Whitefly (Bemisia tabaci)

What is the WHITE FLY?

Whiteflies proliferate in temperate and humid climates, so they appear mainly in the hottest periods of the year (spring and summer). Physically, they are very small, measuring between 1 and 3 millimeters, and among their family more than a thousand different species can be distinguished.

It is an insect that once it has appeared is very difficult to control, since its life cycle is between 10 and 30 days.

During these they can reproduce several times laying between 80 and 300 eggs each time, so their proliferation is very fast.

The whitefly attacks plants through its sucking mouthparts that feed on plant sap. It weakens them so much that even if left unchecked it kills the plant.

Why do whiteflies COME OUT on our plants?

Whiteflies spread mainly through the wind, with a short, fast and direct flight to the plant, another of the main causes of their appearance are the humidity and temperature conditions, that is why it is more common to see them in spring and summer and not so much in the cold seasons such as autumn and winter.

Whiteflies are very common in greenhouse crops where temperature and humidity conditions are stable and can occur throughout the year. Fortunately, the pest is less damaging in gardening, concentrating its activity period only in spring and summer (Mediterranean area).

In warmer climates (Canary Islands, Central America…) the situation can last throughout the year, being a very persistent pest.

How does the whitefly AFFECT our plants?

Symptoms of whitefly attack are similar to those produced by other pests such as aphids or mealybugs. The perforation of the tissues causes discolorations (chlorotic spots or stains due to the loss of chlorophyll) that later end with the drying and fall of the leaves. In addition, it often gives rise to twisted or deformed leaves, covered with a shiny and sticky honeydew (fruit of its feeding).

This sugary molasses also generates other indirect problems such as ants, as they are attracted by this sweet delicacy and you will see a constant coming and going around the plants caused by the molasses. As you can see ants are also closely linked to this pest.

And if you thought it was not enough, to complicate it even more, the blackness can appear in a matter of days being another of the consequences of this residue. With favorable humidity conditions, the opportunistic fungus will take the opportunity to settle on the sticky leaves, further aggravating this delicate situation in our plants or crops.

How to ELIMINATE whiteflies naturally?

WHITEFLY PREDATORS

The Nesidiociris ( Cyrtopeltis). It is a native generalist predatory bug although it is often found in association with the presence of the two most important whitefly species in horticultural crops. It appears spontaneously in tomato greenhouses where it is the most widely used biological control agent. It has the particularity that it also has phytophagous habits so that in the absence of prey, it can sting the tomato and cause lesions that devalue the quality of the fruit. It preferentially preys on eggs and larvae by puncturing with its stylet and sucking out the internal juices and leaving the tegument. It also feeds on aphids, thrips, spider mites and lepidopteran eggs.

Macrolophus caliginosus. It is a voracious generalist predator used in whitefly control of both Bemisia tabaci and Trialeurodes vaporariorum. It is abundant and frequent in numerous spontaneous and cultivated herbaceous plants. It is found in North Africa and Southern Europe, including the Balearic and Canary Islands.

Amblyseius swirskii. It is a species present in the eastern Mediterranean regions, such as Israel, Italy, Cyprus and Egypt. It is a predatory mite that can be found in numerous crops, including horticultural crops and citrus plantations. In either case, it is shown to be an effective predator of whitefly eggs and larvae (both Trialeurodes vaporariorum and Bemisia tabaci). In the absence of whiteflies, it is an excellent thrips controller. Its inability to fly limits its rapid dispersal, it can move up to 10 meters in plantations through leaves that are in contact.

PARASITOIDS OF THE WHITEFLY

Eretmocerus Mundus. It is a highly specific and effective indigenous parasitoid of the whitefly Bemisia tabaci on a wide variety of crops. E. mundus is very efficient in its search for prey. It parasitizes all larval stages of B. tabaci, although it prefers and reproduces better on second or third instar larvae. It is considered the best parasitoid of Bemisia due to:

• It parasitizes a greater number of larvae and is therefore indicated as a curative in high infestations.
• It is better acclimatized and supports a very wide temperature range working both in midsummer and winter.
• It is more resistant than Encarsia to phytosanitary products and is therefore more widely used in integrated control programs.

Encarsia Formosa. It is a specific parasite and commonly used in the biological control of the white fly in greenhouses. Nowadays the parasite can be found in Europe, Australia and North America. Optimal conditions for parasitism are in temperature ranges between 15 and 30 degrees Celsius, average luminosity and relative humidity between 50 and 80%.