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Community Linkage for Whitegrub Management

The Chiapas highlands in Mexico are characterized by their indigenous communities of Mayan ancestry, and increasingly, the decline and poverty of their farming systems. Indigenous farmers traditionally grew a mixture of maize varieties in association with beans and they worked full-time on their farm, spending time observing and experimenting. In the last two to three decades, the economic situation and lifestyle of these communities have altered and many now are forced to look for off-farm employment to survive. They have shifted to farm practices which they see as less time consuming and more efficient, such as herbicide and insecticide application, burning of crop residues and monoculture of hybrid maize varieties, while abandoning many traditional cultural crop management methods.

The resulting trend is of soil impoverishment, loss of traditional cultivars, increases in pest incidence and a steady reduction in maize yields. Whitegrubs, in particular, have been encouraged by the changes in soil use and farming practice and are now held to be one of the main production constraints in maize, responsible for grain losses of up to 500 kg/ha. Many farmers carry out two manual weedings and up to three broad-spectrum herbicide applications, leaving the soil devoid of other vegetation. This practice leaves little but maize roots for whitegrubs to feed on, as well as provoking soil erosion. Lodging of maize plants is common in fields which have been burnt, ploughed and cleared of weedy species.

Researchers in the Department of Alternative Production Systems at the College of the Southern Border (ECOSUR) in the Chiapas highlands were aware that scant attention has been paid in Mexico to promoting linkages with smallholder farmers. As well as farmers being the supposed beneficiaries of IPM strategies, their knowledge could provide valuable information for IPM development. ECOSUR staff decided that if viable alternatives to current maize production in the Chiapas highlands were to be developed and implemented, it was necessary to work directly with farmers in a process of discussion and joint analysis. This process would require new methods and strategies for more effective interaction between farmers and researchers, in order to solve problems and support innovative rural development. In 1996, families from the tzeltal indigenous community in Amatenango del Valle requested ECOSUR's collaboration to solve their whitegrub problems and the village of El Madronal was selected for studies in farmers' fields and community activities. Most women in Amatenango make a living from pottery while their menfolk farm part-time, however, the women were very interested in improving maize production and the children take part in farmwork too.

The ECOSUR team began their work in the community by field walks and meetings with farmers using traditional maize-bean systems and modernized maize monoculture. The farmers discussed their recent changes in farming practice and the pressing need to reduce labour time, for instance, by burning maize stalks rather than digging them under, and abandoning the practice of earthing up young plants (which helps to develop a strong root system). The project was presented to farmers in a meeting after the initial fieldwalks, along with possible activities. Farmers and researchers agreed on methods for collaboration, with the latter promising to report back on research progress via participatory workshops. Season-long studies were carried out on nine irrigated and two rainfed farms to determine levels of damage caused by whitegrubs and to try and identify possible control options with the participating farmers. Simultaneously, bioecological information about the pest was collected and the local whitegrub complex identified. The history of use of each field was collected along with detailed management practices recorded throughout 1996, to draw up seasonal calendars. The researchers also sampled floral and insect diversity and whitegrub larval density on each farm.

In the Chiapas highlands there is a large guild of beetles which lives in the soil but only some from the melolonthid family feed on the roots of crops and cause typical whitegrub damage. Farmers know quite a lot about the whitegrub larval stage since it causes direct damage, but it became obvious from the field discussions that they were not aware of the lifecycle of the insect and its non-larval stages. Their usual control method is to apply insecticides, such as carbofuran and phoxim, with grave consequences for their health and the environment and for natural control since the number of beneficial insects is decreased. Current insecticide use is of limited effectiveness as larvae may be deeper than the chemical can reach, heavy rains tend to wash it out and farmers rarely apply at the critical periods to prevent larval growth. The team carried out a pests and diseases survey, with sampling and observation every three weeks with the active participation of the majority of the farm women who accompanied them in their fields. By observing and talking with these women in the field, the team collected ethnobotanical information about properties of weedy species (medicinal, edible, poisonous, harmful or beneficial to the crop, etc.). In August 1996 the first workshop for farm women was run, using field sessions in rainfed maize to teach them how to recognise whitegrub damage and how to distinguish this from other problems (other pests, excess moisture, wind, weeds, or soil-related). The women also presented their opinions of production problems in maize.

These activities served as a platform for discussing potential control options for whitegrubs with the community in early 1997, after which farmers decided on several options they would like to try out. Proposed alternatives were: interplanting maize with climbing beans, Canavalia legume cover, dolichos bean and alfalfa; single weeding combined with earthing up; selecting resistant seed (select from cobs from plants which did not lodge from whitegrub damage to the roots); and increasing planting density. Farmers chose to try the following options: in irrigated maize, they opted for maize with common bean; single weeding; earthing up; and in rainfed maize for maize with common bean; maize with Canavalia; and a community campaign to collect whitegrub adults. From the experiments in rainfed maize, association with legumes did not show any clear effect on whitegrub larval density or damage but the farmers thought it was a useful practice if one, rather than two, rows of beans were sown between maize rows because it reduces weed emergence and hence the need for herbicide application. In irrigated maize the practices of single weeding, earthing up and legume association were considered potential alternatives, depending on seasonal and field-specific variation and individual farmers' resources. Farmers were not so enthusiastic about Canavalia use because they could not see any immediate benefits of interplanting.

The control method which brought most impact was adult beetle collection in the rainfed maize zone. A total of 83 primary school pupils in the village were first taught how to recognise whitegrub pest damage and how to distinguish the pest species in adult form from related beneficial beetles which are decomposers. The collections took place over four weeks in April and May 1997 and every week the children collected beetles and explained to the ECOSUR team how and where they had captured the beetles. The girls mainly collected those attracted to lights while the boys explored to find beetles gathering in certain host tree species, which they shook to release the insects. The researchers took the weekly collections back to the laboratory for identification and to confirm the host tree feeding as observed by the boys. In total the pupils collected 40,995 adults over 27 ha, belonging to six Phyllophaga and Anomala species. The collections were organized as a competition and each child who took part received a school bag with a whitegrub control slogan and containing candies, and the most avid collectors were given notebooks and pencils. To confirm the effectiveness of adult beetle suppression, the team carried out larval density sampling four months after the collections in El Madronal and compared these with another community where no collection took place. Whitegrub densities averaged 1.5 larvae/m² in El Madronal while the control village averaged 17.24 and 13 larvae/m² for two of the most voracious species. These species were those which had been commonest in the children's collections. The results indicate that adult collection can noticeably reduce subsequent larval densities and thus contribute to improved maize yield. Mass capturing of adult whitegrubs has now been shown to be a cheap, efficient, simple and safe management method in rainfed maize zones but which relies on collective organization by the community.

The process of taking ownership of new technologies is slow but the ECOSUR team's experience in 1998 showed that methods with most impact for farmers were being followed up. They are now preparing a simple key for farmers to distinguish good from bad melolonthid and other beetles. The team continues to study other methods for whitegrub integrated management including applications of botanical extracts against small larvae; trap cropping of useful plants with attractive roots for larvae such as mustard and radish; natural enemy studies and entomopathogens; and weed management strategies. This academic linkage project has enabled ECOSUR to build relations with the farmers and potters of El Madronal and now the 'control' community too, where they have also run workshops and where they plan to continue with joint research for safe and effective pest management based on local resources and which can be integrated into farmers' existing farming practices.

By: Adriana E. Castro Ramírez,
Jorge A. Cruz López,
Concepción Ramírez Salinas,
Lorenzo Hernández López and
Javier A. Gómez Méndez
Department for Alternative Production Systems,
El Colegio de la Frontera Sur (ECOSUR), Apdo. Postal. 63,
San Cristóbal de las Casas,
Chiapas 29200,
Mexico
Email: acastro@sclc.ecosur.mx
Fax: +1 967 8 23 22
ECOSUR website: http://www.ecosur.mx