Training News

In this section we welcome all your experiences in working directly with the end-users of arthropod and microbial biocontrol agents or in educational activities on natural enemies aimed at students, farmers, extension staff or policymakers.

Vietnam Showcase

The Vietnam national IPM programme is well on the road to becoming a showcase for vegetable disease management Participatory Action Research (PAR) from which other countries can learn. Since 1996, IPM trainers have been organizing farmer field schools on vegetable IPM. Farmer trainers have emerged from these field schools, and have gone on to train other farmers in formally organized farmer-to-farmer field schools, and as a result some 14,500 farmers have been trained in vegetable IPM since 1996. In addition, some farmers conduct field studies, either in groups or individually, and others organize themselves into IPM clubs and meet regularly to discuss agriculture and related issues. Field schools and follow-up activities have shown that a major reduction in pesticide use in vegetables can be obtained by better understanding of biological control, crop compensation and different cultural practices.

The project to pilot vegetable disease management PAR began in January 1999 with a workshop held in Hai Phong Province. The workshop brought together Training of Trainers (TOT) graduates from three provinces (Hai Phong, Ha Tay and Lam Dong), Plant Protection Department, Regional Plant Protection Centre and National Institute of Plant Protection (NIPP) personnel and representatives from the FAO IPM office in Hanoi and CABI Bioscience.

The workshop aimed at identifying a rough plan-of-action for the trainers to study disease management with farmers. Important diseases were listed, and from these were selected those that cause major yield losses in important crops (tomato, bean, cabbage, cucumber and onion). Each province prioritized the crops for study, and an agreement was reached to focus on soil-related diseases: bacterial wilt in tomato, root rot (fungal disease) in bean, bottom rot (fungal disease) in cabbage and bacterial wilt in cucumber. However, as it became clear that not all diseases had been properly identified, the urgent need for this to happen was agreed.

During the workshop, practical disease exercises were done as refreshers for the trainers, such as characterization of disease, disease 'zoos'/infection studies, and preparation of disease triangles. A session on composting and the use of compost was also held, as it became clear that the term 'compost' created confusion. In Vietnam, a mixture of manure and crop residues is called compost even before it is fully composted. Leaflets describing what compost is and how to go about making it are available in Vietnamese. Much attention was given to the design of PAR and observation and evaluation methods, and drawing up action plans for each province.

After the workshop, the provincial participants, now the facilitators of the PAR, returned to their respective provinces and organized farmer workshops to go through the steps described above and finalize the details of the PAR, with farmers choosing the specific diseases to be studied, and farmers deciding on the various treatments as well as the design of the study.

A second workshop was held in September 1999 as an evaluation and planning forum for IPM trainers and farmers from each of the three provinces and resource personnel from the National Institute of Plant Protection, FAO and CABI. Although the weather during this first season of the project was largely unfavourable for the diseases chosen for study, and some mistakes were made in some experimental designs, farmers and trainers were enthusiastic about the results and what they had learned, and were determined to continue.

For example, the participating farmers in Hai Phong Province focused on compost - how to make it and its impact on cucumber wilt (identification still not clear) and bacterial wilt in tomato (Ralstonia solanacearum). They also evaluated the effects of using pesticides only after weekly agro-ecosystem analysis (AESA) judged them to be necessary, rather than following local pesticide practice. In both crops, the incidence of the disease under study was too low to reach any conclusions in this first season, but farmers were encouraged by what they did experience, and in particular at how IPM practices could make their crops more profitable.

In cucumbers, it was found that adding manure to the planting hole at about 19 t/ha led to better cucumber plant growth and yield, and lower disease ('blight') incidence. The yield was 80% higher than for the farmers' practice treatment and this, together with a reduction of pesticide applications from nine to five per season, led to an almost astronomical increase in profits, from VND 14,000/sao in the farmers' practice treatment to VND 255,000 in the IPM treatment. [1 sao "H 360 m; US$1 "H VND 13,500.]

In the tomato trial, seedlings for the IPM treatments were raised in banana leaf pots filled with clean soil and compost, whereas farmers traditionally raise them in flat field seed beds. At transplanting, the IPM treatments added manure to the planting hole at about 15 t/ha ± crushed lime. Farmers found that there was less damping off in seedlings, and less seed was needed, when plants were raised in clean conditions in pots rather than in traditional seed beds. Results indicated that pest and blossom end rot incidence were similar in all treatments, but AESA led to pesticide applications being reduced from 11 in farmers' practice plots to seven in the two IPM treatments. Yields were also higher by 37% and 50% for treatments with and without lime, respectively. Profits increased from VND 558,000 in the farmers' practice treatment to VND 787,000 in the plus-lime IPM treatment, and VND 1,007,00 in the no-lime IPM treatment.

The farmers also conducted pot experiments to study the effect of clean soil and/or irrigation water on disease spread and infection. They concluded that disease can be harboured in crop residues, soil or water, and that a combined approach to disease management has to be taken, including field sanitation, roguing of diseased plants and using them for composting, and crop rotation (rice-rice-cucumber).

The enthusiasm of the farmers at the workshop was striking. It was clear that the lead was now coming from the farmers and trainers, who had already made plans for the next season and were inviting the resource personnel to come back and help. The first steps in the PAR process have been well documented in this programme, and the national programme intends to make information and results available for exchange after another season of activity.

Contact: Janny Vos,
CABI Bioscience UK Centre (Ascot),
Silwood Park, Buckhurst Road,
Ascot, SL5 7TA, UK
Email:
Fax: +44 1491 829123

Practical Scouting in Zimbabwean Horticulture

Scouting for pests is widely practised in Zimbabwean agriculture, on cotton, tobacco and coffee. For the last ten years, flower, vegetable and fruit exports have been expanding greatly in the country and scouting is being used on these new crops to great benefit. In horticultural crops, pesticides usage is high as the growers must produce a cosmetically near-perfect product. The markets for Zimbabwean horticultural produce are primarily in the European Union but also in Australia, the Far East and South Africa. These markets demand that pesticide usage is reduced whilst still demanding a blemish- and pest-free product. For the Zimbabwean grower it also makes good economic sense to reduce pesticides as these account for a high proportion of the production costs. However, pests and diseases must be managed.

Scouting is proving to be a powerful tool to the Zimbabwean horticultural manager and is axiomatic to successful reduction in pesticide usage whilst still managing pests and diseases. It has a range of benefits:

• Timely discovery of a pest or disease allows for easier control. In many cases, insect pests become more hidden as they grow older making them more difficult to reach with sprays. As they grow they also become decreasingly susceptible to the sprays, as the lethal dose of pesticide increases with body weight.
• Scouting allows management to monitor the effects of applied pest and disease control methods, be they chemical or biological. In Zimbabwe, as in many African countries, non-performance of pesticides is often associated with poor application.
• Scouting allows the application of biological control methods at an early stage. The introduction of biological control agents is most successful when the levels of the pest are low, but sufficiently high to feed the beneficial organisms. It is especially important to apply the beneficials before any deleterious pesticides, such as pyrethroids or sulphur, have been applied in response to economic pressure.
• Much of horticulture is based on the production of edible fresh crops. Early detection of pests and diseases allows the usage of pesticides within accepted harvest interval periods and hence reduces the risk of exceeding maximum residue levels(MRLs).
• Strategically, scouting allows the producer to inform the market of problems, and allows the market time to source product elsewhere if there are production problems. This creates goodwill.
• There is less chance of resistant organisms being present in significant numbers if the pest is discovered early, while the population is still small.

Scouts Get `Phyto-serious'

Scouts can be used for tasks other than straight pest and disease monitoring. One of their most useful functions has been in the development of biological control programmes.

A notable success story has been the use of the predatory mite Phytoseiulus persimilis against tetranychid mites on strawberries and hops in Zimbabwe. These two crops suffered severe economic damage from attacks of Tetranychus cinnabarinus (and possibly Tetranychus urticae) every year in spring. The infections started in August and increased into spring (October), which is hot and dry. The two crops differ greatly in shape and size, being one of the lowest and one of the tallest crops in Zimbabwe. Strangely, this led to the same problem: poor under-leaf cover with acaricides. The hops were difficult to spray up to the full 6 m in height, and the strawberries were difficult to spray as the leaves are close to the ground. P. persimilis was imported from five countries: South Africa, Israel, the UK, Belgium and the Netherlands.

At the start of the growing period, the scouts' role was to advise the manager, as early as possible, that mites were present. This allowed the manager time to draw the licence from the Ministry of Agriculture, order and pay for the consignment of natural enemies, and clear it through customs before the pest had done much damage.

From the time of the scout finding mites to the time of release was typically two weeks. During this period scouting was increased and every plant was inspected. Plants with tetranychid mites were marked using thatching grass (Hyparrhenia sp.) straws. Once the predators arrived they were taken directly from Harare International Airport and released under the supervision of the Ministry of Agriculture. Only those plants marked by straws were treated. The scouts were taught how to release the predators. This is relatively skilled as the predators must be warmed up just prior to release (they arrive refrigerated), they must be evenly spread throughout the vermiculite carrier in the bottles and the carrier-insect mixture must be shaken onto the plants gently to minimize injury to the predators.

After four days, the scouts checked every plant for predators as well as for tetranychid mites. Plants with tetranychid mites alone were marked with Hyparrhenia sp. straws. Those found with predators were marked with sticks from a feral weed, Tagetes minuta, a tall South American marigold species, which is recognized as having certain beneficial (nematicidal) qualities. After the scouting exercise the scouts moved leaves from the Tagetes-marked strawberries or hops to the Hyparrhenia-marked plants.

The predators proved to be extremely effective, and their numbers reached very high levels, to the point where they would swarm to the tips of the plants and blow away in the wind. The scouts, in typical Zimbabwean fashion, invented a nickname for the predators, `Phyto-serious'.

The predatory mites are reasonably cost effective if produced close to the usage area, but become very costly if imported by air, refrigerated, to the middle of Africa. However, the scouts facilitated control of the tetranychid mites in the two crops with one introduction of predatory mites per season. The number of predators used was hence smaller, and proved to be more successful, than for similar applications overseas. This made biological control economically viable in these crops in Zimbabwe.

Scouts can also be used for checking equipment, such as the plastic covers in green houses, irrigation equipment and application, harvest and crop destruction requirements. They should also scout for physiological problems, watering and weeds.

Good Scouts

Scouts are the eyes of management and as such must have certain attributes:

• Obviously they need to have good eyesight. Women generally make better scouts then men because they are almost never colour blind whilst colour blindness amongst Zimbabwean men is common.
• They should be literate. Peg board methods have been developed which illiterate scouts can use. However, when the records are transferred or portrayed graphically, it is most useful to have a scout who is literate.
• They must be trustworthy and trusted. If the manager cannot trust his scouts then he is better off without them.

There are two extremes of scouts, the `includers' and the `excluders'. The includers will mark a pest present if they suspect it is there or feel it should be. They seem to want to impress management with their conscientious scouting skills or wish to insure against missing a problem. Excluders, conversely, leave problems out, as they seem to feel that the presence of pests or diseases are their responsibility. It often seems to come from a `kill the messenger of bad news' attitude of managers who, even at best, will not greet bad news with enthusiasm.

Training and Beyond

Zimbabwe is fortunate in having a scout training school. The Cotton Training Centre*, which trains people to be cotton scouts, is based in Kadoma, two hours drive west of Harare. This institution, which has received much donor funding from USAID amongst others, has a full-time professional staff who prepare courses and train the scouts. Candidates come from commercial and small-scale farming backgrounds. The courses are conducted in the local language, Shona, but there is one course a year in English for non-Shona speakers. The facility offers the course, food and accommodation.

Cotton scouts emerge after two working weeks with a knowledge of cotton pests. They cover most of the pests or beneficials they are likely to encounter on horticultural crops. But for them to become proficient as horticultural scouts, it is important to train them on diseases specific to the crops they will work on and any special pests or beneficials they might encounter.

Scouts need to be re-trained on refresher courses frequently, and at least just before each new season or when a new pest or disease emerges.

It is important to have more than one scout. This allows for leave and sickness, but also for individual variability: a scout should never check the same field more than twice in a row. Many growers get together and swap scouts for a day every month so that they can compare scouts' proficiencies.

Scouts have a responsible place in management and should be rewarded appropriately.

Practical Methods of Scouting in Horticultural Crops

There are a number of patterns which ensure that statistically correct data are derived from scouting. These are based on random selection of sites or plants in a field. However the methods have three major faults: (a) It is often necessary to go back to a particular position to identify a problem a scout has found or to check if the scout has made a correct diagnosis. (b) `Random selection' is seldom random. The includers include plants that have problems, the excluders exclude them. (c) Handling a crop whilst looking for pests and diseases spreads diseases, notably viruses.

Many growers have found that it is a better strategy to place 25 poles, high enough to be easily visible, spread evenly throughout the crop. No unit must be bigger than 10 ha. The scouts visit the poles at least twice a week, more often if there is a problem. The procedure should be:

• scout: discover a problem
• report: action taken
• scout: check if action effective and if other problems have arisen

Scouts inspect an `arms length' of the crop, to the left and right of the pole. They search the crop in a specific order:

1. Look under leaf for whitefly (which fly away if disturbed) and for spider mites, leaf diseases and leaf feeding insects.

2. Inspect the flowers or fruit for thrips and for aphids and diseases.

3. Check the whole plant for general well being.

4. Check for root diseases but with minimal root disturbance.

5. Check other factors such as weeds and irrigation.

The scouts record presence or absence of a pest only, and not numbers. Checking for numbers takes too long and is not as important as trends over a period of time. Economic thresholds are impossible to determine in a horticultural crop as the prices in the market are very fluid. Hence absolute numbers of a pest or disease are less important then their increase or decrease with time. Although economic thresholds are difficult to establish, it is useful to place arbitrary thresholds on different pests and diseases based on previous experience.

In addition to the above, the manager must use all other methods to determine whether a pest or disease is likely to develop. Weather forecasts and laboratory testing, such as pre- planting nematode screening, play major roles in pest and disease management.

*Cotton Training Centre,
PO Box 530, Kadoma,
Zimbabwe
Fax: +263 68 2386 (an extra '2' will be added soon, making the number 22386)

By: Peter Wilkinson,
Xylocopa Systems,
PO Box BW 1011,
Borrowdale, Harare,
Zimbabwe
Email:
Fax: +263 4 883936