Bioactivity of cypress leaf powder (Cupressus macrocarpa) on cowpea weevil (Callosobruchus maculatus Fabr. Coleoptera: Bruchidae) and maize weevil (Sitophilus zeamais Motschulsky, Coleoptera: Curculionidae) in stored maize grains in Cameroon

Abstract Cowpea weevil (Callosobruchus maculatus) and maize weevil (Sitophilus zeamais) are very destructive pests of cowpea and maize respectively. Synthetic chemicals have been used extensively to control these pests. The present study investigated the potential of cypress leaf (Cupressus macropcarpa) powder as a biological agent against these pests. Three doses (g) of cypress leaf powder (2, 5 and 10g) were exposed to 10 adult insects in triplicate and mortality was observed every 24hrs for 3days. A repellency test was also conducted in triplicate using 3 doses (g) (2, 5, and 10g) of cypress leaf powder. The experimental design was Completely Randomised Design (CRD). The experiments were conducted in a laboratory (28 ± 2 o C and 80 ± 10% RH) in the Farm house of the Faculty of Agriculture and Veterinary Medicine, University of Buea, Cameroon The results revealed that, the cypress leaf powder did not cause any significant mortality (p > 0.05) compared to the controlled for both insect pests. The repellency test revealed that the cypress leaf powder showed a very high potential as a repellent agent (p < 0.05) with up to 50 -60% of both insect pests repelled just after 10mins of exposure to the smallest dose (2g). About 90% repellency was observed for both pests from the highest dose (10g) within 10mins of exposure making 10g a perfectly repellent dose. Our research supports strongly that cypress leaf powder has a strong repellency effect on both pests and little or no potential to cause significant mortality. Thus cypress leaf powder is a good candidate to incorporate in integrated pest management (IPM) programmes for control of cowpea and maize weevil in stored grains by poor-resourced farmers and store keepers in Cameroon and the world at large. Thus, appropriate technology transfer systems should be developed and passed on to poor-resources farmers to promote a direct preparation of indigenous pesticides at farm-house level

Laboratory and Field Trials to Identify Reduced-Risk Insecticides for the Control of the Golden Twin-Spot Moth <i>Chrysodeixis chalcites</i> (Esper) (Lepidoptera: Noctuidae) in Banana Plantations

The golden twin-spot moth (Chrysodeixis chalcites) is one of the most important pests in banana production on the Canary Islands (Spain). The efficacy of different biorational insecticides based on bioenzyme complexes (Intruder®), plant extracts: Rutaceae and Piperaceae (Avenger®), Rutaceae and Lauraceae (BioKnock®), cinnamon, citronella, and Menta (Cinamite®), Alliaceae and Solanacea (Garlitrol-Forte®), citrus (Prevam®), and neem oil (Indasol®) was assessed against C. chalcites. Laboratory assays included: choice (repellent effect), no choice, and contact toxicity on C. chalcites 2nd instar larvae. The highest repellent effect was observed with Prevam® (85.19 ± 1.7%), followed by Garlitrol® (68.44 ± 5.7%) and Intruder® (67.54 ± 4.3%). In no choice assays, Prevam® (0.92 ± 0.4%), Indasol® (0.98 ± 0.33%), and Intruder® (2.7 ± 0.33%) had the lowest leaf consumption. The contact toxicity assays showed the highest mortality with Intruder® both at 1 day and 7 days post-application (20.22 ± 2.98% and 77.77 ± 5.7%, respectively). In the screenhouse trial, the best results for C. chalcites larvae mortality, fruit damage, and fruit classification in quality categories 7 days after application of the bioinsecticide were obtained with Intruder®, Prevam®, and Indasol®. An economic analysis of biorational treatments was also performed. The results of this study provide successful alternatives to chemical pesticides for the control of C. chalcites on banana plants in the Canary Islands

Effects of several UV-protective substances on the persistence of the insecticidal activity of the Alphabaculovirus of Chrysodeixis chalcites (ChchNPV-TF1) on banana (Musa acuminata, Musaceae, Colla) under laboratory and open-field conditions.

Alphabaculovirus of Chrysodeixis chalcites (ChchNPV-TF1) has been investigated as a useful bioinsecticide against C. chalcites (Esper) (Lepidoptera: Noctuidae) in banana crops. This study investigated the effects of several substances on the persistence of ChchNPV-TF1 under field conditions in the Canary Islands. Natural photoprotective substances, such as moringa, cacao, green tea, benzopurpurine, charcoal, iron dioxide, benzimidazole, kaolinite, and bentonite, were first evaluated under laboratory conditions using a Crosslinker as UV light source at 200 J/cm2. The photoprotective substances were divided into three groups: low protection (0-8%; kaolinite), intermediate protection (48-62%; green tea, moringa, bentonite and cacao) and high protection (87-100%; charcoal, iron ioxide). Benzopurpurine and benzimidazole did not provide any photoprotective effects. Two of the substances that yielded the best results, 1% cacao and 1% charcoal, were selected for the open-field experiment in a banana plantation. The persistence of ChchNPV-TF1 OBs (occlusion bodies) on leaf surfaces with sunlight exposure was analysed by comparing the initial mortality of 2nd instar C. chalcites larvae with the mortality observed at various intervals postapplication. The mortality rates decreased over time in all treatments and were always higher in the UV-protective substance-treated parcels. The 1% charcoal treatment exhibited the highest protection in both the laboratory and field experiments. No specific interference of UV-protective substances on the maximum photochemical efficiency of banana plants was observed under field conditions