Letteratura scientifica selezionata sul tema "Roots (Botany) Diseases and pests"

Abstract This chapter describes the different diseases and pests that affect yams and various methods for their control. It particularly covers the following aspects: field fungal diseases; postharvest fungal diseases; specific fungal diseases; control of fungal diseases; bacterial diseases; viral diseases; physiological disorders; insect pests; and nematode pests.

Nematodes are the most plentiful animals on earth, commonly found in soil or water, including oceans. Some species of nematodes are parasites of plants and animals. Plant-parasitic nematodes are non-segmented microscopic, eel-like round worms, obligate parasite possess stylets that live in soil causing damage to plants by feeding on roots or plant tissues. Plant-parasitic nematodes feed on roots, either within the root, some nematodes feed leaves. These nematodes cause breakdown of resistance to fungal diseases in fruit crops. Plant-parasitic nematodes living host tissue to feed on to grow and reproduce. Nematode life cycle consists of an egg, 4 pre-adult stages (juveniles) and an adult, life cycle depending on the species and the temperature. Nematodes do not move long distances (less than 6 inches per year). They are usually transported over long distances on machinery, in nursery stock, transplants, seeds, or by animals, moves soil, water and wind. They acquire nutrients from plant tissues by needle-like feeding structure (stylet/spear). Nematodes can be classified into three groups depending on feed on the plants such as ectoparasitic nematodes are always remaining outside the plant root tissues. Migratory endoparasitic nematodes move through root tissues sedentary endoparasitic nematodes penetrate young roots at or near the growing tip. They steal nutrients, disrupt water and mineral transport, and provide excellent sites for secondary pathogens (fungus and bactria) to invade the roots and decay. Several nematode species that cause problems in fruit orchards that are major limiting factors in fruit crop production cause extensive root necrosis resulting in serious economic losses. The root-knot nematode (Meloidogyne spp.), burrowing nematode (Radopholus similis) and citrus nematode (Tylenchulus semipentrans) are the major nematode pests that infect fruit crops. Parasitic nematodes that can damage tree fruit roots. Many kinds of nematodes have been reported in and around the roots of various fruit crops, only few are cause serious damage, including Root-knot nematodes (Meloidogyne spp.), Lesion nematodes (Pratylenchus species), Ring nematodes (Mesocriconema spp) are cigar-shaped that are strictly ectoparasitic, Dagger nematodes (Xiphinema spp) are relatively large ectoparasites that feed near root tips, Sting nematodes (Belonolaimus species) are ectoparasitic, Citrus nematodes (Tylenchulus semipenetrans) are sedentary semi-endoparasites. Nematodes reduce yield without the production of any noticeable above ground symptoms. Typical above ground symptoms of nematode infections stunting, yellowing and wilting. Major nematodes associated in large number of vegetables crops in India such as root-knot nematodes (Meloidogyne spp.), cyst nematodes (Heterodera spp.), lesion nematodes (Pratylenchus sp.), reniform nematodes (Rotylenchulus sp.) lance nematodes (Hoplolaimus spp.), stem and bulb nematode (Ditylenchus spp.) etc. Root-knot nematodes are important pests of vegetables belonging to solanaceous (brinjal, tomato, chili), cucurbitaceous (biter ground, cucumber, pumpkin, bottle gourd) leguminous (cowpea, bean, pea), cruciferous cauliflower, cabbage, broccoli, brussels, sprout), okra and several other root and bulb crops (onion, garlic, lettuce, celery, carrot, radish). Four species (M. incognita, M. javanica, M. arenaria and M. hapla) are more than 95% of the root-knot nematode population worldwide distribution. Stem and Bulb nematode (Ditylenchus spp.) commonly attacks onion, garlic, potato, pea and carrot etc. The nematodes spread from one area to another mainly through infested planting materials, water drains from infested areas into irrigation system, soil that adheres to implements, tyres of motor vehicles and shoes of plantation workers. Management recommendation through bio-pesticides, cultural practices, enrichment of FYM, Neem cake and other organic amendments.

The success of the UN Sustainable Development Goals in reducing hunger and poverty is limited by crop losses. Globally, plant pests and diseases account for 40% yield losses which threatens food and nutrition security, livelihoods of citizenry and erode the resources of local and national economies. Phytophthora diseases are among the most important diseases in sub-Saharan Africa which result in severe socio-economic consequences. Roots and tubers and cash commodity crops are important staples and foreign exchange earner crops in Ghana which are significantly challenged by the incidence and severity of Phytophthora diseases. To ensure food availability, safeguard the local financial ecosystem and protect the environment, innovative and sound management practices are needed and this chapter reviews the different Phytophthora diseases on crops; more specifically with (cocoa and taro as case studies), the consequences and available management options that can be applied to manage the disease situation in Ghana.

Soybean (Glycine max L. Merr) is the most important legume and threaten by diverse pests and diseases. Complex interactions among rhizosphere organisms are found in all agro-ecosystems. Results of these interactions can be positive and/or negative in terms of plant production. Soil nematode community consists of different trophic groups of nematodes. Nematodes are the most abundant soil invertebrates. Several nematode species penetrate soybean roots as parasites, and can cause loss in yields. Arbuscular mycorrhiza fungi are obligate plant symbionts that colonize soybean roots naturally. The aim of the study was to evaluate effects of irrigation and amendments of bioproducts containing beneficial soil microorganisms (ABM) on nematode community and mycorrhizal root colonization in soybean. Field experiments were conducted in soybean in 2013 in Osijek, Croatia. The plots were either rain fed or irrigated to 60-100% field water capacity (FWC). We tested soil amendments and soil + foliar amendments of three commercial products containing beneficial organisms. Average number of nematodes per soil sample varied from 186,67 (soil ABM in non-irrigated plots) to 297,57 (soil+foliar ABM in plots with 60-100% FWC), and there were no significant differences between the treatments. Bacterial feeding nematodes were the most abundant, while plant parasitic genus Pratylenchus was the most abundant among other plant parasitic nematodes. There was no clear influence of any of the treatments on soil nematode community. Amendments of the bioproducts increased mycorrhizal root colonization in rain fed plots, while it decreased the mycorrhizal root colonization when soybeans were irrigated. Irrigation increased mycorrhizal root colonization in plots without amendments of the bioproducts, and mycorrhizal colonization differed significantly between the sampling dates. Further research is needed to determine if irrigation alters the potential of mycorrhiza to colonize the roots.