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Parasitología al día

versão impressa ISSN 0716-0720

Parasitol. día v.24 n.3-4 Santiago jul. 2000

http://dx.doi.org/10.4067/S0716-07202000000300003 

Anti-tick repellent effect of Andropogon gayanus grass on plots of different ages experimentally infested with Boophilus microplus larvae

CARLOS CRUZ-VAZQUEZ * and MANUEL FERNANDEZ RUVALCABA **

ABSTRACT

The anti-tick repellent effect of Andropogon gayanus grass was evaluated on plots of different ages experimentally infested with Boophilus microplus larvae, using Cenchurus ciliaris as control grass. Four infestations were made, at different plant ages, 3, 6, 9 and 12 months old. The effect was evaluated by recovery of larvae from the experimental plots by flagging during a four week period after each infestation. The anti-tick repellent effect observed in A. gayanus grass was manifested only in mature plants, of 6 months old or more where highly differences were detected (p < 0.01) with control grass. The live larval recovery percentages in A. gayanus grass were 16.2%, 11% and 12% in plants of 6, 9 and 12 months old respectively while in C. ciliaris were 22.5%, 19% and 24.5% respectively. The effect of plant age on live larval recovery was greater than the effect of the grass species. Further studies are necessary to determine the potential use of this grass in field conditions as part of an integrated tick control package.
Key words: Andropogon gayanus, anti-tick repellent effect, Boophilus microplus.

INTRODUCTION

The cattle tick Boophilus microplus is one of the most serious problems to the cattle industry in tropical and subtropical countries, where control is usually carried out by regular acaricide applications.1 The use of anti-tick grasses can be an alternative non-chemical method for tick infestations in these regions.2

An experiment conducted with six grass species, demonstrated that molasses grass, Melinis minutiflora and Gamba grass, Andropogon gayanus, exhibit anti-tick repellent properties for larvae of B. microplus, which prevent larvae from ascending the grass.3 In some tropical and subtropical livestock regions of Mexico informal communications from producers about the cattle pastured in A. gayanus grass suggest that tick infestation levels are smaller than on animals pastured on others grasses.

The objective of the present study was to evaluate the anti-tick repellent effect of A. gayanus grass on plots of different ages experimentally infested with B. microplus larvae.

MATERIAL AND METHODS

The study was carried out at the experimental station of the Centro de Bachillerato Tecnológico Agropecuario Nº 194, located in the municipality of Miacatlán, Morelos, México. The site is at an altitude of 1054 m above sea level, with an annual mean precipitation of 800 mm with rainfall occurring primarily in summer thus producing a tropical, subhumid climate. The experimental area was on shallow soil, light brown in colour and containing a high percentage of stones. The area was wire fenced to exclude grazing animals. The experimental design used in the study was factorial (2 x 4) in a random block,4 of eight treatments with eight replicates, Factor A was grass species, A. gayanus (treatment) and Cenchurus ciliaris var. Biloela (grass control without anti-tick properties5), and Factor B, was plant age, 3, 6, 9 and 12 month old. The area of each experimental plot was 4.8 m2 (3 m x 1.6 m ) and each plot was separated by a vegetation free barrier that was 0.5m wide. On July 6, 1996, the experimental plots were seeded at a rate equivalent to 12 kg/ha for both grasses.6 The plots were fertilized after seeding. All plots were clipped to a height of 25cm at 1.5 months intervals to simulate the effects of grazing and clippings were collected and removed. The plots were irrigated weekly from January to May, 1997. The number of plants per plot (using a quadrant of 50cm x 50cm) and the estimated percentage of ground covered were recorded on October 2, 1996, and on January 4, April 5 and July 4, 1997. A colony of B. microplus ticks ("Zapata" strain), free of Babesia spp and susceptible to acaricides, was established by bovine passage at the Cenid-Parasitología Veterinaria laboratory. Batches of 0.5 g of eggs (10,000 larvae) were held in glass vials and incubated at 28oC and 95% R.H. until eclosion. Larvae were 15 days old at the time the infestation was initiated. The experimental plots were clipped to 25cm in height one week before experimental larval infestation. Four infestations were made, on October 9, 1996 and on January 11, April 12 and July 11, 1997, the plots were infested on every occasion, with 10,000 larvae (one vial per plot) by lineal distribution outline and seven days after larval infestation the vegetation in each plot was sampled using a double flannel flag technique . Sampling was repeated at weeks 2, 3, and 4. The live tick larvae recovered in each sample were counted under a stereoscopical microscope and the mean values were calculated. The data were analysed by Analysis of Variance and differences among the means were determined by Tukey´s test.4

RESULTS

The anti-tick effect of A. gayanus grass on plots of different ages is shown in Table 1. The mean number of live ticks recovered from A. gayanus grass in the first infestation (plant age 3 month old) were not different (p > 0.01) from the number collected from C. ciliaris. However, in all subsequent infestations highly differences with control grass were detected (p < 0.01); between infestations, in A. gayanus grass, differences were detected between first infestation with all others, but not between second, third and fourth infestations (p > 0.01). The live larval recovery percentage in A. gayanus grass were 26.1%, 16.2%, 11% and 12% for each infestation, in the control grass these values were 25.1%, 22.5%, 19% and 24.5% , when the effect was calculated based on the initial infestation level (10,000 larvae). In the control grass there was no difference in the mean of live ticks recovered (p > 0.01) in according to the different plant ages studied. The number of plants per plot and ground cover percentage of the experimental plots are shown in Table 2. A. gayanus grass showed differences in number of young plants (p < 0.01) with C. ciliaris grass (3 months old) and has differences between young and mature plants of its own species (6 month old or more); however, when mature there are always similar number of plants and differences with mature control grass. The ground cover percentage was different (p < 0.01) between A. gayanus and C. ciliaris on plots of 3 and 6 month old, but not on plots of 9 and 12 month old (p > 0.01).


Table 1. Anti-tick repellent effect of Andropogon. gayanus grass observed on plots of
different ages experimentally infested with Boophilus. microplus larvae. Mean numbers
of live Boophilus microplus larvae recovered after each infestation


Grass species

Age plants (months old)
  3 6 9 12
  Mean SD Mean SD Mean SD Mean SD

1. A. gayanus 2614.0a + 35.6 1623.1b + 32.4 1100.5b + 31.8 1203.1b + 30.7
2. C. ciliaris 2514.2a + 33.3 2255.5a + 28.9 1904.0a + 30.2 2453.3a + 31.8
 
Values within a column followed by the same letter are not significantly different at p< 0.01

 

Table 2. Agronomical characteristics of experimental plots of Andropogon gayanus
and Cenchurus ciliaris grass

Grass species

Age plants (months old)

  3 6 9 12
  NP % NP % NP % NP %

1. A. gayanus 830b 67b 272.a 65b 273a 62a 272a 63a
2. C. ciliaris 1774a0 87a 365a 79a 365a 66a 365a 66a
 
Values withing a column followed by the same letter are not significantly different al p < 0.01. NP = number of plants per plot; % = ground cover percentage.

DISCUSSION

Some grasses, such as M. minutiflora and A. gayanus, exhibit anti-tick repellent properties for larvae of B. microplus. Although the two grass species reduced tick survival significantly, there were still 15-20% of the number of tick larvae on other grasses 14 days after the infestation.3 Barros and Evans,8, 9 conducted experiments under laboratory conditions in young plants in which A. gayanus did not show any anti-tick effect (by repellence or presence of volatile agent) against B. microplus larvae.

In the present study an anti-tick repellent effect was observed in A. gayanus grass manifested only in mature plants (6 month old or more). The live larval recovery percentage were 16.2%, 11% and 12% in plants with 6, 9 and 12 months old respectively while in C. ciliaris were 22.5%, 19% and 24.5% respectively. The possible cause of the repellent anti-tick effect detected can be due to the high density of long non-glandular hairs most important in mature plants than in young plants which prevent larvae from ascending the grass and perhaps a presence of volatile agent. The effect of plant age on larval survival observed in our study was higher than the effect of the grass species. An anti-tick effect has been demonstrated in ropical legumes, Stylosanthes spp, in which the anti-tick effect depends on plant age and ground cover percentage.5, 10 According to our results, in A. gayanus grass both factors are also important, in special plant age; the ground cover percentage always acceptable. The experimental plots have good agronomical characteristics considered similar to those reported in the literature.6 The control grass has a larval survival similar to those reported under same conditions in México.5, 7

Our results demonstrate that A. gayanus grass has a certain anti-tick repellent effect in mature plants, the grass is easily cultivated in the study area but further studies are necessary to add to the knowledge about this grass in order to establish its use in field conditions as part of an integrated tick control package.

RESUMEN

Se evaluó el efecto repelente anti-garrapata del pasto Andropogon gayanus en parcelas de diferentes edades que fueron infestadas experimentalmente con larvas de Boophilus microplus, utilizado a Cenchurus ciliaris como pasto control. Se realizaron cuatro infestaciones, a los 3, 6, 9 y 12 meses de edad de la planta, evaluando el efecto por la recuperación de larvas vivas de las parcelas por la técnica de bandera, durante un periodo de cuatro semanas después de cada infestación. Se observó un efecto anti-garrapata en A. gayanus que se manifestó únicamente en plantas maduras, de seis o más meses de edad, en donde se detectaron diferencias altamente significativas (p < 0,01) con respecto al pasto control. Los porcentajes de recuperación de larvas vivas en A. gayanus fueron 16,2%, 11% y 12% en plantas de 6, 9 y 12 meses de edad, respectiva-mente, mientras que en C. ciliaris fueron de 22,5%, 19% y 24,5%, respectivamente. El efecto de la edad de la planta en la recuperación de larvas vivas fue tan alto como el efecto de la especie de pasto. Es necesario realizar estudios para determinar el uso potencial de esta planta en condiciones de campo como parte de un paquete de control integrado de garrapatas.
_____________________________
* Instituto Tecnológico Agropecuario de Aguascalientes. AP 1439, C. Camionera. CP 20270. Aguascalientes, Ags. México.
** Cenid-Parasitología Veterinaria (INIFAP-SAGAR) AP 206, CIVAC. CP 62500 Jiutepec, Mor. México.

REFERENCES


1.- PEGRAM R G, TATCHELL R J, DE CASTRO J J et al. Tick Control: New concepts. World Anim Rev 1993; 74-5: 2-11.         [ Links ]

2.- KAAYA G P. Non-chemical agents and factors capable of regulating tick populations in nature: a mini review. Insect Sci Applic 1992; 13: 587-94.         [ Links ]

3.- THOMPSON K C, ROA E, ROMERO N. Anti-tick grasses as the basis for developing practical tropical tick control packages. Trop Anim Health Prod 1978; 10: 179-82.         [ Links ]

4.- STEEL R G, TORRIE J H. Bioestadística: Principios y Procedimientos p 328-363. 2a. ed. McGraw-Hill. México, 1988.         [ Links ]

5.- CRUZ-VAZQUEZ C, FERNANDEZ R M, SOLANO V J, GARCIA V Z. Anti-tick effect observed in mature plants of tropical legumes Stylosanthes humilis and Stylosanthes hamata. Parasitol al Día 1999; 23: 15-8.         [ Links ]

6.- HUMPREYS L R. A guide to better pastures for tropics and subtropics p 46-50. Wright Stephenson Co. Australia, 1980.         [ Links ]

7.- FERNANDEZ R M. Comparación de cuatro técnicas de colecta de larvas de Boophilus microplus bajo condiciones de campo en infestación controlada. Tec Pecu Mex 1996; 34: 175-82.         [ Links ]

8.- BARROS A T, EVANS D E. Acao de gramíneas forrageiras em larvas infestantes do carrapato dos bovinos, Boophilus microplus. Pesq Vet Bras 1989; 9: 17-21.         [ Links ]

9.- BARROS A T, EVANS D E. Forrageiras com potencial anticarrapato. Acao de substancias voláteis em larvas infestantes de Boophilus microplus. Pesq agrop bras 1991; 26: 499-503.         [ Links ]

10.- SUTHERST R W, JONES R J, SCHNITZERLING H J. Tropical legumes of the genus Stylosanthes immobilize and kill cattle ticks. Nature. 1982; 295: 320-1.         [ Links ]  

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