Agriculture Reference
In-Depth Information
(bacterivores and fungivores), and tertiary con-
sumers (omnivores, carnivores, and predaceous
nematodes) (Yeates et al.
1993
). Nematodes play
multiple and contrasting (positive and negative)
roles in regulating productivity of plant- and
animal-based production systems.
Nematodes feed on a wide range of soil organ-
isms (bacteria, fungi, slug eggs, insect larvae) as
well as plant roots. Herbivorous nematodes can
cause crop losses especially in root crops like
potatoes and beets grown mostly in Europe, but
also in soybean grown in Asia (IPCC
2007
).
Many nematode species work as natural enemies
of insect larvae and slugs.
Herbivore nematodes feed on plant parts
mostly on roots. It is estimated that nematodes
cause crop losses worth US$ 125 billion annually
in agriculture (Chitwood
2003
). Bacterial and
fungal feeding nematodes are benefi cial to crop
growth because they help in enhancing the nutri-
ent availability to crop plants. Predatory nema-
todes predate on plant-parasitic nematodes and
thus have potential for biocontrol. Insect parasitic
or entomopathogenic nematodes are benefi cial to
crop production as they help in biocontrol of
insect pests of crop plants and in reducing the
consumption of chemical pesticides (Grewal
et al.
2005
). Animal parasitic nematodes whose
free-living stages also occur in soil adversely
affect the productivity of livestock and health of
agricultural workers. By virtue of their trophic
diversity, they form an important energy pathway
from primary production and detritus to higher
trophic groups. Therefore, they constitute a fun-
damental group of biological indicators that
needs to be investigated from the perspective of
climate change impacts.
Ditylenchus
Xiphinema
Globodera
Radopholus
The estimated overall average annual yield
loss of the world's major crops due to damage by
plant-parasitic nematodes is 12.3 % (Table
9.1
).
For the 20 crops (left-hand column) that stand
between man and starvation (life-sustaining hor-
ticultural crops), an estimated annual yield loss
of 10.7 % is reported. The 20 crops (right-hand
column) that represent a miscellaneous group
important for food or export value were reported
to have an estimated annual yield loss of 14 %.
Monetary losses due to nematodes on 21
crops, 15 of which are life sustaining, were esti-
mated at US$ 77 billion annually based on 1984
production fi gures and prices.
These fi gures are staggering, and the real
fi gure, when all crops are considered, probably
Table 9.1
Estimated annual yield losses due to damage
by plant-parasitic nematodes - World basis (Sasser and
Freckman
1987
)
Economically
important
horticultural
crops
Life- sustaining
crops
Loss (%)
Loss (%)
Banana
19.7
Cocoa
10.5
Barley
6.3
Citrus
14.2
Cassava
8.4
Coffee
15.0
Chickpea
13.7
Cotton
10.7
Coconut
17.1
Cowpea
15.1
Corn
10.2
Eggplant
16.9
Field bean
10.9
Forages
8.2
Millet
11.8
Grapes
12.5
Oat
4.2
Guava
10.8
Peanut
12.0
Melons
13.8
Pigeon pea
13.2
Misc. other
17.3
Potato
12.2
Okra
20.4
Rice
10.0
Ornamentals
11.1
9.1
Crop Losses
Rye
3.3
Papaya
15.1
Sorghum
6.9
Pepper
12.2
On a worldwide basis, the ten most important
genera of plant-parasitic nematodes were reported
to be as follows (Sasser and Freckman
1987
):
Soybean
10.6
Pineapple
14.9
Sugar beet
10.9
Tea
8.2
Sugarcane
15.3
Tobacco
14.7
Sweet potato
10.2
Tomato
20.6
Meloidogyne
Rotylenchulus
Wheat
7.0
Yam
17.7
Pratylenchus
Helicotylenchus
Average
10.7 %
Average
14.0 %
Heterodera
Tylenchulus
Overall average - 12.3 %
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