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C. MALAMBO, J. CHAKUPURAKAL, A. SUMANI, A. SAKALA, K. KASHWEKA, C. CHISONGO & G. CHIPABIKA
Mount Makulu Research Station, Chilanga, Zambia
Background
The spread of Larger Grain Borer (LGB) in seven provinces in Zambia namely Northern, Luapula, Central, Copperbelt, Lusaka, Southern and Eastern Provinces poses a significant threat to Zambian agriculture. The pest was first detected in Nakonde District in Northern Province in September 1993, and in two years time its movement to other six provinces has been hastened through the importation/distribution of LGB infested maize from Tanzania to off-set the maize shortfall brought about by four years of drought. A control and containment programme was put in place, which called for simple control recommendations for existing infestations at farm and storage level, extended nation-wide surveys to assess the spread of the pest, implementation of classical biological control, strengthening of phytosanitory and quarantine resources/facilities, and training and awareness campaigns to make the strategy effective. A legislation was enacted to make it possible to control the movement of LGB infested commodities from infested to non-infested areas. Studies are also being carried out to strengthen the household food security through on-farm storage, by enhancing the quality of grain stored in improved storage structures.
Introduction
The national Biological Control Programme (NBCP) of Zambia was established in response to an emergency situation brought about by the invasion of the country by two exotic pests of cassava: the cassava mealybug and the cassava green mite. The invasion of these pests had resulted in near famine conditions in some northern and western regions of the country with a heavy dependence on cassava. The initial objective of the programme, involving the nation-wide implementation of the classical biological control of cassava mealybug, was successfully achieved during the first phase of the project. Considerable progress was made on the subsidiary objectives of the project, which were the development of a similar technology to tackle the cassava greenmite problem and the development of capability to undertake environmentally-sound pest management operations against a wide variety of other economically important pests, including the Larger Grain Borer.
As Larger Grain Borer was identified as a serious pest of agriculture in neighbouring countries such as Tanzania, Kenya, Burundi, Uganda and Malawi, Zambia was already in a stale of preparedness, and monitoring surveys have been carried out as far back as 1981 in areas bordering Tanzania. This paper summarises the control and containment activities undertaken since 1981. More detailed reports are available in Zambia (Chakupurakal, 1995; Chakupurakal et al., 1996a; Chakupurakal et al., 1996b; Chakupurakal et al., 1997a; Chakupurakal et al., 1997b).
Regular monitoring surveys were carried out since 1992 using pheromone traps to detect the pest when traps were set up in 27 villages/locations in Nakonde District, Northern Province, but no pests were detected. During 1993, surveys carried out in Nakonde District; some 64 traps were set out and a total of 23 LGB specimens caught from seven villages.
LGB control and containment strategy
The invasion of Zambia by LGB poses a very grave situation as it has the potential of spreading to all maize and cassava growing areas of Zambia, causing severe damage to standing or stored maize, dried cassava, beans, groundnuts bamboo timber and many other products. LGB control and containment strategy put in place basically include the control of known infestation, monitoring the spread of infestation, training/educational campaign, improvement of quarantine resources and facilities and research into improved monitoring, control and storage methods.
The immediate control programme aim to ensure that farmers are fully aware of the threat posed by LGB, are able to recognise it and be given sufficient training to permit the safe and effective use of insecticide dusts on the shelled maize. Particular attention is also being given to an integrated approach to control LGB including the application of classical biological control.
Implementation of the control and containment of LGB
Monitoring the spread of infestation
By April, 1994, larger grain borer had moved eastwards from Nakonde 30 km along the road to Malawi and 80 Km westwards along the road to Mbala and the total catch had risen to some 700 individuals. By the end of the same year, the pest was detected in 65 out of 72 villages sampled and trap catches exceeded 2000, though the infestation remained confined to Nakonde, a relatively small part of the country.
The major extension of the range of LGB was first detected in 1995. Whereas in April/May of that year, LGB was still only detected in Nakonde and adjacent Mbala districts of Northern Province, after September, the infestation spread very rapidly into Central, Lusaka, Southern, Eastern, Luapula and Copperbelt provinces, apparently through the importation of infested maize from Tanzania (to off-set the maize short-fall brought about by four years of drought) (Tab. 1. Fig. 1 and 2)
A monitoring pheromone trap network was established in all the LGB affected areas, between 1996 until January 1997. Provincial LGB co-ordinators were appointed and together with the assistance of the extension branch of the Department of Agriculture, the trap network brings in LGB infestation data regularly.
| Fig. 1. |
Pheromone trap
catches of larger grain borer (LGB) in Zambia, 1993-1994. |
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| Fig. 2. |
Pheromone trap catches of larger
grain borer (LGB) in Zambia, 1995-1996.
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Public awareness and training campaigns
Since 1994 several seminars were organised for farmers in LGB affected areas on the dangers posed by larger grain borer, reporting, sample collection procedures and possibilities of chemical and biological control.
Training courses were also arranged for extension officers, customs official and local dignitaries, to create awareness about the dangers of LGB. These courses covered topics such as Grain handling/Storage losses, Factors of grain deterioration in storage, Storage pests and their control, LGB biology Recognition, Distribution, Control and containment, Impact of grain movement in and out of Zambia, Management and economics of grain storage structures and construction of on-farm storage structures (practical demonstrations). Descriptive information posters, stickers and leaflets in English and local languages were distributed in the LGB-affected areas.
| Tab. 1. | Number of P. truncatus (Pt) recorded in the pheromone traps, Zambia 1993-1997. |
| Province | District | Months/Year |
No. of traps |
P.t. trapped |
| North | Nakonde |
09/93 |
64 |
21 |
|
| Centre | Serenje Mkushi Kapiri-Mposhi Kabwe |
12/95 |
4 |
19 |
|
| Lusaka | Lusaka Lusaka Chilanga |
01/95 |
2 |
127 |
*6 |
| South | Mazabuka Mazabuka Monze Choma Choma Kalomo Livingstone Gwembe Siavonga |
12/95 |
5 |
68 |
|
| East | Nyimba Petauke Katete Katete Katete Chadiza Chadiza Chipata Chipata Chipata Mambwe Lundazi Lundazi Lundazi Chama Chama Chama |
06/96 |
4 |
0 |
|
| Copperbelt | Luanshya Ndola Mansa Mwense Nchelenge Samfya |
12/96 |
1 |
- |
*8 |
*1 two traps lost; *2 two traps lost; *3 one trap lost; *4 one trap lost and five specimens recorded in imported maize; *5 all traps lost; *6 five specimens recorded in imported maize; *7 nine crushed specimens; *8 one trap lost.
Improvement of quarantine resources and facilities
An efficient quarantine system with proper legislation can fulfil its role as the first line of defence, against any exotic pest or disease. Efforts are being made improve the quarantine resources and facilities though a ‘DANIDA’ funded Plant Health Inspection and Quarantine Serial Programme. This programme when fully implemented will improve boarder post inspection and quarantine procedures and post sufficient quarantine inspectors to cover all the boarder posts of entry in Zambia.
A legislation "The Plant Pests and Diseases (control of Larger Grain Borer LGB) Regulations, 1996 was enacted as Statutory Instrument No. 153 of 1996 under the Plant Pests and Diseases Act (Laws, volume VII, Cap 346) for the effective control and containment of LGB.
Research into improved monitoring, control and storage methods
There will be provision for comprehensive long-term back-up research to make the LGB control and containment programme fully effective. These studies will take into consideration further development of monitoring techniques an integrated approach to control LGB, improved tolerant crop varieties, possibilities for manipulating the harvest time of cassava (as means of reducing infestation) and socio-economic impacts.
A special study was initiated on Household food security through on-farm storage to assess the existing storage structures in relation to household food security in rural areas. These studies will greatly help to assess the knowledge and capability of extension workers and emerging farmers in the field of post-harvest technology and protection.
Biological control
Since the control of LGB using chemicals alone is neither practical nor feasible on such a vast infestation, the application of an environmentally sound classical biological control was adopted as an integral part of an approach to tackle the LGB problem. Biological Control has the advantage of not only solving a pest problem, but also protecting the environment, including the health of the people. It is self-sustaining, hence no further input needed from the farmer and ecologically and economically sound. The only drawback is that biological control will not work overnight, but in compensation it will work over generations.
Biological Control of Larger Grain Borer is currently under development, especially by GTZ, NRI, and IITA. The release of a predatory beetle, Teretriosoma nigrescens Lewis (Coleoptera: Histeridae), as a classical biological control agent has reached an advanced stage of field evaluation in countries such as Togo, Benin, Kenya and Ghana. Establishment of the natural enemy has been readily achieved and it is spreading rapidly and increasing in abundance in these countries. An intense international effort is underway to evaluate the impact of T. nigrescens more conclusively (3.4). During June 1996 a shipment of T. nigrescens was brought in from IITA for local rearing and release purposes. Local rearing of the predator is progressing well at Mount Makulu Research Station. In June 1996 some 1,900 specimens of T. nigrescens were released in Kapiri-Mposhi at the dry port, at a warehouse near Tazara Railways and some in the open within the warehouse premises. Further releases were also made at the Old Fife Research Station orchard 1 km away from Katongo area, some 24 km away from Nakonde and Sansamwenje area, 70 km from Nakonde (Tab. 2). Follow-up surveys made during the rainy season proved the establishment of the predator in all the release areas. A second shipment of some 500 predators were added to the rearing culture in November, 1996.
| Tab. 2. | Releases of T. nigrescens
(Tn) and number of trapped P. Truncatus (Pf), Zambia, 1996-1997. |
| Province/District | Site |
Months/Year |
Pt trapped |
Tn released |
| Centre |
| Kapiri-Mposhi Kapiri-Mposhi North Nakonde Nakonde Isoka Lusaka |
Tazara
Station' |
06/96 |
- - - - - |
300 600 300 100 600 |
| Lusaka Lusaka Lusaka Lusaka Lusaka Lusaka Lusaka Lusaka South |
LDS |
03/97 |
76 327 280 66 34 34 104 152 |
50 100 100 40 40 40 50 120 |
| Mazabuka Siavonga Siavonga Siavonga Siavonga Monze Gwembe Gwembe Namwala Namwala Choma |
Nalwama |
03/97 |
40 586 <2000 598 428 180 98 143 - 234 46 |
50 160 100 200 100 50 50 50 100 50 50 |
Monitoring surveys in 1996 in six provinces of Zambia, namely Northern, Lusaka, Southern, Eastern, Copperbelt and Luapula Provinces, helped to ascertain the spread and the infestation intensity of LGB. Release sites for the first releases in 1997 were thus pre-selected from the monitoring network data of 1996.
During March - April 1997 T. nigrescens releases were made in 22 localities in Lusaka and Southern Provinces. These localities included Barastone, Lilanda, Barclay-LDS, Kabanana, Chawama, Chamba Valley, Ibex Hill, Namalombwe, Lukolongo and Kasaka in Lusaka Province; Nalwama, Siantotola, Choma, Kabulamwanda, Namwala, Chipepo, Munyumbwe, Chikanzaya, Zambezi Farmer’s Training Centre (Siavonga) and Queens Peace Parish (Siavonga) in Southern Province.
Further T. nigrescens releases were made towards the end of April 1997 in Mbala in Northern Province, Mwense and Samfya in Luapula Province and Kapiri Mposhi in Central Province (Tab. 2, Fig. 3). Follow-up surveys will be carried out during October 1997, to assess T. nigrescens establishment in the new release areas. Some large-scale releases are expected during the 1997 rainy season. This will be done with paired release and non-release sites, replicated across the districts with sites spread as apart as possible to prevent the rapid movement of the predator from swamping out the experiment. The baseline data collected from these early monitoring surveys and T. nigrescens release campaigns will provide adequate baseline against which to assess the subsequent impact of the biological control of larger grain borer.
The late April releases were assisted by Dr. Christian Borgemeister, the leader of IITA’s Larger Grain Borer Programme. During the same period Mr. Cyrille Adda of PHMD/IITA visited the T. nigrescens rearing facilities at Mt. Makulu and suggested ways and means to improved the natural enemy production.
Results
For some time increasing LGB populations have only been recorded in the wider environment and to a lesser extent in the imported maize. However, the recent surveys of Lusaka and Southern Provinces in March/April, 1997 have recorded several localities with severe LBG infestation on locally produced maize both in storage and in the field.
The Larger Grain Borer is beginning to show that it is a serious pest of farm-stored maize in Zambia. So far several localities in both Lusaka and Southern Provinces have recorded severe losses of locally produced maize (standing crop, cob and stored bags). These localities include Barastone (Lusaka district), Chikanzaya and Ibbwe Munyama (Siavonga district). In these areas, LGB was also found infesting wooden storage structures (cribs).
In the Barastone area (Lusaka), two bags of shelled maize in the store were heavily infested with LGB. The farmer buys stock feeds from the millers in gunny bags, which may have been infested with LGB. The standing crop of maize, a few metres away from the infested store is at high risk of being infested before and after harvest.
| Fig. 3. |
Releases of T. nigrescens in
Zambia, 1996-1997.
|
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In Siavonga district (Southern Province), LGB is already causing severe damage to the maize harvest of 1995/96 season. These are Chikanzaya and Ibwee Munyama where about 14 villages have recorded heavy infestations of LGB in cob-stored maize in timber/thatch cribs, wooden crib fabric, and the standing crop in the fields. Infestation in these villages is reported to be as high as 90% so far.
In Gwembe district, the infestation of the stored cob maize was confirmed during the predator releases at Chipepo. The Chief’s palace at Chipepo was used as the distribution centre for the relief maize in 1996 and this is the place where LGB was first recorded in Southern Province. The cob stored maize belonging to the Chief and many other villages were already turned into dust.
Other districts such as Mazabuka, Monze, Choma and Namwala have recorded high catches of LGB in traps but the pest has not yet descended on to stored maize. In many areas, however, this year’s harvest is likely to be infested particularly where traps have recorded catches of more than 200 over a period of weeks.
Farmers’ attitude towards change of storage practices
In both Siavonga and Gwembe where farmers have already suffered heavy losses to their stored maize, the appeal for implementation of improved storage methods is beginning to be readily accepted. The demand for construction of improved storage structures may not be met by the Household Food Security (HFS) project based in Choma.
However, those farmers who are not affected by LGB still take such campaigns lightly and thus are reluctant to move away from the traditional practice of storing maize on - the - cob in open ventilated cribs.
Conclusion
The spread of Larger Grain Borer is identified as a significant threat to agriculture in Zambia. Larger Grain Borer Control and Containment programme is a mammoth task and every effort is being made to make the strategy work. The success of this programme will have crucial impact as the whole of the country is potentially at risk due to LGB presence and the failure of this programme will have catastrophic effects with the country facing severe food shortage which will threaten the lives of millions of people in Zambia. An integrated approach to control LGB with special emphasis on the use of classical biological control can reduce losses to below the threshold’ level providing an acceptable level of pest control, reducing the abuse of chemicals, health hazards and thereby protecting the environment. This will, in due course, help to reduce losses due to LGB infestations, considerably enhancing food security in the nation.
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