Effectiveness of Some Bio-insecticides on Spodoptera frugiperda (J. E. Smith) and Sesamia cretica Lederer (Lepidoptera: Noctuidae).

INTRODUCTION

The family Noctuidae (order: Lepidoptera) is the second largest family in Noctuoidea, with about 1,089 genera and 11,772 species worldwide (Zhang, 2011).The Fall Armyworm (FAW), Spodoptera frugiperda (J. E. Smith) (Fam: Noctuidae) is a polyphagous insect pest that feeds on leaves and stems of more than 80 plant species such as maize, rice, sorghum, sugarcane, cotton and other vegetable crops (Pogue, 2002; Nagoshi, et al. 2007; Bueno et al., 2010; Barros, et al.,2010; Gamil, 2020). Maize is the preferred host for FAW in the countries where it has been recorded. In the absence of control methods, S. frugiperda can reduce the corn annual production by 21-53% (Huang et al., 2020). S. frugiperda has a high ability to spread to new areas (Mohamed et al., 2022), it was detected in the Nile Delta of the northern part of Egypt, since it was transferred from the Upper Egypt governorates (Rashed, et al., 2022). The greater sugarcane borer (GSB), Sesamia cretica (Fam: Noctuidae) is one of the most important sugarcane and corn borers species in Egypt. This insect pests attacks the maize plants at about 4 – 7 weeks old (Soliman & Mihim 1997; Ezzeldin, et al., 2009; Darwish, et al. , 2019). Its damage to young maize plants ranges from feeding on the whorl leaves (causing dead-heart) to feeding on older plants causing longitudinal tunnels (Soliman & Mihim 1997). To avoid harmful effects of the intensive use of chemical insecticides on environment and/or the non-target organisms, alternative materials have been initiated using safe and effective insect pathogens such as microbial insecticides (Crickmore 2006). Microbial pathogens such as bacteria and pathogenic fungi are good bio-control agents. Due to their eco-friendliness and bio-persistence behavior and their easy preference to kill insect pest species at different developmental stages, crop protection based on biological control of insect pests with microbial agent has been recognized as a valuable tool in integrated pest management programs and therefore utilization of bio-insecticides has increased day-by-day in the recent years (Lomer, et al. 2001; Bhattacharya et al., 2003, Goettel, et al. 2005; Pell, 2007; Hajek, et al., 2012). Keeping in view the above-mentioned information, the current experiment was undertaken to study the effect of five bio-insecticides on the larvae of FAW and GSB under laboratory and field conditions.

MATERIALS AND METHODS

1- Laboratory studies

The tested bio-insecticides includes:

-          Spinosad (Tracer 24%SC) from Dow AgroSciences Co.,

-          Abamectin (Vertemic 18% EC) from Syngenta Co.,

-          BioPower (containing 1x10⁹ Beauveria bassiana spores/ml) (T. Stanes Co. limited, India)

-          Bio-Catch (containing 1x10⁹ Lecanicillium lecanii spores/ml) (T. Stanes Co, limited, India)

-          Priority (containing 1x10⁹ Paecilomyces fumosoroseus spores/ml) (T. Stanes Company limited, India)

Insects used

The newly moulted 3^rd instars larvae of Spodoptera frugiperda and Sesamia cretica were obtained from a sensitive reared culture for several generations under laboratory conditions and used in this experiment (27.0 ± 1.0 ºC & 70.0 ± 5.0%RH).

Bioassay

Serial concentrations were prepared for each bio-insecticides as follow; 0.25X10⁹, 0.5x10⁹, 1x10⁹ and 1.5x10⁹ spores / 1000 ml (in 1000 ml distilled water) from BioPower, Bio-Catch and Priority, 1, 5, 10 and 20 ppm of Spinosad and 1, 2, 4 and 8 ppm of Abamectin.

Concerning the entomopathogenic fungi (BioPower, Bio-Catch and Priority), ten newly moulted 3^rd instar larvae of S. frugiperda and S. cretica were placed in a Petri dish (9 cm in diameter) lined with filter paper were sprayed with 2.0 ml from each concentration per treatment using hand sprayer. After air drying, the treated larvae were transferred carefully to a 2-L flask containing fresh new corn leaves. Each concentration was repeated three times. Ten larvae sprayed with distilled water served as a control. The leaf dip technique was used as described by Aydin et al. (2005) for spinosad and abamectin. Mortality percentages were measured after two, four and six days and they were corrected by Abott's formula (1925). The LC₂₅, LC₅₀ and LC₉₅ values and 95% confidence limits were calculated according to Finney (1971) by using LdP-line, Ehab Software (http://www.ehabsoft.com/ldpline/). Also, the percentage of pupation and moth emergence were recorded for each bio-insecticide and the different used concentrations.

The susceptibility indexes

In this study, the toxicity index method (Sun, 1950) which used to determine the degree of toxicity of different insecticides by comparing them with a standard one was adopted to find out the degree of susceptibility insect to an insecticide than the other insect to the same insecticides by dividing the LC₂₅, LC₅₀ or LC₉₀ for less susceptible insect by the LC₂₅, LC₅₀ or LC₉₀ for the more susceptible one.

2- Field studies

Efficacy of five bio-insecticides against the Spodoptera frugiperda and Sesamia cretica:

Field experiments were carried out in a private farm at El-Bostan, El-Delengat district, Beheira Governorate, Egypt throughout two successive seasons of 2021 and 2022. The experiments were planned to evaluate the efficacy of five bio-insecticides against S. frugiperda and S. cretica on maize plants (cv. yellow single cross 168). An area of about one feddan was divided into 48 plots of 60 m2 each (24 plots for each insect). Each treatment (bio-insecticide) was replicated four times in addition to four control plots. The replicates were separated from the adjacent ones by about one meter as a belt to minimize the interference of spray drift among them. The maize plants were sown in the beginning of May. The treatments for S. cretica were achieved after one month from the sowing date while the treatments for S. frugiperda were achieved in 24 separated plots after 45 days from the sowing date. The number of alive larvae of S. frugiperda or S. cretica on randomly selected ten maize plants from each plot were examined and recorded before treatment and after 1, 4, 7 and 14 days of the treatment. Tracer 24%SC and Vertemic 18% EC were applied at a rate of 0.5 ml/l, while both BioPower, Bio-Catch and Priority were applied at rates of 5ml/L. The reduction percentages of population of S. frugiperda larvae or S. cretica were calculated according to the Henderson and Tilton equation (1955) as follows:

% reduction = 100*1- ((n in Co before treatment*n in T after treatment) / (n in Co after treatment*n in T before treatment))

Data analysis:

The collected data were statistically analyzed using analysis of variance (ANOVA) and the means were separated by the Least Significant Difference (LSD test) (SAS Statistical, 1988).

RESULTS AND DISCUSSION

Laboratory studies:

Data presented in Table (1) show the lab effectiveness of five bio-insecticides on the 3^rd instar of Spodoptera frugiperda. After 48 h, the most effective entomopathogenic fungus was Bio-Power insecticide where LC₅₀ and LC₉₀ values were 0.764x10⁹ and 5.662 x10⁹ spores/1000ml, respectively. Followed by the entomopathogenic fungi Priority (LC₅₀ = 1.503 x10⁹) while Bio-Catch was the least and achieved LC₅₀=1.78x10⁹ spores/1000ml. On the other hand, LC₅₀ and LC₉₀ values of spinosad were 6.982 and 49.801 ppm, respectively while these values for the abamectin insecticide were 3.038 and 20.607 ppm. After 96 h exposure time (Table 2), the toxicity of the entomopathogenic fungi was increased and recorded 0.463 x10⁹, 1.474 x10⁹ and 1.229 x10⁹ as LC₅₀ for Bio-Power, Bio-Catch and Priority, respectively. The toxicity of spinosad and abamectin also increased after 96 h and recorded LC₅₀ of 4.885 and 2.327 ppm, respectively. After 144 h (Table 3), the toxicity of the bio-insecticides significantly increased with increasing exposure time whereas the LC₅₀ values were 0.487 x10⁹, 0.659 x10⁹, 1.108 x10⁹, 3.537 ppm and 1.966 ppm for Bio-Power , Priority, Bio-Catch, spinosad and abamectin, respectively.

Concerning the GSB, as shown in Table (1) the effectiveness of the five bio-insecticides on the 3^rd instar after 48 h, clearly demonstrated that the most effective entomopathogenic fungus was Bio-Power whereas the LC₅₀ and LC₉₀ values were 1.277x10⁹ and 7.288x10⁹ spores/1000ml, respectively. Followed by the entomopathogenic fungi, Priority (LC₅₀ = 2.412x10⁹) while Bio-Catch was the least and achieved LC₅₀=2.627x10⁹ spores/1000ml. On the other hand, the LC_25, LC₅₀ and LC₉₀ values of Tracer were 3.598, 9.962 and 68.96 ppm, respectively. These values for the Vertemic insecticide were 1.615, 5.19 and 47.73 ppm. After four days post treatment (Table 2), the toxicity of the entomopathogenic fungi was increased and recorded 0.822x10⁹, 1.655x10⁹and 3.055x10⁹ as LC₅₀ for Bio-Power, Priority and Bio-Catch respectively. The toxicity of spinosad and abamectin also increased after four days and recorded LC₅₀ of 8.079 and 4.446 ppm, respectively. After 144 h (Table 3), the toxicity of the bio-insecticides significantly increased with increasing of the exposure time whereas the LC₅₀ values were 0.578x10⁹, 1.199 x10⁹, 2.164 x10⁹, 4.913 ppm and 2.927 ppm for Bio-Power, Priority, Bio-Catch, Tracer and Vertemic, respectively.

Table 1. Lab effectiveness of five bio-insecticides against Spodoptera frugiperda and Sesamia cretica 3^rd instar larvae at 48 h post treatment.

Table 2. Lab effectiveness of five bio-insecticides against Spodoptera frugiperda and Sesamia cretica 3^rd instar larvae at 96 h post treatment.

Table 3. Lab effectiveness of five bio-insecticides against Spodoptera frugiperda and Sesamia cretica 3^rd instar larvae at 144 h post treatment.

The current results concluded that the Biopower insecticide (Beauveria bassiana) was the most effective entomopathogenic fungi insecticides on FAW and GSB larvae than Bio-Catch (Lecanicillium lecanii) and Priority (Paecilomyces fumosoroseus). The results of El-Hawary and Abd El-Salam, 2009 are in agreement with our results, they found that B. bassiana (Bio-Power) was more effective against the larvae of Spodoptera littoralis and P. fumosoroseus (Priority) was more potent against the larvae of Agrotis ipsilon. Also, Metwally, 2010 investigate the effect of B. bassiana on the three corn borers, Ostrinia nubilalis (Hbn.), Sesamia cretica (Led.) and Chilo agamemnon (Bles.), and found that all the tested concentrations induced different mortalities. Idrees, et al, 2022 tested the pathogenicity of 12 isolates of B. bassiana in the immature stages and feeding efficacy of the FAW, S. frugiperda, they found that the B. bassiana isolates caused significant mortality rates ranging from 71.3 to 93.3% at two weeks’ post-treatment and reduced the efficacy of larval feeding consumption from 69.4 to 77.8% at two days’ post-treatment. Sabbour and Singer, 2014, found that the LC₅₀ of Paecilomyces fumosoroseus and Paecilomyces lilaceous recorded 122X10⁴ and 106X10⁴ conidia/ml, respectively against Phthorimaea operculella under laboratory conditions. On the other side, Abd El-Salam, et al., 2012 investigated the effect of Beauveria bassiana, Verticillium lecanii, Metarhizium anisopliae and Paecilomyces fumosoroseus compared with Nimbecidine against the cowpea aphid, Aphis craccivora in broad bean field and found that V. lecanii was the most effective insecticide followed by Nimbecidine, Bio-Magic, Priority and the least effective was B. bassiana.

The susceptibility indexes

As shown in Tables (4) the 3^rd instar FAW larvae were more susceptible to the five bio-insecticides than the 3^rd instar larvae of GSB. Concerning the entomopathogenic fungi, the FAW was more susceptible by 1.19, and 1.95 and 1.82 fold than the GSB according to the LC₅₀ after 144 h for Biopower, Biocatch and Priority. These ratios reach 1.39 and 1.49 for Tracer and Vertemic, respectively.

Table 4. The susceptibility index of Spodoptera frugiperda compared with Sesamia cretica 3^rd instar larvae to the tested bio-insecticides:

The effectiveness of the tested insecticides on the development of S. frugiperda and S. cretica:

Data in Tables 5 and 6 showed the effect of five bio-insecticides with serial concentrations on the 3^rd instar larvae and the effect on the developmental (pupation and moth emergencies) of S. frugiperda and S. cretica under laboratory conditions. The obtained results showed that for all bio-insecticides used there was a regular direct relationship for each concentration between the percentage of mortality and the increase in the period of exposure. For the effect on insect developmental, the five bio-insecticides showed fluctuations in both the percentage of pupation and the percentage of moth emergency, all the treated FAW larvae died before pupation in the case of treating by each of Biopower (1x10⁹ and 1.5x10⁹ spores / 1000ml), Tracer (10 and 20 ppm) and Vertemic (8 ppm). Also, all the GSB larvae treated with Biopower (1.5x10⁹ spores / 1000ml), spinosad (20 ppm) and abamectin (8 ppm) died before pupation.

Table (5): Effect of five bio-insecticides on 3^rd instar larvae of the fall army worm, Spodoptera frugiperda under laboratory conditions.

Table (6): Effect of five bio-insecticides on 3^rd instar larvae of the greater sugarcane borer, Sesamia cretica under laboratory conditions.

Field studies:

Data presented in Tables 7 and 8 showed the efficacy of five bio-insecticides on the numbers of larvae of FAMwhich were recorded before and after treatment 1, 4, 7 and 14 days in 2021 and 2022. There were significant differences between the treatments with respect to the reduction percentages of FAW larvae. The general means of reduction percentages of FAWlarvae could be arranged in descending order as follows: Vertemic 18% EC (87.26), Tracer 24%SC (82.49), BioPower (76.92), Bio-Catch (71.87) and Priority (67.59) in the 2021 season. These reduction percentages were increased in the 2^nd season 2022 and recorded 90.48, 88.01, 80.29, 75.49 and 71.15 %, respectively. Among the tested insecticides, Vertemic 18% EC and Tracer 24%SC gave the highest reduction percentages (lowest number of S. frugiperda per plant) after 1, 4, 7 and 14 days of application as compared to BioPower, Bio-Catch and Priority. The current results are in agreement with the results of Bajracharya, et al. 2020, who tested spinosad, chlorantraniliprole, emamectina benzoate, imidacloprid and azadirachtin against FAW, and found that the spinosad, chlorantraniliprole and emamectin benzoate were found promising for FAW management in maize. Mian et al., (2022), found that deltamethrin insecticide was recorded the most toxic insecticide followed by chlorantraniliprole and the bio-insecticides emamectin benzoate insecticides.

Table 7: Efficacy of the tested bio-insecticides on the fall army worm populations under field conditions during the 2021 season.

Means followed by the same letter(s) within the same column are not significantly differ (P ≤ 0.05)

Table 8: Efficacy of the tested bio-insecticides on the fall army worm populations under field conditions during the 2022 season.

Means followed by the same letter(s) within the same column are not significantly differ (P ≤ 0.05)

On the other hand, the data presented in Tables 8 and 9 illustrated the effect of the five bio-insecticides on the larvae of S. cretica. The GSB larvae were more resistant to the treatment than the larvae of FAW, whereas the recorded general means of reduction percentages were recorded 56.66, 65.31, 69.63, 76.89 and 81.17% during the first season (2021). During the 2^nd season, 2022 these percentages recoded 58.81, 63.74, 67.81, 81.28 and 84% for Priority, Bio-Catch, BioPower, Tracer and Vertemic, respectively. The current results are in agreement with El- Sappagh, (2016) and Darwish, et al. (2019), who tested the effect of different bio and chemical insecticides on the GSB (S. cretica)and found that all the treatments were effective in reducing the infestation rates by this insect. The 1^st author found that the chemical insecticide Neomyl was found the most effective insecticide against S. cretica followed by Bestban and Tempo Xl, respectively. While the 2^nd author recorded that the emamectin benzoate was the most effective insecticide followed by chlorantraniliprole, lufenuron, Bacillus thuringiensis and finally spinetoram insecticide.

Table 8: Efficacy of the tested bio-insecticides on the greater sugarcane borer populations under field conditions during 2021 season.

Means followed by the same letter(s) within the same column are not significantly differ (P ≤ 0.05)

Table 9: Efficacy of the tested bio-insecticides on the greater sugarcane borer populations under field conditions during 2022 season.