Photo Credit: Unknown Source If you are all year round farmers; then at a certain time of the year, you would certainly have this whiti...
 |
| Photo Credit: Unknown Source |
If you are all year round farmers; then at a certain time of the year, you would certainly have this whitish angelic visitor called white-flies coming for a visit. It looks as though they come in peace but could turn your farm investment into pieces if their population is not well managed. Come along with me as I unraveled the world of white-flies and the secret to its management saving you of all your crop farm investment.
Characteristic
White-flies are miniature, sap-sucking insects that are often notice when the plant infested is shaken which cause them to fly off. They undergo complex stages of development which often make them to be very difficult to control. All the stages except pupae are parasitic in nature. There are three pre-pupae stages after the eggs called the instars that are difficult to neither notice nor differentiate before the adulthood. They multiply rapidly under favourable condition.
They excrete sticky honeydew and if left unabated would cause yellowing or death of leaves by extension the whole crop in some cases. Honeydew is a liquid rich in sugars. Up to 2,000 nymphs (1st and 2nd instars) may be found on a single bean leaf, each capable of producing 20 drops of honeydew in an hour. Sooty moulds grow on this sugary solution and affect plant photosynthetic property of the plant. Although honeydew helps parasites locate the white-fly, excessive amounts make it difficult for tiny parasitic wasps, such as Encarsia, to walk on these surfaces. The sooty mould that grows on the leaf and fruit surface can significantly affect the appearance and marketability of the crop.
You may also want to read on Management of aphids in crop farm
 |
| Sooty Mold on leaves (Photo Credit: Unknown source) |
Season of explosion
Whiteflies are common during very dry part of the year as they do not like moisture or wet condition. The reason is that wet condition often affects their flying ability, hence, interrupting their normal trend of development. They develop rapidly in warm weather and when natural enemies are ineffective and when weather and host plants favor outbreaks. Large colonies often develop on the undersides of leaves. Some of the common species such as greenhouse whitefly (Trialeurodes vaporariorum) and sweet potato whitefly (Bemisia tabaci) have a wide host range that includes many weeds and crops. These make them to be difficult to eradicate as most farmers concentrate eradication of whiteflies on their farms whereas another population explosion is occurring on the adjacent non-cropped land whereas the later serves as reservoir for their multiplication and attack-lunching site.
Ants and dust also encourage outbreaks.
You may also want to read on Management of aphids in crop farm
Effect of severe infestation and economic losses
This insect looks tiny but causes massive damages if their population and activities are left unabated. The following are the common damages they cause:
1. Sucking sap from plants: they suck nutrients rich sap from the phloem (the food-conducting tissues in plant stems and leaves) therefore depriving the host crops of necessary nutrients essential for full productivity. In most cases, this reduces the productivity of the host crops sometimes to zero.
2. Uncontrolled, white-fly stunt the growth, reduce yields and can kill a plant by direct feeding, loss of leaf quality and water loss.
3. Transmit viral diseases particularly leaf curl virus which can wipe out the whole farm in the case of host crop without certain degree of resistance to the disease.
4. Like aphids, Larval instars of white-fly produce vast quantities of honeydew during feeding which spreads on lower leaf surfaces therefore reducing the marketability and market value of the leaves.
You may also read on Management of downy mildew on veggies
 |
| Complete cycle of whiteflies (Photo Credit: Unknown source) |
Control
Outbreaks often occur when the natural biological control is disrupted. Management is difficult once populations are high. One size fit all control approach would not necessarily work for this insect. Successful management of whiteflies requires an integrated control approaches that focuses on preventive measures. Some of the approaches may be culturally and biologically inclined to get positive result. While the use of recommended active ingredients in insecticides may be required in some cases, they should come as last resort or complementary to early effort.
Integrated Approach
A combination of approaches being biologically and culturally inclined aim at preventing population explosion is obviously the major solution. Some of the following are likely workable control measures:
The insecticidal soap: You may not necessarily go for commercial brand if you can lay your hand on local black soap. Dissolve this adequately in clean water until it foams and the water is slurry and sticky. Sieve the slurry water into your spraying tank to prevent tiny particles from entering the tank which would often block the lans/nozzle; you may decide to add neem oil to increase its potency. Spray this heavily on infested crop early in the morning ensuring that it has direct contact with both the adult flying white-flies and immobile stages under leaves of the crops.
The sticky soap often renders the adults unable to fly therefore killing them in the process while it also has the ability to remove the glossy waxy cover on the immobile non-feeding stages therefore exposing them to desiccation.
Yellow sticky tape: This is only effective in a confined location such as greenhouses where it can be used to monitor level of infestation, reduce the matured flying population therefore controlling their fecundity. You do not necessarily need to buy commercial package, it is something you can make yourself. Take a shoe making gum , smear it over a yellow card board and hang it with string around 1m to 2m above ground level.
Flushing: White-flies does not like wet condition, under a small farm setting, they could be flushed off the crop with pressured water. This approach is not feasible on a large commercial farm but the use of aerial wetting/irrigation method on large scale farm too can work. Some of the aerial irrigation methods are spray-tube, sprinklers, rain guns etc. Please ensure that any of this irrigation method is suitable for your goal before making a choice and irrigate mostly early in the morning.
Removing notorious weed host plant: There are some weeds notorious for hosting whiteflies, ensure that you identify them on your farm and eradicate them as soon as possible.
You may also read on Management of downy mildew on veggies
Chemical approach and Limitation of Synthetic approach
In many situations, natural enemies will provide adequate control of whiteflies; outbreaks often occur when natural enemies are disrupted by excessive insecticide applications. Insecticides only have a limited effect on whiteflies as most only work when they come in direct contact with the whiteflies. Harsh synthetic chemicals will generally kill all the natural enemies of the whiteflies before they kill the whiteflies themselves, thus encouraging population explosion.
There are also few insecticides ’active ingredients that work against whiteflies:
Insect growth regulator e.g. teflubenzuron and buprofezin
Pesticide: pymetrozine, imidacloprid, thiacloprid and acetamiprid.
Please note that over use of the same chemical family can lead to resistance.
I strongly believe that with some of the knowledge extracted therein this article; you can put this monster in its place on your farm. Please do come back to me at the instance of any question, comment and critic. Cheers.
COMMENTS