CABI - Biocontrol News and Information 20(3) September 1999 News

Biocontrol News and Information

September 1999, Volume 20 No. 3

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.

Making Use of the Good Bugs in Cotton

In Peru, organic cotton production started in 1993 in the Cañete Valley, and the Peruvian Action Network on Alternatives to Agrochemicals (RAAA) has been working for three years on organic cotton promotion and training. In 1997 some 700 tonnes of organic cotton were produced in Peru, but this constituted less than 2% of national tonnage.

The international seminar on Alternative Production and Marketing Systems for Organic Cotton in Latin America held on 5-8 April 1999 in the Cañete Valley (organized by RAAA and the North American and Latin American Pesticide Action Networks) provided participants with the opportunity of exchanging experiences, and for seeing how some farmers put these into practice. They visited the farm of Mr Jorge Bustamante, RAAA activist and key member of the Cañete Cottongrowers' Association, who has established a sophisticated system of conservation and augmentation of natural enemies. Mr Bustamante owns 40 ha in NE Cañete on which he rotates around 25 ha of organic cotton with asparagus and maize, and the remainder is under grazing and citrus. He has been growing organic cotton since 1996 as part of an eco-technological renovation of his farm. Under RAAA's IPM programme, he had successfully reduced insecticide applications to one per season before converting to organic production. He places equal importance on improving soil organic matter, as fertility is the main constraint on his land.

In the first year of conversion, he had foci of early season aphid (Aphis gossypii) attacks (these can delay plant development) but was confident in the power of natural enemies to deal with these. Mr Bustamante had noticed ladybird beetles feeding on aphids on nutsedge weed (Cyperus sp.) and after checking with local entomologists that the aphids were not cotton-feeding species, he collected weed infested with ladybird egg masses or larvae and transferred these to his cotton aphid `hotspots'. When trying to make larger collections of ladybirds, he observed larval cannibalism and now instructs his staff to make sure prey is included in collection jars. Mr Bustamante is convinced that natural enemy numbers must be augmented for effective aphid control in cases when ladybird beetles are not sufficient. He has also found that irrigation can help water-stressed plants tolerate aphid attack.

To improve aphid control further, he collected parasitized aphid mummies from other crops for distribution in his cotton. At first, the mummies dehydrated under full sun and adult Aphytis wasp emergence was low so he now uses shade covers. To increase numbers, he started on-farm rearing-out of parasites and their reproduction in simple emergence and exposure cages made of wood, gauze and plastic sweet containers. He deployed the emergence cages at one per hectare for adult wasp release but found that aphid numbers did not decrease as expected. After consultation with the university, he realized that his rearing unit contained a large proportion of hyperparasites of Aphytis spp. He now uses smaller recuperation cages and checks regularly to identify emerging adults. He has tried Rotebiol (rotenone) for aphid control but found that underleaf coverage is very important and that the product can kill other natural enemies.

For bollweevil control, he collects damaged squares on a regular basis and plans to rear out possible parasitoids. For Heliothis virescens bollworm, he plants cheap fodder maize every four rows and every 4 m, using a lemonade bottle attached to the seeding plough to deliver the maize seed to avoid extra labour costs. Mr Bustamante has observed that maize generates a large number of predatory bugs and beetles due to its rapid growth and these have built up to good levels by the time the cotton is at boll stage. He stakes and marks Heliothis egg masses to check progress but on many occasions the eggs disappear after a day or so, indicating high predation levels. This monitoring has enabled him to save on the expense of Trichogramma releases, which are recommended at an action threshold of 6-10 bolls with eggs. When Trichogramma releases are unavoidable, he prefers to make small releases every three or four days rather than one mass release.

If the cotton-associated maize is left to form cobs, Pocosera spp. caterpillars can become problematic in the cotton. He prefers to take out the maize at this stage and use it directly for fodder. Neighbouring maize fields may also encourage Pocosera infestation at the boll stage so regular monitoring is needed. For pink bollworm, Pectinophora gossypiella, Mr Bustamante uses pheromone traps for monitoring and collection but still gets around 8% boll attack. Whilst conventional farmers resort to pesticides to reduce this level of pink bollworm damage, he has observed that the cotton plant's natural defence mechanism often seals the larva in one lobe of the boll and thus eventual yield loss is only a quarter of the percentage boll damage. Incorporating cotton stalks into soil post-harvest can cause pink bollworm carry-over so he makes sure all boll remains and semi-open bolls are removed from plants and burnt before crop residues are ploughed in.

Mr Bustamante has adapted the use of black strip lights with winged trap plates to collect both pest and beneficial insects. The insects hit the plates and fall through a sieve, which separates them by size. The traps are inspected early each morning and the beneficials redistributed to plots with low natural enemy numbers. Pest species are killed and used as compost or fed to chickens. One record night's catch was 7 litres of Heliothis moths. He uses 16 one-metre length light traps over a 7-ha area. He also uses them in sweetpotato to catch potato weevils. Other biocontrol practices on his farm are planting mandarin and strips of late-sown weedy maize as natural enemy refuges and control of nutsedge by enclosing geese in 2 × 2 × 1 m cages over weedy patches where they uproot and feed on the rhizomes. Mr Bustamante's current sophisticated and time-consuming biocontrol practices cost around four times as much in labour as insecticide application inputs, thus the organic premium is essential to be competitive. His organic cotton plot gives yields of 1260-3150 kg/ha with an average of 2700 kg. `Break-even' point is 2250 kg.

Mr Bustamante has also experimented with a bean-cotton rotation but found that sucking pests are worse and Rhizoctonia fungal disease can be serious in cotton planted on land previously sown to beans. He is therefore only using beans as an associated crop rather than in rotation. He is currently experimenting with different rates and combinations of manure and guano (seabird droppings) for fertilization and he uses copper sulphate for seed disinfectant. In the El Niño-induced whitefly outbreaks in 1998, he recorded massive infestations (over 800 nymphs/cm2) in conventional farmers' sweetpotato fields where pesticides were applied. He also reported fungal epizootics causing 90-100% mortality of whitefly in heavily-infested sweetpotato and beans in late 1998. This fungus was identified as Paecilomyces farinosus by the National Plant Protection Service, SENASA, and continued epizootics have controlled whitefly in 1999 in many parts of the Cañete Valley.

Mr Bustamante is an example of the medium-scale farmer who has become convinced of the merits of biocontrol through his own observations and who is actively experimenting with organic systems with support from research colleagues and with organic expertise from RAAA. He also works with smallholders to train them in natural enemy recognition. Peru has a long history in the use of classical biological control, however, it is only in recent years that farmers and their associations have been actively involved in conserving and augmenting natural enemies. A multi-institutional National Biological Control Programme was set up in 1995, under the supervision of the National Plant Protection Service, which administers a network of 109 biocontrol laboratories run by private and public sector agencies including growers' associations and non-governmental organizations. Currently the network produces 14 species of parasitoids and predators and five species of fungal and viral microbial control agents. For cotton lepidopteran pests, five species of trichogrammatids are reared commercially while two encyrtids and one braconid species are regularly collected from the field and redistributed for aphid and scale control. Some farmers are now starting to try out Beauveria bassiana mycopesticides for the increasing whitefly problem.

Contact:
Mr Jorge Bustamante and Ms Neber Barras,
RAAA-Cañete Valley
c/o Action Network for Alternatives to Agrochemicals,
RAAA, Lima 1,
Apartado Postal 11-0581,
Peru
Telefax: +51 1 3375170
Email: raaaper@mail.cosapidata.com.pe