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Recent analysis
suggests that Africa will only be able to achieve food security if it
invests in crop intensification like increased fertiliser and pesticide
input per hectare. But the expansion of agricultural production areas
can also improve this.
A complicating factor in African agriculture is that most of the production comes from relatively small farms.
Most of these are less than 2 hectares in size. This is much smaller
than in Europe and the Middle East where most farms are greater than 10 hectares. In Latin America most farms exceed 50 hectares.
This means that
addressing issues that affect small scale farmers' productivity can play
an important role in food security. Most farmers simply can't afford
pest management control. Often, these methods are lacking in rural
areas. And where there are products it can be adulterated or misused.
Agricultural pests
are one of the key factors affecting small holder farmer production. In
many parts of Africa large population outbreaks of rodents occur often
and can sometimes lead up to 100% crop loss.
Rodents can damage nearly every crop people try to grow. It's often
difficult to measure chronic damage because it happens over the entire
growing season and even after the crop is harvested.
The neglected rodents
Efforts to control
pests face a number of challenges. Firstly, management is often limited,
because of the high cost of herbicides, insecticides and rodenticides.
On top of this they aren't readily available in local farming areas. And
most pest control focuses on invertebrate pests like stem borers,
armyworm and locusts. Very little attention is paid to vertebrate pests
like rodents or birds like the red-billed quelea (Quelea quelea).
Rodents are a
particularly important group of pests. Agriculturally, they can inflict
considerable economic damage because of their abundance, diversity,
feeding habits and high reproduction abilities.
Research on rodent
pest control tends to be neglected. But some community based development
programmes are looking at how rodents can be controlled using ecological methods. Ecologically-based rodent management
involves, firstly, increasing our understanding of their population
biology, social behaviour, taxonomy and community ecology. These
insights can then be used to develop effective and sustainable
management strategies. This approach has been effective in reducing pest
damage as well as reducing reliance on rodenticide poisons in many countries.
There is little
data on the effects of pest control on rodents, particularly when it
comes to small holder farming systems. To gain a better understanding we
did a systematic review on the effect of rodent pests on small holder farming in Africa and the island nation of Madagascar.
Rodent management in Africa
Our review
highlighted several important findings. We found median crop losses
(midpoint of reported losses) attributed to rodent pests were around
15%. This has a significant impact on small holder grain yields and is
comparable to losses from cereal stem borers in Africa where much
greater investments have been made in control programmes.
But there was a big
discrepancy in estimated and reported losses, which highlights the
importance of standardising research protocols. For example, very little
research has been done to try and find a link between rodent density to
crop impact. This limits the setting of reasonable management
thresholds on when to control rodents based on their density.
Most importantly, we found a paucity of research investigating effectiveness of control measures on rodent pests.
We made several
detailed recommendations that we feel will improve the robustness of
rodent pest research. The most important ones included the fact that
researchers must adopt a "meta-analytic" framework.
For example, they must place their study in the context of prior
literature and they must report on the effect of rodent control,
particularly making the comparison between studies and strategies more
explicit. This framework has been successfully applied to other evidence
based research fields like medical research.
Another was that researchers and funding organisations must be encouraged to establish and fund long-term studies.
Once a firm foundation has been established on understanding the
drivers of population cycles of the dominant rodent pest species, other
important aspects like management and community ecology can be
successfully developed.
For example, in
some African countries - like Tanzania - there have been great
improvements in understanding the ecology of pest rodent species.
Researchers showed that rainfall plays an important role in predicting
rodent pest outbreaks. This facilitated regional planning to control
rodent pests in agricultural areas.
We also found that
researchers must focus more on empirical treatment control studies that
test a management action compared to no management actions. These must
be done with suitable replication that investigates management actions
on rodent pest populations and associated crop losses. For example, our recent meta-analysis showed that avian predators, like barn owls, can reduce rodent pests.
Lastly, we suggest
that ecologically based rodent management activities and research should
be carried out by multidisciplinary and interdisciplinary teams. In
this way research can be sustained over a longer period if there's
collaboration, knowledge is transferred and communities are involved.
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