1. Module M 3801-420: Crop Production Systems
I: Pest and weed Management
and
Dr. Abuelgasim Elzein
University of Hohenheim,
Institute of Plant Production and Agroecology in the Tropics and Subtropics;

2. 1. Yield losses caused by pests, diseases and weeds
Contents
1. Yield losses caused by pests, diseases and weeds
2. Pests and diseases of rice and cassava: examples
3. Principles of IPM
4. General aspects of weed control
5. Principles of biological pest and weed control

3. Estimated losses of the 8 most important food- and market-crops1 during the period , analysed per continent

4. Yield losses caused by pests, diseases and weeds
Yield losses caused by pests, diseases and weeds
Crop
Yield losses (%)
Diseases
Pests
Weeds
Total
Rice
15,1
20,7
15,6
51,4
Wheat
12,4
9,3
12,3
34,0
Barley
10,1
8,8
10,6
29,4
Maize
10,8
14,5
13,1
38,3
Potato
16,4
16,1
8,9
41,4
Soybean
9,0
10,4
13,0
32,4
Cotton
10,5
15,4
11,8
37,7
Coffee
14,9
14,9
10,3
40,0
Mean
12,4
13,8
12,0
38,1
(Oerke et al 1994)

5. Insect pests in rice: Hopper burn – outbreakes of leafhoppers
Sogatodes spp.
Asia
Control: systemic insecticides

6. Eggs Adult Nymph Insect pests in rice: Rice bug: Leptocorisa oratoria
Sucking damage at glumes, shrinking
and drying up panicles andg grains
Control: rotation, planting time
Insecticides
Eggs
Larven und Adulte saugen den milchigen Saft sich entwickelnder Körner an den Rispen  Körner bilden sich nicht normal aus und vertrocknen  weißliche Rispen. Späte Reissorten entgehen dem Befall, da dann die Population gering ist.
Adult
Nymph

7. Cassava - Diseases and pests
African mosaic virus
Virus transmited by insect
(Bemisia tabasi)
Symptoms: yellowish leaves
Control:
Use of rsistance cultivars
Chemical and other means of control of the vector instect

8. Strategies in crop protection
Preventive measures (plant guarantine)
Cultural or agronomical control
Physical control
Chemical control
Biological control
Integrated pest mamagement

9. Eggs Adult Nymph Insect pests in rice: Rice bug: Leptocorisa oratoria
Sucking damage at glumes, shrinking
and drying up panicles andg grains
Control: rotation, planting time
Insecticides
Eggs
Larven und Adulte saugen den milchigen Saft sich entwickelnder Körner an den Rispen  Körner bilden sich nicht normal aus und vertrocknen  weißliche Rispen. Späte Reissorten entgehen dem Befall, da dann die Population gering ist.
Adult
Nymph

10. Eggs 5. Nymphal stage Adults Green rice bug – Nezara viridula
Weit verbreitet in den Tropen und Subtropen. Saugen an milchreifen Körnern von Reis  Schrumpfen
5. Nymphal stage
Adults

11. Definitions of Integrated Pest Management “IPM”
FAO definition
German Plant Protection Law
„A pest management system that, in the context of the associated environment and the population dynamics of the pest species, utilises all suitable techniques and methods in as compatible manner as possible and maintains the pest population at levels below those causing economically unacceptable damage or loss”
„A combination of techniques which, giving preference to biological, biotechnological, plant-breeding, cultivation and cropping methods, restricts the application of chemical pesticides to the necessary minimum“

12. Principles of IPM
IPM is a holistic, interdisciplinary approach which considers the ecological and socio-economic conditions of a site as one unit, and strives to maintain the productivity of the agroecosystem on a sustainable basis.
Measures to control pest infestation take into account all anticipated ecological, toxicological and economic impacts: preference is given to non-chemical methods over the application of chemical pesticides.

13. What are “weeds”? Weeds are plants that cause more damage than use.
“Weeds” are internationally defined as all not desired plant species of very different habitats.
Apart from weeds of agricultural crops and pastures or respectively aquatic systems, not desired trees and shrubs of the natural vegetation are defined in this way, too.

14. Weed competition during the
Why weed control?
Qualitative yield reduction
pollution of harvest products by weed seeds
Quantitative yield reduction
competition for growth factors (nutrients, water, light)
Weed competition during the
emergence of potatoes

15. Why weed control?
Difficulties concerning cultivation- and harvest labour
Flaveria trinerva infestation at potato cropping in the Republic of Yemen

16. Why weed control? Toxic effect of pasture weeds
Favourable conditions for the transmission of plant diseases and pests
hosts or intermediate host
Solanum nigrum parasitized by
Orobanche cernua

17. Why weed control?
Displacement of endemic species through accidentally imported plants
Pistia stratiotes
Eichhornia crassipes

18. Positive effect of weeds
Better soil tilth (tillage), and erosion protection by shading and root penetration of the soil
Support of the beneficial fauna (permanent crops annual crops)
Segetal vegetation besides
fields in potato production
in the Republic of Yemen

19. semi-arid regions of the
Positive effect of weeds
Weeds used as additional forage source esp. for small- holder systems of the semi-arid tropics and subtropics
Use of Echinops spp. in
semi-arid regions of the
Republic of Yemen
Weeds as medicinal crops
Weeds as green manure
Weeds as potential genetic pools for crop breeding

20. Instruments for weed control
1. Preventive measures (seed cleaning, crop residues, machines and equipment)
2. Mechanic measures (hoe, harrow, weed harrow)
3. Physical measures (flaming, solarisation)
4. Chemical measures (herbicides)
5. Biological measures (insects, pathogens)

21. Basic components of weed control
1. Identification of weeds and their level of infestation
2. Biology and ecology of the weed species
3. The competitive effects and economic thresholds
4. Technically effective, economically viable and environmentally safe methods of control

22. The most serious weeds in the world
Rank
Species
Growth form 1
Cyperus rotundus L. P M 2
Cynodon dactylon
(L.) Pers P M 3
Echinochloa curs-galli
(L.) P. Beauv. A M 4
Echinochloa colona
(L.) Link A M 5
Eleusine indica
(L.) Gaertn. A M 6
Sorghum halepense
(L.) Pers P M 7
Imperata cylindrica
(L.) Rauschel P M 8
Eichhornia crassipes
(Mart.) Solms P
D Aq. 9
Portulaca oleraceae L. A D 10
Chenopodium album L. A D 11
Digitaria sanguinalis
(L.) Scop. A M 12
Convolvulus arvensis L. P D 13
Avena fatua
L. and relatives A M 14
Amaranthus hybridus L. A D 15
Amaranthus spinosus L. A D 16
Cyperus esculentus L. P M 17
Paspalum conjugatum
Berg P M 18
Rottboellia cochinchinensis
(Lour.) W.D. Clayton A M
* A = annual; Aq = aquatic; D = dicotyledon; M = monocotyledon; P = perennial
From Holm et al. 1977

23. Module M 3801-420: Crop Production Systems
II: Principles of biological pest and weed control
and
Dr. Abuelgasim Elzein
University of Hohenheim,
Institute of Plant Production and Agroecology in the Tropics and Subtropics;

24. Biological Control What is Biological Control: definitions
Historical Background
Why is biological control
Principles
Biological control mechanisms
Selected successful examples:
Plant diseases
Insects
Nematodes
weeds

25. What is Biological Control?
Definitions:
The utilisation of organisms (micro or macro) for the regulation of plant pests (weeds, diseases, insects, nematodes) densities below the economic threshold.
The use of parasitoids, predators, pathogens and competitors to supress a pest population, making it less abundant and thus less damaging than it would otherwise be.

26. What is Biological Control?
A Microbiologist’s Perspective
Pest suppression with biological agents operating in a background of integrated control that does not depend on host resistance, sterilization of the target pathogen, or modification of pest behavior.
A Practical Perspective
Pest suppression with biological agents, derivatives of, or products of biological agents applied in a background of integrated control.

27. Is Biological Control Biotechnology?
Biotechnology is a set of tools that utilize living things (and more recently, derivatives of living things) to solve problems or to produce products.
Of course it is!

28. Historical Background
The term biological control was first used by Smith (1919) to describe the introduction of exotic natural enemies for the permanat supression of insect pest.
BC was first applied, long before its definition, when man began keeping cats to protect stored grain from damag by rodents.
During the Pre-Scientific Era (Pre – 1880), in China and Yeman colonies of ants were introduced and relaesed in order to control citrus and date pests.
During the 19th century, after microbes were discovered and insects life cycle began to be understood, some attempts were made to use other kind of organisms.

29. A chronology of biological control

30. What Kinds of Things Function as Biological Control Agents?
Microorganisms
Bacteria
Fungi
Nematodes
Viruses
Macroorganisms
Insects
Man
Animals

31. Concept of biological control of pest
To introduce natural enemies of a target pest that will reduce and supress the density of the pest to a level that is acceptable (threshold level).

32. Natural enemies of pests (1)
Pathogens (include viruses,
bacteria, fungi and protozoa)
cause infection diseases in their host which lead to their death.
Beauveria infected beetle

33. Natural enemies of pests (2)
Parasitoides put the host to death during their development:
Egg parasitoids, larval parasitoids, adult and nymphal parasitoids
Aphelinus spp. parasitizing an aphid

34. Natural enemies of pests (3)
Predators kill their prey after catching. They need more than one prey for its development.
Coccinella septempunctata

35. Where do you find BC agents?
Suppressive soils
Old world
New world
On plant materials
On “sick” pathogens and pests
By accident
Suppressive soil:
A soil in which certain disease(s) fail to develop because of the presence of microorganisms in the soil antagonistic to the pathogen.