Climate change, fall armyworm (Spodoptera frugiperda) dynamics and maize production: a global perspective
Absztrakt
Maize (Zea mays) is one of the most important cereals globally. It is consumed by humans in different forms (fresh, grain, flour or bread), feeds for the livestocks in fresh or processed form, used in the production of biofuel, as well as other industrial uses. Its production however has been constrained by biotic (pests, diseases and weeds) and abiotic factors due to increased effects of climate change. Fall armyworm (FAW), Spodoptera frugiperda (J.E Smith, 1797), a native species of tropical and sub-tropical Americas is one of the most devastating invasive polyphagous pest of maize. Its larvae damage both vegetative and generative parts of maize including stem, leaves, cobs, silk, tassels and the seeds resulting in reduction of plant growth vigor and up 60% yield loss. Its first occurrence outside Americas was reported in 2016, in the southern part of Sub-Saharan Africa and since then, it has been confirmed in more than 70 countries globally. Due to the yield and quality losses, it causes in maize production, different studies have reported effects climate change on the population dynamics and spread of FAW and different control possibilities against them. The main objective of this review was to evaluate the current advances in FAW and maize production from a global perspective based on published literature. The specific objectives were: i) To assess the current key areas of focus in research of FAW and maize production at global level in order to highlight the gaps and set priorities for further works. ii) To assess the interactive impact of climate factors on FAW and maize production to find the most important ones and iii) To establish and evaluate the current technologies used in the management of FAW in maize production at a global level to find the most efficient ones can be suggested for application. Literatures were obtained from the “Web of Science” data base for each objective using different unique search equations. Certain inclusion and exclusion criteria were used to screen literatures and only those that met these criteria were used. Secondary data graphs were extracted using WebPlotDigitizer v3.4 (beta), processed and analysed using Microsoft Excel and VOSviewer version 1.6.18 software. The result showed that, Kenya is currently the global leader in research related to FAW, climate change and maize production. The current areas of research are focusing on; the use of control agents (parasitoids, Bacillus thuringiensis, pathogenic fungus, nematodes and predators) in FAW management, monitoring (sex pheromones and use volatiles), survival, resistance breeding, IPM, effects of different climatic variables on FAW and chemical management of FAW. The duration of development is generally shorter at higher temperatures (32-35℃) but with lower survival rate as compared to when the temperature is at 28℃. Pupation in the soil is not possible at 88-100% RH. FAW can tolerate temperature below 10℃ and or above 40℃. Its fecundity, survival rate and mating success is generally higher at 28℃ while the development at from egg to pupa was shortest at 35℃. Chemical control is the most widely used control method against FAW. Many active substances used belong to pyrethroid, and organophosphate chemical classes. There is also an increase in the number of active substances with mixed mode of action due to increased resistance against insecticides with single mode of action. Most FAW parasitoids belong to Hymenoptera order, and the most susceptible stages are eggs and pupae. The predators are mainly from Coleoptera and Dermaptera orders. Entomopathogenic fungi, bacteria and nematodes are also used in management of FAW. Conclusively, the colonization of new area within and across continents by FAW is continuously increasing but, no report its establishment has been confirmed within the European Union territory and Europe as a whole and it remains a quarantine pest in the region. Besides, some areas within the EU (Spain) remains a potential area of invasion due to its suitable climatic conditions. IPM technologies need to be promoted for sustainable management of FAW.