War of insects: biological control can reduce disease in orange

Use of wasps in orchards can reduce by 68% the incidence of greening, says survey Esalq / Usp
by Viviane Taguchi

The greening attacks orchards to wither them; wasps can help control vectors

The use of wasps Tamarixia radiata in the orchards of orange can be very effective to combat greening, principal - and threatening - disease that attacks the feet of the fruit. Research conducted by the School of Agriculture Luiz de Queiroz (Esalq) USP, in Piracicaba (SP), shows that their use can reduce by 68% the incidence of the disease. This is because, in the field, Tamarixia radiata "fight" with Diaphorina citri, which are wasps disease vectors.

According to the engineer Alexandre José Ferreira Diniz, responsible for research, Tamarixia radiata lead the best in the race and eliminating the vectors, ultimately reducing the incidence of greening. He also stresses that this implies a significant reduction of insecticide applications in the field.

The greening has been a nightmare for growers since 2004, when nearly destroyed the orchards in the interior of São Paulo. Diniz explains that it is caused primarily by three bacteria of the genus Candidatus Liberibacter, arriving at the orchard through insect vectors.

"The bacterium causes a clogging in the vessels of plants, which prevents movement of the sap, causing the trees start to decline and eventually die" explains Diniz. "The disease is able to end the production of orchards assets in five years and the new can not produce."

How it works

In the "Biological Warfare", wasps Tamarixia radiata are loose in the orchard. There, they start looking for eggs to deposit their own. By finding the eggs of insects, small wasps 'kill and eat' the embryo that is in there and lay their own eggs. Thus, the vector population begins to be controlled.

In surveys Diniz, the wasps were distributed in six different regions and, according to him, in some of them, the reduction was 100%. But he says that biological control has yet to be used as a complement to other techniques to combat greening.

"Using biological control, along with a selective insecticide, which removes only the vector, it is possible to reduce costs and the risk of environmental contamination, oranges and producer himself."

For now, the agronomist says the technique is quite effective if applied in orchards that were abandoned on account of illness, to prevent the continued spread of the plague.

Source: Globo Rural magazine