Defined as any organisms capable of causing injuries to plants, human and animals, the impact of pests on agricultural production can never be overstated.
Pests will reduce both the quality and quantity of farm produce, thus, frustrating the efforts of farmers in providing food for their nation and making a fortune from agricultural activities.
Although there are countless species of organisms which act as a pest to field crops, however, whiteflies are arguably one of the pests with the most significant impacts on plant production.
As a farmer that has been on the field for a very long time, you would have probably experienced the impacts that whiteflies can have on crop production and your revenue especially when this annoying creature is left uncontrolled.
Here, we have written a comprehensive guide on different methods of you can employ in controlling whiteflies, and why the use of pesticides can be the only practical approach available to you as regards to controlling whiteflies in commercial farms.
What You Should Know About Whiteflies
If you have spent a minimum of one year working on the field whether as a farmer, agricultural extension officer, pathologist or a researcher, you would have come across whiteflies on the field.
Whiteflies are tiny winged insects with a soft body that is closely related to mealy bugs and aphids.
Also referred to as Aleyrodidae, whiteflies are collected on the undersides of leaves and appear in masses projecting into a white cloud around plants.
Whiteflies are more of annoying creatures on the farm than a threat to farmers.
However, they can be surprisingly persistent coupled with their incessant disappearance and sudden return.
When you do not control whiteflies on your farm, they produce sticky honeydews that infiltrate plants parts sapping fluids.
After a continuous feeding on plants, you will notice that the plant gradually change to yellow color and eventually drop dead.
Another terrible feature of whiteflies is the difficulties farmer experience in controlling them. Once they have carved out a territory for themselves on the farm, you can prepare for a battle before you can eliminate them.
Whiteflies exist in virtually all regions of the world. However, they often camouflage as they are very tiny to be easily spotted by farmers.
Existing in clusters, whiteflies can overwinter and often reproduce all year round in warmer climate, which implies that if you are a farmer from a tropical region, you will most likely feel the effects of whiteflies the more.
Unlike similar pests that are nocturnal, whiteflies are active in the daytime.
Thus they carry out their destructive acts more during the day which gives you an opportunity as a farmer to better control them.
Different Species of whiteflies
Over the years, about 1550 species of whiteflies have been identified, and they all typically feed on undersides of leaves.
However, the degrees of destruction of species differ. While some are avid eaters, some are not. Irrespective of the species present in your farm, you must spare no effort in eliminating them.
Some of the commons species of whiteflies include ash whitefly, Aleurodicus disperses, greenhouse whitefly, Encarsia Formosa, Silverleaf whitefly, Aleurothrixus floccosus, Aleurocanthus woglumi, Trialeurodes abutiloneus, and several others.
More often, you will see a lot of people searching for “cotton whitefly, whitefly sugarcane, whitefly tomato” and other terms. This is because different whiteflies species have a wide range of preferred plants they feast on.
Off the field, whiteflies are familiar sights in greenhouses from mid to late summer when warm.
Some of the plant’s whiteflies love to feed on include the ornamentals such as pomegranate, banana, lantana, hibiscus, Bradford pear, gardenia, ficus, and fushia.
Also, they attack crops like okra, sweet potato, sugarcane, cotton, eggplant, tomato, pepper, cabbage, etc.
How to Identify Whiteflies Attack on Plants
Just like every other pest, whiteflies possess a specific mode of attacking plants. Understanding how whiteflies orchestrate destruction can help you in easily identifying if the signs and symptoms you see are whiteflies inflicted or not.
Typically, whiteflies suck plant juice and also leave a sticky substance (honeydew) they produce on plants.
The honeydew, in turn, leads to the formation of fungal diseases on leaves.
Also, they feed by penetrating plant phloem to get direct access to the food supply.
When whiteflies feed on plants, they suck out the sap, leaving the affected plant extremely weak as they will be deprived of carrying out photosynthesis.
As the infestation progresses, the plant turns yellow or pale, wilt and suffer stunted growth.
The most significant indicator of whiteflies presence is the observation of honeydew which implies that whiteflies have been feasting on plant leaves for many days.
Consequently, you may also notice the appearance of ants as they are attracted to honeydew.
As we stated earlier, whiteflies exist in the cluster, if you suspect the existence of whiteflies on the farm, check the undersides of the leaves.
They may appear as invisible, but a mild shake of leave will make them fly away in swarms.
Alternatively, you can check for the eggs nestled by the leaves undersides which signify the beginning of a new generation.
Whitefly larvae have a teeny white shape with no legs. Notwithstanding, they drag themselves to succulent leave parts and start to suck the plant juice the moment they are hatched.
Mature female whitefly lays an average of 400 eggs per cycle and the hatching period is usually between a week and one month.
Eggs are laid in in a circular pattern and come in pale yellow when fresh which gradually transmogrify to brown when setting for hatching.
You can isolate these larvae by hands and cross-examine them based on the attributes of whiteflies we have highlighted above so that you can know the best method of control to engage.
Life Cycle of Whiteflies
Irrespective of the species, whiteflies typically have six stages in completing their life cycle. They include the egg stage, four nymphal stages, and the adult.
Whiteflies are distributed worldwide. However, they favor the latter part of spring as their breeding period. The time spent to develop is dependent on the available temperature. For whiteflies to enjoy the optimum breeding, 10 – 32ºC is ideal for proper development. On the contrary, low temperature can lead to increased egg mortality. Thus, whiteflies are more prevalent in the hotter region and warmer season.
- The Egg Stage
The mature female whiteflies lay between 200-400 eggs in concentric patterns at the back of the leave. Between 5 – 10 days after been laid, the eggs hatch into nymph after which they progress a short distance away from their egg cases and start to feed on plant leaves sucking saps from tissues.
- The Nymphal Stages
After about 10 days, the first instar nymphs emerge and feed on until they experience their first molt.
From there, the second nymphal stage begins where nymphs glue to one side of the leaf, usually undersurface and evolve into creamy or pale green flattened bodies that look precisely like scales.
The third molt leads to the pupa or puparium stage. Here, they are less flattened compared to the initial stages.
Overall, this stage runs for 2 – 4 weeks depending on how favorable the weather condition is, precisely the temperature. The fourth instar stage can be particularly hard to identify as the young whiteflies shun mobility and attach firmly to the underside of their host leaf. Owing to their color, they blend perfectly to whichever leaf they patch on.
- The Adult Stage
After the completion of the nymphal stage, the pupae metamorphosis into you adult and shed its old skin. Also, at this stage, the red eyes of the adult can be observed through the integument. The tiny whitefly can live for a couple of months before they die.
However, it is essential to note that they would have recreated themselves before the end come which can make it particularly hard to eliminate them from the field.
Also, some species of whiteflies can reproduce without any form of mating (parthenogenesis). However, an unmated female can only produce male offspring.
The Detrimental Effects of Whitefly on Agricultural Produce
There are two forms through which whiteflies exert damages on the crop;
- Direct Effects
- Piercing and sucking of nutrients
All stages of whiteflies depend on the nutrients from the tissue of plants for their sustenance. From the nymph to the adult stage, whiteflies suck sap from leaves subjecting the plants to other infections
- Prevention of photosynthesis
Whitefly infestation is often associated with the paleness and discoloration of plants. As such, there will be an impediment to photosynthesis which in turn leads to stunted growth.
- A withering and premature drop of leaves
Plants attacked by whiteflies suffer withering and premature dropping of leaves. Also, in tomato, for instance, there is irregular ripening of fruits.
- Weakening of plants
When plants lose their ability to carry out photosynthesis, weakening of plant parts is inevitable.
- Reduced yield and loss of income
This is the part that best resonates with all playmakers in agricultural sectors, from farmers to agronomist and extension officers. Farmers all over the world have lost a considerable high amount of their income to the infestation of whiteflies.
- The eventual death of plants
It is very uncommon to witness the death of plants due to whiteflies attack, but in extreme cases, it is inevitable.
- Indirect Effects
The indirect effects of whitefly infestation can also be subdivided into three;
Production of honeydew
Whiteflies are associated with the production of honeydew. Honeydew acts as a substrate for sooty mold that impedes photosynthesis. Thus, reduction in the quality and quantity of crop produces of the plants attacked.
Invitation to ants attack
Honeydew is yummy food for ants; as such, it indirectly invites ants to the plants which may cause several other damages.
- Vectors to diseases
The most significant effects of whitefly attack that best resonates with farmers, agronomists and extension officers are the transmission of over 100 viral diseases. This has served as a limiting factor in for the cultivation of many crops in the open field and greenhouses as well.
Whitefly is the only vector for geminivirus diseases which account for 20 – 100% reduction in the yield of certain crops. Some of the diseases attributed to whitefly infestation include yellow leaf curl disease in tomato, cotton leaf crumple disease, cassava mosaic disease, cucumber vein yellowing virus, lettuce infectious yellows virus, brown streak disease in cassava, cucumber vein yellowing virus and several others.
Different methods of controlling whiteflies
How to get rid of whiteflies
There are two broad methods of controlling whiteflies; the organic solution and the use of pesticides.
A. Organic Solution
The organic approach has to do with the use of natural remedies in the regulation of whiteflies in a diverse ecosystem. The organic method focuses on the use of tools and practices that minimize harm to native pollinators and the other beneficial microorganisms found in the field.
Some of the notable organic approaches are;
- Manual removal of infected leaves and branches
- Vacuuming the plant
- Repelling whiteflies with companion plants
- The use of sticky yellow traps
- Spraying field with organic insecticidal soap
- Introduce earthworm casting at plant bases
- Set up reflective mulches
- Spray with neem extract
- Engage natural predators.
The organic solution for controlling whiteflies is definitely good; however, as you have probably noticed, it only works with a backyard garden or greenhouses.
For large scale farmers and serious crop producers with hectares of farmland to manage, the use of the organic approach is not a realistic method of controlling whiteflies. Thus, there is a need to harness more effective, economical and commercial way of getting rid of whiteflies which leads us to examine another alternative – the use of pesticides.
B. The Use of Pesticides
What are pesticides?
Pesticides are biological or chemical substances that are manufactured for the purpose of controlling pests through killing, incapacitation or inhibition. Contrary to popular belief, pesticides are in many ways broader than insecticide. It encompasses every chemical that is meant to offer protection to human, livestock, and crops. They include fungicide, insecticide, herbicide, bactericide, nematicide, disinfectant, antimicrobial, etc.
However, for this guide, we shall be focusing majorly on pesticides for the control of whiteflies and other insect pests.
How do pesticides work?
Pesticides work by releasing a harmful chemical which acts as a poison that either kills the pest or incapacitate them completely.
For the control of whiteflies, insecticides are the category of the pesticide used, and they exist in two forms which are contact and systemic.
- Contact Pesticide for the Control of Whiteflies
Contact insecticide as the name implies only kill the whiteflies when the active ingredients in this insecticide come in contact with them. For the larva and pupa, the pesticide will deprive them of oxygen thus leading to suffocation and eventual death.
Contact insecticides kill whiteflies faster compared to systemic. However, to have total control of whiteflies, you must ensure an excellent coverage of the field because those areas not covered by the spraying are a safe zone to these annoying creatures.
- Systemic Pesticide for the Control of Whiteflies
Systemic pesticides are harmful substances that are applied to a farm to get rid of pests. When you apply a systemic insecticide, the plants absorb the hazardous active ingredients in their tissue covering the whole parts of plants from the leaves to stem, roots, flowers, and fruits.
When you apply a systemic pesticide to your field, the whiteflies after feeding on plants leaves ingest the poisons in the pesticide which destroys their nervous system and eventually kill them.
Although systemic pesticides is a little slower in action compared to contact, however, it is overall more effective as it doesn’t have to come in contact with the whitefly directly.
Common insecticides for the control of whiteflies
Acetamiprid is a highly soluble and volatile pesticide with full approval from the EU. It is a well-known irritant and toxic to pests which can include birds and earthworms. Acetamiprid is very effective in the control of whiteflies and other pests such as leafminer, aphids, vine weevil, spider mites, leafhoppers, and mirids. It doesn’t penetrate the soil to the underground water but can relatively affect the aquatic ecosystem so you must be careful to follow all procedures that guarantee safety while using it in your farm or garden.
Acetamiprid can be used to combat whiteflies infestation on a farm with crops like fruit, vegetables, ornamental plants, and flowers.
Chlorpyrifos is a contact pesticide that acts as a poison to a wide variety of pests. Categorized under the class of organophosphates, Chlorpyrifos mode of action is through the interference with the activities of the enzyme cholinesterase which is responsible for normal functioning of the nervous system of the targeted pests.
Chlorpyrifos exists in many forms such as emulsifiable concentrate, powder, granule, dust, flowable, wettable powder and spray. It is rated as a broad spectrum insecticide with the ability to destroy whiteflies and numerous other pests such as termites, cutworm, flies, corn rootworms, flea beetle and grubs.
Classified as a synthetic pyrethroid insecticide, cypermethrin is highly effective against many pests. It is regarded as a multipurpose pesticide is that it can be used in farms including places such as crevice, cracks, and treatment of stored produces, greenhouses, laboratories and many more.
Cypermethrin has a fast action in the control of whiteflies in cotton, vegetable, and fruits. It is available in many forms including ULV, wettable powder formulations, and emulsifiable concentrate.
Technically, cypermethrin is a combination of eight different isomers with each possessing its own biological and chemical characteristic
Acephate is an organophosphate foliar spray offering reasonable persistency in its residual systemic activities for 10-15 days when you apply it at the recommended rate. Acephate is considered a non-phytotoxic on several crops but dangerous to many biting and sucking pests including whiteflies and aphids. It can also be used in the elimination of pests such as sawflies, leaf miners, thrips, lepidopterous larvae, and bugs.
It is highly effective in farms having crops like fruits, vegetables, horticultural plants, etc.
Also classified as organosulphate, Diazinon causes a loss of the control of the nervous system on pests of crops. This eventually leads to the death of such intruders in farms. You can get Diazinon in several forms such as granules, liquid, concentrates ad dust. It is highly effective in farms with nut, vegetable, and other crops.
Thiacloprid belongs to the neonicotinoid class of insecticide with the mode of action similar to that of neonicotinoids. Thiacloprid works by causing a disorder in the nervous system through the stimulation of nicotinic acetylcholine receptors. It is highly effective in getting rid of whiteflies and other sucking and chewing insects including aphids, codling moth, blossom midge, and pollen beetles. If you sight any infestation of the pests above in your apple, citrus, pear, cauliflower, carrot, cabbage or potato farm, thiacloprid can be a lifesaver.
Cartap is a soluble powder insecticide belonging to the thiocarbamate class. It doubles as both an analog and precursor of Nereistoxin which affects the nervous system of insect pests. It functions as both contact and systemic pesticide and is efficient in the crops such as peas, potatoes, tomatoes beans, cabbage, and many other plants. Cartap kills a wide range of field pests including whiteflies.
Tips for getting the best from Pesticide Application
- Ensure that you can identify the pests you want to control before deciding on which brand or types of pesticide to use.
- Choose the product that will give you the best result considering the weather condition of your region.
- Read the entire label carefully before and after you make a purchase.
- Apply the exact volume recommended by the manufacturer
- Make sure you wear all the protective gears; nose mask, boot, glove, overall, etc.
- Wash all equipment before and after every use
- Do not consume food, drink or smoke while applying chemicals
- Do not spray while it is raining or on a windy day
- In case of accidental consumption of pesticides, do well to get the first aid and visit the hospital as soon as possible.
- Securely dispose all pesticide containers and keep out of the reach of children.
Whitefly impacts are massive on crop production as they can affect both the quality and quantity of farm produce. Of all the available method of whitefly control, the use of pesticides has proven to be the most reliable and scalable for commercial farming.
Ensure you follow all the recommendations in this post to get rid of whiteflies from your farm completely.
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