Potential of Stylosanthes plants as a component in an integrated pest management approach to tick control

Preventive Veterinary Medicine, 2 (1984) 579--588

579

Elsevier Science Publishers B.V., A m s t e r d a m -- Printed in The Netherlands

POTENTIAL OF STYLOSANTHES PLANTS AS A COMPONENT PEST MANAGEMENT APPROACH TO TICK CONTROL R.H.

IN AN INTEGRATED

ZIMMERMAN !/, G.I. GARRIS ~/, and J.S. BEAVER ~/

iDepartment of Crop Protection, University of Puerto Rico Mayaguez Campus, Mayaguez, Puerto Rico 00708 (USA) 2United States Department of Agriculture, Agricultural Research Service, Tropical Tick Research Laboratory, P.O. Box 70, Mayaguez, Puerto Rico 00709 (USA) (to whom reprint request should be sent) 3Department of Agronomy and Soils, University of Puerto Rico Mayaguez Campus, Mayaguez, Puerto Rico 00708 (USA)

ABSTRACT Zimmerman, R.H., Garris, G.I., and Beaver, J.S. 1984. Potential of Stylosanthes plants as a component in an integrated pest management approach to tick control. Prev. Vet. Med.,2: 579-588. Greenhouse tests to screen 15 genotypes of the genus Stylosanthes for their effect on the behavior and survival of larvae of Boophilus microplus (Canestrini), the southern cattle tick, were co~du~ted in Puerto Rico. Larvae were released onto 15 genotypes of ~tylosanthes plants. The lowest survival 2 days after releasing occurred on S. scabra genotype PI-387954 (58.8%) and S. viscosa genotype PI-377961 (-~.5%). On day 7, only 24.8 and 7.~% o---~larvae placed on S. scabra and S. viscosa, respectively, survived. The highest s~rvival on day 2 was ~edorded from a genotype of S. gui~nensis - PI-383437 (88.5%). The highest survival on day 7-(7~.0~) was-recorded from a different genotype of S. guianensi_s (PI-387949). Of the original 15 genotypes, 3 were selected for further study: 2 genotypes (PI-379661 and PI-405088) of S. guianensis and 1 of S. scabra (PI-387954). Also an additional g~notype of ~. viscosa (PI-387962) was used. Mean tick survivorships after-7 ~F~-ys were 60.9, 64.5, 55.9 and 48.3%, respectively. Tick mortality was highest for all varieties during experiment i. It is suggested that plant age and windy conditions could have affected results in experiments 2-4. Similar results were obtained from studies with Amblyomma variegatum (Fabricius) larvae and nymphs on S. scabra (PI-387954) and S. viscosa (PI-387962). Surviving B. microplus larvae and A. variegatum larvae and nymphs present on all genotypes of S.-scabra and S. viscosa responded poorly to touch. The potential use of Stylosanthes plants as a component in an integrated pest management approach (IPM) to tick control is discussed. - -

INTRODUCTION Ticks, tick-borne

diseases

and poor nutrition

due to forages

580

important factors limiting the p r o d u c t i v i t y

of poor quality are of cattle

in Tropical

America.

70% of the 2S0 million cattle and South America were B o o p h i l u ~ mic~oplus this tick ranged Control

acaricides

and that annual

However,

can result

management

]n harmful

of acaricide control

and M a n s i n g h

programs

o£ acaricide

more e c o l o g i c a l l y Sutherst of the

et

(1982)

The v a l u e

of these

until

early

the

(Townsville Australia

Stylo)

(Burt

ticks

to simultaneously o f B. m i c r o p l u s m i g h t be a f f e c t e d the

can kill

introductions

improve native

cultivars

recognized o f S. h u m u l i s in

of Stylosanthe

improvement in 1981),

of Stylosanthes

Puerto

Rico

Also,

quality

other

(Fabricius),

by t h e s e

which can kill

of using

these

plants

and r e d u c e p o p u l a t i o n s

important the

tick

tropical

species,

such

bont tick,

forages.

paper

is

to present

of genotypes

results

of Stylosanthes

s u r v i v a l o f ~ . m i c r o p l u s l a r v a e a n d ~. v a r i e g a t u m nymphs u n d e r l a b o r a t o r y c o n d i t i o n s . The p o t e n t i a l forages

plants ticks.

pastures

species

Staples,

the possibility

improve pasture

effects

control.

certain

1981), and South America ( R o l a n d o , 1978, 1979, M i l e s , 1982). The i d e n t i f i c a t i o n of

raises

of this

to t i c k

l e g u m e was n o t

for pasture

ticks.

of acaricide

that

legume,

as f o r a g e s

as Amblyomma v a r i e g a t u m

determine

reported

1979;

Wharton

the need to develop

approaches

More r e c e n t l y

and n u t r i t i o u s

The p u r p o s e

significance indicate

as a f o r a g e

and W i l l i a m s ,

of the

the current w o r l d w i d e

1967).

(V61ez-Santiago et el., A l b u q u e r q u e and L i s b o a , or immobilize

clearly

were f o u n d t o

have been evaluated

productive

reviewed

1 9 0 0 ' s when a c c i d e n t a l

(Humphreys,

Australia

Trinidad and (]uyana

Kitts,

a tropical

plants

Recently,

St.

recently

genus Stylosanthes,

the likeli-

strains

sound integrated

el.

can increase

resistance.

in

Also, mis-

identified

p r o b l e m and t h e

These f i n d i n g s

on

of

and milk or

1981).

to certain pesticides.

(19771) have

resistance

in meat

(Drummond,

southern cattle tick in Jamaica,

(1976) and D r u m m o n d

in a p p l i c a t i o n

residues

(1978) have

with low levels of resistance

resistance.

losses due to

tick is p r e s e n t l y dependent errors

of the environment

hood of the development

acaricide

that

Basin,

from $6-$13 per head.

of the southern cattle

contamination

the Caribbean

infested with the southern cattle tick,

(Canestrini)

the use of acaricides.

Rawlins

I.ombardo (1975) estimated in Mexico,

as a c o m p o n e n t i n an i n t e g r a t e d

pest

of studies plants

to

on t h e

l a r v a e and use of these

m a n a g e m e n t (IPM)

581

approach

to tick control

MATERIALS

AND METHODS

Preliminary conducted

screening

experiments

in an enclosed

were conducted in standard mixture. dia.,

is discussed.

in an open-sided

with ~. microplus and secondary

greenhouse.

larvae were

screening

tests

Plants were germinated

20 cm diameter pots with a 50% soil and 50% Promix

Pots were

4 cm high)

that escaped was placed

greenhouse

individually

placed

in aluminum pans

and pans were filled with water

from the pots.

To further prevent

(23..cm

to catch ticks escape,

sticky tape

around outer edges of all aluminum pans.

Plant height was maintained in the p r e l i m i n a r y

between

20-30 cm.

All plants used

tests and the first secondary

tests with B. - -

microplus

larvae were

used older plants

started

The control plant

found in Puerto

Seeds were obtained Station,

United

Research

Service,

Genotypes

In additional

that had been used previously

to the desired height. sedge commonly

from seed.

States Department

used are listed

a Cyperus

Plant

sp.;

a

Introduction

of Agriculture,

Region,

Experiment,

in Table

The age of the B. microplus

but were cut back

Rico pastures.

from the Regional

Southern

was

tests we

Agricultural

Georgia,

U.S.A.

i.

larvae used in all experiments

- -

ranged from 3-4 weeks. vial.

One hundred

One vial was positioned

and the stopper removed. within

24 hours,

upright

they were removed

at the base of each plant

from the vials

Preliminary

Secondary

A split plot arrangement

experiments

tests had 5 replicates of a randomized

If ticks moved,

were considered flannelette collect

per genotype. block design was

Tick mortality

at day 2 and 7 post exposure

All larvae were collected with forceps and tape.

and placed had 2 replicates

complete

used and means were compared using LSD's. havior were evaluated

alive.

into a

If the larvae did not leave the vials

directly on the plants. per genotypes.

larvae were aspirated

whether

to the plants.

from each plant,

stuck to the plant

pot, water,

or not,

After all ticks were collected,

cloth was placed

and be-

they

a white

around the base of each plant to

any ticks which may have been overlooked.

Because ~. v a r i e g a t u m

is under

strict quarantine

all tests with this species were conducted maintained

at 25~2

°C and 80~5% RH.

in Puerto Rico,

in a growth chamber

Because ~. v a r i e ~ a t u m

582

larvae

and

25 l a r v a e plant.

nymphs or

Their

post B.

to

for

the

all

microplus.

(P[-38795g)

of

~.

1-2

for

behavior

plan~s.

S.

were

I~. m i c r o p l u s

of

each

evaluated

Results

life

from

were

7 days

containers stage

6-8

on e a c h

a~

x,'cro a s

(PI-387982)

ranged

larv. ae,

h;{nd p : l a c e d

variegatum

vlscosa

tested

larvae.

than wore

The e x p e r i m e n t a l

~ , ' i t h A.

replicates and

variegatum

weeks

t-~'equently experiment

and

tests

Five

scabra the

more

in each

mortality

exposure

procedures

moved

~ymFhs

and

were

only

used.

weeks

compared

and

desc,ibed

for

using

for ~.

The

nymphs

ages and

t-tests.

RESIJLTS Boophilus

microplus

Preliminary of

Stylosanthes

most vival

(Table

and

larvae

S.

The h i g h e s t PI-383437 the

of

than

one

plants,

greater

than

Because

larvae

they

Results

of

genotypes results

of

were

S.

showed day

2 to

guianensis

similar day

7;

the

scabra

least

of

number

number

Results in

survival

larvae

1,

for arc

in

to but

on all

S.

S.

viscosa

S.

7.0~i

o[

guianensi_ s, PI-387949

the

preliminary

results

of

not

On t h e the

inhibit

had

2 genoclimb

control

top

of

the

movement

of

study.

scabra, in

S.

in

viscosa

Table in in

3 and

were

(Table

and

did to

to

control

Control

varieties.

and

viscosa

climbed

viscosa

larvae

scabra

respectively. of

S.

a decrease

the

S.

S.

2a.8

plants.

further

with

larvae. live

the

experiment

and

only

Pl-405088),

presented

for

on

genotype

appeared

with

trends

and

live of

similar

experiment

larval

the

except

control

Stylosanthes greatest

of

genotypes

(PI-379661),

guianensis,

height

guianensis

sur-

7.

survi~,ed,

scabra,

the

tests

the

larvae

7 (75.0%).

o n S.

selected

were

live

in lar~al

day

occurred 7,

15 g e n o t y p e s

viscosa

of

on a genotype

and

secondary

S.

decrease

guianensis

(PI-379661 95% o f

and

2 to

viscosa

on day larvae

~'ith

number

On d a y

S.

occurred

these

the

[rom day

Stylosanthes

third

scabra

survi.vorship

and

microplus

larvae

a general

(67.5%).

scabra

guianensis

greater

from

viscosa

survivorship

S.

plants.

was

lowest

S.

lowering

tested

survivorship

Boophilus

the

the

microplus

that

in

There

(88.5%).

highest

types

1].

o n S.

B.

showed

genotypes

2 days

(58.~%)

of

genotypes

on all

After the

spp.

effective

present

studies

screening

the

2.

plants

2 the

larval

survival

experiment

1,

2 cultivars

experiment

the

and

Overall,

of

_

S.

4.

2 genotypes always

~.

with

had

the

the

2). screening

experiments However,

2-4

tests showed

were

obtained

greater

when compared

to

583 TABLE 1

Effects

of

15 g e n o t y p e s

of

Stylosanthes

on survival

of B. _

larvae

microplus

Species

after

2 and

identification*

Stylosanthes

Stylosanthes

Stylosanthes

(~yperus Plant

85.0 74.0 83 0 75 0 86 B 88 B 73 5 79 5

62.0 61.0 75.0 65.0 67.0 63.5 66.0 65.0

Australia " Brazil Panama Rhodesia

78.0 71.0 80.0 72.5 78.5

63.5 70.5 63.5 56.5 68.5

Australia

58.5

24.5

Mexico

67.5

7.0

75.5

47.0

sp.)

Puerto

Introduction

number.

Rico

2 number

Stylosanthes

_

Australia " " " Argentina Malawi Peru S. A m e r i c a

viscosa

PI-387961

TABLE

on 7

scabra

PI-387954

Mean

(%) Day

humilis

PI-379664 PI-344107 PI-322649 PI-337666 PI-400311

= USDA

survival 2

guianensis

Stylosanthes

*PI

Avg. Day

Source

PI-379661 PI-380523 PI-387949 PI-401502 PI-405087 PI-383437 PI-401510 PI-405088

Control

7 days.

Genotype

~ S.E. after

of live 2 and

B. m i c r o p l u s

1

Day

larvae

present

on

7 days.

2

3

4

Control

2 7

75.4 78.2

5 ~

3.8 7.1

90.2 74.2

~ ±

5.9 7.7

85.8 75.4

5 2.1 ~ 2.0

73.4 85.8

~ 5

S. g u i a n e n s i s PI-379661

2 7

58.4 44.4

~ ~

4.0 4.1

79.6 61.2

~ ~

5~6 8.6

63.0 63.8

5 5.6 ~ 4.0

56.6 60.2

~ 12.0 5 9.~

S. g u i a n e n s i s PI-405088

2 7

56.2 47.6

~ 4.3 ~ i0.5

83.8 66.0

~ +

5.3 6.6

70.8 67.0

~ 3.9 ~ 3.9

54.2 7014

~ ~

S.

2 7

42.8 39.8

~ ~

5.9 8.2

73.6 54.4

~ 7.3 ~ ii.0

63.4 53.4

~ 8.0 ~ 6.1

65.0 54.8

~ ii.6 ± 3.3

2 7

35.8 13.6

5 ~

8.2 3.0

74.0 61.8

~ ~

5.5 6.0

50.2 45.8

5 6.2 ~ 2.9

50.6 54.2

~ i0.7 ~ 5.5

than

that

used

scabra

S. v i s c o s a P I ~ Australia*

* A c c e s s i o n and PI n u m b e r p r e l i m i n a r y tests.

are

_

different

in

5.2 3.9

8.1 9.~

584

controls,

a lower survival

S. viscosa was still

apparent

were no s i g n i f i c a n t

7 were combined

ments,

(ANOVA, ~

Since there or the

0.05),

days

2 and

The overall control means d i f f e r e d

from all other genotypes

the controls differed

experiment

2-4.

for the g e n o t y p e - d a t e

interactions

(Table 3).

larvae on S. scabra and

:in experiments

differences

experiment-genotype-date

significantly

of B. m i c r o p l u s

(R

0.05).

Within experi-

from other genotypes

except

2 when it was not s i g n i f i c a n t l y different

in

from S. - -

viscosa

(p

0.05).

TABLE 3 C o m b i n e d means

(2 and 7 days)

of live ~. m i c r o p l u s

larvae present

on Stylosanthes.

Variety

Experiment* 3

1

2

4

Overall mean

Control

76.8 a

82.2 a

S. guianensis -PI-379661

80.6 a

79.6 a

79.8 a

51.9 b

74.9 ab

68.9 b

62.3 b

64.5 b

S. guianensis -PI-4DS088 S. scabra PI-387954

51.4 b

70.4 ab

63.4 bc

58.4 b

60.9 bc

41.3 b

64.0 b

58.4 c

59.9 b

55.9 c

S. viscosa PI-3-~

24

.7 c

67.

9a b

48.

0d

52.

4b

48.2

5d

*Numbers with the same letter in each column are not s i g n i f i c a n t l y different (LSD P 0.05). Overall, (Table 3). S. v i s c o s a

S. viscosa had less

live larvae than did S. scabra

Only during experiment than on S. scabra.

no s i g n i f i c a n t

difference

b e t w e e n S. v i s c o s a

2 did fewer larvae survive on

However,

(LSD, 0.05)

in experiment

2, there was

in larval s u r v i v o r s h i p

and S. scabra.

In all 4 e x p e r i m e n t s

live ~. ~ i c r o p l u s

larvae present

on ~.

scabra and S. viscosa

for 7 days did not respond to touch.

on the control plants

and on the ~. guianensis

responded

to touch and attached

to ones'

genotypes

Larvae

readily

hand.

A m b l y o m m a v a r i e g a t u m studies Nymphal

survival

on S. scabra and S. viscosa was s i g n i f i c a n t l y

less than on the controls

(t=0.07)

(Table 4).

Larval survival was

585

also less on S. scabra and S. viscosa larvae present

(t=0.05).

Live nymphs

and

on S. scabra and S. viscosa did not react to touch _

or attach to ones' immediately

hand.

responded

Nymphs

and larvae on the control plants

to touch.

TABLE 4 Mean number

of Amblyomma

variegatum

larvae and nymphs

alive on

day 7. Larvae* Experiment 1 Experiment

__Variety Control

Nymphs** Experiment 1 Experiment

2

19.0

22.2

21.8

25.0

S. scabra PI-387954

5.4

10.4

14.4

18.1

S. viscosa PI-387962

4.0

6.6

5.0

16.7

*Controls were (t=O.01).

significantly

**Controls were significantly (t=O.05) except the control was different at t=O.07.

different

2

from other varieties

different from other varieties a n d S. s c a b r a in experiment 1 which

DISCUSSION Results Sutherst vival

of these experiments

et al.

confirmed

(1982) on the effects

of B. microplus

larvae.

Also,

those presented

of Stylosanthes these experiments

by

on the surshowed that

- -

S. scabra nymphs

and S. viscosa

and larvae.

ticks on S. scabra

and S. viscosa

attachment

indicated

(Sutherst,

personal

attach

decreased

is probably 1983)

ability

7 days,

decreases.

observed

in experiments

new plants were

germinated.

which was conducted windy.

rapid diffusion

plants

in an open-sided

Windy weather of the volatile

communica-

in age their

A decrease

in plant

to the lower tick

2-4 for ~. microplu~

of previous

Also,

of ticks to

infestation.

personal

plants mature

with age may have contributed

During these experiments,

effects may be low

cattle

(Sutherst,

larvae.

tests were used.

during experiment greenhouse,

No

2,

the weather was

could have contributed components

live

to touch or

the inability

great enough to prevent

to cause tick mortality

unusually

1983)

of A. variegatum

by the remaining

that though the acaricidal

that as the Stylosanthes

effectiveness mortalities

after

communication,

It has recently been suggested tion,

the survival

The lack of response

involved

to a more

in tick

586 mortality

(Sutherst

acaricide

during

et

al.,

1982)

experiment

There are 3 inajor methods host resistance al.,

1979).

and pasture

used to control spelling

198]).

For example,

the

oI- t h e

techniques

and ecological

contribute

acarickdes,

]977,

Sutherst

et

used would

region in question

All three of these methods have

acaric]des

effect

ticks:

(Powell,

The c o m b i n a t i o n of control

depend on the tick species (Sutherst,

and d e c r e a s e d

2.

to chemical

drawbacks.

selection,

host

resistance can lead to selection of breeds

that are nor as profit-

able as

spelling

costs;

less ie.

resistant

breeds,

supplemental

feed,

and p a s t u r e fences,

labor,

can

increase

and t r e a t m e n t

equip-

ment. Thompson e t

al.

to

pastures

and s t r a t e g i c

use

tick

(1978)

approach

of host

pasture the

management

need

for

acaricides could

their

decrease

approach

to

farms,

use

tick

control

schemes.

techniques) tick

seems

Also,

population

outbreaks. and

countries. nitrogen

on e x p e n s i v e

to

the

chemical

production.

Such an

in a r e a s

where

avail-

is limited and land costs are high;

in the Caribbean.

and

preclude

fertilizers

and c o n t r i b u t i n g

appropriate

the

pastures

might

of chemical

of animal

practical

of anti-tick

anti-tick

i n many d e v e l o p i n g

dependence

cost

with

during price

ticks

the the

space for grazing

the islands

except

an e c o n o m i c a l

a combination

application

spelling

in the

by k i l l i n g

and l o w e r

able

(pasture

increase

products

that

involve

in combination

acaricidcs

limits

Stylosanthes,

suggested could

acaricide

resistance

The r e c e n t

soil,

control

For the animal p r o d u c e r

i.e.

on small

the high costs a s s o c i a t e d with such an IPbl program could be

reduced through the d e v e l o p m e n t It is concluded

of communal

from th[s study that:

grazing areas.

i) certain genotypes

Stylosanthes not only increased m o r t a l i t y of B. microplus and A. v a r i e g a t u m

larvae and nymphs,

seeking or attaching

to a host,

but also prevented

2) more genotypes

need to be tested for their effects on ticks, tick control methods be examined

integrated with

attachment

ability.

larvae

them from

of Stylosanthes

3) combinations

of

Stylosanthes programs need to

in present day c a t t l e - f o r a g e p r o d u c t i o n

starting with small-scale plot

of

testing of survival

systems, and host

587 REFERENCES Albuquerque, B.W.P De and Lisboa, P.K.B., 1979. Algumas plantas utilizadas como forrageiras un com possibilidades do seu uso na agropecu~ria na Amazonia. Manus-AM, Brazil, Instituto Nacional de Pesquisas da Amazonia, 62 pp. Brolmann, J.B., 1979. Evaluation of various Stylosanthes accessions in South Florida. Soil and Crop S ~ . Soc. of 39~ 102-104. Burr, R.L. and Williams, W.T., 1979. Strategy of evaluation of a collection of tropical herbaceous legumes from Brazil and Venezuela #1I. Evaluation in the quarantine glasshouse. AgroEcosystems, 5:119-134. Drummond, R.O., 1977. Resistance in ticks and insects of veterinary importance. In: D.L. Watson and A.W.A. Brown (Editors), Pesticide Management and Insecticide Resistance, Academic Press, New York, pp. 303-319. Drummond, R.O., 1981. Problems with external parasites of livestock in the Caribbean. In: Proceedings of Seminar and Workshop, Pest and Pesticide Management in the Caribbean, 3-7 November 1980, at Christ Church, Barbados, W.I., 2:98-102. Humphreys, L.R., 1967. Townsville lucerne: history and prospect. J. Aust. Inst. Agric. Sci. 34:3-13. Kretschmer, A.E., Jr. and Snyder, G.H., 1982. Comparison of mixtures of seven tropical legumes and six tropical grasses in South Florida. Proc. Soil Crop Sci. Soc. FI. 41:67-72. Lombardo, R.V., 1975. Socioeconomic importance of tick problems in the Americas. In: 8th Inter-American meeting at the ministeral level on foot and mouth diseases and zoonosis control, 16-19 April 1975, at Guatemala. World Health Organization pp. 86-97. Miles, J.W., 1982. Efecto del m~todo de siembra en Stylosanthes guianensis. Pastos Tropicales, Bolet~n Informativo, Centro I n t e r . de A g r / c . T r o p i c a l , 7:1-7. Ocumpaugh, W.R., C o e l h o , R.W. and B r o l m a n n , J . B . , 1 9 8 2 . I n f l u e n c e s of l e a f i n e s s on p r o t e i n c o n t e n t and d i g e s t i b i l i t y i n f o u r s p e c i e s of S t y l o s a n t h e s . P r o c . S o i l Crop S c i . Soc. F1. 4 1 : 1 0 8 - 1 1 1 . Powe11, R . T . , 1977. Project tick control. Queensland Agric. Jour., 104:1-34. R a w l i n g s , S.C. and M a n s i n g h , A . , 1978. Acaricidal susceptibility o f f i v e s t r a i n s o f B o o p h i l u s m i c r o p l u s from f o u r C a r i b b e a n countries. J. Econ. E n t . , 7 1 : 1 4 2 - 1 4 4 . R o l a n d o , A . C . , 1978. Leguminosas forrajeras para el tr6pico ecuatoriano. Ecuador, Instituto N a c i o n a l de I n v e s t i g a c i o n e s Agropecuarias. Estaci6n Experimental Tropical Pichilingue. B o l e t ~ n T ~ c n i c o , No. 26, 12 p p . Staples, I . B . , 1981. The t e c h n o l o g y o f T o w n s v i l l e S t y l o (Stylosanthes humilis): A continuing need? Jour. Aust. Inst. Ag~-~., 45:200-210. Sutherst, R.W., 1981. Is the Australian pest management approach to t i c k c o n t r o l r e l e v a n t to A f r i c a ? I n : T i c k B i o l o g y and Control. P r o c e e d i n g s o f an I n t e r n a t i o n a l C o n f e r e n c e , 27-29 J a n u a r y 1981, a t Rhodes U n i v e r s i t y , Grahamstown, South Africa, 222 p p . Sutherst, R.W., N o r t o n , G . A . , B a r l o w , N . D . , Conway, G . R . , B i r l e y , M. and C o m i n s , H . N . , 1979. An a n a l y s i s o f m a n a g e m e n t strategies for cattle tick (Boophilus microplus) control in Australia. Jour. Appl. Ecol. 16:359-382.

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Sutherst, R.W., Jones, R . J . and Schitzerling, H.J., 1982. Tropical legumes of the genus Stylosanthes immobilizes and kill cattle ticks. Nature 295:320-321. Thompson, K.C., Roa, J. and Romero, T., 1978. Anti-tick grasses as the basis for developing practical tropical tick control packages. Trop. Anim. Illth. Prod. i0:179-182. V~lez-Santiago, J., Sotomayor-Rlos, A. and Lugo-LSpez, M.A., 1981. Potential of Stylosanthes guianensis as a forage crop in the humid mountain region of Puerto Rico. J. Agric. Univ. P.R. 65:232-240. Wharton, R.H., 1976. Acaricide resistance and alternative methods of tick control. World Anim. Rev. 20:8-15.