Cassava is a staple food for millions of households in tropical and subtropical regions worldwide. However, despite its hardy and resilient nature, cassava production is often threatened by a variety of pests and diseases that drastically reduce its yields, compromise its quality, and threaten food security, especially in regions where cassava has become a major food and economic staple.
The most common cassava pests include mealybugs, whiteflies, and cassava green mites, which infest leaves and stems, weakening growth and reducing photosynthetic capacity. Simultaneously, viral bacterial diseases such as cassava mosaic disease and cassava bacterial blight spread rapidly through infected planting materials or insect vectors, thereby wiping out entire crop fields if not well managed. These pests and pathogens not only affect the physical condition of the crop but also contribute to economic losses through reductions in marketable yield and increased production costs.
Therefore, proper and timely management of pests and diseases is crucial for sustaining healthy cassava production. Let’s explore some of the most prevalent diseases and pests in cassava production, as well as ways to control them:
Common Pests Affecting Cassava
The most prevalent cassava pests, which cause damage to cassava crops and transmit diseases, include the cassava mealybug, cassava green mite, variegated grasshopper, and whiteflies. Many of them attack the leaves and stems, while others feed on the stems and roots, causing different degrees of damage.
The following are some common leaf and stem pests of cassava plants:
- Cassava Mealybugs – There are two types of cassava mealybugs: the green mealybug and the striped mealybug. These sucking insects damage the leaves and stems of the cassava crops, hence causing the leaves to deform, wilt, grow stunted, and develop poor tubers. In severe cases, the mealybug’s infestation can result in high yield losses that may go up to 80%.
- Cassava Green Mite – CGM is one of the most destructive cassava pests in Africa, and particularly in Nigeria. These mites infest cassava leaves and shoot tips, causing damage that increases during the dry season. They cause the yellowing and drying of leaves, leading to defoliation and reduced photosynthesis. Leaves that are attacked by these insects become stunted and deformed. Tuber yield can be reduced by 13 to 80% under heavy mite infestations.
- Variegated Grasshopper – This pest chews the leaves, petioles, and the bark of cassava stems. It causes total defoliation in more severe cases. The destruction done to the cassava crops is severe on older cassava rather than young cassava.
- Whiteflies (Bemisia tabaci) – These are some of the most prevalent pests that lower the productivity of cassava in Africa, particularly in Nigeria. Whiteflies feed by sucking sap from cassava leaves and, in the process, inject viruses into the plants, transmitting the two most devastating cassava diseases in Africa–cassava mosaic disease and cassava brown streak disease. These diseases cause leaf distortion, yellowing, stunted growth, and root rot, severely affecting yield and crop.
Common Diseases Affecting Cassava
Some of the common diseases that affect cassava crops include:
- Cassava Mosaic Disease (CMD) – This is a viral disease characterized by mosaic patterns and curling of leaves. It is caused by the African mosaic virus, transmitted by infected cassava cuttings and whiteflies(Bemisia tabaci). Infection shows varied symptoms on the plants, which range from yellowing and distortion of leaves to misshapen and twisted leaflets; such infected plants later appear mottled with dark green blisters and exhibit an overall reduction in size.
The symptoms are more pronounced on the younger plants, especially those below six months, than the older ones. It is even worse for the farmers as it can reduce yields by up to 90 percent.
- Cassava Brown Streak Disease (CBSD)–
CBSD is a devastating threat to cassava production worldwide. It is another widespread disease transmitted by whiteflies or through infected planting materials.
CBSD is caused by two distinct ipomovirus species, namely cassava brown streak virus and the Ugandan cassava brown streak virus. This disease affects both the quantity and quality of cassava roots, making it completely unharvestable, especially when roots have stayed in the soil for more than nine months. Symptoms include yellow patches on the leaves, dark brown streaks on stems, and cracks with discolorations on cassava roots.
This ruthless disease, capable of causing a root yield loss as high as 100% in the worst-affected areas, has become one of the most alarming threats to food security and agricultural sustainability; hence, the need for disease-resistant varieties and clean planting materials.
- Cassava Bacterial Blight (CBB) – This is the cassava disease caused by Xanthomonas bacteria; it occurs on the leaves and stems. The disease spreads by means of rain splash, insects, infected cuttings, and contaminated tools. Symptoms include leaf wilt, water-soaked lesions, and dieback of stems.
If left uncontrolled, this disease can spread rapidly across the fields. It reduces yield by 20 to 100%, depending on the type of cassava, bacterium strain, and prevailing environmental conditions.
- Cassava Root Rot – This disease results from different fungi living in the soil that is poorly drained during intense rainy periods. The cassava plants affected by root rot develop brown, wilted leaves that look scorched. The disease destroys both the feeder roots and the storage roots; the infected storage roots have an unusual odor with a light brown color.
Cassava crops are often badly affected if the diseases are not noticed early. The same principle applies to pest control in general; early detection drastically enhances control. Therefore, always be on the lookout for unusual leaf color, strange growth patterns, or visible insects on the plants.
Best Practices for Farmers to Prevent Cassava Pests and Diseases
Here are some of the key best practices you can try in order to manage cassava’s pests and diseases:
- Plant Healthy Stem Cuttings:
Many diseases of cassava are transmitted via infected stem cuttings. Plant only those stem cuttings from healthy plants that have no symptoms of leaf chlorosis, shoot tip dieback, canker, fungus patches, or streaks on the stems. Stems should be acquired from reputable nurseries and stored correctly to prevent contamination until planting.
- Choose Improved, Disease-Resistant Cassava Varieties:
Grow improved cassava varieties that are tolerant or resistant to common pests and diseases like mosaic virus, CBSD, and bacterial blight.
Using the right varieties of cassava not only gives your crop a natural layer of protection but also enhances yield.
- Practice Appropriate Crop Rotation:
Adopt crop rotation practices by rotating cassava with other plants like maize or beans to break the life cycle of pests and pathogens in the soil. For example, planting cassava with maize and melon tends to reduce cassava bacterial blight greatly. It prevents infestation and maintains soil health.
- Adopt Biological and Organic Pest Control Options:
This is a sustainable and environmentally friendly approach that allows you to conserve and promote natural enemies of pests for the suppression of pest populations in the field. These natural enemies, also known as beneficial insects such as lady beetles, lacewings, and parasitic wasps that target eggs and larvae of pests, help in the suppression of mealybugs, mites, and whiteflies.
You may encourage these natural allies by planting flowering plants around your cassava field. Also, making use of certain helpful fungi that target pests naturally, helps to minimize the need for chemicals.
In addition, natural repellents like neem seed oil, garlic extract, or certain biopesticides such as “Green Muscle” can also serve the purpose of keeping pest infestation under control.
- Ensure Proper Weed Control:
Weeds can drastically reduce cassava yields by harbouring pests and competing with the crop for basic resources such as moisture, space, nutrients, and even sunlight. Since cassava stem cuttings and sprouts grow slowly at the early stages, the crop is particularly susceptible to weed pressure during the first 3–4 months after planting. In addition, weeds tend to host pests and diseases causing damage to cassava plants and their root tubers; proper and timely control of weeds will definitely help in keeping cassava fields healthy and free from possible yield losses.
- Leverage Optimal Planting Procedures:
It is recommended to plant cassava in those seasons of the year when the pests are less active. Early planting, particularly at the beginning of a rainy season, allows cassava to establish strong roots and promotes healthy growth; thus, it gives the plants a greater chance of resisting disease. Adequate spacing also improves air circulation, reduces humidity, and limits conditions that favor pests such as whiteflies.
- Regularly Remove Affected Plants:
Regular monitoring should be done on cassava plants; remove or destroy any infested plants from the field immediately. This prevents pest and disease buildup and spread. After harvesting, ensure you destroy any cassava stem and tuber showing symptoms of disease. Generally, clean and well-managed fields are less attractive to pests and have reduced chances of disease outbreaks.
By embracing integrated pest management strategies that include planting resistant varieties, good cultural practices, the use of biological controls, and frequent field monitoring, you are able to reduce the impact of pests and diseases. With these measures consistently practiced, you are sure to have healthier crops, increase yields, and ultimately promote national food security.
