Plant Description
Striga gesnerioides (Willd.) Vatke is a parasitic plant species belonging to the family Orobanchaceae. This herbaceous plant grows upright, reaching a height of 20-60 cm. It produces erect stems that can branch out along the way. Its leaves are small, scale-like, and lack chlorophyll. The plant's small pink or purplish flowers emerge from the stem or leaf axils in the spike-like inflorescence. It produces a small capsule that contains thousands of minute seeds with minute light brown appendages called elaiosomes.
Plant Origin and Distribution
The Striga gesnerioides originated from Africa, especially West Africa, where it is known as ‘witch weed’ or ‘Sugo.’ The plant also grows in many other African countries, including Uganda, Tanzania, Sudan, and Nigeria, where farmers consider it a major problem. It is also found in several other regions worldwide, such as Asia, Australia, and the Pacific region, where it has been introduced.
Common name and Use
The plant Striga gesnerioides (Willd.) Vatke is commonly known as the Lesser Witchweed, in contrast to its sister species, the Greater Witchweed (Striga hermonthica). Unfortunately, it is an invasive weed that poses a significant threat to the food security for sub-Saharan Africa's rural population. It parasitizes root systems of maize, millet, sorghum, and other crops at different growth stages leading to a severe yield loss of up to 100% under severe infestations. The plant is also associated with farmers' losses, especially since it belongs to a family of parasitic plants with no known benefit to the human race globally.
Light Requirements
Striga gesnerioides thrives well in a bright environment with moderate shading. It requires a minimum light intensity of approximately 600 ?mol/m2/s for optimal growth. Insufficient light levels may result in stunted growth, elongated internodes, and yellowing of leaves.
Temperature Requirements
Striga gesnerioides grows best in warm temperatures ranging from 25-35 °C. At temperatures below 20 °C, the growth rate decreases, while temperatures above 35 °C may lead to leaf scorching and reduced growth. It is important to maintain consistent temperatures to support the overall growth and development of Striga gesnerioides.
Soil Requirements
Striga gesnerioides prefers well-draining soils with good aeration and high fertility. A pH of 5.5-7.5 is optimal for its growth. Sandy loam or loamy soils are preferred; however, it can grow in a range of soil types. It is crucial to avoid waterlogged soils, which can lead to stunted growth and rots. Regular soil testing and amendment with organic matter can help maintain soil quality and fertility.
Cultivation Methods
The plant Striga gesnerioides (Willd.) Vatke is a parasitic weed, and its cultivation methods vary depending on the host plant in which it grows. This weed commonly affects cowpea and soybean plants. Thus, to grow these plants successfully, it is essential to adopt proper cultivation methods to prevent Striga's growth. Farmers need to use Striga-resistant varieties of cowpea and soybean or rotate their crops with non-host plants to minimize the weed's spread in the soil. Soil sterilization is another technique used to control Striga growth, but it can be costly and time-consuming.
Watering Needs
Striga gesnerioides (Willd.) Vatke requires moderate to high soil moisture levels. However, watering frequency should be adjusted based on the host plant's water needs. Frequent watering can encourage the germination of Striga seeds in the soil, leading to an eventual infestation. Therefore, farmers should avoid overwatering or watering late in the day when Striga is most likely to germinate.
Fertilization
Fertilization is crucial for Striga gesnerioides (Willd.) Vatke management, and farmers must adopt an integrated soil fertility management approach. The use of organic manure and phosphate fertilizers improve soil fertility and plant health, which in turn reduces Striga infestation. Nitrogenous fertilizers should be used sparingly as they increase vegetative growth but also encourage Striga growth. Farmers may consider using bio-fertilizers such as rhizobium and mycorrhiza that enhance plant growth and limit Striga growth.
Pruning
Pruning is not necessary for Striga gesnerioides (Willd.) Vatke as it is a parasitic weed that depends on the host plant for its sustenance. However, farmers need to remove the host plant once Striga has formed attachments to the host. Timely removal of the host plant minimizes the production of Striga seeds, which can lead to re-infestation.
Propagation of Striga gesnerioides
Striga gesnerioides, commonly known as cowpea witchweed, is a parasitic plant that can cause significant damage to cowpea crops. If you're interested in propagating this plant, it's important to understand the propagation methods that are available.
Seed Propagation
The most common propagation method for Striga gesnerioides is seed propagation. The plant produces small, brown seeds that are about 0.5 mm in size. To propagate the plant using seeds, you can follow these steps:
- Collect the seeds from the mature plant when they are fully developed.
- Place the seeds in a well-draining potting mix and cover them with a thin layer of soil.
- Water the soil to keep it moist but not waterlogged, and ensure the potting mix is well-draining to prevent rotting.
- Keep the pot in a warm place (ideally around 25-30°C) with plenty of light but not direct sunlight, and the seeds should germinate within 2-3 weeks.
Vegetative Propagation
While seed propagation is the most common method, Striga gesnerioides can also be propagated vegetatively. However, this method requires some expertise and is not as reliable as seed propagation. To propagate the plant vegetatively, you can try these steps:
- Take a cutting of a healthy plant and trim it to around 10-15 cm in length.
- Remove the lower leaves and dip the cut end of the stem in rooting hormone powder.
- Place the stem in a potting mix and keep it well-watered and out of direct sunlight.
- After a few weeks, roots should develop, and you can plant the new plant in a larger pot or in the garden.
Overall, it's possible to propagate Striga gesnerioides using either seeds or vegetative methods, but seed propagation is the most reliable method and is recommended for beginners.
Disease management
Striga gesnerioides is susceptible to a range of fungal infections such as Fusarium wilt, powdery mildew, and root rot. These diseases can cause stunted growth, wilting, yellowing, and eventually death of the plant. To manage these fungal diseases, it is necessary to ensure proper sanitation practices and good growing conditions. Use of disease-free seeds and planting material, crop rotation, drainage management, and controlled irrigation are some of the effective ways of managing fungal diseases. Fungicide sprays can also be used to control the spread of fungal diseases.
Pest management
Striga gesnerioides is affected by various pests, including nematodes, aphids, whiteflies, and spider mites. Presence of these pests can often lead to yellowing of leaves, curling or distortion of leaves, stunted growth, and reduced yield. To manage pests, it is essential to scout regularly for their presence and use targeted treatments. Biological control measures such as using predatory insects and parasitoids can also be effective. Use of insecticidal soaps, oils, and chemical insecticides can also help manage pests, but it is important to use them judiciously and follow label instructions carefully to avoid causing harm to the plant and the environment.
