Pests and diseases
Plant pests and diseases can wipe out farmers’ hard work and cause significant losses to yields and incomes, posing a major threat to food security.
Globalization, trade and climate change, as well as reduced resilience in production systems due to decades of agricultural intensification and biodiversity loss, have all played a part in the dramatic increase and spread of transboundary plant pests and diseases.
Pests and diseases can easily spread to several countries and reach epidemic proportions. Outbreaks and upsurges can cause huge losses to crops and pastures, threatening the livelihoods of farmers and the food and nutrition security of millions at a time.
Plant pests and diseases spread in three principal ways:
- Trade or other human-migrated movement
- Environmental forces – weather and windborne
- Insect or other vector-born – pathogens
What we do: We work to combat the following pests and diseases
- Bean root rot disease: Numerous soil-borne fungal pathogens are widespread throughout bean-growing areas of the tropics, which can completely wipe out yields, especially when adverse environmental conditions persist after planting and through flowering. CIAT combats the most common diseases and their pathogens: Fusarium root rot or dry rot (Fusarium solani f. sp. phaseoli), Fusarium wilt or yellows (Fusarium oxysporum f. sp. phaseoli), Rhizoctonia root and pod rots (Rhizoctonia solani), and Pythium damping off, wilt and pod rot (various Pythium species).
- Mealybug: A pest that can cripple yields by feeding on and drawing essential nutrients out of the plant.
- Witches’ Broom: Causes cassava leaves to discolor and to proliferate, in a distinctive bunch reminiscent of a broom.
- Whitefly: A pest that feeds on and causes direct damage to cassava and other crops, and can even obliterate the entire crop.
- Frogskin disease: Characterized by the failure of the roots to accumulate starch. Although most plants do not show symptoms of disease in the above-ground parts, some affected plants do have symptoms in the leaves.
- Cassava Brown Streak Disease (CBSD): An unseen killer, the disease consumes the cassava roots while they are still in the ground, without producing visible symptoms in the rest of the plant. Only at harvest do farmers discover the blighted, inedible roots which, when cut open, reveal trademark brown blotches of destroyed flesh that give the disease its name.
- Spittlebugs: A pest which absorbs nutrients from the roots of pastures, reducing their nutritional quality.
- Rhizoctonia solani: A plant pathogenic fungus best known to cause collar rot and root rot.
- Bacterial panicle blight: A disease that provokes rice grain and plantlet rotting caused by the Burkholderia glumae that inhabits the soil, other crops, as well as weeds associated with rice fields.
- Rice blast disease (Magnaporthe oryzae): Rice blast, caused by a fungus, forms lesions on leaves, stems, peduncles, panicles, seeds, and even roots.
- Rice hoja blanca: CIAT jointly with FLAR work to identify sources of resistance against rice hoja blanca (RHB) and its insect vector. RHB is produced by a virus, which is transmitted by the insect vector Tagosodes orizicolus or Sogata – its common name. In susceptible varieties, RHB can cause losses between 75 and 100% of total yields. It is one of the most important diseases in Latin American rice-growing areas. We are the only institution capable to evaluate 20,000 materials, on average, in the field.
How we do it: Breeding for resistance and Integrated Pest Management (IPM)
According to the definition proposed by the United Nations Food and Agriculture Organization (FAO), Integrated Pest Management (IPM) is an ecosystem approach to crop production and protection that combines different management strategies and practices to grow healthy crops and minimize the use of pesticides. IPM is an approach-based method for analysis of the agro-ecosystem and the management of its different elements to control pests and keep them at an acceptable level (action threshold) with respect to the economic, health and environmental requirements.
Several kinds of pests can infest the different parts of plants/crops, and damage them partially or sometimes completely, seriously affecting the quantity and quality of the yield. Moreover, certain crop production intensification practices (e.g. early season spraying of pesticides in rice fields) can even increase the impact of pests on plants. In order to protect their plants, farmers used to spray chemical products (pesticides). However, these chemicals could have a negative effect on and cause serious damage to health and the environment as well as, sometimes, on to the health of the plant itself.
IPM includes the necessary phytosanitary measures, monitoring and diagnostic system, good agricultural practices and the management of natural enemies with the minimum amount of pesticides (when needed and of good quality).
CIAT also relies on the agrobiodiversity stored in our genebank at headquarters to find and develop crops with natural resistance to pests and diseases.
Biological control is the use of natural enemies — predators, parasites, pathogens, and competitors — to control pests and their damage. Invertebrates, plant pathogens, nematodes, weeds, and vertebrates have many natural enemies.
Cultural controls are practices that reduce pest establishment, reproduction, dispersal, and survival. For example, changing irrigation practices can reduce pest problems, since too much water can increase root disease and weeds.
Mechanical and physical controls
Mechanical and physical controls kill a pest directly, block pests out, or make the environment unsuitable for it. Traps for rodents are examples of mechanical control. Physical controls include mulches for weed management, steam sterilization of the soil for disease management, or barriers such as screens to keep birds or insects out.
Chemical control is the use of pesticides. In IPM, pesticides are used only when needed and in combination with other approaches for more effective, long-term control. Pesticides are selected and applied in a way that minimizes their possible harm to people, non-target organisms, and the environment.
Breeding for resistance
Crop varieties are domesticated and their continued cultivation depends on continuous breeding programs for insect, disease, and virus resistance, since large-scale monocultures are generally more susceptible to variable pathogens. Pest and disease resistance has been a desired trait for crop breeders for many years. Crucial to these efforts, CIAT safeguards wild, undomesticated, and other biodiversity that can help in the fight against pests and diseases.
In 2003, CIAT and partners released a new cassava variety (under the name Nataima-31) which was bred for high whitefly resistance, high yield and good cooking qualities. It has attained yields of 33 t/ha, out yielding the regional farmers’ variety in Tolima department of Colombia with no pesticide applications. Nataima-31 is now being grown commercially in several areas of Colombia, Ecuador, and Brazil.
CIAT virologists have developed a diagnostic technique to efficiently detect the presence of viruses infecting cassava, including those ones associated with cassava frogskin disease (CFSD).
In response to the recent appearance of cassava mealybug in Indonesia, scientists from Bogor Agricultural University released about 3,000 wasps into a confined cage during September 2014, with support from CIAT and FAO. This effort helped subdue a major threat to the country’s second most important staple after rice.
Pests and diseases | CIAT Blog Science to Cultivate Change
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