Evaluating the Efficacy of Sea Cucumber (Stichopus horrens) as a Biocontrol Agent against Blattella germanica and Periplaneta americana

The management of cockroach populations in urban environments has become increasingly critical due to their role as vectors for various pathogens and allergens, which can significantly impact public health (Harris, 2020). Among the species of concern are the German cockroach (Blattella germanica) and the American cockroach (Periplaneta americana), both of which are prevalent in domestic and commercial settings and contribute to substantial health and economic burdens (Miller et al., 2019). Traditional chemical control methods, while effective, often come with environmental and health risks, including the development of resistance in target populations (Gorman et al., 2019). As such, there is a growing interest in alternative, sustainable approaches to pest management.

Biocontrol, the use of natural enemies to manage pest populations, offers a promising alternative to conventional chemical control strategies (Van Driesche and Bellows, 2020). Among the myriad potential biocontrol agents, marine invertebrates are emerging as novel candidates due to their diverse biological activities and ecological roles (Ding et al., 2021). One such candidate is Stichopus horrens, a species of sea cucumber that has been investigated for its potential biocontrol properties against various pests (Li et al., 2022).

Stichopus horrens is known for its biochemical and ecological characteristics that might be leveraged for pest control. Recent studies suggest that this sea cucumber produces bioactive compounds with insecticidal properties, which could inhibit or kill cockroaches upon exposure (Xie et al., 2023). Additionally, its ecological adaptability and non-toxic nature to humans and other non-target organisms enhance its appeal as a biocontrol agent (Zhang et al., 2022).

The efficacy of Stichopus horrens as a biocontrol agent against B. germanica and P. americana warrants thorough investigation due to the potential benefits of integrating such a marine invertebrate into pest management strategies. Blattella germanica, a common in door pest, is notorious for its high reproductive rate and ability to rapidly develop resistance to chemical treatments (Miller et al., 2019). Similarly, Periplaneta americana poses challenges due to its large size, high mobilityand resistance to many standard insecticides (Gorman et al., 2019). Evaluating the impact of S. horrens on these cockroach species could provide insights into alternative control mechanisms and contribute to more sustainable pest management practices.

In this study, we aim to evaluate the efficacy of Stichopus horrens as a biocontrol agent against Blattella germanica and Periplaneta americana. We will assess the impact of S. horrens on the survival, reproductionand behavior of these cockroach species. By comparing the effectiveness of this marine invertebrate to conventional chemical control methods, we seek to determine whether S. horrens could serve as a viable component of integrated pest management strategies. The findings from this research could pave the way for innovative approaches to pest control, reducing reliance on chemical pesticides and enhancing ecological sustainability.

Cockroach collection

Blattella germanica (German cockroach) and Periplaneta americana (American cockroach) were collected from Jeddah city. Cockroaches were maintained in standard laboratory conditions with a temperature of 25°C±2°C, relative humidity of 60%±5% and a 12:12 light-dark cycle. Both species were kept in separate plastic containers (40 cm×30 cm×30 cm) lined with paper towels and provided with a diet of commercial cockroach food and water ad libitum (Miller et al., 2019).

S. horrens collection

S. horrens was obtained from a marine aquaculture facility from Jeddah, Saudi Arabia. S. horrens were acclimatized in a 500-liter marine aquarium with natural seawater, maintained at 25°C±1°C and filtered to remove particulates. The S. horrens were fed a diet of algae and detritusand their health was monitored weekly (Li et al., 2022).

Preparation of biocontrol agents

The bioactive compounds of S. horrens were extracted using a methanol-based solvent extraction method. S. horrens were washed, driedand ground into a fine powder. The powder was then mixed with methanol (1:10 w/v) and stirred for 24 hours at room temperature. The mixture was filtered through Whatman No. 1 paperand the solvent was evaporated under reduced pressure using a rotary evaporator to obtain a concentrated extract (Xie et al., 2023). The extract was stored at -20°C until use.

Toxicity assays

The efficacy of the S. horrens extract was assessed using a contact toxicity assay. Filter paper discs (3 cm diameter) were impregnated with 0.5 mL of S. horrens extract at concentrations of 0.1%, 0.5% and 1% (w/v). Control discs were treated with methanol alone. The discs were allowed to dry completely before use. For each concentration, ten adult cockroaches of each species were placed in separate containers (20 cm×20 cm×15 cm) with the treated or control discs. Mortality was recorded at 24-, 48- and 72-hours post-exposure. The experiment was replicated three times.

Repellency assays

Repellency of the S. horrens extract was evaluated using a dual-choice arena. A circular whatman filter paper (30 cm diameter) was divided into two equal sections. One section was treated with S. horrens extract at a concentration of 0.1%, 0.5% and 1% (w/v), while the other section was treated with methanol as a control. Ten cockroaches of each species were placed in the center of the arenaand their location was recorded at 1-hour intervals for a total of 6 hours. The experiment was conducted in triplicate.

Data analysis

Mortality rates were analyzed using Kaplan-Meier survival curves and compared between treated and control groups using the Log-rank (Mantel-Cox) test (GraphPad Prism 9). Repellency data were analyzed using a chi-square test to compare the proportion of cockroaches in each arena section. Behavioral data were analyzed using ANOVA followed by Tukey’s post-hoc test for multiple comparisons.

Toxicity effects of S. horrens Extract against B. germanica and P. americana

The toxicity assay revealed a concentration-dependent increase in mortality rates for both B. germanica and P. americana when exposed to S. horrens extract. Table 1 summarizes the mortality rates at different concentrations and exposure times.



For B. germanica, mortality significantly increased with higher concentrations of
S. horrens extract, reaching 93.3% at 1% concentration after 72 hours. Similarly, P. americana showed a substantial increase in mortality, with 90% mortality at the highest concentration after 72 hours. This suggests that S. horrens possesses strong insecticidal properties, with greater efficacy observed against B. germanica than P. americana.

The differences in mortality rates between the two species may be attributed to their varying physiological and behavioral characteristics. Blattella germanica is known for its rapid reproduction and adaptability to environmental stressors, which might make it more susceptible to the bioactive compounds in S. horrens (Miller et al., 2019). On the other hand, Periplaneta americana, with its larger body size and thicker exoskeleton, might exhibit a degree of resistance, although the high mortality at 1% concentration indicates that S. horrens is still highly effective.

The findings of this study demonstrate the potential of S. horrens as a biocontrol agent against B. germanica and P. americana. The concentration-dependent mortality observed in both species suggests that S. horrens contains bioactive compounds with strong insecticidal properties. These results align with previous studies that have highlighted the insecticidal potential of marine invertebrates, particularly sea cucumbers, due to their production of secondary metabolites with biological activity (Xie et al., 2023).

Repellent Effects of S. horrens Extract against B. germanica and P. americana

Table 2 summarize the repellent effect of S. horrens extract was observed to be weaker compared to its toxicity, with a maximum repellency of 56.6% for B. germanica and 53.3% for P. americana at 1% concentration after 72 hours.



These results indicate that while S. horrens has a moderate repellent effect, it may not be sufficient as a standalone repellent agent.

The differences in repellent efficacy between the two species may be influenced by their distinct behavioral responses to environmental stimuli. Blattella germanica is known for its tendency to avoid light and seek out cracks and crevices, which may make it more responsive to repellent stimuli (Gorman et al., 2019). Conversely, P. americana’s preference for larger, open spaces may reduce its sensitivity to surface treatments, potentially explaining the lower repellency observed.

However, the moderate repellency observed suggests that S. horrens may be more effective as a toxicant than as a repellent. The application of S. horrens extract in integrated pest management (IPM) strategies could, therefore, focus on its use as a contact insecticide rather than relying solely on its repellent properties. This approach could reduce the environmental and health risks associated with chemical pesticides, particularly in indoor settings where B. germanica and P. americana are commonly found (Van Driesche and Bellows, 2020).

Further research should explore the identification and characterization of the specific bioactive compounds responsible for the observed toxicity. Additionally, studies could investigate the synergistic effects of S. horrens extract when combined with other biocontrol agents or reduced-risk insecticides, potentially enhancing its efficacyand expanding its application in pest management.

The study highlights the significant insecticidal potential of S. horrens extract against B. germanica and P. americana. A concentration-dependent increase in mortality was observed for both species, with B. germanica exhibiting higher susceptibility (93.3% mortality at 1% concentration after 72 hours) compared to P. americana (90% mortality under similar conditions). This suggests that the bioactive compounds in S. horrens possess strong toxic effects, particularly against smaller and more adaptable species like B. germanica. Although the repellent effect of S. horrens was moderate, with maximum repellency rates of 56.6% for B. germanica and 53.3% for P. americana, the extract demonstrates greater potential as a contact toxicant. These findings support its use in integrated pest management (IPM) strategies to mitigate reliance on chemical pesticides. Future research should focus on isolating the active compounds, assessing their mechanisms of actionand exploring synergistic applications to optimize efficacy.

The present study was supported by the author.

Disclaimers

The views and conclusions expressed in this article are solely those of the author and do not necessarily represent the views of their affiliated institutions. The author is responsible for the accuracy and completeness of the information provided, but do not accept any liability for any direct or indirect losses resulting from the use of this content.

Informed consent

All animal procedures for experiments were approved by the Committee of Experimental Animal care and handling techniques were approved by the University of Animal Care Committee.

The author declares that there are no conflicts of interest regarding the publication of this article. No funding or sponsorship influenced the design of the study, data collection, analysis, decision to publish, or preparation of the manuscript.