PAPER SESSION V: MANAGEMENT AND CONTROL OF MITES AND TICKS
CHAIRPERSON: Dr. E. Kairu
PAPER 17
Screening of tomato accessions for resistance to Tetranychus urticae and T. evansi
M. Knapp1, D.M. Apiyo2, B. Mvere3 & S.G. Agong2
1International Centre of Insect Physiology and Ecology (ICIPE), P.O. Box 30772, Nairobi, Kenya, E-mail: mknapp@icipe.org
3Horticultural Research Centre, P.O. Box 810, Marondera, Zimbabwe
Red spider mites, mainly Tetranychus urticae and T. evansi are a major problem in tomato production in eastern and southern Africa. Control with acaricides is difficult to achieve for small-holder farmers and in the case of T. evansi natural enemies are rare. Resistant varieties are an environmentally friendly and cost-effective way of reducing pest damage, rendering them a most desirable tool for resource-poor small-scale agriculture. We tested 48 tomato accessions for resistance to T. urticae in a series of experiments with potted plants in a screen house. The variety Money Maker was included as a check since it is known to be very susceptible to spider mites. Eight accessions had significantly lower numbers of motile mite stages and 12 accessions had significantly lower numbers of eggs than Money Maker 12 days after inoculation, among them several commercial varieties, which could be recommended directly to farmers after further testing in the field. In Zimbabwe 20 accession wee tested with the same set-up for resistance to T. evansi. Results of these experiments indicate 7 varieties with significantly lower numbers of motile stages and 2 varieties with significantly lower numbers of eggs than Money Maker.
PAPER 18
BREAKTHROUGH IN THE MICROBIAL CONTROL OF THE CASSAVA GREEN MITE BY THE FUNGUS NEOZYGITES FLORIDANA (ENTOMOPHTHORALES: NEOZYGITACEAE)
F.C.C. Hountondji, R. Hanna & A. Cherry
Biological Control Centre for Africa, International Institute of Tropical Agriculture (IITA), 08 BP 0932, Cotonou, Benin, E-mail: f.Hountondji@cgiar.org
The cassava green mite Mononychellus tanajoa (Bondar) was accidentally introduced from the Neotropics into Africa in the early 1970s, where it became a serious threat to cassava production. Because of the exotic nature of M. tanajoa, classical biological control was chosen as the first and most appropriate control method against this pest. Most of the biocontrol efforts have been devoted to the identification and introduction of phytoseiid predators from South America, which has resulted in the establishment of three phytoseiid predators, of which Typhlodromalus aripo DeLeon has shown the greatest success in establishing and spreading, and is now found in 20 countries in sub saharan Africa. To complement M. tanajoa control by phytoseiid predators, several isolates of the entomophthoralean acaropathogenic fungus Neozygites floridana (Weiser and Muma) were imported from Brazil, where they were often associated with frequent epizootics and rapid decline in M. tanajoa populations. N. floridana is also present in Africa, but epizootics of this fungus were never observed and infection rates were not known to regularly exceed 1%. An in vivo release procedure was developed and field experimental releases were conducted in two agroecological zones in Benin to determine the performance of two Brazilian and one Beninese isolates of N. floridana. Cassava fields inoculated with the Brazilian isolates showed significantly higher infection rates of M. tanajoa, twelve months after the releases, than those inoculated with the Beninese isolate or the non-release control. High infections, up to 55% (mean per isolate), were recorded at the release sites in the year following releases. Subsequent surveys to monitor spread of the fungus around release sites indicated the prevalence of higher N. floridana infections up to 20-km radius at least. The availability of release technology and the potential of establishment and spread of Brazilian N. floridana isolates in Benin provide a substantial background for a wider application of this microbial control in Africa. The development of molecular tools to differentiate between the isolates and confirm their respective performance is underway.
PAPER 19
EFFICACY OF A DELTAMETHRIN BASED POUR-ON IN THE CONTROL OF TICK-BORNE DISEASES AND TRYPANOSOMOSIS IN KWALE DISTRICT OF KENYA
G.R. Muraguri1, A. McLeod2 & J.J. McDermott3
1National Veterinary Research Centre, P.O. Box 32, Kikuyu, Kenya, E-mail: tbd-muguga@africaonline.co.ke
2University of Reading, VEERU, Reading, RG6 6AT, UK.
3International Livestock Research Institute (ILRI), P.O. Box 30709, Nairobi, Kenya
A one-year longitudinal study was conducted in 92 smallholder dairy farms in Kwale district, in the Coast province of Kenya, to evaluate the efficacy of Spot-on Ò(10% deltamethrin pour-on) in the control of East Coast fever, anaplasmosis, babesisosis and trypanosomosis. A comparison of the annual incidence and mortality rates of these diseases was made among four Spot-on application regimes: biweekly, monthly, bimonthly and Spot-onÒ untreated control groups. Application of the Spot-on and diagnosis of the diseases was carried out by one trained monitoring team to reduce variation. The incidence of East Coast fever, ranging from 2.6% to 6.8% among the treated animals, was statistically lower than in the control group (18.8%). Although the incidence of anaplasmosis ranged from 2.6% to 13.5%, the differences among the treatments were not statistically significant. There were only seven confirmed cases of babesiosis and therefore no statistical comparisons of the incidence rates were made. The incidence rate of trypanosomosis ranged from 28.2% in the bi-weekly treated group to 72.6% in the control group. The incidence rates of trypanosomosis in the bi-weekly and monthly treated animals were statistically lower than in the bi-monthly and control groups. It was concluded that Spot-on applied on monthly intervals could significantly reduce the incidence of tick-borne diseases and trypanosomosis in cattle in the coastal lowlands.
PAPER 20
COULD SELECTION OF CATTLE BE USED TO CONTROL AMBLYOMMA VARIEGATUM TICKS?
F. Stachurski
CIRDES (Centre International de Recherche-Développement en zone Sub-humide, BP454, Bobo-Dioulasso, Burkina Faso, E-mail: stachurski@fasonet.bf
It is well known that tick infestation levels are highly variable between cattle of the same breed. Consequently, the selection of animals with low infestation was considered to be a promising strategy for tick control. Such observations and considerations were also done with Amblyomma variegatum in various parts of Africa. However, during an experiment carried out in Cameroon, it was observed that calves from bull and dams with low attractivity for A. variegatum adults did not have lower infestation levels than other calves, especially than those born from breeders with high infestation levels. Consequently, studies were implemented in order to identify the reasons for the variability of tick infestation. It was observed that some animals were able to reject part of the attached ticks, but that this behaviour disappeared when male ticks succeeded to attach for a few days: A. variegatum seems therefore to be able to affect the immunological reactions of the hosts. The relationship between cattle behaviour and their infestation was also examined. It was observed that animals with low infestation were more mobile than highly parasitised ones, grazed more, laid down less often, and were generally seen in front of the herd. Their low infestation level was thus the result of various characteristics: they picked up fewer ticks on the pastures when grazing, they did not attract them when lying down, and they were able to remove some of the attached ticks. It was also noted that, after removal of the highly infested animals of a herd, the infestation of the remaining animals increased. All these observations indicate that the selection of animals with low attractivity for A. variegatum would probably not lead to an important reduction of the infestation level of a herd.
PAPER 21
Survival of Theileria parva-infested nymphal and adult Rhipicephalus appendiculatus under laboratory and quasi-natural conditions
H. Ochanda
Department of Zoology, University of Nairobi, P.O. Box 30197, Nairobi, Kenya, E-mail: hochanda@uonbi.ac.ke
no abstract available
PAPER 22
IN VITRO FEEDING OF RHIPICEPHALUS APPENDICULATUS (NEUMANN) NYMPHS AND ITS APPLICATION IN THE PRODUCTION OF THEILERIA PARVA STABILATES
J. M. Musyoki1, E.D. Kokwaro2, J.K. Kiara3
1Kenya Agricultural Research Institute, National Veterinary Research Centre, Muguga, P.O. Box 32, Kikuyu, Kenya, E-mail: tbd-muguga@africaonline.co.ke
2Kenyatta University, Department of Zoology, P.O. Box 43844, Nairobi, Kenya
3International Livestock Research Institute (ILRI), P.O. Box 30709, Nairobi, Kenya
Rhipicephalus appendiculatus nymphs were fed on heparinised bovine blood infected with Theileria parva parasites in an in vitro feeding system. The in vitro fed nymphs had a mean feeding duration of 7.4±0.34 days and a mean engorgement weight of 5.94±0.32 mg. These were not significantly different from the respective values of 6.2±0.26 days and 6.35±0.36mg for nymphs fed on steers. A mean of 63% of the in vitro fed nymphs moulted successfully compared to 84% of those fed on steers. Assessment of infection with T. parva in adults indicated that females from the in vitro system had an infection rate and infection abundance of 54% and 1.38 respectively. These values were not significantly different from those of the in vivo fed females of 50% and 1.4 respectively. Sporozoite stabilate made from both the in vitro and in vivo fed adults were found to be equally infective and caused fatal ECF in naïve friesian steers. There were no significant differences in all the parasitological and haematological parameters. When given a lethal homologous challenge the two groups of steers were found to be solidly immune.