FAO TRAINING ON WEED MANAGEMENT

R. Labrada

Weed Officer

Plant Protection Service

FAO, Rome

Summary

FAO training activities on weed management over the past four years and regions where they have been implemented are described in this paper.

At present the main areas of training are Weed Eco-biology and Competition, Herbicide Resistance and Waterweed Control. Such courses are usually organized at regional level and given by leading weed scientists actively working on relative topics of interest. To date three regional courses on weed ecology and competition have been carried out, as well as a further three on herbicide resistance. Waterweed control training is usually conducted within the framework of ongoing FAO projects on aquatic weed control.

FAO foresees the continuation of the courses on waterweed control in countries where training is still required. New courses on improved weed management in crop areas are due to start, where training should cover suitable methods for the control of existing weed complexes in the field. This will be carried out in two ways, through national training of researchers and extensionists as well as brief fellowships overseas for young weed scientists. The other area of interest in the future is training technicians from developing countries on risk/benefit assessment of Herbicide Resistant Crops (HRCs).

1. Introduction - The status of weed management

Despite the progress made in weed science over the last 40 years, weeds remain one of the major constraints to agricultural production in developed and developing countries. Losses caused by weeds in the developing world are still at least 15% annually and in certain regions, such as the arid Sahel in Africa, losses can be up to 50-60% in cereal-growing areas heavily infested with Striga parasitic weeds (Labrada, 1992).

In the developing world, progress on weed management is also being achieved and new weed control technologies have been introduced and adapted in several countries of Asia and Latin America. These control methods have to some extent alleviated the traditional drudgery of farmers. Herbicides are increasingly used in crops such as rice, wheat, sugarcane, cotton, soybean, sunflower and others. Already in 1991 Latin American countries were consuming 8% of the total herbicide market while Asia consumed nearly 15% (Terry, 1996). Cover crops are widely used in fallow areas and in the crop inter-rows of orchards; minimum and no tillage systems are expanding rapidly in various regions.

Despite the real progress made in weed management, several weed species continue to interfere seriously with crops, reducing their yields and quality, and farmers are still not aware of the basic elements of rational weed management.

New weed control methods introduced in the developing world have been implemented in many cases without taking account of prevailing local weed flora, its composition and characteristics. In several places, three to four years after these introductions new troublesome species still thrive, causing subsequent crop losses in affected areas.

Examples of such phenomena are to be found in direct-seeded rice, where the use of herbicides has been unable to reduce the growth and reproduction of weedy Oryza sativa (red or weedy rice) and/or the incidence of the ever-present Echinochloa spp.

Cases of herbicide resistance also occur increasingly in several developing countries, particularly in rice and wheat.

All these problems are the consequence of the rapid process of introduction of weed control measures. In many cases, the technology is derived from positive results achieved with a particular weed control method or chemical without taking into consideration other aspects of the prevailing weed complex, its characteristics and possibilities of new weed species becoming predominant.

It is no secret that in many developing countries there is a lack of understanding of the importance of studies on weed eco-biology, the process of weed interference and other aspects of weed behaviour.

Several weed problems together cannot be solved by using a single control method. The control of parasitic and perennial weeds, for example, requires the implementation of more than one control measure to effectively reduce existing infestation.

Nevertheless, it is considered that in order to promote improved weed management practices effectively, it is essential to train technicians and scientists in developing countries on the basic aspects of weed management, including some key control methods.

2. The content of training on weed management

Training on weed management in the 60-70s was based mainly on promoting safe handling and use of herbicides with scarce weed eco-biology elements.

A good basis for the development of an integrated approach to weed management could be the use of data related to weed growth cycles, rate and mode of plant reproduction, weed seed bank in soil and weed interference with crops.

Weed research programmes in many developing countries have been drastically reduced. Such reduction has also reached some International Centres of the CGIAR system. Weed research has suffered in much the same way over the past few years. In many cases it was believed that to control weeds it is enough to be familiar with the use of chemical herbicides, and many weed activities were devoted solely to herbicide testing. In the 70s, the only activity of many agricultural centres in developing countries was testing of all new herbicides in different crops. Once this herbicide "boom" was over the institutions started to abolish weed research posts. The technical justification for studies of weed population dynamics and/or seed bank in soil was not given or planned, so it was thought there was no scope for weed research.

While developed industrialized countries, which depend less economically speaking on their agricultural production, retain the work of their weed science societies and strengthen their research/extension programmes, the developing world still underestimates the importance of improved weed management.

Greater awareness of the importance of weed control is still needed, and it should be emphasized that weed management is responsible for 80% of the success in cropping. Land preparation (no matter whether conventional, minimum or zero tillage systems are used), cultivation, use of cover crops, mulching, inter or multi-cropping plus weeding (either mechanically or manually) all have more to do with weed control than with any other aspect of cropping.

3. Weed Eco-biology as a basis for sound weed management

The spread of weeds is largely determined by abiotic factors, such as climate and soil, as well as by competition and current cropping practices.

The basis of sound weed science is a knowledge of weed ecology and biology (table 1).

Table 1 Eco-biological attributes of weed behaviour

Another practical aspect for farmers to understand is when to weed, something that will surely save them and their families time. Knowledge of methods for determining weed-free periods and critical periods of weed competition will help farmers to understand the importance of early removal of weeds to minimize crop losses caused by weed competition.

In no less than 80% of developing countries there is a lack of data on weed ecology (behavioural ecology of weeds) and biology, and in half of them no studies of critical periods of weed competition have ever been carried out.

The development of applied ecology has been of enormous value for better management of natural resources and improvement of agricultural production, including weed management.

In addition, the weed management component should be ecologically based if it is to be included in IPM programmes. Therefore, assistance to countries by giving training to still existing weed scientists or agronomists on methods to study weeds, their life cycle, reproduction, weed seed bank and weed competition, is essential for the sound development of weed management.

The first phase of such development should avoid the inclusion of mathematical modelling in the training syllabus. It is essential first to study the weeds and to gather as many data as possible. Once this is done and the study process is established, then modelling may take place.

4. Aspects related to the use of herbicides

The introduction of herbicides in nearly all countries has been carried out through internal pesticide registration procedures. This process normally includes some field tests in order to study the effectiveness of the product in weed control and its possible phytotoxicity to crops. Only in a few developing countries have such tests included other studies of herbicide carry-over and any other indirect effect from the use of these agro-chemicals.

The problem of weed resistance is not new. In the past, Gressel (1978) presented an interesting review of this problem and presented his ideas of what might occur. Nowadays weed resistance is a problem in nearly all developed countries and is also becoming an important issue in several developing countries, particularly in Latin America and Asia where herbicides have been used for 20 or more years in various crops. In addition, the use of new molecules of imidazolines, sulfonylureas and aryloxyphenoxyalkanoic acid esters (post-emergence selective graminicides) has produced problems of weed resistance in a relatively short period of time.

5. Water weed control

Waterweeds are a major problem in nearly all tropical and sub-tropical countries. These weeds cause problems to fishing, irrigation networks and hydroelectric power supplies and may serve as habitats for the development of vectors of human diseases, such as malaria and bilharziasis.

The introduction and spread of several plants, such as water hyacinth (Eichhornia crassipes) and water fern (Salvinia molesta), in tropical countries has been a disaster to the water bodies of these nations. These plants, particularly water hyacinth, were introduced as potential ornamentals and for taxonomic studies without the presence of their natural enemies. The latter fact has been the main cause of their rapid dissemination in the countries. Sometimes this phenomenon even touches countries with nearly temperate climate, as is the case of water hyacinth establishment in Portugal and in Tarija province in Bolivia.

Another waterweed problem in polluted water bodies of several countries is water lettuce (Pistia stratiotes), whose presence has increased enormously in recent years.

Affected countries urgently need training and advice on how to control these floating weeds and prevent their further dissemination. It is well known that floating aquatic weeds are good targets for biological control, but to implement such control methods training is required on safe introduction, rearing and release of effective biological control agents.

6. FAO training programme on weeds

Based on the problems described above, FAO has implemented training on various aspects of weed management as an initial step towards increasing technical capabilities in the countries. Training is conducted on the three major aspects mentioned above, i.e. weed eco-biology and competition, herbicide resistance and aquatic weed control.

Since each training programme has different objectives, the duration also varies. Relevant weed research personnel conduct the training courses, which include lectures, seminars and field demonstrations and activites. The main aim is to provide an understanding of the fundamental aspects of each method of evaluation and/or control.

6.1. Training on weed eco-biology and competition

Courses on these topics have already been conducted in three region, Latin America (Lima, 1999), Asia (Bangkok, 2000) and French-speaking Africa (Cotonou, 2000). To date, weed scientists from 24 developing countries have been trained in weed eco-biology and competition. Two additional courses are foreseen for the period 2001-02, one in Ethiopia for English-speaking African countries and the one for countries of the Middle East. The content of these courses is shown in table 2.

The content of the course is based mainly on the recommendations made by an international panel of experts in a technical consultation on weed ecology and management organized by FAO (1997a).

The advantage of the courses is that the participants discuss weed problems in their own countries and usually receive advice from the other participants. In some cases, workshops are organized on particular topics, such as the one conducted in Cotonou on Imperata cylindrica control or one held in Asia where participants formulated a regional project profile on weed management.

Once the cycle of courses is finished, a second phase of field research involving farmers is foreseen in pilot countries. The idea is to use data from these studies in ongoing IPM programmes.

Table 2 Content of Courses on Weed Eco-biology

6.2 Training on herbicide resistance

This type of training has only been carried out in regions where herbicides are known to be used in one major or several crops. Thus the first regional training as such was organized in Jaboticabal, Brazil (FAO, 1997b), with the participation of eight Latin American countries, while a second was carried out in Taegu, Korea (FAO, 1998), with the participation of seven Asian countries. The third course was a modest sub-regional workshop for Baltic countries (Estonia, Latvia and Lithuania) (FAO, 1999).

The content of the course is shown in table 3. In addition to lectures on herbicide resistance and demonstration of methods for detection of resistance, seminars are also included in order to discuss the status of herbicide use in each country and related problems.

Increased use of herbicides in other developing regions will indicate whether there is a need to organize courses on weed resistance in other developing regions.

Table 3 Content of Courses on Herbicide Resistance

6.3 Training on integrated water weed control

Due to severe problems caused by water weeds, several affected countries have requested technical assistance from FAO to implement control programmes, particularly of water hyacinth.

Since 1991 FAO has implemented 11 projects: two in Latin America and the rest in Africa, four of which were regional. One of the main components of these projects is strengthening national capabilities in biological control of aquatic floating weeds. In these activities national personnel receive training on methods for surveying aquatic weeds, rearing and release of relevant biological control enemies and on survey of their establishment in treated areas.

The existence of various sound rearing units of biocontrol agents, as well as personnel already trained and experienced in these activities, permit collaboration among African countries in issues related to water weed control. The content of the training programme on waterweed control is shown in table 4.

Training on waterweed control refers mainly to floating waterweeds, i.e. E. crassipes, S. molesta and P. stratiotes.

In this training, experience gained by other countries in waterweed control in the region is discussed.

FAO has also promoted waterweed control in Latin America, and a regional seminar on this topic was organized in Cuernavaca, Mexico, with the participation of five countries.

Table 2 Content of Training on Water Weed Control in Africa

7. Future activities and complement

For the immediate future, three types of training are planned:

1. Improved weed management. There is a need to implement improved weed management in many developing countries, where the fundamental aspects of appropriate weed control are still not used. Instead of implementing projects on a single harmful weed species, the development of projects comprising rational control of weed complexes in economically important crops of the countries is foreseen.

Training on integrated weed management will be included in the work plan of these projects. This should be done in two ways: a national training course for various participants (researchers, extensionists, others) and brief overseas training for one or two weed scientists.

2. Water weed control. Training on this aspect should continue in those countries still requiring the implementation of integrated waterweed control. The training should be included in the work plan of projects specific to this topic.

3. Herbicide Resistant Crops. The issue of Herbicide Resistant or Tolerant Crops (HRCs) is gaining in importance. Developing countries should decide individually whether or not to use these transgenic crops, for which they would need tools to evaluate possible risks and/or benefits of their use.

FAO is at present finalizing guidelines for the evaluation of HRCs, which may be used by the countries as the step prior to the possible introduction of these crops. Certainly, guidelines alone will not be enough. Therefore training is essential for correct implementation of this type of evaluation.

Within the limited funds available, FAO will continue to assist the countries in matters related to integrated weed management. It is also important to point out that this assistance has also been made possible through the active participation of several outstanding weed scientists, who kindly agreed to share their knowledge and experience with technicians from the developing world.

References

FAO,1997a. Expert Consultation on Weed Ecology and Management. FAO, Rome, 22-24 September 1997, FAO Plant Production and Protection Division. 107 pp.

FAO, 1997b. Informe, Reunión Regional Resistencia de Malezas a Herbicidas Jaboticabal, UNESP, Brasil 27 de octubre 1997. FAO División de Producción y Protección Vegetal. 20 pp.

FAO, 1998. Report, Regional Meeting on Herbicide Resistance, Taegu, Korea 29 June-3 July 1998. FAO Plant Production and Protection Division. 22 pp.

FAO, 1999. Report, Sub-Regional Meeting on Herbicide Resistance and Herbicide Resistant Crops for Baltic Countries. Tallinn, Estonia 17-21 May 1999. FAO Plant Production and Protection Division, 14 pp.

Gressel J., 1978. Factors influencing the selection of herbicide resistant biotypes of weeds. Outlook on Agriculture 9:283-287.

Labrada R., 1992. Tropical Weeds: Status and trends for their control. In Proc. "1st Intern. Weed Control Congress", Melbourne 17-21 February. vol 2 p. 263-276.

Terry J., 1996. The Use of Herbicides in the Agriculture of Developing Countries. In

2nd Intern. Weed Control Congress, Copenhagen, Denmark, 25-28 June. Edited by H. Brown, G.W. Cussans, M. D. Devine, S.O. Duke, C. Fernandez-Quintanilla, Arne Helveg, R. Labrada, M. Landes, P. Kudsk and J. Streibig. p. 601-609.