I. Hosts and Damage Caused by *Bemisia tabaci*
The primary host plants in the city's agricultural areas include cucumbers, tomatoes, eggplants, cowpeas, and cotton. Infestations of *Bemisia tabaci*, commonly known as whiteflies, result in a range of symptoms such as white stems, yellowing leaves, leaf drop, and damage to crops like cabbage and broccoli. Affected leaves often show signs of wilting, discoloration, and reduced growth, which can significantly impact yield and crop quality.
II. Identification Features of *Bemisia tabaci*
Eggs: The eggs are elongated, pear-shaped, with a small stalk that is oriented vertically relative to the leaf surface. They are typically found scattered on the underside of leaves. Initially, they appear pale yellow-green, darkening as they approach hatching.
Nymphs: There are three nymphal instars. The first instar is light green to yellow, with functional antennae and legs, allowing it to move and feed. After molting, the second and third instars lose their antennae and legs, becoming sessile and feeding directly on plant sap. By the third instar, the nymph forms a pupa, and the shed skin hardens into a shell-like structure, which is a key characteristic for identifying whitefly species.
Pupa (Cocoon): The cocoon is oval or slightly concave, often asymmetrical. It has a triangular opening, longer than wide, with a spoon-shaped tongue that extends beyond the edge. The back of the cocoon is covered in fine hairs, which vary depending on the host plant. On hairy leaves, the cocoon has prominent bristles, while on smooth, hairless leaves, the back is more uniform without long hairs.
Adults: The adult whitefly is pale yellowish-white, measuring 0.85 to 0.91 mm in length. It has wings that are white and coated with a waxy powder, without any distinct spots. The head has a bifurcated vein pattern, and when the wings are closed, they form a ridge-like structure along the body.
III. Occurrence and Impact in Urban Agriculture
Whiteflies have been observed in various crops within the city, including cotton, cucumber, and tomato fields. When adult whiteflies gather in large numbers, they can cause severe damage, leading to significant economic losses and reduced crop productivity.
IV. Chemical Control Measures
For effective management, a 25% flucarbazide solution diluted at a ratio of 1000–1500 times is recommended for both preventive and curative applications. This treatment helps reduce whitefly populations and minimize crop damage when applied according to guidelines. Regular monitoring and timely intervention are essential for long-term control.
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