Improved fallows or the rotation of fast growing nitrogen-fixing legume species with cereals have been shown to accumulate nitrogen and organic matter, recycle nutrients in the soil and improve soil physical and chemical properties, and increase crop yield compared to traditional fallows. However, the effect of soil nutrients added by fallow species on the incidence of pests, weeds and pathogens in the subsequent crop has not been assessed in southern Africa. In this study, we assessed the relationships between nutrients in the soil after fallows of crotalaria (Crotalaria grahamiana), pigeon pea (Cajanus cajan), sesbania (Sesbania sesban), tephrosia (Tephrosia vogelii), and their mixtures, and the incidence of soil insects, namely, snout beetles (Diaecoderus sp.) and termites, and weeds in eastern Zambia. Rotational fallows of sesbania+crotalaria, sesbania+tephrosia, sesbania+pigeon pea and tephrosia+pigeon pea increased infestation of maize by snout beetles as compared to the natural fallow or unfertilised maize grown continuously in monoculture. The beetles showed aggregated spatial distribution, influenced mainly by the nitrate and total inorganic nitrogen content of the soil. Termite incidence was higher in maize after a natural fallow and pure crotalaria, which had 11 and 7 times as much damage as maize planted after pigeon pea+tephrosia mixture. Total weed biomass in maize grown after a natural fallow was six times higher than in maize planted after pure sesbania fallows. The weed biomass was correlated positively with the potassium content of the top 20 cm soil and negatively with plant litter on the soil surface. It is concluded that organic inputs from pure sesbania, sesbania+pigeon pea, sesbania+tephrosia and tephrosia+pigeon pea reduce infestation by termites and weeds, and give maize grain yield comparable with the recommended rates of inorganic fertilisers. However, these fallows have the potential to increase infestation by snout beetles. This is the first study on the snout beetle in Africa, and we recommend more systematic investigation on its ecology in agroforestry systems.
Tag: insects
Pest management in miombo fruit trees
In this review, the available information on pests and diseases of priority miombo fruit tree species based on published literature and current studies, identify gaps and suggest management options are summarized. The pest complex of most wild miombo fruit tree species is not known and there is little, if any, published information on pest biology and population dynamics. The bulk of the information in the following discussion is based on observations from ongoing work in eastern Zambia, southern Malawi, southern Mozambique and Zimbabwe
Detecting declines of West African Goliath beetle populations based on interviews
Goliath beetles (genus Goliathus) are among the largest and most charismatic insects in the world. In West African forests, two species (G. cacicus and G. regius) and natural hybrids are found. These beetles are widely collected for the entomological trade. We carried out standardized interview campaigns in Liberia and Ivory Coast to explore local persons’ perceptions of the status and population trends of these beetles, as well as information on their ecology and use by humans. Only relatively few interviewed communities reported the presence of beetles, all agreed that Goliath beetle populations were declining, especially G. cacicus. On the other hand, G. regius was generally considered less rare by the interviewees and was also known in a larger number of communities than G. cacicus. Because of the high deforestation rates in Liberia and Ivory Coast, as well as the impact of the international trade at specific collection localities, we suggest that these species are in peril of extinction if no immediate conservation actions are taken to reverse their status.
Fungi and insects as models of extraordinary symbiosis
Symbiosis among microorganisms represents an interesting relationship that takes different shapes. Obligatory, facultative, and endosymbiotic relationships have all been reported between different microorganisms. Whether it is mutualism, commensalism, amensalism, or parasitism, understanding every association is of great importance to science and humanity. Knowing how these creatures benefit from each other may be useful for biocontrol purposes, or even for discovery of novel metabolites that result from these associations, and which may not be produced by the individual species. In this review, five examples of symbiosis were presented, including among the Laboulbeniales; Septobasidium; Ambrosia Fungi and Beetles; Leaf-cutter ants and their fungus gardens; and finally, termites and Termitomyces. Moreover, the benefits each partner is getting were highlighted, and uniqueness in every form of those symbiosis models was simply described.
Valorizing plastic waste by insect consumption
Insects first began evolving hundreds of millions of years ago, and aided by gut microbes, they have been consuming hydrocarbon polymers ever since. Few man-made plastic polymers are chemically novel, so it is reasonable that insect/microbe systems can be found or developed to degrade them rapidly. However, remediation of global plastic waste problems should involve more than just conversion into CO2. Some industry-scale microbial enzymatic degradation of plastic polymers may yield valuable monomers, but the plastic waste starting material must be of uniform chemistry and clean. This adds cost to the process. Many insect species can be utilized for animal feed as well as human food. Some of these insects have the capability to degrade plastic polymers. However, valorizing plastic wastes by producing edible insects or useful frass has largely been overlooked. Here we assemble the current knowledge of plastic degradation rates by insects. In addition, we also show the first instance of insect degradation of polyurethane and the first identification and isolation of insect gut fungi as directly aiding insect degradation.