Silverleaf whitefly (Bemisia tabaci) is a major pest of eggplants and many other crops worldwide. It belongs to the family Aleyrodidae and is one of the most destructive pests due to its ability to transmit plant viruses, cause direct damage to plants, and produce large amounts of honeydew, which attracts ants and promotes the growth of sooty mold.
Management of Silverleaf Whitefly in Eggplant
The life cycle of Silverleaf Whitefly
- The life cycle of the Silverleaf whitefly consists of four main stages: egg, nymph, pupa, and adult. The duration of each stage varies depending on temperature and other environmental factors.
- The life cycle begins when adult females lay small, oval-shaped eggs on the undersides of leaves. The eggs are translucent and usually hatch within five to seven days.
- After hatching, the first instar nymphs emerge and feed on the plant sap. The nymphs have legs and antennae and can move around the plant to find suitable feeding sites. After the first molt, the nymphs lose their legs and antennae and become immobile, remaining attached to the leaf surface for the rest of their development.
- Over the next three instars, the nymphs feed and grow, gradually changing from pale yellow to yellow-green. Once the fourth instar is complete, the nymphs enter the pupal stage, transforming into adults.
- Adults emerge from the pupal stage and typically begin to mate within 10-20 hours. Male adults usually emerge first in the morning, followed by females. The timing of emergence is temperature-dependent, with earlier emergence at higher temperatures.
Identification of Silverleaf Whitefly in Eggplant field
Adults are very small, measuring only about 0.06 inches (1.5 mm) in length, and have a yellowish body with four white wings. The wings are held at a slight angle, forming a roof-like structure over the body, and do not touch or overlap over the back, leaving a small space between them. The nymphs of silverleaf whiteflies can also be identified on the undersides of leaves. They are small and oval-shaped, with a flat, disc-like appearance.
Damage symptoms of Silverleaf Whitefly in Eggplant field
- One of the most noticeable symptoms is the presence of large numbers of tiny white insects on the undersides of leaves. These insects feed on the plant’s sap, leading to stunted growth, wilting, and yellowing of the leaves.
- As the whiteflies feed, they excrete large amounts of sticky honeydew, which can cover the leaves and fruit of the eggplant.
- This honeydew attracts ants and other insects and can also promote the growth of black sooty mold, further reducing the plant’s ability to photosynthesize and produce healthy fruit.
- The black mold can also make the fruit unattractive and difficult to market.
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Management of Silverleaf Whitefly in Eggplant by Cultural Method
- Reflective mulching: As mentioned in the introduction, reflective mulching can effectively manage silverleaf whiteflies in eggplant. Before transplanting, cover the planting beds with reflective polyethylene mulches. This will help repel adult whiteflies and delay the buildup of damaging populations.
- Sanitation: Regular removal of crop debris and plant residue can reduce the number of whiteflies that overwinter in the field. Remove and destroy any infested plant debris as soon as possible.
- Crop rotation: Rotate eggplant with non-host crops such as legumes or cereals to reduce the buildup of whiteflies. This also helps to break the pest cycle by interrupting the development of immature whiteflies.
- Early planting: Planting eggplant early in the season can help to avoid peak whitefly populations. Early planted crops will mature before the whitefly populations reach damaging levels.
- Companion planting: Intercropping eggplant with plants that repel or deter whiteflies, such as marigolds, can help to reduce the number of whiteflies that infest the crop.
- Pruning: Regular pruning of the eggplant can reduce the number of whitefly eggs and nymphs on the plant. Remove infested leaves and stems and prune them to promote good air circulation and reduce humidity.
Management of Silverleaf Whitefly in Eggplant by Chemical Method
- Acetamiprid: Apply Assail 30SG at a rate of 0.047 to 0.075 lb ai/A with a PHI of 7 days. Do not exceed 0.3 lb ai/A per season, and limit four applications per season. The RET interval is 7 days, and the REI is 12 hours.
- Afidopyropen: Apply Sefina Inscalis at a rate of 0.01 lb ai/A with a PHI of 0 days. Do not exceed 0.09 lb ai/A per year. The RET interval is 7 days, and the REI is 12 hours.
- Beta-cyfluthrin/imidacloprid: Apply Leverage 360 at a rate of 0.096 lb ai/A with a PHI of 7 days. Do not exceed 0.12 lb ai/A beta-cyfluthrin or 0.24 lb ai/A imidacloprid per season. The RET interval is 7 days, and the REI is 12 hours.
- Bifenthrin: Apply Brigade WSB at a rate of 0.033 to 0.08 lb ai/A with a PHI of 7 days. Do not exceed 0.2 lb ai/A per year. The RET interval is 7 days, and the REI is 12 hours.
Management of Silverleaf Whitefly in Eggplant by Organic/Natural Method
- Horticultural oil: Apply horticultural oil to the eggplant, which suffocates the whiteflies by coating their bodies with oil. Some formulations are OMRI-listed for organic use.
- Insecticidal soap: Apply insecticidal soap to the eggplant, which disrupts the cell membranes of the whiteflies and causes them to dehydrate and die. Some formulations are OMRI-listed for organic use.
- Azadirachtin (neem oil): Apply a neem oil product to the eggplant, which works by interfering with the whiteflies’ feeding and reproduction. Some formulations are OMRI-listed for organic use.
- Plant-derived essential oils: Apply plant-derived essential oils, such as rosemary, peppermint, or clove oil, which can act as repellents or toxicants to the whiteflies. Some formulations are OMRI-listed for organic use.
- Pyrethrins: Apply a pyrethrin-based product derived from the chrysanthemum flower, which is toxic to whiteflies. Some formulations are OMRI-listed for organic use.
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Conclusion
Managing silverleaf whiteflies in eggplant requires a multifaceted approach incorporating cultural and chemical methods. By implementing cultural practices such as crop rotation, removing infected plant material, and managing irrigation, growers can reduce the incidence and severity of whitefly infestations. In cases where chemical intervention is necessary, growers can choose from various insecticides labeled for use on eggplant, such as acetamiprid, afidopyropen, beta-cyfluthrin/imidacloprid, and bifenthrin.
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