laboratory conditions using cotton plants grown without Si or fertilized with 150 (300 kg ha⁻¹) or 300 mg Si kg⁻¹ soil (600 kg ha⁻¹). Silicon accumulated in cotton leaves in a dose-dependent manner, significantly impairing insect performance. Larval survival declined from 89.6% in the control to 10.4% at the highest Si dose, and no larvae completed pupation under this treatment. The intermediate Si dose reduced pupal weight, increased the proportion of males in the offspring, and decreased fecundity and egg viability. These results demonstrate that soil-applied Si enhances cotton resistance to A. argillacea by reducing its survival, development, and reproductive potential, supporting its use as a sustainable component of integrated pest management.

Keywords:
Gossypium hirsutum; cotton leafworm; Si-induced resistance; plant nutrition; pest control; integrated pest management

Resumo

O curuquerê-do-algodoeiro, Alabama argillacea (Hübner, 1818) (Lepidoptera: Noctuidae), é uma importante praga desfolhadora da cultura do algodão. Embora as tecnologias Bt atualmente disponíveis no Brasil controlem essa espécie de forma eficiente, ela continua sendo uma praga relevante em áreas de refúgio estruturado, sistemas de produção orgânica e cultivos de algodão de fibra colorida, nos quais são necessárias estratégias alternativas de manejo. Este estudo avaliou os efeitos da adubação com silício (Si) sobre o desenvolvimento, a sobrevivência e a reprodução de A. argillacea. O experimento foi conduzido em casa de vegetação e laboratório utilizando plantas de algodoeiro cultivadas sem Si ou fertilizadas com 150 (300 kg ha⁻¹) ou 300 mg Si kg⁻¹ de solo (600 kg ha⁻¹). O silício acumulou-se nas folhas de algodoeiro de forma dependente da dose, comprometendo significativamente o desempenho do inseto. A sobrevivência larval foi reduzida de 89,6% na testemunha para 10,4% na maior dose de Si, e nenhuma lagarta completou a pupação nesse tratamento. A dose intermediária de Si reduziu o peso das pupas, aumentou a proporção de machos na progênie e diminuiu a fecundidade e a viabilidade dos ovos. Esses resultados demonstram que a aplicação de Si ao solo aumenta a resistência do algodoeiro a A. argillacea, reduzindo sua sobrevivência, desenvolvimento e potencial reprodutivo, e reforçam o uso desse elemento como um componente sustentável do manejo integrado de pragas.

Palavras-chave:
Gossypium hirsutum; lagarta desfolhadora; resistência induzida por Si; nutrição de plantas; controle de pragas; manejo integrado de pragas

1. Introduction

Defoliating Lepidoptera, notably the cotton leafworm Alabama argillacea (Hübner, 1818) (Lepidoptera: Noctuidae) because of its high feeding capacity and reproductive potential (Ramalho et al., 2014, 2017; Santos et al., 2021) and reaching high population densities, reduce photosynthesis and productivity of cotton plants (Gossypium hirsutum L.) (Sharma et al., 2022).

Alabama argillacea infests cotton plants from their initial to mature stages (Nascimento et al., 2011; Ramalho et al., 2014, 2017). The widespread adoption of Bt cotton cultivars has reduced the economic importance of A. argillacea in the major cotton-producing regions of the Brazilian Cerrado. Nevertheless, this pest remains relevant in production systems that do not rely on Bt technology, including organic and agroecological farming and structured refuge areas, reinforcing the need for complementary management strategies such as silicon (Si)-induced resistance within integrated pest management programs (Perdomo et al., 2022; Santos et al., 2021).

Silicon (Si) enhances plant resistance to herbivorous insects by strengthening cell walls, increasing leaf toughness, and activating biochemical defense pathways. These responses reduce leaf palatability and stimulate the accumulation of defensive secondary metabolites, such as phenolic compounds and flavonoids, thereby impairing insect feeding and development. Such effects have been reported for Acheta domesticus (Linnaeus) (Orthoptera: Gryllidae) (Hall et al., 2020) and Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) (Islam et al., 2023), while Si-mediated resistance has also reduced damage caused by the cotton leafworm A. argillacea (Perdomo et al., 2022), decreasing the need for chemical insecticide applications.

Previous studies have shown that foliar silicon application adversely affected the biological performance of A. argillacea, reducing the larval period from 8.46 to 7.97 days (5.8%) and pupal weight from 0.2317 to 0.2000 g (13.7%), while increasing the pupal period from 6.37 to 6.83 days (7.2%) (Tomquelski et al., 2007). These findings indicate that silicon-induced resistance can impair the development of this cotton defoliator. However, whether silicon supplied through the soil produces similar or even stronger effects on the complete life history of A. argillacea remains unclear, highlighting the need to evaluate soil-applied silicon as a strategy to enhance cotton resistance.

The hypothesis is that silicon supplied through soil application is absorbed and accumulated in cotton leaves, where it alters physiological or biochemical processes that ultimately influence the development and reproduction of A. argillacea. The aim of this research was to evaluate the development, survival and reproduction of A. argillacea fed on leaves from cotton plants grown with different Si doses applied to the soil.

2. Material and Methods

2.1. Study location

The work was carried out in a greenhouse (7° 13’ 31” S latitude and 35° 54’ 18” W longitude) and in the Entomology Laboratory (7° 13’ 32” S latitude and 35° 54’ 19” W longitude) of Embrapa Algodão in the municipality of Campina Grande, Paraíba state, Brazil.

2.2. Insects, plant material and soil

Specimens of A. argillacea were obtained from stock colonies of the Entomology Laboratory at Embrapa Cotton where larvae of this insect are fed on leaves detached from the cotton plants (Bestete et al., 2017). Cotton seeds (cultivar BRS 286), obtained from Embrapa Cotton Active Germplasm Bank (BAG), were sown in a greenhouse with Eutrophic Regolithic Neosol (WRB classification) soil collected in the arable layer, 0-20 cm deep, in an area of 4m² in Embrapa Cotton experimental field, left fallow for more than ten years (Santos et al., 2018). Soil samples were analyzed at the Embrapa Soil Fertility Laboratory, and soil acidity and fertility were corrected according to the recommendations for cotton cultivation (Borin et al., 2014), except that potassium was intentionally omitted. This macronutrient was later applied to the soil in the form of potassium silicate so as not to affect the treatments.

2.3. Determination of Si content in cotton leaves

The Si content in cotton leaves was determined (Silva, 2009) as follows:

2.3.1. Sample preparation

Thirty days after emergence, the third fully expanded true leaf, counted from the apex to the base and excluding the cotyledonary leaves, was collected from each treated and untreated cotton plant. The collected leaves were washed with a 0.2% detergent solution, rinsed twice with deionized water to remove possible contaminants, and dried on paper towels. They were then placed in paper bags and oven-dried at 70 °C with forced air circulation for 72 h. The dried samples were ground in a Wiley mill, passed through a 1.0-mm mesh sieve (20 mesh), and stored in sealed plastic bags until chemical analysis.

2.3.2. Extraction of chemical elements from plant tissue by dry digestion

Crushed leaf samples (500 mg) were transferred to porcelain crucibles and incinerated in an electric muffle furnace with the temperature gradually adjusted to 500º C and kept at this temperature for three hours.

2.3.3. Determination of Si by molecular absorption spectrometry

Fifty mL of NaOH solution (1%) was added to the ash resulting from incineration of cotton samples and kept in an 80 mL polyethylene tube. Two mL of this solution was transferred, mixed with 18 mL of distilled water and 5 mL transferred to a 50 mL plastic container. After this, a 1.0 mL of 1.0% molybdate, 1.0 mL of 2% oxalic acid, 1.0 mL of 1.5 M H₂SO₄and 0.03g of ascorbic acid were added to this solution, which was left to react for 20 minutes before being read using a spectrophotometer (660nm). The concentration of Si in the leaf tissue was calculated using the Equation 1:

$$Sigk{g}^{(-1)}\left(DrymatterorDM\right)=mg{L}^{-1}Siinthereadingsolutionx1.0$$ (1)

2.4. Biology bioassays

Cotton seeds were planted in 30 five-liter plastic pots with soil from the fallow received 20 mL of nutrient solution of the correction solution (Novais et al., 1991) and fertilized. The Si was applied in the form of potassium silicate using the commercial product Flex Silicio® (12% Si (165.60 g/L), 12% Potassium (165.60g/L)). Seedlings were thinned to three plants per pot, leaving three per pot and the leaves collected 30 days after germination to start the bioassay.

Alabama argillacea eggs were separated into groups of 48 per treatment in Petri dishes 10 cm in diameter and 0.9 cm high, lined with filter paper until caterpillar hatching. Newly hatched caterpillars were transferred to plastic trays with 12 wells (5.5 cm long × 2.5 cm wide × 2.5 cm high each well), individualized per plastic well and distributed in the treatments with leaves from plants fertilized or not with Si.

The experimental design was in randomized blocks, with three treatments randomly distributed per block with four replications. The treatments had A. argillacea caterpillars fed on pieces of leaves collected from cotton plants without Si (T1) or fertilized with 150 mg kg^-1 (300 kg of Si.ha^-1) (T2) and 300 mg kg^-1 of this element in the soil (600 kg of Si.ha^-1) (T3). Each replication consisted of 12 individualized larvae per treatment. The initial Si concentration of the soil was common to all treatments and therefore was not considered a treatment effect.

The A. argillacea caterpillars were fed ad libitum with two-centimeter-diameter discs of cotton leaves from the different treatments, which were replaced every two days or whenever they were completely consumed by the caterpillars. The wells of the plastic trays were closed with plastic lids of the same size and kept in an air-conditioned chamber at 25 °C, 60 ± 10% relative humidity and a 12-hour photoperiod until the end of the observations.

Immediately after pupation, when the pupal cuticle had become fully sclerotized and darkened, the pupae were weighed to the nearest 0.0001 g using an AY220 analytical balance (Shimadzu Corporation, Columbia, MD, USA), separated by sex, and maintained in PVC cages until adult emergence (Medeiros et al., 2003). The sex ratio was calculated by dividing the number of females by the total number of males and females. Ten A. argillacea couples were individualized per cage for mating and laying eggs, receiving a 10% honey solution until the end of their life cycle.

Biological observations were made daily at 8:00 A.M. and 2:00 P.M using an EL224 stereomicroscope (BEL Engineering, Monza, Milano, Italy) with 20x magnification, until adult death. The width of the cephalic capsule was measured with software Image J version 1.53s (Rasband, IL, USA. US National Institutes of Health; Bethesda, MD, USA) in images of caterpillars immobilized using surgical forceps and a brush, 24 hours after ecdysis. The duration and survival of the larval period and of the first, second, third and fourth instar, pre-pupa, pupa and reproductive characteristics (pre-oviposition, oviposition and post-oviposition periods, longevity, incubation period, fecundity, number of eggs and viable eggs) were evaluated.

2.5. Data analysis

The normality of the data was checked using the Lilliefors test, before submitting them to the parametric and non-parametric statistical analysis. Data on survival and duration of immature stages, pupal weight, cephalic capsule width, growth rate and reproductive characteristics of A. argillacea were transformed, where necessary, to the square root of x + 0.5 to improve normality before analysis. Data following normal distribution were not transformed. All variables except head capsule width were analyzed by ANOVA at p≤0.05 and differences between treatments indicated by the Tukey test. The cephalic capsule width data was subjected to two-way ANOVA (p≤0.05) and differences between treatments indicated by the Tukey test. Statistical analyses were carried out using the Statistical and Genetic Analysis System (SAEG).

3. Results

The initial Si concentration in the fallow soil was 17.4 mg kg⁻¹. Silicon fertilization significantly increased Si concentrations in both the soil (F₂,₂₇ = 40.75; P < 0.01) and cotton leaves (F₂,₃₈ = 149.70; P < 0.01) (Figure 1). Soil Si increased from 17.44 ± 0.88 mg kg⁻¹ in the unfertilized control to 25.30 ± 1.17 and 37.76 ± 2.36 mg kg⁻¹ following the application of 150 and 300 mg Si kg⁻¹, respectively. A similar likewise was observed in the leaves, where Si concentrations increased from 77.80 ± 10.56 mg kg⁻¹ in the control to 187.93 ± 5.63 and 608.52 ± 43.59 mg kg⁻¹ at the intermediate and highest Si doses, respectively.

Figure 1
Silicon concentration (mean ± SE) in cotton leaves (A) and soil (B) after soil application of 0 (control), 150 (300 kg Si ha⁻¹), and 300 mg Si kg⁻¹ soil (600 kg Si ha⁻¹). Different letters indicate significant differences among treatments (Tukey test, P ≤ 0.05).

Survival of the first (F₂,₆ = 1.11; P > 0.05) and second (F₂,₆ = 0.37; P > 0.05) instars of A. argillacea was unaffected by Si supplementation. In contrast, survival differed among treatments for the third (F₂,₆ = 6.75; P = 0.03), fourth (F₂,₆ = 4.06; P = 0.05), and fifth instars (F₂,₆ = 55.64; P < 0.01). Survival of the third and fourth instars was higher in the control than at 300 mg Si kg⁻¹, whereas the 150 mg Si kg⁻¹ treatment did not differ from either. For the fifth instar, survival declined progressively with increasing Si concentration (Table 1).

Table 1
Survival (%; mean ± standard error) of the larval instars and the overall larval, prepupal, and pupal stages of Alabama argillacea (Lepidoptera: Noctuidae) fed cotton leaves from plants grown in soil containing 0 (control), 150 (300 kg Si ha⁻¹) or 300 mg Si kg⁻¹ soil (600 kg Si ha⁻¹).

Stage	Instar	Dose (mg kg-1)
		0	150	300
	First	91.67 ± 3.40 a	100.00 ± 0.00 a	93.75 ± 6.25 a
	Second	95.83 ± 4.17 a	91.67 ± 4.81 a	90.28 ± 4.61 a
	Third	100.00 ± 0.00 a	95.42 ± 2.67 ab	70.18 ± 9.40 b
	Fourth	100.00 ± 0.00 a	87.40 ± 4.91 ab	78.13 ± 10.67 b
	Fifth	100.00 ± 0.00a	96.43 ± 3.57 a	44.82 ± 19.13 b
Larva		89.58 ± 3.99 a	75.00 ± 10.21a	10.41 ± 3.99 b
Prepupa		100.00 ± 0.00 a	88.20 ± 1.75 b	00.00 ± 0.00
Pupa		100.00 ± 0.00 a	96.88 ± 3.13 a	-

• Insects were maintained at 25 ± 1 °C, 60 ± 10% relative humidity, and a 12-h photoperiod. Averages followed by the same letter in the row do not differ by Tukey's test (p≤0.05). (-) No data.

Larval survival was also affected by Si supplementation (F₂,₆ = 21.85; P < 0.01). Survival was similar between the control (89.58%) and 150 mg Si kg⁻¹ (75.00%), but both were significantly higher than at 300 mg Si kg⁻¹, where only 10.41% of larvae survived (Table 1). Prepupal survival differed among treatments (F₁,₃ = 2038.81; P < 0.01), decreasing from 100.0% in the control to 88.20% at 150 mg Si kg⁻¹. No prepupae survived at 300 mg Si kg⁻¹, preventing pupal formation (Table 1).

Silicon supplementation affected the duration of the first (F₂,₆ = 25.00; P < 0.01) and second (F₂,₆ = 6.19; P = 0.03) instars, which were longer only at 150 mg Si kg⁻¹ than in the control, whereas the highest Si dose did not differ from the control (Table 2). The third instar was unaffected by treatment. In contrast, the fourth (F₂,₆ = 14.38; P < 0.01) and fifth instars (F₂,₅ = 7.29; P = 0.03) were shorter at 300 mg Si kg⁻¹ than in the control, while the intermediate dose remained similar to the control (Table 2).

Table 2
Developmental duration (days, mean ± SE) of the larval stage, individual larval instars, prepupal stage, and pupal stage of Alabama argillacea (Hübner) (Lepidoptera: Noctuidae) fed cotton leaves from plants grown in soil containing 0 (control), 150 (300 kg Si ha⁻¹), or 300 mg Si kg⁻¹ soil (600 kg Si ha⁻¹).

Stage	Instar	Dose (mg kg-1)
		0	150	300
	First	1.00 ± 0.00 b	1.83 ± 0.17 a	1.00 ± 0.00 b
	Second	2.41 ± 0.12 b	2.84 ± 0.04 a	2.55 ± 0.14 ab
	Third	3.09 ± 0.08 a	2.88 ± 0.09 a	3.00 ± 0.19 a
	Fourth	3.21 ± 0.07 a	2.97 ± 0.09 a	1.76 ± 0.29 b
	Fifth	3.84 ± 0.13 a	3.79 ± 0.36 a	1.38 ± 0.63 b
Larva		13.55 ± 0.28 ab	14.55 ± 0.19 a	9.25 ± 3.10 b
Pre-pupae		1.00 ± 0.00 a	1.00 ± 0.00 a	-
Pupae		6.46 ± 0.12 a	7.39 ± 0.31 a	-

• Insects were maintained at 25 ± 1 °C, 60 ± 10% relative humidity, and a 12-h photoperiod. Averages followed by the same letter per row do not differ by Tukey's test (p≤0.05). (-) No data.

The overall larval period differed among treatments (F₂,₅ = 7.77; P = 0.03), being shorter at 300 than at 150 mg Si kg⁻¹, whereas neither treatment differed from the control (Table 2). Prepupal (F₁,₃ = 0.00; P > 0.05) and pupal (F₁,₃ = 4.66; P > 0.05) durations did not differ between the control and 150 mg Si kg⁻¹. Because larvae fed leaves from the highest Si treatment failed to pupate, pupal duration could not be determined (Table 2).

Head capsule width increased with successive instars with larval development in all treatments. However, larvae fed leaves from the control had greater head capsule widths than those fed leaves containing 150 mg Si kg⁻¹ during the first five instars, whereas the last instar did not differ between treatments (Table 3). Pupal weight was lower and the sex ratio decreased at 150 mg Si kg⁻¹ compared with the control (F₁,₃ = 13.05; P = 0.04). Because no pupae were formed at 300 mg Si kg⁻¹, pupal weight and sex ratio could not be evaluated for this treatment (Table 3).

Table 3
Head capsule width (CW), growth ratio (GR), pupal weight, and sex ratio of Alabama argillacea (Hübner) (Lepidoptera: Noctuidae) fed cotton leaves from plants grown in soil containing 0 (control), 150 (300 kg Si ha⁻¹), or 300 mg Si kg⁻¹ soil (600 kg Si ha⁻¹).

Instar/Stage	Treatments (Dose (mg kg-1)
	0		150		300
	CW	GR	CW	GR	CW	GR
First	0.29 ± 0.00 aE	-	0.28 ± 0.00 bE	-	0.25 ± 0.00 cE	-
Second	0.39 ± 0.00 aD	1.34	0.37 ± 0.00 bD	1.36	0.35 ± 0.00 cD	1.40
Third	0.59 ± 0.00 aC	1.51	0.57 ± 0.00 bC	1.51	0.52 ± 0.00 cC	1.48
Fourth	0.79 ± 0.00 aB	1.33	0.76 ± 0.00 bB	1.35	0.71 ± 0.00 cB	1.36
Fifth	1.18 ± 0.00 aA	1.50	1.17 ± 0.01 aA	1.53	1.06 ± 0.00 bA	1.49
Mean GR	-	1.42 a	-	1.44 a	-	1.43 a
Pupal weight	0.18 ± 0.00 a		0.15 ± 0.00 b		-
Sex ratio	0.54		0.36		-

• Insects were maintained at 25 ± 1 °C, 60 ± 10% relative humidity, and a 12-h photoperiod. Means followed by the same lowercase letter in the row and uppercase letter in the column do not differ by Tukey's test (p ≤ 0.05). - No data.

Reproductive performance was also affected by Si supplementation. Females from the control treatment had longer postoviposition periods (F₁,₉ = 182.25; P < 0.01), greater longevity (F₁,₉ = 36.00; P < 0.01), higher fecundity (F₁,₉ = 6062.09; P < 0.01), more eggs per day (F₁,₉ = 12.64; P < 0.01), and higher egg viability (F₁,₉ = 512.57; P < 0.01) than females from the 150 mg Si kg⁻¹ treatment. Oviposition period did not differ between treatments (F₁,₉ = 1.00; P = 0.34), whereas the preoviposition period was longer at 150 mg Si kg⁻¹ (F₁,₉ = 16.00; P < 0.01) (Table 4).

Table 4
Reproductive parameters (mean ± SE) of Alabama argillacea (Hübner) (Lepidoptera: Noctuidae) fed cotton leaves from plants grown in soil containing 0 (control), 150 (300 kg Si ha⁻¹), or 300 mg Si kg⁻¹ soil (600 kg Si ha⁻¹).

Parameter	Dose (mg kg-1)
	0	150	300
Pre-oviposition	2.00 ± 0.00 b	3.00 ± 0.00 a	-
Oviposition	7.00 ± 0.00 a	7.00 ± 0.00 a	-
Post-oviposition	1.80 ± 0.13 a	0.00 ± 0.00 b	-
Longevity	10.80 ± 0.13 a	10.00 ± 0.00 b	-
Number of eggs per female	726.00 ± 5.99 a	323.40 ± 2.84 b	-
Number of eggs per day	103.71 ± 16.99 a	46.20 ± 5.29 b	-
Viable eggs	92.91 ± 0.53 a	70.41 ± 0.95 b	-

• Insects were maintained at 25 ± 1 °C, 60 ± 10% relative humidity, and a 12-h photoperiod. Means followed by the same letter in the row do not differ by the F test (p ≤ 0.05). - No data.

4. Discussion

Silicon fertilization effectively increased Si accumulation in cotton leaves, with leaf concentrations rising proportionally to the dose applied to the soil. This response was expected because plants absorb silicon as monosilicic acid, a beneficial element that accumulates in plant tissues and subsequently deposited in epidermal tissues, where it forms silica–cuticle double layer that enhance tissue rigidity and reinforce structural defenses (Korndörfer et al., 2001; Sakr, 2017; Silva et al., 2023). The sandy soil used in this study, characterized by low initial Si availability, likely favored silicon uptake by the plants (Korndörfer et al., 2001; EL-Sayed et al., 2019).

The negative effects of Si on A. argillacea became evident from the third larval instar onward. Early instars were not affected, probably because newly hatched larvae preferentially feed on softer leaf tissues with lower silica deposition (Hochuli, 2001; Zalucki et al., 2002). As larvae aged and consumed larger amounts of leaf tissue, the increased silicon accumulation likely reduced leaf digestibility and palatability through greater tissue hardness and abrasiveness, resulting in lower survival, particularly at the highest Si dose (Reynolds et al., 2016; Perdomo et al., 2022).

The complete mortality of prepupae and the absence of pupal formation at 300 mg Si kg⁻¹ demonstrate the strong impact of high silicon accumulation on the development of A. argillacea. Similar reductions in survival of lepidopteran pests have been reported for Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae) fed on silicon-treated maize (Pereira et al., 2021; Haq et al., 2022), supporting the role of silicon as an inducer of plant resistance against chewing insects.

Silicon also altered larval development. The longer duration of the first and second instars at the intermediate Si dose suggests that moderate silicon levels reduced food quality sufficiently to delay development without causing high mortality. In contrast, larvae exposed to the highest Si concentration exhibited a shorter overall larval period because only a small proportion of individuals survived to later instars, resulting in strong mortality before pupation rather than accelerated development. Similar developmental responses have been associated with silicon-induced changes in leaf mechanical properties and plant defensive chemistry (Bakhat et al., 2018; Reynolds et al., 2016).

The reduction in head capsule width observed in larvae fed leaves with higher Si concentrations indicates impaired larval growth, although the average growth ratio remained consistent among treatments and followed Dyar's rule. This suggests that silicon reduced larval size without altering the normal molting pattern. Likewise, the lower pupal weight at the intermediate Si dose indicates reduced nutritional conversion during larval development, a response commonly associated with increased leaf toughness in silicon-enriched plants (Han et al., 2015; Mondego et al., 2018).

The effects of silicon extended to adult reproduction. Adults originating from larvae fed silicon-treated leaves exhibited a longer pre-oviposition period, lower longevity, and substantial reductions in fecundity and egg viability. These reproductive impairments are consistent with the lower nutritional reserves accumulated during larval development and have also been reported in other herbivorous insects feeding on silicon-treated host plants (Korndörfer et al., 2011; Nascimento et al., 2018). The male-biased offspring observed at the intermediate Si dose may likewise reflect nutritional stress during immature development, as female fitness generally requires greater energetic investment (Quezada-García et al., 2014).

Overall, our results demonstrate that soil-applied silicon negatively affected multiple biological parameters of A. argillacea, including survival, development, pupal formation, and reproduction. These findings indicate that silicon fertilization enhances cotton resistance to this defoliator and may represent a valuable component of integrated pest management, particularly in organic production systems, structured refuge areas, and other cropping systems where Bt technology is unavailable or less effective.

5. Conclusions

Soil-applied silicon increased Si accumulation in cotton leaves and negatively affected the biological performance of A. argillacea. The highest Si dose prevented pupal formation, whereas the intermediate dose reduced pupal weight and reproductive performance. These findings indicate that silicon fertilization may represent a useful complementary strategy for integrated management of the cotton leafworm, particularly in non-Bt, organic and refuge cropping systems.

Data Availability Statement

The data supporting the findings of this study are available from the corresponding author upon reasonable request.

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Edited by

• Editor:
  Takako Matsumura Tundisi

Publication Dates

• Publication in this collection
  18 Sept 2026
• Date of issue
  2026

History

• Received
  04 Nov 2025
• Accepted
  19 Aug 2026