What Are the Common Species of Citrus Whitefly? A Detailed Guide to Integrated Control Techniques
Citrus whitefly is one of the common pests in citrus cultivation. Once it breaks out, it can have a major impact on the quality and yield of citrus. Therefore, growers need to fully understand this pest. Let's take a look below at what common species of citrus whitefly there are, along with integrated control techniques.
I. What common species of citrus whitefly are there?
There are 4 common whitefly species. The whiteflies that cause greater damage in China are the black-winged whitefly and the citrus whitefly.
Natural enemies of whitefly include Aschersonia aleyrodis, Aschersonia placenta, Encarsia smithi, Encarsia formosa, Encarsia nipponica, Encarsia clypealis, Amitus hesperidum, Stethorus punctillum, Amblyseius obtusus and lacewings.
II. Causes of citrus whitefly outbreaks
1. Wide feeding habits and abundant food sources
The citrus whitefly has a wide feeding habit and can feed on many plants such as glossy privet and persimmon. When multiple varieties are planted together in a citrus orchard, different varieties have different growth periods and management measures, and new shoots emerge alternately. Tender leaves are constantly present in the orchard, and various intermediate host plants are often found nearby, providing an abundant food source for the citrus whitefly.
2. Unreasonable planting density
Excessive planting density in citrus, closed tree canopies, and crossing branches and leaves create light, temperature and humidity conditions favorable to pest growth. In addition, because branches and leaves shade one another, the effect of pesticide spraying is affected.
3. Unreasonable control methods
The unreasonable use of chemical pesticides, excessive clearing of weeds and other practices kill natural enemies of whitefly such as Encarsia formosa and Aschersonia aleyrodis, reducing the role of natural enemies in controlling citrus whitefly and leading to large-scale whitefly outbreaks.
4. Incorrect timing of pesticide application
Because the eggs and larvae are small, pale, transparent and close in color to branches and leaves, they are not easy to detect, so the optimal control period (the peak egg hatching period) is often missed. Pesticides are applied only when adults appear, but adults are prone to migration; after emerging, they mate on the underside of leaves and lay eggs on tender branches. The eggs and nymphs, which are protected by a waxy surface, have strong pesticide resistance, so spraying during the adult stage gives unsatisfactory results. This pest has multiple generations per year, with overlapping generations in the field, and overwinters as larvae or pupae, making it difficult to control. In addition, citrus orchards are mostly individually owned, and control measures and timing vary from person to person, with no unified organized control.
III. Integrated control techniques for citrus whitefly
Agricultural control is the foundation, chemical control is the key, and unified control is the safeguard.
1. Reasonable pruning: In combination with winter and spring pruning of citrus, thin out overly dense branches and diseased and pest-infested branches, improve ventilation and light conditions, and reduce overwintering pest sources.
2. Yellow sticky board trapping: After adult emergence, hang yellow sticky boards to trap and kill adults, at 35-40 boards per mu.
3. Winter orchard cleaning: In orchards where this pest occurs, use rosin mixture, lime sulfur mixture, petroleum oil emulsion, etc. to kill overwintering pest sources.
4. Chemical control: Focus control on the key period when the 1st-2nd instar nymphs of citrus whitefly are at peak occurrence. That is, during the peak egg hatching periods (late March, mid-to-late May, mid-July to early August, early-to-mid October), it is recommended to spray the leaf surface in the early morning or evening with pesticides such as buprofezin, thiamethoxam and acetamiprid used in rotation.
When spraying, in addition to focusing on the inner canopy and the underside of leaves, attention should also be paid to spraying weeds in the orchard for control.