CABI - Biocontrol News and Information 19(3) September 1998 News

Integrated pest management (IPM) involves the use of many techniques, including biological control, to provide effective control of crop pests with minimum harmful side-effects. Those techniques which are compatible with the use of biological control or have little impact on natural enemies have been described as `biorational'.

As anyone with an elementary knowledge of chocolate knows, it is not a good idea to leave large blocks of it in the sun. Now it appears that the same applies to cocoa trees - this was the concensus amongst ornithologists, ecologists, foresters, ethnobotanists, conservationists, cocoa scientists, economists, cocoa growers and representatives of all the major chocolate producers who attended a workshop on sustainable cocoa in Panama in March*.

The workshop brought together two normally allopatric groups: industry and ornithologists/bird ecologists. The bird experts are concerned by the threat to the 'Mesoamerican Corridor' for migratory birds posed by expanding agriculture concomitant with forest clearance. The chocolate manufacturers face an ever-increasing worldwide appetite for chocolate, while production threatens to fall. Disease is seen as the main constraint to cocoa production worldwide [see BNI 18(2)], particularly witches' broom (Crinipellis perniciosa) and monilia pod rot (Moniliophthora roreri) in South America, and black pod disease (Phytophthora spp.) in Africa. In the Mesoamerican Corridor, monilia is the major threat. Insect pests are also regionally important, including the cocoa pod borer (Conopomorpha cramerella) in Southeast Asia and mirids in Africa.

The cocoa tree evolved as an understorey tree in humid tropical forests - multi-layered forest systems with a diverse arboreal canopy providing both shelter from intense sun and rain and nutritious leaf litter. It is still a common understorey tree in the Amazon Basin rainforests. In its natural environment, shade is probably the single most important factor controlling its physiology, and hence growth. Traditionally, and in accordance with its forest origins, it was cultivated under thinned forest or planted permanent tree shade. Then in the 1950s research in Guyana and Trinidad showed that cocoa grew more vigorously and produced more flowers (and thus pods) in full sunlight. Accordingly, shade trees were cut down. It subsequently transpired that there was a price to pay, and short-term yield gains were offset by a loss in tree vigour after about ten years. This decline was thought to be due to a combination of factors including water and pest stresses. In Malaysia, it was found that zero shade was only beneficial on superior sites and where the cocoa canopy remained intact. However, cocoa is notoriously susceptible to pathogen-induced die-back, especially when exposed to direct sunlight.

The story consistently recounted at the Panama workshop, from the cocoa-growing regions of South and Central America, West and Central Africa and Southeast Asia, was that although growing cocoa trees in unshaded conditions may lead to an initial increase in yield, it leads inevitably to early decline of the trees, at least in part owing to a greater susceptibility to disease. There was also almost universal disenchantment with large-scale production and a conviction that reliance on chemical sprays was economically inefficient and also left the crop more prone to disease. On the other hand, it was acknowledged that cocoa requires and responds to individual attention, so the outlook for pest and disease control is potentially better in traditional more-intensively farmed smallholder systems. It was argued that for the foreseeable future small farmers will produce most of the world's cocoa. Naturally following from this was the recognition of the need to focus on developing low-tech approaches to disease and pest management for cocoa, techniques suitable for small-scale farmers with limited resources. One such successful technique for managing cocoa pod borer in Indonesia relies on the possession only of a traditional machete, together with an investment of the farmers' time.

Following the meeting, the chocolate industry declared its intention of putting its future in the hands of small farmers growing cocoa on shaded, forested, intensively managed land. This was good news for the conservationists who see smallholder cocoa as a useful tool in preserving forest biodiversity: it was agreed by participants that cocoa, in the shape of smallholder shaded (traditionally) cultivated cocoa, was the best sustainable solution to maintain a corridor for migratory birds, not only in the Panamanian isthmus, but throughout the humid tropics where forested corridors or buffer zones need to be left for genetic exchange of both fauna and flora. The Workshop concluded that "...cocoa can have an important continuing role in maintaining and enhancing a diverse and sustainable biologically diverse agricultural system, is capable of providing lasting positive, economic, social and environmental benefits".

Although cocoa, in common with many plantation crops, has a long tradition of over-dependence on chemical pesticides, it does have the distinction of being a birthplace of IPM. In the 1960s, the ecologist Gordon Conway identified chemical insecticides as the cause of outbreaks of bagworms and nettle caterpillars on cocoa in Sabah, and worked out the process of the `pesticide treadmill' long before these concepts became popular in the USA and Europe. But while research into IPM of food crops and major cash crops progressed in the intervening decades, IPM for smallholder cocoa did not. Yet if the quest for sustainable smallholder cocoa production set in motion at the Workshop is followed through, then a happy ending and a secure future for both bedtime cocoa and birds are assured.

The proceedings of the Workshop are available on the Internet at
http://www.si.edu/smbc/cacaop.htm
and the Smithsonian Institute plans to produce, on the basis of the Workshop, a comprehensive review in the form of a white paper on the future of sustainable cocoa production.

*The First International Workshop on Sustainable Cocoa Growing, organized and hosted by the Smithsonian Institution at the Smithsonian Tropical Research Institute in Panama, with financial support from Mars, Inc.

India Fights Bollworm Upsurge

Unprecedented Damage by Helicoverpa armigera in India

In India, old world bollworm (Helicoverpa armigera) has been recorded on 181 species of host plants belonging to 45 families of which about a dozen are important hosts in different parts of the country. Helicoverpa armigera was recorded as, at most, a minor pest on cotton in the 1960s. However, it inflicted heavy losses in Punjab during 1983-84 owing to a massive outbreak spreading from pigeonpea (a newly introduced crop) in the preceding season to cotton. Helicoverpa armigera caused severe damage to cotton in Andhra Pradesh in 1977-78 and 1988-89. In 1997-98, outbreaks in Punjab, Haryana, Andhra Pradesh, Karnataka, Maharashtra and Madhya Pradesh have shattered the economy of the farming community, causing widespread despair. Sudden changes in indiscriminate use of non-selective pesticides have resulted in increased pest incidence and this has ultimately trapped the farmers in a vicious cycle of increased pesticide use.

Management practices suggested to contain the pest include simultaneous timely sowing of crops, growing short duration (early maturing) crop varieties, application of organic manure/bio-fertilizers, application of need-based irrigation, adoption of suitable cultural practices including intercropping with marigold/foxtail millet/maize/cowpea and destruction of pupae in the soil by chisel hoeing, conservation of predators through erecting bird perches and installing paper wasp nests, monitoring pests by scouting in situ and through pheromone traps, creation of village-level farmers' teams for crop protection, and need-based application of natural enemy-safe pesticides. It is hoped that H. armigera and associated pests and diseases can be managed by providing assistance to the farmers, primarily by creating the proposed village-level farmers' teams for crop protection and supply of bioagents such as Trichogramma chilonis (including a pesticide-tolerant strain), Trichogramma pretiosum, Chrysoperla carnea (including a pesticide-tolerant strain), Helicoverpa armigera nuclear polyhedrosis virus (HaNPV) and Spodoptera litura NPV, Nomuraea rileyi and Trichoderma/Pseudomonas species, etc.

The importation of biological control agents such as Telenomus sp. nr. triptus, Microplitis demolitor and Heteropelma scaposum from Australia, Telenomus ullyetti from Africa, Copidosoma obscura from Turkmenia and Microplitis croceipes from the USA for testing against Helicoverpa armigera may be considered.

New Endosulfan Tolerant Strain of Egg Parasitoid Developed in India

In India, endosulfan is used to control Helicoverpa armigera on cotton and many other crops. However, egg parasitoids, particularly Trichogramma chilonis, are also used extensively for pest suppression in many crops including cotton. Work was initiated at the Project Directorate of Biological Control (PDBC), Bangalore in 1989-90 to develop an endosulfan tolerant strain of T. chilonis for use in cotton and other crop ecosystems. A strain physiologically tolerant to endosulfan was developed by treating the parasitoid with endosulfan, initially at 0.004%, this dosage being gradually increased to 0.008%, 0.017%, 0.026%, 0.035%, 0.043%, 0.052%, 0.061% and 0.07%. Using this process, it took more than 325 generations and about eight years to develop the endosulfan tolerant strain. The performance of the tolerant strain released in net houses was significantly superior to that of a spray of endosulfan.

The product developed was transferred to M/s Excel Industries, Mumbai. The company has already started using the tolerant strain of T. chilonis on a large scale in many states. This strain has been named as `ENDOGRAM'. Endogram - the endosulfan tolerant strain of T. chilonis developed by PDBC, Bangalore - is the first of its kind in the world.

By: Dr S. P. Singh, Project Directorate of Biological Control (ICAR), P. B. No. 2491, H. A. Farm Post, Bellary Road, Bangalore - 560 024, India.
Email:
Fax: + 91 080 3411961

Sweetpotato IPM in Cuba

The results of a project in Cuba involving CIP (Centro Internacional de la Papa/International Potato Center) and INIVIT (Instituto de Investigaciones de Viandas Tropicales), have indicated that IPM in sweetpotato is achieving a better level of pest control than chemical pesticides.

Until the end of the 1980s, Cuban agriculture was conventional by late twentieth century standards, characterized by a heavy dependence on synthetic pesticides and fertilizers. However, Cuba relied on subsidized imports of chemicals from the Soviet Union. These ceased following the collapse of the soviet trading bloc, precipitating an agricultural crisis. Faced with having urgently to develop alternative production systems and control strategies, Cuba embarked on an unprecedented transition from high external input to low input organic agriculture, including the implementation of biological control-based IPM approaches to pest management.

One of the victims of the crisis was sweetpotato cultivation. The absence of pesticide spraying led to massive damage to the crop throughout the country, principally from the sweetpotato weevil (Cylas formicarius), and this led to the collapse of some of the largest plantations. A cooperative project involving CIP and INIVIT, the Cuban national agricultural research institute with responsibility for root crops and bananas, was initiated in 1992 to develop an IPM strategy for sweetpotato. The first step was to ensure a thorough understanding of the biology and phenology of the pest, the second to identify IPM component technologies to control it. On-farm research in two provinces in the centre of the island identified four effective components: sex pheromone traps, the fungus Beauveria bassiana, local predatory ants (Pheidole megacephala), and short-season cultivars.

CIP identified the use of pheromone traps as key to the success of the IPM strategy devised in this project. The traps are used for mass-capture of male weevils: some 128,000 traps were used throughout the project area in 1996. Farmers generally use 16 traps per hectare, although this may be reduced to five or six under favourable conditions. Currently the pheromone is imported from the Netherlands, although discussions are underway to try and come to an arrangement that will allow its production locally.

As an adjunct to this, B. bassiana is applied around the traps to kill escaping weevils. The fungus is produced locally, one of the products of a national initiative aimed at increasing the country's capacity in natural enemy and biopesticide production. This programme has resulted in the establishment of over 200 Centres for Production of Entomophages and Entomopathogens (CREEs). Beauveria bassiana is one of the biopesticides manufactured by the Centres. Although there are logistic problems (production supply may not match demand particularly during the height of the growing season) and difficulties in monitoring product quality effectively, in 1994 national production of B. bassiana was already 781 tonnes.

Predatory ants were already known to be important predators of sweetpotato weevils, and they have been used in control programmes since the early 1980s. Reservoir populations were established where they were naturally abundant, and colonies were then moved into sweetpotato fields - up to 99% control has been reported. INIVIT devised a simple but highly effective system for mass-rearing these ants in artificial nests made of rolled banana leaves, which is their natural habitat. In field trials, 60 such nests per hectare reduced weevil infestations to 3-5%.

The use of short-season cultivars means the crop matures before weevil populations build up to damaging levels. In addition, farmers have implemented cultural practices common to many IPM programmes: the use of healthy planting material, crop rotation and destruction of crop residues. Intercropping systems have also become popular, particularly a maize-sweetpotato system.

During the era of chemical protection, farmers had relied on an average of 12 sprays per season, which still only reduced weevil damage to about 8%. Once pesticide applications ceased, damage rose dramatically, with up to 100% infestation recorded during the dry season, and in some places sweetpotato cultivation was no longer viable. But in 1997, with the use of the integrated control approach, damage fell dramatically: some fields registered only 2% infestation, and production on many farms was tripled. In 1998 the IPM programme will be covering about 30,000 ha of sweetpotato - about 50% of the national crop.

Sources:
CIP (1997) Annual Report.
Rosset, P.; Moore, M. (1997) Food security and local production of biopesticides. ILEIA Newsletter (LEISA) 13(4), 18-19.