White fly plague threatens U.S. agriculture

A whitefly is abundant in nurseries, market gardens... and has just been found in the wild in the United States. Resistant to pesticides and carrier of many viruses, it threatens crops, particularly in Florida.

Ce are like snowflakes in the middle of summer. Whiteflies or small white flies smear the leaves with small white dots. Known in horticulture and greenhouse crops, these tiny pests have just been discovered in the wild in Florida. For several years, they have been reported in nearly twenty American states, in nurseries and market gardens. An invasion that worries farmers who have gathered near Miami to learn about the risks and solutions to this invader.

"These tiny flies may never be eradicated, fears Lance Osborne, professor of entomology at the University of Florida.because they are resistant to pesticides". The insect is a whitefly, known to infest greenhouses. This is the first time it's been found in the wild... "It could be the result of global warming...The project is planned by Pierre-Henry Gouyon, a specialist in evolutionary sciences at the Muséum d'histoire nationale d'histoire naturelle (MNHN). It is possible that the insect may have become resistant through selection pressure, due to excessive use of certain pesticides".

However, the French geneticist is not as pessimistic as Lance Osborne because he knows biological control solutions that have been developed against this sap-sucking pest. Parasitic wasps (Encarsia Formosa, Eretmocerus eremicus and Eretmocerus mundus) have the good idea to lay their eggs inside the larvae... Likewise predatory bugs (Macrolophus Caliginosus, Dicyphus hesperus.) love to devour these parasites. There are also two entomopathogenic parasitic fungi on the market, Beauveria bassiana and Isaria fumosorosea, which are hosted by whiteflies. The main producers of these biocontrol beneficials are Biobest (Begique) or Koppert (Netherlands).

READ ALSO IN UP' : The era of biocontrol has arrived

Bean-suckers, polyphagous and virus propagators

Lovers of ornamental plants such as hibiscus, geranium, fuschia or even wild plants such as chelidoine..., these tiny whiteflies can settle in cotton fields or citrus orchards. So they are very polyphages and attack hundreds of cultivated plant species (tomatoes, beans, cucurbits, potatoes, sweet potatoes, citrus). Lance Osborne points out the enormous potential impact of this pest: "In addition to the fact that it is resistant to pesticides, we are also concerned about the number of plants it can tolerate. It will always find something in the soil to attack.

Whiteflies sting the leaves, causing them to turn brown and compromise photosynthesis. More seriously, these insects carry viruses that weaken plants and can render fruits and vegetables inedible. "Bemisia whiteflies are believed to transmit more than 60 viruses and greenhouse whiteflies are believed to contribute to the spread of beet yellowsweet virus in cucumbers, reads like a Ontario Ministry of Agriculture fact sheet.

It's hard to get over it.

Their resistance to chemical treatments probably comes from the fact that the larvae and eggs are protected by an impermeable waxy film: thus insecticide sprays are only effective on adults. "The best treatment we have killed 90-91% of them." takes over Lance Osborne.

There are dozens of different whiteflies all over the world. This one, known as biotype Q, is thought to originate in Mediterranean regions, probably in tomato fields in Spain and Portugal, where it has meanwhile become resistant to pesticides. The danger is taken very seriously in Europe, where the authorities are calling farmers to be vigilant, and as far away as Israel, where the fly is also resistant to treatment. According to the UK Environment Ministry, the insect "has the potential to become a major scourge". The "Q biotype" has not yet caused much damage in Florida, but the authorities are stepping up controls and inspections, preparing plans to try to control the proliferation of this tiny insect by imposing quarantines when necessary.

A risk for the agricultural industry

"The Q biotype whitefly is a serious risk to Florida's $120 billion agricultural industry and the two million jobs that depend on it, warns Adam Putnam, Florida's Commissioner for Agriculture.

Other types of flies are considered to have contributed to famines in Africa and wreaked havoc on the agricultural community in the southern United States in the 1980s and 1990s.

Lance Osborne called on farmers not to panic: the arsenal of insecticides available today is more effective than 30 years ago and "can better control infestations if products are combined and a control program is established", he did well. And given the resilient nature of the opponent, natural or organic solutions would not work, Osborne said.

When a whitefly becomes an aphid!

Surprisingly, the Miami entomologist does not mention any biocontrol solutions. "Because there is a risk of reverting to biological solutions, in the face of the mess created by both global warming and chemical impregnation by pesticides," insists Pierre-Henri Gouyon.

The media must also be careful not to confuse flies and aphids, as is often the case. Goodplanet and Answer Conso. Even vacations produce... mutations!

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