Acta agriculturae Slovenica, 121/3, 1–9, Ljubljana 2025 doi:10.14720/aas.2025.121.3.21587 Original research article / izvirni znanstveni članek Efficacy and economic assessment of commercial Beauvaria bassiana (Bals.-Criv.) Vuill. in managing cucumber (Cucumis sativus L.) insect pests in a derived savanna agroecosystem Caroline Oyindamola FILANI 1, 2, Busola Ajoke OGUNIYI 1, Olufemi Richard PITAN 1 Received January 09, 2025; accepted September 01, 2025. Delo je prispelo 9. januar 2025, sprejeto 1. september 2025 1 Federal University of Agriculture, Abeokuta, College of Plant Science and Crop Production, Department of Crop Protection, Ogun State, Nigeria. 2 Corresponding author’s e-mail: filanico@funaab.edu.ng Efficacy and economic assessment of commercial Beauvaria bassiana (Bals.-Criv.) Vuill. in managing cucumber (Cucumis sativus L.) insect pests in a derived savanna agroecosystem Abstract: A study was conducted in 2021 and 2022 plant- ing seasons to determine the most efficient and profitable rate and frequency of applying Beauvaria bassiana to control insect pests on cucumber crop. Beauvaria application produced sig- nificantly lower insect pest numbers compared to untreated plots. Although leaf and fruit damage were statistically similar in the treated plots, the values were lower than the untreated plots. Significantly higher fruit yield (14.43 tons ha-1 and 13.44 tons ha-1) was obtained when Beauvaria was applied at 8 kg ha-1 once a week relative to the control 2.26 tons ha-1 and 2.34 tons ha-1, 2021 and 2022, respectively, resulting in a corresponding increase of 84 % and 83 % over the control. The relationship between insect pest infestation and yield was negative and sig- nificant (r = -0.90 and r = -0.80). In addition, the highest profit- ability index of 1.00 was obtained when Beauveria was applied at 8 kg ha-1 once a week in both years. Key words: Beauveria bassiana, fruit damage, insect pest infestation, cucumber, application rate, application frequency, economic assessment, derived savanna Učinkovitost in ekonomsko ovrednotenje komercialnih sevov glive Beauvaria bassiana (Bals.-Criv.) Vuill. pri uravna- vanju žuželčjih škodljivce na kumarah (Cucumis sativus L.) v ekosistemu prehodne savane Izvleček: Raziskava je bila narejena v rastnih sezonah 2021 in 2022 za določitev najbolj učinkovite in donosne up- orabe glive Beauvaria bassiana za nadzor žuželčjih škodljivcev na kumarah. Uporaba omenjene glive je povzročila znantno manjši napad žuželčjih škodljivcev v primerjavi z netretiranimi ploskvami. Čeprav so bile poškodbe listov in plodov statistično podobne na obravnavanih ploskvah, so bile vrednosti manjše kot na neobravnavanih. Značilno večji pridelek plodov (14,43 t ha-1 in 13,44 t ha-1) je bil dosežen, ko je bila gliva Beauvaria uporabljena 8 kg ha-1 , enkrat na teden v primerjavi s kontrolo (2,26 t ha-1 in 2,34 t ha-1, v letih 2021 in 2022). V primerjavi s kontrolo je bilo povečanje pridelka za 84 % in 83 %. Razmerje med napadom žuželk in pridelkom je bilo značilno negativno (r = -0,90 in r = -0,80). Največja vrednost indeksa dobičkonosnosti (1,00) je bila dosežena, kadar je bila gliva Beauveria uporabljena z 8 kg ha-1 enkrat na teden v obeh letih. Ključne besede: Beauveria bassiana, poškodba plodov, napad žuželčjih škodljivcev, kumara, velikost odmerka, pog- ostost uporabe, ekonomska ocena, prehodna savana Acta agriculturae Slovenica, 121/3 – 20252 C. O. FILANI et al. 1 INTRODUCTION A significant vegetable crop of the family Cucurbi- taceae, cucumber (Cucumis sativus L. (Elum, 2016) are grown throughout West Africa, including Nigeria (Ok- pani et al., 2023). Cucumber plays a very important role in improving human nutrition and health as it contains substances that stimulate digestion. It acts as laxatives or diuretics with its pectin and phenolic compounds regulating the pH of intestines (Victor and Amujoyegbe, 2019). It is well known for its diuretic effects and thus can serve as an active drug for secreting and promoting flow of urine (Okpani et al., 2023). Potassium, dietary fibers, manganese, phosphorus, pantothenic acid, copper, mag- nesium, as well as vitamins A, C, K, and B6 are all abun- dant in cucumbers (Ajibola and Amujoyegbe, 2019). Cucumbers are extremely beneficial to human health, but insect pests limit their production in Nige- ria. Insect pests such as Podagrica uniforma Jacoby, 1903 (Coleoptera: Chrysomelidae), Aphis gossypii, Glover, 1877 (Hemiptera: Aphididae) Myzus persicae, Sulzer, 1776 (Hemiptera: Aphididae) Bemisia tabaci, Gennadi- us, 1889 (Hemiptera: Aleyrodidae) Aulacophora foveicol- lis, Lucas, 1849 (Coleoptera: Chrysomelidae), Epilachna chrysomelina (Fabricius, 1775) (Coleoptera: Coccinelli- dae) and the fruit flies, Bactrocera invadens Drew, Tsu- ruta & White, 2005 (Diptera: Tephritidae) and Dacus ciliatus Loew, 1862 (Diptera: Tephritidae) are a major threat to the crop’s productivity (Adeoti and Pitan, 2023). They cause substantial reduction in cucumber fruit yield through their damaging activities (Akinkunmi et al., 2021). In response to the insect pest infestations most farmers heavily apply conventional insecticides without which production could be unprofitable. These insec- ticides, if effective at all, provide short-term dividends. This practice is unsustainable and affects human health and causing severe effects on entire planet (Pitan et al., 2013). Hence, there is an urgent need for non-chemical alternatives. Biological control, which involve using natural enemies like bacteria, viruses, and fungi, are one type of non-chemical alternative. Entomopathogenic fungi are a potential alterna- tive to chemical insecticides against many insect pests infesting vegetables and legumes (Flinn and Scholler, 2012; Rumbos and Athanassiou, 2017; Batta and Kav- allieratos, 2018; Wakil et al., 2021). Host-specific and contact-based, entomopathogenic fungi are considered an environmentally safe and acceptable management strategy. (Shahid et al., 2012). They have been reported to be effective against aphids, thrips, whiteflies, weevils, locusts, scarabs and caterpillars (Bahadur, 2023). Beau- veria bassiana [(Bals.-Criv.) Vuill., 1912] belongs to the soil-borne Entomopathogens class. The fungus has been proven to be effective in controlling many dipterans and coleopterans (Galecki et al., 2019; Wakil et al., 2021). B. bassiana creates enzymes and attaches itself to cuticular substrates to assault insect hosts in order to facilitate in- sect cuticle disintegration and penetration (Pedrini et al., 2013). According to Rai et al. (2014), B. bassiana causes white muscardine disease by acting as a pathogen on a variety of insect species. A range of toxins such as beau- vericin, bassianin, bassianolide, beauverolides, tenellin, oosporein, and oxalic acid are produced by B. bassiana after it invades insect hosts. These poisons aid in the par- asitization and eventual death of the hosts by B. bassiana (Wang et al., 2021). According to Atwa et al. (2009), B. bassiana (F2) and B. bassiana (F1) reduced insect popu- lations of cauliflower under field conditions, while Nouh et al. (2022) found that B. bassiana efficiently suppressed the main insect pests of cabbage. Thus, the study assessed the bioactivity of B. bassi- ana against insect pests of cucumber for improved fruit yield. 2 MATERIALS AND METHODS 2.1 DESCRIPTION OF THE STUDY AREA The study was carried out at the Federal University of Agriculture Abeokuta’s Teaching and Research Farm in Abeokuta, Ogun State (7º 15´N, 3º 25´E; 159 m above sea level). The location is in southwest Nigeria’s derived savannah zone. The field trials were conducted in the late season of 2021 and early season of 2022. 2.2 EXPERIMENTAL SETUP The trials were conducted using the ’Saira F1’ cucum- ber, a variety notable for its susceptibility to insect pests and Beauveria bassiana, CGA IPFBS-012, a fungal strain marketed under the trade name FIXIT-GA (1.15% WP). The study was set up using a 4 x 3 factorial arrangement with three replicates in a randomized complete block design (RCBD). Treatments included three application frequencies of B. bassiana (once a week, once every two weeks, and once every three weeks), a control, and four application rates of B. bassiana (8, 6, 4, and 3 kg ha-1). The field measured 53 m by 10 m in total, and each plot meas- ured 3 m by 2 m, with a 2 m boundary separating each plot. Two cucumber seeds were sown per hole at a dis- tance of 1 m × 1 m apart and at two weeks after plant- ing (WAP), the number of cucumber plants per stand was Acta agriculturae Slovenica, 121/3 – 2025 3 Efficacy and economic assessment of commercial Beauvaria bassiana ... (Cucumis sativus L.) insect pests in a derived savanna agroecosystem reduced to one plant. Manual weeding was done once every two weeks while neither fertilizer nor herbicide was applied throughout the duration of the experiment. Five hundred litres (500 litres) of water were used to suspend a 1.25-kilogram powder formulation of the fungus strain. This mixture was prepared to achieve a final concentration of 2 x 10^8 colony-forming units (CFU) per gram, which was manufacturer’s recommended concentration (dosage) for optimal efficacy against target insect pests. Foliar ap- plication of the bio-insecticide was carried out between 7.00 and 8.00 a.m. (local time) when insect pests were less active with a 4-litre capacity handheld sprayer. Applica- tion commenced two weeks after planting cucumber until fruit maturity. Control plots were sprayed only with wa- ter according to treatment plans (once a week, once every two weeks, and once every three weeks) using a handheld sprayer. There was also no herbicide or fertilizer applica- tion to the control plots throughout the experiment. Beauveria bassiana were applied at 8, 6, 4, and 3 kg ha-1 rates once a week, once every two weeks, and once eve- ry three weeks depending on the treatment plans for each plot. Applications were done in evenings between 5.00 and 7.00 p.m. (local time), at weekly intervals for once a week, every two weeks for once every two weeks and every three weeks for once every three weeks application frequencies. There was re-application of B. bassiana in every B. bassi- ana-treated plots after heavy rainfall throughout the study to reduce wash-off effects of rain on the fungi’s efficacy. 2.3 INSECT PEST INFESTATION ASSESSMENT Weekly visual counts of insect pests were conducted in the plots starting two weeks after planting (WAP) cu- cumber and continued until fruit maturity on five tagged plants from the central rows between 7:00 and 9:00 a.m. Additionally, data on fruit damage, blossom abortion, leaf damage (%), and leaf damage intensity were collected. Cucumber fruit harvesting began 8 WAP until 10 WAP with harvesting occurring at three-days intervals. The per- centage of fruit damaged was determined after the fruits were sorted into categories of undamaged and damaged. A cost-benefit analysis was conducted on the marketable yield, which consisted of the undamaged fruits (Dormon et al. 2007). 2.4 DATA ANALYSES Analysis of variance (ANOVA) tests were per- formed on the data collected using the General Statistical Software package (GEN STAT 12th edition, VSNI, Hemel Hempstead, UK) at p < 0.05. Prior to analysis, the square root method (√X + 0.5) was used to transform the num- ber of insects. When significant differences were found, they were separated using the Student Newman Keul’s Test (SNK). Analysis of the correlation between fruit damage and insect pest density was also arried out. 3 RESULTS AND DISCUSSION 3.1 RESULTS In the late season of 2021, plots sprayed with B. bassiana at 8, 6, 4, and 2 kg ha-1 showed significantly (p < 0.05) lower population densities of Aulacophora ni- gripennis Motschulsky, 1857 (Coleoptera: Chrysomeli- dae), Aulacophora hilaris (Boisduval, 1835) (Coleoptera: Chrysomelidae), Coridus viduatus Fabricius, 1794, (Het- Parameters Values pH 5.75 Particle size Sand (%) 88.60 Silt (%) 6.20 Clay (%) 5.20 Exchangeable bases (cmol kg-1) Ca 3.70 Mg 0.80 K Acidity 0.08 EC 4.12 Base (Sat) Total available (mg kg-1) N (%) 0.08 P 3.27 Organic carbon 0.65 Fe 1.65 Zn 0.85 Cu 0.45 Mn 3.60 Table 1: Physicochemical properties of soil used for the study during 2021 and 2022 cropping seasons Ca: Calcium, Mg: Magnessium, K: Potassium, EC: Electrical conductiv- ity, N (%): Nitrogen (percentage), P: Phosphorus, Fe: Iron, Zn: Zinc, Cu: Copper and Mn: Manganese. Acta agriculturae Slovenica, 121/3 – 20254 C. O. FILANI et al. eroptera: Dinidoridae) and Epilachna chrysomelina (Fab- ricius, 1775) (Coleoptera: Coccinellidae), Aulacophora foveicollis Lucas, 1849 (Coleoptera: Chrysomelidae) than untreated plots. The control plots, however, had consid- erably greater densities of A. foveicollis, A. hilaris, and E. chrysomelina (11.00, 11.33, and 14.00), whereas the plots sprayed with B. bassiana at 8, 6, 4, and 2 kg ha-1 weekly in the early season of 2022, had the lowest densities (Table 2). The frequency of B. bassiana application had a sig- nificant impact on floral abortion, fruit damage, leaf damage, leaf damage intensity, and relative yield loss in Season  Frequency Rate (kg ha-1) Aulacophora foveicollis Aulacophora nigripennis Aulacophora hilaris Bactrocera cucurbitae Coridius viduatus Epilachna chrysomelina Late season, 2021 Once a 8 1.33f 1.00g 0.33e 0.32bc 1.67d 2.10f week 6 2.00f 1.67g 1.00e 0.67bc 3.33d 3.02f 4 1.33f 1.33g 0.67e 1.00bc 1.67d 2.33f 2 1.67f 1.67g 1.00e 0.67bc 2.33d 3.40f Once every 8 3.67e 3.67f 3.00d 2.00bc 7.33c 7.30de two weeks 6 6.33b-d 4.67ef 4.33cd 2.67a-c 8.00bc 6.00e 4 5.33cd 5.67c-e 4.33cd 2.67a-c 10.33b 6.02e 2 7.33b 5.33de 6.33b 3.00a-c 10.33b 8.67c Once every 8 5.33d 4.33ef 3.33d 2.67a-c 8.00bc 8.03cd three weeks 6 7.33b 6.33b-d 4.67cd 1.33bc 9.33bc 7.40de 4 6.67bc 7.00bc 5.67bc 3.00a-c 9.33bc 8.33cd 2 7.33b 7.33b 7.00b 3.67ab 9.00bc 10.33b Control 0 10.00a 9.67a 10.33a 5.00a 12.00a 13.10a SED 0.52 0.55 0.66 0.90 0.80 0.54 F-value 57.50 46.67 38.62 4.58 41.28 75.88 p-value < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 Early Season, 2022 Once a 8 2.33f 2.00e 1.33e 1.33c 2.67h 3.00f week 6 3.00f 2.67e 2.00e 1.67bc 4.33g 4.00f 4 2.33f 2.33e 1.67e 2.00bc 2.67h 3.33f 2 2.67f 2.67e 2.00e 1.67bc 2.67h 4.00f Once every 8 4.67e 4.67de 4.00d 3.00bc 8.33cd 8.00de two weeks 6 7.33b-d 5.67d 5.33cd 3.67a-c 9.00bc 7.00e 4 6.33cd 9.67b 5.33cd 3.67a-c 6.33df 7.00e 2 8.33b 6.33cd 7.33b 4.00a-c 8.33cd 9.67c Once every 8 6.33cd 5.33d 4.33d 3.67a-c 9.00bc 9.00cd three weeks 6 8.33b 7.33c 5.67cd 2.33bc 10.33ab 8.00d-e 4 7.67bc 7.33c 6.67bc 4.00a-c 7.67c-f 9.33c 2 8.33b 8.33b 8.00b 4.67ab 8.33b-e 11.33b Control 0 11.00a 10.67a 11.33a 6.00a 11.00a 14.0a SED 0.78 0.79 0.91 0.81 0.82 0.91 F-value 46.21 37.34 30.90 4.12 30.96 49.32 p-value < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 Table 2: Insect pest densities on cucumber treated with Beauveria bassiana at different application rates and frequencies in the late season, 2021 and early season, 2022 Mean values along the same column within a season followed by similar alphabets are not significantly different from one another using SNK at p < 0.05. SED, Standard error of the differences of the mean. Acta agriculturae Slovenica, 121/3 – 2025 5 Efficacy and economic assessment of commercial Beauvaria bassiana ... (Cucumis sativus L.) insect pests in a derived savanna agroecosystem Frequency Rate (kg ha-1 ) Leaf damage (%) Leaf damage intensity (%) Flower abortion (%) Fruit damage (%) Relative yield loss (%) Once a week 8 6.75j 23.67f 12.28d 13.57f 14.16d 6 9.57i 27.44e 13.75d 14.17f 12.94d 4 10.44ef 25.32f 14.93cd 15.90f 12.63d 2 13.23e 24.94f 15.95cd 14.93f 15.58cd Once every two weeks 8 16.55d 32.43cd 20.66b-d 30.27de 32.86bc 6 16.95d 31.79cd 29.62b-d 26.00e 32.95ab 4 16.95d 32.31cd 24.43b-d 28.70de 31.51bc 2 18.51bc 34.60c 40.09ab 40.00c 46.37ab Once every three weeks 8 22.05b 35.76c 32.86b-d 44.17c 41.94ab 6 24.49b 34.03c 39.12ab 37.03cd 38.03ab 4 25.09b 39.79b 36.14b-d 31.93de 43.55ab 2 23.81b 38.17b 40.35a-c 54.30b 48.33ab Control 0 60.46a 60.17a 60.17a 62.70a 72.72a SED 7.91 4.03 0.55 3.04 0.24 F-value 5.80 5.12 7.39 52.81 57.53 p-value < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 Mean values along the same column within a season followed by similar alphabets are not significantly different from one another using SNK at p < 0.05.SED, Standard error of the differences of the mean. Table 3: Characteristics of insect-induced damage on cucumber treated with Beauveria bassiana at different application rates and frequencies in the late season, 2021 Frequency Rate (kg ha-1) Leaf damage (%) Leaf damage intensity (%) Flower abortion (%) Fruit damage (%) Relative yield loss (%) Once a week 8 17.44f 11.88e 13.94d 9.87h 12.25e 6 21.77de 16.97de 16.37d 14.00g 15.79e 4 19.91e 17.88de 16.91cd 16.50g 15.12e 2 19.09e 22.57de 18.33cd 25.47ef 25.68de Once every two weeks 8 24.10de 29.73cd 23.37b-d 34.70e 39.34cd 6 26.52d 20.33de 32.40b-d 34.33e 37.98cd 4 26.80d 29.44cd 25.86b-d 35.70e 35.01cd 2 30.40c 28.70cd 39.50ab 43.90cd 55.10bc Once every three weeks 8 31.05c 37.13bc 34.60b-d 40.00cd 51.85c 6 29.46c 42.10b 39.73a-d 47.73c 45.16d 4 36.01b 48.31b 37.61b-d 42.40cd 52.83c 2 33.94c 44.02b 43.18a-c 54.53b 59.62b Control 0 47.64a 80.64a 61.36a 61.97a 72.51a SED 4.28 4.62 0.55 8.98 0.45 36.18 3.99 7.39 6.06 20.23 < 0.001 0.002 < 0.001 < 0.001 < 0.001 Mean values along the same column within a season followed by similar alphabets are not significantly different from one another using SNK at p < 0.05.SED, Standard error of the differences of the mean Table 4: Characteristics of insect-induced damage on cucumber treated with Beauveria bassiana at different application rates and frequencies in the early season, 2022 Acta agriculturae Slovenica, 121/3 – 20256 C. O. FILANI et al. both seasons. The control plots had the greatest levels of leaf damage and leaf damage intensity, however, there was no significant difference among the treated plots. Notably, fruit damage was lower in plots treated with 8, 6, 4 and 2 kg ha-1 of B. bassiana weekly relative to the control plots (Table 3 and 4). Cucumber fruit yield was the highest in plots treat- ed with 8 kg ha-1 compared to other treatments, while the control plots had the lowest yield. Yield increase of more than 80 % over the control were observed in both 2021 and 2022 seasons in plots treated with B. bassiana at 8 kg ha-1 relative to other treated plots (Table 5). Additionally, leaf and fruit damage were significantly correlated with insect pest densities except A. nigripennis (Table 5). Most insect pests showed positive and significant correlations with leaf damage (r = 0.66 and r = 0.69) and fruit damage (r = 0.84, and r = 0.68), indicating that higher insect den- sities led to more significant damage in both 2021 and Late season, 2021 Early season, 2022 Frequency Rate (kg ha -1) Yield plant -1 (kg) Yield (ton ha -1) YI (%) Yield plant -1 (kg) Yield (ton ha -1) YI (%) Once a week 8 0.97a 14.43a 84.34 0.86a 13.44a 82.59 6 0.74c 13.57ab 83.35 0.64c 12.06b 80.60 4 0.83b 13.50ab 83.26 0.73b 11.22bc 79.14 2 0.65d 12.23b 81.52 0.55d 10.48c 77.67 Once every two weeks 8 0.47ef 7.12de 68.26 0.37ef 6.24e 62.50 6 0.59d 8.88c 74.55 0.49d 8.20d 71.46 4 0.50e 7.51cd 69.91 0.39e 6.686e 65.02 2 0.37gh 5.60ef 59.64 0.27gh 4.44fg 47.30 Once every three weeks 8 0.36f-h 5.45ef 58.53 0.26f-h 4.38fg 46.58 6 0.44e-g 6.57d-f 65.6 0.34e-g 5.64ef 58.51 4 0.35f-h 5.31ef 57.44 0.25gh 4.23fg 44.68 2 0.31h 4.63f 51.19 0.21hi 3.47gh 32.56 Control 0 0.15i 2.26g - 0.14i 2.34h - SED 0.06 0.67 3.79 40.51 3.41 69.31 53.59 58.01 < 0.001 < 0.001 < 0.001 < 0.001 Table 5: Yield of cucumber sprayed at different rates and frequencies of Beauveria bassiana application in late season, 2021 and early season, 2022 Mean values along the same column within a season followed by similar alphabets are not significantly different from one another using SNK at p < 0.05. SED, Standard error of the differences of the mean, YI = Yield increase over control (%) Late season 2021 Early season, 2022 Insect Leaf damage (%) Yield ha-1 Fruit damage (%) Leaf damage (%) Yield ha-1 Fruit damage (%) Aulacophora foveicollis 0.62** -0.89** 0.86** 0.76** -0.87** 0.82** Aulacophora hilaris 0.71** -0.87** 0.86** 0.79** -0.88** 0.79** Aulacophora nigripennis 0.67** -0.90** 0.85** 0.44 -0.45** 0.41 Epilachna chrysomelina 0.71** -0.9** 0.94** 0.81** -0.95** 0.82** Coridius viduatus 0.57** -0.92** 0.79** 0.66** -0.87** 0.73** Bactrocera cucurbitae NA NA 0.72** NA NA 0.48* Table 6: Correlation coefficients of the relationship between insect pest densities, fruit damage and cucumber yield in the late sea- son, 2021 and early season, 2022 ** = significant at p < 0.01, NA = not applicable Acta agriculturae Slovenica, 121/3 – 2025 7 Efficacy and economic assessment of commercial Beauvaria bassiana ... (Cucumis sativus L.) insect pests in a derived savanna agroecosystem 2022 planting seasons. A strong negative and significant correlation (r = -0.90 and r = -0.80) was observed be- tween fruit yield and pest density, suggesting that higher insect densities reduced cucumber fruit yield (Table 6). The highest profit margins, exceeding 100 %, were obtained using B. bassiana at 8 kg ha-1 weekly, and 6 kg ha-1 once every two weeks in both 2021 and 2022 plant- ing seasons, respectively (Table 7). 3.2 DISCUSSION Insect pest infestations were considerably reduced, and insect-induced damage to cucumber leaves and fruits was mitigated using Beauveria bassiana according to findings of the study. These findings align with the re- port of Dannon et al. (2020) that the fungus B. bassiana strain RSB was effective against western flower thrips Frankliniella occidentalis Pergande, 1895 (Thysanoptera: Thripidae) on broccoli causing a mortality of 69-96 % in laboratory and green house trials. Mehinto et al. (2014) also reported similar efficacy of B. bassiana in controlling Maruca vitrata (Fabricius, 1787) (Lepidoptera: Crambi- dae). Also, B. bassiana has demonstrated efficacy in man- aging pests that have evolved a high level of resistance to chemical insecticides, including whiteflies, aphids, thrips and spider mites (Kliot et al., 2016). Similar reports on the effectiveness of B. bassiana for pest control have been documented in cotton (Dannon et al., 2020), potato (Bo- hata et al., 2024), beans (Mutue et al., 2016), and grape- vine (Jaber, 2015). In this study, B. bassiana also proved effective against fruit flies, particularly with applications at 8 kg ha-¹ once every week and 6 kg ha-1 once every two weeks, which emerged as the most cost-efficient treatment regimens. These results are corroborated by other studies that show fruit flies are extremely vulnerable to entomopathogenic fungus, with B. bassiana exhibiting remarkable patho- genicity against both pupal and adult stages (Hamzah et al., 2021). Mortality rates of 82–100 % have been report- ed for fruit flies treated with B. bassiana (Shahzad et al., 2019). Moreover, contact application methods have been shown to yield higher virulence compared to alternative approaches, such as oral treatments (Gul et al., 2015). A notable positive correlation was observed among the presence of leaf and fruit pests and the percentage fruit damage in both 2021 and 2022, planting seasons. This implies that higher number of leaf pests, E. chrysomelina, A. hilaris, A. nigripennis, and A. foveicollis observed in both 2021 and 2022 planting seasons led to higher leaf damage observed on cucumber in both seasons. It also, revealed that as the density of fruit pest, B. cucurbitae (Coquillett, 1899) observed on cucumber increased, the damage to cucumber fruits also increased. This aligns with the findings of Akinkunmi and Pitan (2021), that a strong association exists between E. chrysomelina density Late season, 2022 Early season, 2022 Frequency Rate (kg ha-1) Number of spray Additional revenue ($) Additional cost ($) Marginal return   Additional revenue ($) Additional cost ($) Marginal return Once every week 8 6 6,582.19 3,430.10 1 7,204.18 3,430.10 1 6 6 6,117.06 3,389.00 0.8 6,308.52 3,389.00 0.86 4 6 6,079.20 3,245.67 0.87 5,763.34 3,245.67 0.78 2 6 5,392.31 3,090.98 0.74 5,283.06 3,090.98 0.71 Once every two weeks 8 3 2,628.55 1,768.59 0.49 2,531.20 1,768.59 0.43 6 3 3,580.45 1,748.31 1.05 3,808.28 1,748.31 1.18 4 3 2,839.48 1,728.03 0.64 2,816.77 1,728.03 0.63 2 3 1,806.45 1,707.75 0.05 1,362.95 1,707.75 -0.2 Once every three weeks 8 2 1,725.32 1,541.43 0.12 1,324.01 1,541.43 -0.14 6 2 2,331.08 1,511.69 0.54 2,141.78 1,511.69 0.42 4 2 1,649.61 1,476.53 0.12 1,226.67 1,476.53 -0.17 2 2 1,281.82 1,324.55 -0.03 733.4 1,324.55 -0.45 Control 0 - - -     - - - Table 7: Profitability of cucumber grown at different rates and frequencies of Beauveria bassiana application in late season, 2021 and early season, 2022 Based on N250.00 and 300.00 per kg of cucumber in late season, 2021 and early season, 2022, respectively. Costs of labour/ha = N10,000, Cost of water usage /ha = N3000, and treatment cost/spray/ha = N22,500. Also, conversion rate to dollar ($) is N 462.232 Acta agriculturae Slovenica, 121/3 – 20258 C. O. FILANI et al. and cucumber fruit damage. The most prevalent insect species found in the study included E. chrysomelina, A. hilaris, A. nigripennis, A. foveicollis, Coridus viduatus, and B. cucurbitae. These pests played important roles in influencing outcomes in cucumber production. Similar pest profiles have been highlighted by Tamoghna et al. (2018) as key contributors to cucumber production chal- lenges. The potential mechanisms underlying the negative and significant relationship between insect pest density and cucumber fruit yield is (r = -0.90 and r = -0.80) sug- gests a strong influence of insect species densities on cucumber fruit yield. Pest pressure drastically reduces crop yield such that simultaneous attack by multiple in- sect pests interactively affected biomass and fruit yield of cucumber through reduction in plant growth. However, the magnitude of such attack and damage is dependent on the densities and frequency of attack. All most all of the pests, E. chrysomelina, A. hilaris, A. nigripennis, and A. foveicollis and B. cucurbitae cause serious damage in cucumber production which lead to yield loss. Attack on crop plants by many pests affect plants survival, growth and reproduction and as a consequence influence crop yield (Oerke, 2006). According to Stephen et al. (2013), the effects of insect attack on plants growth and yield is negative. 4 CONCLUSIONS Epilachna chrysomelina is a highly destructive pest that poses a significant threat to cucumber cultivation. 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