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How to identify and control Whiteflies on Plumeria?
How to Identify and Control Whiteflies on Plumeria: A Comprehensive Guide
Whiteflies are Hemiptera insects belonging to the Aleyrodidae family. They are considered a significant pest for plumeria because they cause considerable damage. They feed by sucking the sap from the host plant. They are polyphagus, meaning that they feed on many different plants, so they represent a hazard for most crops and feed off wild plants and weeds that act as a reservoir for the pest. The characteristic white color of these insects is due to a layer of white powder covering their bodies and their two pairs of wings. The two species of Whitefly that affect plumeria are Bemisia tabaci, or tobacco whitefly, and Trialeurodes vaporariorum or glasshouse Whitefly. The main morphological difference that distinguishes these insects from one another is the position of the wings. In B. tabaci, they are joined to the body and in T. vaporariorum they are parallel to the leaf’s surface. Furthermore, the adult and pupa of T. vaporariorum usually have a greater quantity of waxy powder than B. tabaci.
What are Whiteflies?
Whiteflies are hemipterous insects belonging to the Aleyrodidae family. They can cause considerable damage and loss of production.
What can you see?
Discolored patches on the leaf areas where the insects have been feeding can be observed.
What can you do?
One of the main objectives when controlling Whiteflies is to prevent the crop from being infected by a virus that the insects can carry.
Biological cycle of Whitefly
The entire life cycle of the Whitefly lasts between 15 and 40 days, depending on environmental conditions, particularly the temperature, since eggs will develop into adults more quickly when the temperature is higher. The Whitefly usually lays its eggs on the underside of the leaves, which the eggs stick to.
The Whitefly usually lays its eggs on the underside of the leaves and the eggs stick to them utilizing a pedicel. The larva or nymphs emerge from the eggs and in their first stage of development, they are mobile enough to move along the leaf until they find the right place to insert their stylus and begin to feed off the sap of the phloem, which is rich in sugars. The nymphs then pass through several more stages of development, during which they remain in the same place and continue to feed off the plant until the adult emerges from the last nymph stage. Non-fertilized eggs produce males, while fertilized eggs produce females.
Symptoms and Damage of the Whitefly
The direct damage is caused to the plant when the whitefly feeds. The sucking of the sap causes discolored patches on the parts of the leaf where they have been feeding. Furthermore, as they suck out the sap, they release toxic substances into the phloem, spreading throughout the plant. This leads to metabolic imbalances in the plant and general weakening, chlorosis and changes to the flowers and fruit. Regarding indirect damage, the molasses excreted by the nymphs enables fungi, such as sooty mold (Capnodium sp.), to form on the leaves. This mold acts as a screen and reduces the plant’s photosynthetic capacity.
However, the most severe damage that the Whitefly can cause to crops is the transmission of viruses. These include the TYLCV (Tomato yellow leaf curl virus), the ToCV (Tomato chlorosis crinivirus), or the TYMV (Tomato Yellow Mosaic Virus).
How to prevent the pest?
One of the main objectives when controlling Whiteflies is to avoid the crop being infected by any virus that the insects may be carrying. It is, therefore, important that any weeds or remains of other plants near the crop are removed because these can act as a habitat for whiteflies. Furthermore, if a whitefly feeds off a weed that has a virus and then reaches your crop, the virus can quickly spread. Protective barriers such as nets and covers are also a good option for preventing infestations.
Biological Control
A range of entomophagus insects, parasites, and some entomopathogenic fungi are used to control whiteflies.
Most predators used to feed on the eggs and nymphs of the Whitefly. This category includes the Delphastus catalinae beetle. The Chrysopidae larva and some bedbugs are also suitable biological controllers of this pest.
The tiny wasps of the Aphelinae family are parasites of the whitefly larva, where the wasps lay their eggs and develop by feeding off their host. They are the most commonly used parasite wasps and are specific to the pests they live off. This results in quicker pest control, even though their specific nature means they are useless against other phytophagous insects.
Entomopathogenic fungi can also be used. This infects and grows inside the Whitefly and eventually kills it. New spores emerge from the corpse and infect other individuals. One example is the Verticillium lecanii fungus.
Whitefly (Bemisia tabaci) emerged from its final nymphal stage, the fourth-instar nymph (pupa). The surface of the leaf. A high magnification (5x) image shows this insect’s soft, waxy appearance. This Whitefly has a size of less than 1mm.
Cultural control measures
One of the main objectives when controlling Whiteflies is to avoid the crop being infected by a virus that the insect can carry.
Therefore, any weeds or remains of other plants that are near the crop should be removed as these can act as a habitat for the Whitefly. Furthermore, if a whitefly feeds off a weed that contains a virus and then reaches your crop, the virus can easily be spread. Protective barriers such as nets and covers are also a good option for preventing infestations.
Phytosanitary treatments
The aim is to provide the plant with maximum protection during the earliest stages of the crop, thus preventing any whitefly from getting established. In these earliest stages, a viral infection will cause the most significant damage as the virus will spread throughout the plant and show all its symptoms as the plant begins to produce blossom and fruit. This is why insecticides are applied to the seeds in some crops. These act systematically as soon as the seedling grows and continue to protect it for several weeks.
In later stages, insecticides can be applied to the leaves to ensure protection for the longest time. It should be noted that the use of non-systematic ingestion insecticides is not usually effective in combating Whiteflies in their larval stage since many of the larvae lack mobility. Using insecticides that act physically is also an excellent choice to fight this larval stage.
Whitefly Pest
Hosts:
They were recorded on plumeria and 38 genera of plants from 27 plant families and over 100 different species.
Common on plumeria, vegetables, ornamental, fruit and shade tree crops in Hawaii, including avocado, banana, bird-or-paradise, breadfruit, citrus, coconut, eggplant, kamani, Indian banyan, macadamia, mango, palm, paperbark, papaya, pepper, pikake, poinsettia, rose, sea grape, ti, and tropical almond.
Distribution:
Native to Central American and the Caribbean region. It was first reported in Hawaii in 1978 and is now present on all major islands.
Damage:
- Direct – damage caused by piercing and sucking of sap from foliage. The majority of feeding is done during the first three nymphal stages. Usually insufficient to kill plants.
- Indirect – damage due to accumulated honeydew and white, waxy flocculent material. The honeydew is a substrate for sooty mold, which blackens the leaf, decreases photosynthesis and plant vigor, and can cause disfigurement. The wind spreads the flocculent material and can create an unsightly nuisance.
- Virus transmission – damage from virus transmission can be considerable. These viruses cause over 40 diseases of vegetable and fiber crops worldwide.
Management:
This insect thrives in warm, dry weather. Heavy rains and cool temperatures may reduce populations.
- Non-chemical control – five natural enemies were introduced into Hawaii from the Caribbean to control whitefly populations. One of the three coccinellid beetles (ladybugs) has proved effective with high population densities of whiteflies. Two parasitic wasps have proven effective against low populations of Whitefly. These biological controls generally provide adequate control to minimize damage to plants.
- Chemical control – contact and systemic insecticides recommended for other pests on the same plant hosts may temporarily reduce whitefly populations. However, such insecticides may also harm whitefly predators and should be avoided.
The Spiraling Whitefly (Aleurodicus dispersus) has proven to be a nuisance and has caused damage to plumeria and native vegetation.