POSTERS:

 

POSTER 1

GEOMETRIC MORPHOMETRIC ANALYSIS OF THE MALE AND FEMALE BODY SHAPE OF AMBLYOMMA GEMMA, A. VARIEGATUM AND A. HEBRAEUM

 

E. Pretorius1 & F.C. Clarke2

1Deptarment of Anatomy, Faculty of Medicine, Univ. of Pretoria, P.O. Box 2034, Pretoria, 0001, South Africa, E-mail: clark@medunsa.ac.za

2Department of Biology, Faculty of Science, P. O. Box 139, MEDUNSA, 0204, South Africa

 

There are presently 10 species of the genus Amblyomma that are capable of transmitting Cowdria ruminantium in Africa. Amblyomma hebraeum and A. variegatum are the two main vectors of C. ruminantium and A. gemma is probably the main vector of C. ruminantium in the very dry areas of East Africa. The three species are very similar in adult appearance, they exhibit the same host prevalence as adults, they occur in the same habitat types and their distributions overlap, covering virtually the whole of sub-saharan Africa. A geometric morphometric analysis of the male and female body shape of the three was performed. This analysis compared the body shape of the ticks with each other by collecting seventeen landmarks from the ventral area of males and females and analysing this with geometric morphometrics. Relative warp analyses were performed on the male and female data sets and the results of the first two relative warps (for each of the male and female data sets) plotted against one another. The first two relative warps are indicative of the most variation between structures that were studied. Thin-plate-spline analyses were also performed on the consensus shape of the males and females. Results from thin-plate spline analysis indicated which landmarks were responsible for shape variations. Results from this analysis indicated that the body shape of A. gemma and A. variegatum females cannot be distinguished from each other. The male body shapes of these two species are also very similar as indicated by the consensus thin-plate splines. The relative warp and the thin-plate spline analyses separate A. hebraeum from the other two species.

 

 

POSTER 2

New Trends in Control of Ticks and Tick-borne Diseases

 

E. Kibuka-Sebitosi

Department of Biochemistry, University of Pretoria, Pretoria-0002, South Africa, E-mail: esthersebitosi@hotmail.com

 

The control of ticks and tick-borne diseases in the past has relied on the use of acaricides, chemotherapy, cultural practices and keeping cattle breeds that are resistant to diseases. Following the introduction of modern technology, new approaches to tick control have been developed. These include: searching for novel antigens to serve as vaccine candidates in the tick vector tissues (salivary glands, guts, haemolymph), modulation of the immune responses and searching for effective vaccines based on different parasite stages in the lifecycle.

These ideas are discussed in light of the modern technologies available and underscore the need for developing integrated control packages for controlling ticks and tick-borne diseases for different parts of Africa.

 

 

POSTER 3

HARD TICKS (ACARI: IXODIDAE) FROM LARA STATE, VENEZUELA

 

Ríos Y., J. Morales & J. Gallardo

Universidad Centroccidental "Lisandro Alvarado", Decanato de Agronomía. Venezuela, E-mail: cvasqz@yahoo.com

 

The distribution and host range of ixodid ticks were surveyed during 1996 to 1997 at Lara state, Venezuela. Fifty samples of hard ticks were taken in nine districts from various host including cattle, horses, donkeys, sheep, goats, dogs, rabbits, snakes, iguanas and toads. Specimens were taken to the Laboratorio de Zoología Agrícola, Universidad Centroccidental "Lisandro Alvarado", preserved in vials containing 70% isopropyl alcohol and labelled. Then, specimens were separated according to its host and location and a database was made. All genera were determined using the key proposed by Keyrans and Litwak (1989). Four genera were identified according to the following: cattle: Amblyomma and Boophilus, horses: Anocentor and Boophilus, sheep: Anocentor, dogs and sheep: Rhipicephalus, and snakes, iguanas and toads Amblyomma.

 

 

POSTER 4

Eriophyd mites inhabiting avocado trees, persea americana mill

 

C. Vásquez & C. Sánchez

Universidad Centroccidental "Lisandro Alvarado". Decanato de Agronomía. Lara State, Venezuela, E-mail: cvasqz@yahoo.com

 

Eriophyid mites associated with avocado trees were sampled from July 1997 to December 1999 at the Experimental Orchard of the Agronomy Faculty, Universidad Centroccidental "Lisandro Alvarado", Lara state, Venezuela. Leaf and flower cluster samples were taken to the Agricultural Zoology Laboratory. These samples were examined under magnification to separated the eriophyid mites. These were then clarified using Kono Medium and mounted in Keiffer's Medium. Each specimen was examined in a phase-contrast microscope. The results were that there was just one eriophyid mite species, Tegolophus perseaflorae Keiffer, 1969 (Acari: Eriophyidae) a serious pest in avocado trees in Brazil and more recently in Florida, U.S.A. This species is reported for the first time in Venezuela.

 

 

POSTER 5

AVOCADO MITES IN AN ORCHARD IN VENEZUELA

 

C. Vásquez & C. Sánchez

Universidad Centroccidental "Lisandro Alvarado". Decanato de Agronomía. Lara State, Venezuela, E-mail: cvasqz@yahoo.com

 

Mites were collected from avocado trees between July 1997 to December 1999 at the Experimental Orchard of the Agronomy Faculty, Universidad Centroccidental "Lisandro Alvarado", Lara state, Venezuela. Leaves and twigs were taken into the Agricultural Zoology Laboratory. Each sample was examined under magnification to separate mites from other living organisms. The specimens were clarified using lactophenol and microscopic slides were prepared on Hoyer's medium. Ten species and/or genera in five mite families were identified: Cheletogenes ornatus (Canestrini and Fanzago) and Cheyletus sp. [Cheyletidae], Amblyseius sp. and Euseius sp. [Phytoseiidae], Suctobelbella sp. [Suctobelbellidae], Brevipalpus obovatus Donnadieu and B. phoenicis (Geijskes) [Tenuipalpidae], Lorryia formosa (Cooreman), Pronematus ubiquitus (McGregor) and Tydeus californicus (Banks) [Tydeidae].

 

 

POSTER 6

SPIDER MITE PESTS OF TOMATOES IN SOUTH AFRICA.

 

L. Steynberg, A.M. van den Berg & E.A. Ueckermann

Agricultural Research Council Plant Protection Research Institute, Mite Expert Centre, Private Bag X 134, Pretoria 0001, South Africa, E-mail: Rietls@Plant2.Agric.za

 

Mites are regarded as one of the most important pests in certain agricultural crops, with 65 phytophagous species regarded of economic importance in agriculture. Mites acquired their pest status about 50 years ago when synthetic organic insecticides were used extensively for the first time in farming practices. These pesticides affected the natural enemies of phytophagous mites severely, which in many cases resulted in uncontrolled outbreaks of mites in crops. Adding to the problem was the ability of some species of plant feeding mites to develop resistance against some pesticides. Tomato, Lycopersicon esculentum Mill., is one of the most important vegetables produced worldwide, with an annual world production of 54,24 million metric tons. Tomatoes are prone to several diseases and insect and mite pests that may have severe adverse affects on its production. The most important spider mites pests on tomatoes in South Africa are Tetranychus urticae Koch, T. lombardinii Baker & Pritchard, T. evansi Baker & Pritchard and T. ludeni Zacher. The ability of these mites to double their population size in one day make them an acute problem. The first signs of damage on tomato plants, due to the feeding of spider mites are visible as chlorotic stipples on the leaves An IPM programme for tomatoes in South Africa was initiated in 1999 by researchers at the ARC-PPRI in collaboration with the Tomato Producers' Organisation. The project includes surveys of pests and natural enemies on tomatoes in the major tomato production area in South Africa, laboratory evaluation of natural enemies as potential biological control agents and glasshouse trials. The predatory mite Phytoseiulus persimilis Athias- Henriot was collected in the Brits area with T. lombardinii. Evaluation of this strain of P. persimilis as potential biological control agent for spider mites on tomatoes in South Africa is currently underway.

 

 

POSTER 7

THE ROLE OF WILDLIFE IN MAINTAINING TICK POPULATIONS COMPARED TO DOMESTIC ANIMALS

 

F.D Wesonga 1, J. Jonyo2 & G.O. Orinda1

1 National Veterinary Research Centre, P.O. Box 32, Kikuyu, Kenya, E-mail: tbd-muguga@africaonline.co.ke

2 Deceased

 

The main objective of the study was to determine the possible influence of host species on the maintenance of ticks in the field by determining the relative contribution of wild animals compared to domestic animals. The study was carried out on a game ranch adjacent to the Nairobi National Park. Tick counts were carried out on 30 zebu cattle aged 1 to 3 years and 20 Red Maasai sheep aged 6 months to 1 year grazing in a common area of about 10 km2 for a period of 1 year. Half body counts were carried out on cattle and sheep on a weekly basis. To avoid excessive stress the animals were dipped in TriatixR (Amitraz) whenever the half body count exceeded 100 fully engorged female ticks of any species recorded on the ranch. The cattle were dipped three times during the period of study. Tick counts on the wild animals were carried out during the weekly cropping of the herbivores. From the results cattle were found to have a significantly higher infestation of ticks compared to wildlife. It was concluded that cattle appear to make an unproportionally large contribution to the tick population on pasture compared to wildlife.

 

 

POSTER 8

A SEM STUDY OF A new and unique species of Erythrites Southcott (Acari: Erythraeidae) from South Africa

 

L.R. Tiedt1, E.A. Ueckermann2 & P.D. Theron3

1Lab. for Electron Microscopy, Potchefstroom Univ. for C.H.E., Private Bag X6001, Potchefstroom, 2520, South Africa. E-mail: emslrt@puknet.puk.ac.za

2ARC-Plant Protection Research Institute, Private Bag X134, Pretoria, 0001, South Africa. E-mail: rieteau@plant2.agric.za.

3School of Environmental Sciences and Development, Potchefstroom Univ. for C.H.E., Potchefstroom, 2520, South Africa. E-mail: drkpdt@puknet.puk.ac.za.

 

Knowledge of the family Erythraeidae from South Africa is few and it is also the first time that this genus is recorded from South Africa. Members of the family Erythraeidae are parasitic in the larval stage and free-living predators in the nymphal and adult stages. Specimens of Erythrites sensilaris n. sp. were collected from rocks and several plant species in six of the nine provinces of South Africa and is one of four new Erythrites species from South Africa. The mite samples were fixed in 70% ethanol, dehydrated in an acetone series and critical point dried in liquid co2. The dried mites were mounted on SEM-stubs with double-sided carbon tape, coated with gold/palladium and viewed under the SEM. Erythrites sensilaris n. sp. is unique in that it is the only species in the genus Erythrites, which has the sensory setae on the two sensory areas of the crista metopica, setose and distally expanded. The idiosoma is decorated with uniform, spiculate and leaf-shaped setae.