Rice is a cereal grain, and in its domesticated form is the staple food for over half of the world's human population, particularly in Asia and Africa. Rice is the seed of the grass species Oryza sativa or, much less commonly, O. glaberrima. Asian rice was domesticated in China some 13,500 to 8,200 years ago, while African rice was domesticated in Africa some 3,000 years ago. Rice has become commonplace in many cultures worldwide; in 2021, 787 million tons were produced, placing it third after sugarcane and maize. Only some 8% of rice is traded internationally. Three countries, China, India, and Indonesia together account for 59% of global consumption. Between 8% and 26% of the rice produced in developing nations is lost after harvest through factors such as poor transport and storage. Rice yields can be reduced by many pests including insects, rodents, and birds, as well as by weeds, and by diseases such as rice blast. Integrated pest management seeks to control damage from pests in a sustainable way.
Oryza sativa, also known as rice, is the plant species most commonly referred to in English as rice. It is the type of farmed rice whose cultivars are most common globally, and was first domesticated in the Yangtze River basin in China 13,500 to 8,200 years ago.
A leaf spot is a limited, discoloured, diseased area of a leaf that is caused by fungal, bacterial or viral plant diseases, or by injuries from nematodes, insects, environmental factors, toxicity or herbicides. These discoloured spots or lesions often have a centre of necrosis. Symptoms can overlap across causal agents, however differing signs and symptoms of certain pathogens can lead to the diagnosis of the type of leaf spot disease. Prolonged wet and humid conditions promote leaf spot disease and most pathogens are spread by wind, splashing rain or irrigation that carry the disease to other leaves.
The brown planthopper (BPH), Nilaparvata lugens (Stål) is a planthopper species that feeds on rice plants. These insects are among the most important pests of rice, which is the major staple crop for about half the world's population. They damage rice directly through feeding and also by transmitting two viruses, rice ragged stunt virus and rice grassy stunt virus. Up to 60% yield loss is common in susceptible rice cultivars attacked by the insect. The BPH is distributed throughout Australia, Bangladesh, Bhutan, Burma (Myanmar), Cambodia, China, Fiji, India, Indonesia, Japan, North and South Korea, Laos, Malaysia, India, Nepal, Pakistan, Papua New Guinea, Philippines, Sri Lanka, Taiwan, Thailand, and Vietnam. Their alternative host plant other than rice is Leersia hexandra.
Gibberella zeae, also known by the name of its anamorph Fusarium graminearum, is a fungal plant pathogen which causes fusarium head blight (FHB), a devastating disease on wheat and barley. The pathogen is responsible for billions of dollars in economic losses worldwide each year. Infection causes shifts in the amino acid composition of wheat, resulting in shriveled kernels and contaminating the remaining grain with mycotoxins, mainly deoxynivalenol (DON), which inhibits protein biosynthesis; and zearalenone, an estrogenic mycotoxin. These toxins cause vomiting, liver damage, and reproductive defects in livestock, and are harmful to humans through contaminated food. Despite great efforts to find resistance genes against F. graminearum, no completely resistant variety is currently available. Research on the biology of F. graminearum is directed towards gaining insight into more details about the infection process and reveal weak spots in the life cycle of this pathogen to develop fungicides that can protect wheat from scab infection.
Aphelenchoides ritzemabosi is a plant pathogenic nematode. It was first scientifically described in 1890 in England. This nematode has a wide host range. Among the most important species affected are Chrysanthemums and strawberries. A. ritzemabosi is a migratory foliar feeding nematode. It can feed both ectoparasitically and endoparasitically, with the later causing the most significant damage. When adequate moisture is present, this nematode enters the leaves and feeds from inside the tissue. Typical damage is characterized by necrotic zones between the veins of the leaves. Its lifecycle is short; only ten days from egg to mature adult. A single female can lay as many as 3,500 eggs. This pest can be difficult to control. Host plant resistance, hot water treatments, and predatory mites are recommended.
Ditylenchus dipsaci is a plant pathogenic nematode that primarily infects onion and garlic. It is commonly known as the stem nematode, the stem and bulb eelworm, or onion bloat. Symptoms of infection include stunted growth, discoloration of bulbs, and swollen stems. D. dipsaci is a migratory endoparasite that has a five-stage lifecycle and the ability to enter into a dormancy stage. D. dipsaci enters through stomata or plant wounds and creates galls or malformations in plant growth. This allows for the entrance of secondary pathogens such as fungi and bacteria. Management of disease is maintained through seed sanitation, heat treatment, crop rotation, and fumigation of fields. D. dipsaci is economically detrimental because infected crops are unmarketable.
Hirschmanniella oryzae, i.e. rice root nematode (RRN), is among the major pests of rice and is the most common plant-parasitic nematode found on irrigated rice. Recent modifications in cultivation practices have led to a substantial increase in rice production, which has been accompanied by heightened levels of RRN. The proportional increases in RRN with rice production can be explained by the nematode's impeccable adaptation towards constantly flooded conditions in which irrigated rice is often being grown.
Xiphinema americanum, the American dagger nematode, is a species of plant pathogenic nematodes. It is one of many species that belongs to the genus Xiphinema. It was first described by N. A. Cobb in 1913, who found it on both sides of the United States on the roots of grass, corn, and citrus trees. Not only is Xiphinema americanum known to vector plant viruses, but also X. americanum has been referred to as "the most destructive plant parasitic nematode in America", and one of the four major nematode pests in the Southeastern United States.
Heterodera sacchari, the sugarcane cyst nematode, mitotic parthenogenic sedentary endoparasitic nematode. This plant-parasitic nematode infects the roots of sugarcane, and the female nematode eventually becomes a thick-walled cyst filled with eggs. Aboveground symptoms are species specific and are similar to those caused by other Heterodera species. Symptoms include: stunted and chlorotic plants, and reduced root growth. Seedlings may be killed in heavily infested soils.
Rice ragged stunt virus (RRSV) is a plant pathogenic virus of the family Reoviridae.
Foliar nematodes are plant parasitic roundworms in the genus Aphelenchoides. The three most economically important species are Aphelenchoides fragariae, A. ritzemabosi, and A. besseyi. Foliar nematodes are becoming a widespread and serious problem for the ornamental and nursery industries. A. fragariae causes damage on hundreds of different plants including chrysanthemum, begonia, gloxinia, African violet, cyclamen, and a wide variety of bedding plants and ferns, causing brown to black, vein-delimited lesions on leaf tissue, defoliation, and possible stunting of plants.
Broken rice is fragments of rice grains, broken in the field, during drying, during transport, or during milling. Mechanical separators are used to separate the broken grains from the whole grains and sort them by size.
Strawberry foliar nematode, or strawberry crimp nematode, is a disease caused by Aphelenchoides fragariae, a plant pathogenic nematode. It is common in strawberries and ornamental plants and can greatly affect plant yield and appearance, resulting in a loss of millions of dollars of revenue. Symptoms used to diagnose the disease are angular, water soaked lesions and necrotic blotches. Aphelenchoides fragariae is the nematode pathogen that causes the disease. Its biological cycle includes four life stages, three of which are juvenile. The nematode can undergo multiple life cycles in one growing season when favorable conditions are present. The crowns, runners, foliage, and new buds of the plant via stylet penetration or through the stomata can be infected. The best management practices for this disease are sanitation, prevention of induction of the pathogen to the environment, and planting clean seed or starter plants.
Oryza glaberrima, commonly known as African rice, is one of the two domesticated rice species. It was first domesticated and grown in West Africa around 3,000 years ago. In agriculture, it has largely been replaced by higher-yielding Asian rice, and the number of varieties grown is declining. It still persists, making up an estimated 20% of rice grown in West Africa. It is now rarely sold in West African markets, having been replaced by Asian strains.
Aphelenchoides is a genus of mycetophagous nematodes. Some species are plant pathogenic foliar nematodes.
Perennial rice are varieties of long-lived rice that are capable of regrowing season after season without reseeding; they are being developed by plant geneticists at several institutions. Although these varieties are genetically distinct and will be adapted for different climates and cropping systems, their lifespan is so different from other kinds of rice that they are collectively called perennial rice. Perennial rice—like many other perennial plants—can spread by horizontal stems below or just above the surface of the soil but they also reproduce sexually by producing flowers, pollen and seeds. As with any other grain crop, it is the seeds that are harvested and eaten by humans.
Korean natural farming (KNF) is an organic agricultural method that takes advantage of indigenous microorganisms (IMO) to produce rich soil that yields high output without the use of herbicides or pesticides.
Scutellonema bradys, also known as yam nematode, is a migratory endoparasitic nematode causing major damage to yam crop in many African tropical regions, as well in parts of South and Central America and Asia. They can cause reduction of 20-30% in tuber weight at harvest.
Rice-sheath blight is a disease caused by Rhizoctonia solani, a basidiomycete, that causes major limitations on rice production in India and other countries of Asia. It is also a problem in the southern US, where rice is also produced. It can decrease yield up to 50%, and reduce its quality. It causes lesions on the rice plant, and can also cause pre- and post-emergence seedling blight, banded leaf blight, panicle infection and spotted seed.
