LIBRO-CONGRESO-CITRUS

PC07
Biological control and citrus: a long time fruitful story
Jacques Brodeur
Plant Biology Research Institute. Montreal University, Montréal, Qc, Canada.
From the earliest days, agriculture has been plague by pests. Growers have to deal with outbreaks of insects,
weeds, and plant pathogens. There has been a continual increase in arthropod pest species invading citrus
over the past century. Citrus systems are replete with mite and insect pests, both in terms of their abundance
and diversity. Growers rely on several approaches to pest control, including mechanical, cultural, chemical
and biological methods. In this conference I outline the practice of biological control.
Biological control refers to the use of living organisms, or products derived from living organisms, such as
toxins, for control of insect pests, weeds and plant diseases
Biological control is considered by many to be the best alternative to pesticides. Biological control is efficient,
safe for humans and the environment, and in most cases cheaper than chemical control. Natural enemies
exert a significant, continuous and naturally level of pest population regulation in natural or managed
ecosystems. Biological control also refers to the deliberate introduction of specific natural enemies to control
specific populations of weeds, plant diseases or insect pests. Such an approach may involve the discovery
and release into a crop of natural enemies, and in some instances their production and commercialization as
biological control agents. At least 7,000 introductions of natural enemies involving almost 2,700 species have
been made worldwide. The most widely used species have been introduced into more than 50 countries.
In augmentative biological control, more than 170 species of natural enemies are produced and sold, but
some 30 species make up more than 90% of the market worldwide. Biological control has a long tradition
of success in citrus. In 1868, the cottony-cushion scale was found on acacia in California. Ten years later the
citrus industry was at the verge of collapse because of the scale. Natural enemies were sought in the native
home of the pest, southern Australia. This search resulted in the introduction into California in 1888 of a
coccinellid predator, Rodolia cardinalis. The voracious beetle rapidly became established and by late 1889
the cottony-cushion scale was no longer regarded as a threat to citrus. The beetle saved the American citrus
industry and has since become an icon in biological control.
By creation of partnerships that brought together growers, researchers and biological control companies, the
citrus industry has since undertaken a transition from total chemical control to a balance of biological control and
integrated pest management. Because the arthropod community in citrus is very complex, it remains challenging
to conduct biological control and to predict the impacts arising from interactions among biological control agents,
landscape structure and pesticide use. Understanding these factors will help to develop sustainable ecosystem
communities that can maintain pest densities below economically damaging thresholds. A current challenge
relates to the introduction of exotic pests and the subsequent release of exotic natural enemies. Due to its
overall ecological complexity, the citrus orchard is characterized by high level of both stability and capacity for
self-regulation. However, this condition is repeatedly jeopardized by a significant increase of exotic citrus pests
in all producing areas. There is therefore a growing requirement for improved quarantine services and classical
biological control programs that remains the best tool to tackle existing and future alien pest problems. But the
biological control sector is facing increasing problems with access to natural enemies since the international
Convention of Biological Diversity and its Access and Benefit Sharing regime. This situation has added another
level of regulation that may slow, and even stop in certain countries, the use and exchange of biological control
agents around the world. Global climate change is another growing concern for pest management in citrus
orchard. The increasing temperatures, elevated carbon dioxide and changes in rainfall patterns associated with
climate change will affect pest management programs and the movement of exotic organisms. In the near future
we will need to modify the carefully developed pest management programs to respond to climate changes. The
citrus industry will soon have to deal with changes in pest and beneficial species assemblages, developmental
ranges and degree of synchrony between interacting species.
Biological control creates and sustains public good – food security, food quality, reduced pesticide use, human
(farmer and worker) health, invasive alien species control, protection of biodiversity, and maintenance of
ecosystem services. However, the adoption of biological control worldwide has lagged behind our scientific
understanding of its potential. Development of biological control for citrus is a dynamic, constantly-evolving
challenge. Perseverance is critical.
10 - VALENCIA CONFERENCE CENTER, 18th-23rd NOVEMBER 2012