Cassava is mostly grown for its starchy roots, which ensure food security. However, it is heavily attacked by the African root and tuber scale (ARTS) Stictococcus vayssierei in Central Africa. This pest is a severe constraint to the production of cassava, food and income security for smallholder farmers. Crop resistance development through the selection of varieties with resistant traits against targeted pests is a promising approach to pest control. This study investigated cassava genotypes' response to natural infestation and determined their resistance levels against S. vayssierei. Six cassava genotypes (two local and four improved) were planted in a completely randomized block design with four replicates. Agronomic parameters and ARTS density were evaluated at 3, 6, 9 and 12 months after planting (MAP). Biochemical content was determined on the pith and cortex of 12 MAP aged tuberous roots. As a result, the improved Excel variety recorded the highest scale density per plant with 102.83 +/- 4.14 ARTS/P at 9 MAP. At 12 MAP, high activity of total cyanide (69.18 +/- 0.88 and 69.16 +/- 1.44 mg/kg) and phenylalanine ammonia-lyase (0.142 +/- 0.020 and 0.145 +/- 0.010 Delta A/min/mg) were observed in the cortex of the tuberous roots of the improved varieties TMS 96/0023 and TMS 92/0057 which were colonized by the lowest ARTS density. The local variety (Douma) had a high content of total phenols (44.87 +/- 1.15 mu g/g) in the pith. It also produced the highest yield (23.8 +/- 2.9 t ha -1). Varieties TMS 96/0023, TMS 92/0057 and Douma may be the most suitable varieties for the control of ARTS stress.

Background: Annona muricata, or soursop, is a tropical plant known for antimicrobial and antiparasitic properties, widely used in traditional remedies. Extracts from leaves, seeds, and bark show activity against pathogens in humans and plants, making it a promising candidate for natural biopesticide development as safer alternatives to chemical controls. This study evaluates Annona muricata seed extracts as bio-fungicides against Cercospora leaf spot in okra under field conditions. Methods: Capillary gas chromatography and mass spectrometry (GC-MS) analyzed aqueous and organic (acetone, ethyl acetate, and methanol) extracts. Two okra varieties (V1 and V2) were tested in field trials during 2019 and 2020. Six treatments included control, synthetic fungicide (3.33 g/L), aqueous extract (33.33 g/L), and methanol, acetone, and ethyl acetate extracts (1:600 v/v). Disease incidence, severity, and yield were measured. Results: GC-MS identified eight antifungal compounds (hexadecanoic acid methyl ester, hexadecanoic acid ethyl ester, hexadecane, n-hexadecanoic acid, octadecanoic acid methyl ester, 9-octadecanoic acid ethyl ester, and 10-octadecadienoic acid (Z,Z)-methyl ester), though these were not directly tested in this study. The Cercospora incidence at 12 weeks after sowing was significantly reduced from 51.11 % and 47.82 % in control plots during 2019 and 2020, respectively, to 8.88 % and 6.64 % in plots treated with aqueous extract and 9.99 % and 9.76 % in plots treated with methanol extract. Yields were highest with aqueous extract (6.48 and 5.22 t/ha), outperforming methanol extract, synthetic fungicide, and control. Conclusion: Bio-fungicides from Annona muricata extracts offer environmentally friendly options for managing okra cercosporiosis

Aims: In order to find an alternative to chemical control, the insecticidal potential of aqueous extracts of Thevetia peruviana seeds formulated at 16.66 g/l were tested in the field on the maize stalk borer species. Study Design: The factorial design in subdivided plots or "split-plot" with four replicates and two factors studies was used on an area of 250 m². Place and Duration of Study: The experiment was carried out in a field located in the city of Yaounde, Cameroon where cassava was grown beforehand, between July and October 2021. Methodology: The extracts at 250 g per 15 l of water were tested against a synthetic insecticide Cypercal at 37.5 ml per 5 l of water and an absolute control (untreated) in a four replicate split-plot device. Two maize varieties (V1: CMS 8704; V2: local) and three treatments (T1: control; T2: T. peruviana seed extract; T3: Cypercal 12 EC) were used. The aqueous extract of T. peruviana was applied by spraying on stems, leaves and leaf cones from 5th to 9th weeks after sowing (SAS). Data were recorded on growth parameters, stem borer density, and maize grain yield. Results: The results show that the application of the treatments resulted in a good development of the growth parameters in the two maize varieties used. Two species of borer Busseola fusca and Sesamia calamistis belonging to the order Lepidoptera were identified. The density of maize stalk borers was significantly reduced (T2: 3 borers) in the subplots treated with aqueous extracts compared to the control (T1: 10 borers). Treatment T2 (2.05 t/ha) gave higher grain yield than the control (1.41 t/ha). Conclusion: The aqueous extracts of T. peruviana seeds having thus shown a strong insect repellent potential in the field can therefore be integrated into the framework of biological control that protects the environment and human health.

The African Root and Tuber Scale (ARTS) Stictococcus vayssierei R. is a formidable enemy to cassava (Manihot esculenta Crantz) production, responsible for production losses ranging from 60 to 100% in plantations if strong measures are not taken to control its spread. To improve the production of this commodity, a study was carried out to reduce the number of root scale insects, and their effects on cassava production in the field. The present study test the insecticidal activity of aqueous and organic extracts of Thevetia peruviana seeds against Stictococcus vayssierei. The cassava varieties TMS 92/0057 (improved) and Miboutou (local) as well as five treatments (T0= control, T1= aqueous extract, T2= methanol extract, T3= acetone extract and T4= BASTION-SUPER chemical insecticide) were used in a split-plot design with four replicates. Growth parameters, number of live and dead root scale insects per plant and yield were evaluated. The results show that the highest number of live root scale insects per plant is observed on Miboutou variety (125 ARTS/P) in control plots than on the 92/0057 variety in plots treated with aqueous extract (84.13 ARTS/P). The lowest yield of fresh tubers is observed in control plots of the Miboutou variety (11.50 t ha-1). Highest yields are observed in 92/0057 variety in plots treated with acetone extract (15.20 t ha-1) and the Miboutou variety in plots treated with synthetic insecticide (15.05 t ha-1). Thevetia peruviana seeds, through their repressive effect against cassava root scale, would indicate an insecticide potential.

Cercospora malayensis induced leaf spot is a dangerous okra disease that reduces crop yields. The aim of this study is to use leaf extract from Crinum zeylanicum to regulate the growth of Cercospora malayensis in vitro. The pathogen was isolated from okra leaves from the Meyomessala and Akonolinga localities that had typical disease symptoms. Phytochemical screening and GC-MS analysis of C. zeylanicum leaf extracts were carried out. The mycelial growth and germination of C. malayensis isolates 1 and 2 were evaluated with concentrations of 15, 30, 60, and 120 μL mL-1, fungicide (3.33 g L-1), and control. Minimum inhibition concentrations (MIC50 and MIC90) were evaluated. The results showed the presence of alkaloids, phenols, terpenoids and sterols in the leaf extracts. In acetone (AcE), methanol (ME) and aqueous (AqE) extracts, 32; 39 and 10 chemical compounds, respectively were found by GC-MS analysis. The most prevalent biochemically active compounds were n-Hexadecanoic acid (35.04 %), Cis-Vaccenic acid (31.76 %), Quinoline-7-carboxylic acid, 2-phenyl-, methyl ester (26.63 %), 9,12-Octadecadienoic acid (Z,Z)- methyl ester (16.89 %) and 9,12-Octadecadienoic acid (Z,Z) (10.83 %). AqE, AcE and ME extracts at 120 μL mL-1 inhibited 100 % of mycelial growth and conidial germination of isolates 1 and 2 compared to the control. The lowest MICs (MIC50 and MIC90) were 6.79 and 10.98 μL mL-1 for isolate 1 and 7.48 and 11.22 μL mL-1 for isolate 2, respectively. C. zeylanicum it is possible to use extracts for their volatile biochemical substances in a C. malayensis control program.