Module M 3801-420: Crop Production Systems

Dr. Abuelgasim ElzeinDr. Abuelgasim ElzeinUniversity of Hohenheim,University of Hohenheim,

Institute of Plant Production and Agroecology in the Institute of Plant Production and Agroecology in the Tropics and Subtropics; Tropics and Subtropics; Email: gasim@uni-Email: gasim@uni-

hohenheim.dehohenheim.de

I: Pest and weed Management

and

1. Yield losses caused by pests, diseases and weeds

Contents

3. Principles of IPM

2. Pests and diseases of rice and cassava: examples

4. General aspects of weed control

5. Principles of biological pest and weed control

Estimated losses of the 8 most important food- and market-crops1 during the period

1988 - 90, analysed per continent

Continent Production Losses (% )3 Total losses

($ billions) (% ) Diseases Pests Weed (% ) ($ billions)

Africa 13,3 4,02 15,6 16,7 16,6 48,9 12,8

North America

50,5 15,1 9,6 10,2 11,4 31,2 23,0

Latin America

30,7 9,2 13,5 14,4 13,4 41,3 21,8

Asia 162,9 48,6 14,2 18,7 14,2 47,1 145,3

Europe 42,6 12,7 9,8 10,2 8,3 28,2 16,8

U.S.S.R. 31,9 9,5 15,1 12,9 12,9 40,9 22,1

Ozeania 3,3 1,0 15,2 10,7 10,3 36,2 1,9

Total 335,2 100,0 13,3 15,6 13,1 42,1 243,7

(Oerke et al., 1994)

1 Rice, wheat, barley, maize, potatos, soja, cotton, coffee 2 Percental part of the worlproduction 3 Percental part of an achieved production

Crop

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

(Oerke et al 1994)

  Yield losses (%)  

  Diseases Pests Weeds Total

Mean 12,4 13,8 12,0 38,1

Yield losses caused by pests, diseases and weeds

Hopper burn – outbreakes of leafhoppers

Sogatodes spp. AsiaControl: systemic insecticides

Insect pests in rice:

EggsEggs

Rice bug: Leptocorisa oratoria

NymphNymph AdultAdult

Sucking damage at glumes, shrinking and drying up panicles andg grains

Control: rotation, planting timeInsecticides

Insect pests in rice:

African mosaic virus

Cassava - Diseases and pests

Virus transmited by insect(Bemisia tabasi)

Symptoms: yellowish leaves

Control:1. Use of rsistance cultivars2. Chemical and other means of

control of the vector instect

Strategies in crop protection

1. Preventive measures (plant guarantine)

2. Cultural or agronomical control3. Physical control4. Chemical control5. Biological control6. Integrated pest mamagement

EggsEggs

Rice bug: Leptocorisa oratoria

NymphNymph AdultAdult

Sucking damage at glumes, shrinking and drying up panicles andg grains

Control: rotation, planting timeInsecticides

Insect pests in rice:

EggsEggs

Green rice bug – Nezara viridula

5. Nymphal stage5. Nymphal stage AdultsAdults

Definitions of Integrated Pest Management “IPM”

„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“

FAO definition German Plant Protection Law

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.

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.

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

Why weed control?

• Difficulties concerning cultivation- and harvest labour

Flaveria trinerva infestation at potato cropping in the Republic of Yemen

• Favourable conditions for the transmission of plant diseases and pests

-hosts or intermediate host

Why weed control?

Solanum nigrum parasitized by

Orobanche cernua

• Toxic effect of pasture weeds

• Displacement of endemic species through accidentally imported plants

Why weed control?

Eichhornia crassipesEichhornia crassipes Pistia stratiotesPistia stratiotes

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

Positive effect of weeds

• Weeds used as additional forage source esp. for small- holder systems of the semi-arid tropics and subtropics

• Weeds as medicinal crops

• Weeds as green manure

• Weeds as potential genetic pools for crop breeding

Use of Echinops spp. in semi-arid regions of the

Republic of Yemen

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)

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

* A = annual; Aq = aquatic; D = dicotyledon; M = monocotyledon; P = perennial From Holm et al. 1977

The most serious weeds in the worldRank Species Growth form

1 Cyperus rotundus L. P M2 Cynodon dactylon (L.) Pers P M3 Echinochloa curs-galli (L.) P. Beauv. A M4 Echinochloa colona (L.) Link A M5 Eleusine indica (L.) Gaertn. A M6 Sorghum halepense (L.) Pers P M7 Imperata cylindrica (L.) Rauschel P M8 Eichhornia crassipes (Mart.) Solms P D Aq.9 Portulaca oleraceae L. A D10 Chenopodium album L. A D11 Digitaria sanguinalis (L.) Scop. A M12 Convolvulus arvensis L. P D13 Avena fatua L. and relatives A M14 Amaranthus hybridus L. A D15 Amaranthus spinosus L. A D16 Cyperus esculentus L. P M17 Paspalum conjugatum Berg P M18 Rottboellia cochinchinensis (Lour.) W.D. Clayton A M

Module M 3801-420: Crop Production Systems

Dr. Abuelgasim ElzeinDr. Abuelgasim ElzeinUniversity of Hohenheim,University of Hohenheim,

Institute of Plant Production and Agroecology in the Institute of Plant Production and Agroecology in the Tropics and Subtropics; Tropics and Subtropics; Email: gasim@uni-Email: gasim@uni-

hohenheim.dehohenheim.de

II: Principles of biological pest and weed control

and

•What is Biological Control: definitions•Historical Background •Why is biological control •Principles•Biological control mechanisms•Selected successful examples:

–Plant diseases–Insects–Nematodes–weeds

Biological Control

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.

What is Biological Control?

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 Microbiologist’s Perspective

Pest suppression with biological agents, derivatives of, or products of biological agents applied in a background of integrated control.

A Practical Perspective

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!

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.

A chronology of biological control

What Kinds of Things Function as Biological

Control Agents?

• Microorganisms– Bacteria– Fungi– Nematodes– Viruses

• Macroorganisms– Insects– Man– Animals

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).

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

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

Natural enemies of pests (3)

• Predators kill their prey after catching. They need more than one prey for its development.

Coccinella septempunctata

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.