Assessing vegetable farmer knowledge of diseases and insect pests of vegetable and management practices under tropical conditions

Accepted author version posted online: 22 Jul 2013. Published online: 02 Jun 2014

Spodoptera frugiperda Smith (Lepidoptera: Noctuidae) in Cameroon: case study on its distribution, damage, pesticide use, genetic differentiation and host plants

Open Access JournalMaize farmers in sub-Saharan Africa recently experienced unusual damage in their farms, attributed to the fall armyworm (FAW) Spodoptera frugiperda (J. E. Smith). This pest was first recorded in Africa in 2016, but detailed information on its distribution and damage and farmer's response in invaded areas are largely lacking. In this study, we determined FAW distribution, genetic diversity, host plants, crop damage, and farmers' responses. S. frugiperda was recorded in the 10 regions of Cameroon. Average percentage of infested plants and damage severity (on a scale of 1 to 5) were lowest-20.7 ± 7.4% and 2.1 ± 0.1 respectively-in the Sahelian regions and greatest-69.0 ± 4.3% and 3.1 ± 0.1 respectively-in the Western Highlands. Altitude did not influence FAW incidence and severity and its larvae infrequently co-occurred with maize stemborers on the same plants, suggesting possible direct and/or indirect competition between the two groups of maize pests. In response to this new threat to maize production, farmers have opted for the application of synthetic pesticides. Although our experiments were not designed to determine pesticide efficacy, as parameters such as time since application were not considered, our observations suggest lack of a drastic effect on S. frugiperda infestations on maize. There were two haplotypes of FAW co-occurring in Cameroon corresponding to the rice and corn strains and separated by 1.7% sequence divergence, which does not support the existence of cryptic species. S. frugiperda larvae were also recorded on Sorghum bicolor (L.) Moench (10.6%), Solanum tuberosum L. (2.8%), Ipomoea batatas (L.) Lam. (1.9%), Saccharum officinarum L (0.8%), Phaseolus vulgaris L. (0.4%) and Gossypium hirsutum L. (1.9%). This study show that two strains are present in all agroecological zones in Cameroon, and probably in neighboring countries of central Africa sharing the same agroecologies. Management options should therefore consider the use of specific natural enemies and an informed decision of intervention based on strain capture and damage threshold, to avoid pesticide resistance that may arise from inadequate use of chemicals. Further studies should also be undertaken to assess the response of the two S. frugiperda strains to biopesticides and botanical insecticides

Reliability of pheromone trap catches and maize plant damage as criteria for timing fall armyworm control interventions in humid forest agroecology of central Africa

Control of fall armyworm (FAW) Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) since its invasion of Africa still depends on pesticides. Early detection of adults is considered the key to the success of larvae control in the crop field. However, FAW control thresholds based on current monitoring techniques are not well established in Africa. We investigated the efficacy of moth capture frequencies and FAW incidence levels as decision tools for FAW management. Experiments were conducted over two maize cropping seasons during which FAW incidence, severity, and larvae count were recorded during destructive sampling after the application of a homologated insecticide. During the first season, the FAW incidence ranged from 37.5 ± 5.6% in the 25% incidence threshold treatment to 48.1 ± 8.1% in the control. During the second season, the incidence was significantly lower in the 25% incidence threshold treatment (55.8 ± 5.7%) compared with the control (75.7 ± 3.0%). Over the two seasons, no significant difference in FAW damage severity was recorded between the treatments and control. The highest number of larvae per plant (4.0 ± 0.6) was observed in the 10% incidence threshold treatment. Insecticide application did not consistently contribute to reducing FAW incidence and observed plant damage did not translate into yield loss. FAW control needs further investigation to establish a threshold above which damage translates into yield loss, thus necessitating control intervention

Plantain hybrids for the humid forest agroecology of Central Africa – diseases and pests load, fruit yield and farmers perception

Open Access Journal; Published online: 01 Nov 2022Plantain is one of the major staples contributing to food security and income generation in West and Central Africa. Local cultivars in Cameroon are susceptible to pests and diseases causing severe losses in plantain production. This study aimed at evaluating the agronomic performance and producer’s perception of plantain hybrids in the humid forest of Cameroon. Field trials were established in a completely randomized block design with eight genotypes and three replicates. Data on pest and disease as well as farmer perception were collected over two growing cycles. These genotypes included seven improved and one local genotype (check). Improved genotypes were highly tolerant to the Black Sigatoka disease compared to local plantain. While root necrosis index was above 50% in local varieties, indices below 25% were recorded in hybrids. Weevil severity in local was higher (55.0 ± 5.2%) compared to 21.0 ± 4.6% to 28.5 ± 3.2% in improved plantains. Average bunch weight was higher for FHIA 21 with 17.9 ± 0.7 kg in the first and 19.7 ± 0.3 kg for the second cycle, while those of the local Ebang were 9.6 ± 0.5 kg and 12.8 ± 0.9 kg, respectively. FHIA 21 and CRBP 568 were the preferred varieties by farmers (68.8% and 56.3% acceptance) from an agronomic perspective. The consumers’ preferences for all the genotypes varied with types of cooking. The implications of these findings for adoption by farmers and consumers as well as for the promotion of the plantain sector in central Africa are discussed

Vegetable growers perception of pesticide use practices, cost, and health effects in the tropical region of Cameroon

Pesticide use practices of vegetable farmers were investigated during surveys conducted in major vegetable production zones of the humid tropics of Cameroon. The surveys aimed to elucidate farmers’ crop calendar, pesticide spray schedule and frequency. Farmers’ knowledge was determined on pest targets, quantities and major active ingredients used, and training received in vegetable production. It was found that weekly spray of pesticides was the most common practice; 40% of farmers sprayed insecticide, 28% sprayed fungicides. However, 45 and 59% could not identify the insect pests and diseases respectively they were attempting to control. Farmers applied 0.5-9 liters of pesticide per year, 10-49 kg, and 10 to 49 packets of chemicals depending on farm size. Prices of pesticide range from 5000 to 13000 FCFA per liter of insecticide, 6000 to 8500 FCFA per kg of fungicide and 300 to 12000 F per packet. Ninety percent of farmers used a knapsack sprayer and 20% of farmers noticed that their health was affected by pesticides. About 25% of farmers store chemicals at home. Seventy-five percent receive information about agricultural production from other farmers, and have never received any training on pesticide use practices and health effects. The absence of farmer training further increases the danger of pesticide misuse and cost of vegetable production. Less expensive pest management options that are less hazardous to the environment and human health need to be introduced to farmers, and create awareness regarding hazards of mishandling pesticides if the products are to be used by vegetable farmers in Cameroon

Potential of Cameroon-indigenous isolates of the entomopathogenic fungi Beauveria bassiana and Metarhizium anisopliae as microbial control agents of the flea beetle Nisotra uniformis

The flea beetle Nisotra uniformis Jacoby is a widespread pest of malvaceous crops for which synthetic chemical insecticides remain the principal control tool, particularly in sub-Saharan Africa. With the ultimate aim of developing a microbial alternative for N. uniformis control, we conducted laboratory experiments (25 ± 1°C; 70 - 80% RH) to evaluate the biological attributes of three Cameroonian isolates of the entomopathogenic fungi Beauveria bassiana (Balsamo-Crivelli) Vuillemin and Metarhizium anisopliae sensu lato (Metchnikoff) Sorokin. Spore germination rates of the isolates varied from 0.5% after 4 hrs to 100% after 24 hrs on PDA medium, with MIITAC11.3.4 spores germinating fastest. Pathogenicity tests consisted of dipping adult beetles in conidial suspensions. All isolates were pathogenic to N. uniformis, with corrected mortalities varying between 23.3 - 86.7%. BIITAC-O-2 had the lowest LC50 at 5.17 × 106 conidia/ml, while MIITAC11.3.4 and BIITAC6.2.2 had LC50 at 4.11 × 107 conidia/ml, and 2.00 × 108 conidia/ml, respectively. BIITAC6.2.2 produced the shortest time to the highest mortality rate (1.17 days) and the shortest LT50 of 1.64 days but only at the highest concentration, followed by the two highest concentrations of MIITAC11.3.4 (LT50 at 3.43 and 5.70 days). The c parameter in the Weibull model showed that BIITAC-O-2 caused the highest rate of increase in mortality (2.42) at the highest concentration, followed by MIITAC11.3.4 (1.09) and BIITAC6.2.2 (0.50). The results of our study provide the basis for including N. uniformis in the ongoing development of BIITAC6.2.2 and MIITAC11.3.4 into biopesticide while continuing with further laboratory studies on BIITAC-O-2

Ultrafast optical spectroscopy of strongly correlated materials and high-temperature superconductors: a non-equilibrium approach

In the last two decades non-equilibrium spectroscopies have evolved from avant-garde studies to crucial tools for expanding our understanding of the physics of strongly correlated materials. The possibility of obtaining simultaneously spectroscopic and temporal information has led to insights that are complementary to (and in several cases beyond) those attainable by studying the matter at equilibrium. From this perspective, multiple phase transitions and new orders arising from competing interactions are benchmark examples where the interplay among electrons, lattice and spin dynamics can be disentangled because of the different timescales that characterize the recovery of the initial ground state. For example, the nature of the broken-symmetry phases and of the bosonic excitations that mediate the electronic interactions, eventually leading to superconductivity or other exotic states, can be revealed by observing the sub-picosecond dynamics of impulsively excited states. Furthermore, recent experimental and theoretical developments have made it possible to monitor the time-evolution of both the single-particle and collective excitations under extreme conditions, such as those arising from strong and selective photo-stimulation. These developments are opening the way for new, non-equilibrium phenomena that can eventually be induced and manipulated by short laser pulses. Here, we review the most recent achievements in the experimental and theoretical studies of the non-equilibrium electronic, optical, structural and magnetic properties of correlated materials. The focus will be mainly on the prototypical case of correlated oxides that exhibit unconventional superconductivity or other exotic phases. The discussion will also extend to other topical systems, such as iron-based and organic superconductors, (Formula presented.) and charge-transfer insulators. With this review, the dramatically growing demand for novel experimental tools and theoretical methods, models and concepts, will clearly emerge. In particular, the necessity of extending the actual experimental capabilities and the numerical and analytic tools to microscopically treat the non-equilibrium phenomena beyond the simple phenomenological approaches represents one of the most challenging new frontiers in physics