Environmental Engineering Reference
In-Depth Information
into many African nations along with new germplasm resources imported from other countries
and turned into invasive species from 1970 to 1980 because of optimum growing conditions,
wider host range, and lack of natural predators in the new area. The cassava production area
was significantly reduced because of this mealy bug infestation. A research team led by Hans
R. Herren and Peter Neuenschwander at International Institute of Tropical Agriculture (IITA)
successfully identified the presence of the same mealy bug species and its natural predator spe-
cies,
Anagyrus lopezi
(a predator wasp), in South America, the center of diversity for cassava.
Importing of these natural enemies, rearing them at laboratory conditions, and their dispersal in
infested areas in Africa by IITA researchers in collaboration with CIAT significantly controlled
mealy bug infestation.
To increase the effect of biological control of CMB, a complex of natural enemies that include
Acerophagus coccois
and
Aenasius vexans
, were later introduced to contain cassava mealy bug
populations by laying eggs on the mealy bugs and parasitizing them. The spectacular biological
control of the cassava mealy bug was the first of many successes in the history of the Biological
Control Center for Africa set up by IITA (Neuenschwander 2001).
Cassava green mite (
Mononychellus tanajoa
), another sucking pest of cassava, was introduced into
the cassava belt causing an estimated 30-50% reduction in yield. This pest was also brought under
biological control by identifying, introducing, and establishing predatory mites (
Typhlodromalus
aripo
and
T. manihoti
) and later an acaropathogenic fungus (
Neozygites tanajoae
) from climatically
similar areas of Brazil. These efforts have resulted in a 30-65% reduction in green mite density and
a 15-35% increase in the yield of cassava (Mégevand et al. 1987).
Cassava mosaic virus is another such invasive pathogen that threatens this key crop in East
Africa, and the Food and Agricultural Organization (FAO) is currently assisting countries' response
to such transboundary plant pest and disease emergencies and also in developing disease-resistant
cultivars. Stringent regulatory restrictions for germplasm transfer, transgenic crops, and improved
crop management practices alleviate the risks imposed by transboundary and invasive pests and
super weeds.
13.7 Future ProsPects
Global food demand has been projected to double by the year 2050, and research for increased agri-
cultural production has been suggested as key to feeding the increasing world population. Cereal
crops have been the major and preferred food sources across many nations, but their abilities to
grow in difficult climatic and soil conditions are relatively poor. Cassava currently fits as the best
alternative to cereals because it has the ability to tolerate longer periods of drought, disease, and
insect pressure and yet produce economical yields for the poor farming communities. Bringing
marginal lands and poor soils into cassava cultivation and exploring the additional uses of cassava
can help meet global food demand. Exploitation of cassava production not only for human consump-
tion and industrial use but also as feed in the poultry and livestock industry will likely ease the
global pressure on cereal crops.
Diminishing fossil fuel resources has no doubt led to the increased global interest in biofuel pro-
duction efforts in many nations. The use of cereal crops for ethanol production in recent years has
been blamed as the major cause of the global rise in food commodity prices. High starch content in
cassava makes it one of the best alternative candidates for ethanol production. The technology for
converting cassava into biofuel ethanol is currently being perfected and very soon will be applicable
anywhere in the world. Brazil, the world's leading producer of these substitute fuels or biofuels,
makes more than 120 million hL/year from sugarcane (
Saccharum
spp.) and cassava. Establishing
ethanol/biofuel production plants in cassava-growing areas not only aids in meeting fuel demands
but also economically helps the local farming communities. For example, cassava production in
Vietnam (9.39 million tons in 2008) has rapidly changed its role from food crop to an industrial one
(FAO 20 08).
