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
Developing tools to detect, keep track and communicate the occurrence of transboundary pests and diseases in a timely manner is an essential part of our work on crop protection.
PestDisPlace Reporter: Sri Lankan cassava mosaic virus (SLCMV)
SLCMV is one of several viruses that cause Cassava Mosaic Disease (CMD), a major disease of cassava in Africa and Asia. This particular virus isolate was reported for the first time in Sri Lanka in 1998, and its most recent emergence registered in 2015, in Southeast Asia. The PestDisPlace Reporter map below, shows the current information available on the occurrence of CMD caused by SLCMV. In all cases, the virus now reported in Southeast Asia, is more than 93% identical in nucleotide sequence to isolates from the South of India and Sri Lanka. For more info go to: https://pestdisplace.org
PestDisPlace Reporter: Fusarium Wilt (Foc TR4)
Banana production is seriously threatened by a new race of Fusarium oxysporum f.sp. cubense (Foc), the tropical race 4 (TR4). This soil-borne fungus causes a disease called Fusarium Wilt (FW), in a diverse range of banana varieties including Cavendish clones and is no longer restricted to East and Southeast Asia. The transboundary spread of this pathogen is of great concern now in Africa and the Americas. The PestDisPlace Reporter map below, shows the current information available on the occurrence and early warning reports of FW caused by Foc TR4. For more info go to: https://pestdisplace.org
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).
- Bean leaf crumple virus: Bean leaf crumple virus (BLCrV) causes leaves to wrinkle and shrinks the pods, it can prevent the plant from flowering and eventually kills the whole bean crop. At the time of its first report in 2000, it was not yet considered a pathogen of economic importance in Colombia. However recent surveys indicate the virus may be re-emerging in this region. BLCrV is a novel species of geminivirus (a group of viruses that have twin-shaped viral particles and are transmitted by whiteflies), far related to the infamous Bean golden yellow mosaic virus (BYGMV), which can is also present in Colombia. BLCrV is particularly devastating to Andean beans but has a lesser effect on Mesoamerican beans. The Andean kind includes dark and light red kidney, white kidney, and cranberry beans. Andean beans are a staple of Argentina, Chile, Ecuador, and Peru and therefore there is a potential for the virus to spread further in the region.
- 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 Mosaic Disease (CMD): CMD is caused by different species of viruses (geminiviruses), transmitted by whiteflies (Bemisa tabaci) and disseminated through infected cuttings. The most recent outbreak of severe CMD in Africa began in Uganda in the late 1980s and by now the disease has invaded more than 12 countries in East, Central and West Africa, and continues to spread. CMD has also been reported in south India and Sri Lanka. Indian cassava mosaic virus (ICMV) was recorded from South Asia in 1985, followed by Sri Lankan cassava mosaic virus (SLCMV) in 1998. In sub-Saharan Africa, CMD epidemics have caused average storage root yield losses of 20%, and up to 70% in susceptible cultivars. Since 2015, CMD and one species of geminivirus (SLCMV) have been recorded in South East Asia (SEA), affecting important cassava producing regions in Cambodia and Vietnam.
- 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.
Diagnostics and monitoring
By using novel molecular tools such as metagenomics or LAMP in combination with classical phytopathology detection techniques, the time to identify and detect a pest or pathogen is significantly reduced. At the same time we are developing virtual platforms for the rapid communication of diagnostics and field survey results
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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