Page 8 - Volume 5, Issue 1, January 2012

Dembilio & Jacas

6

(this may be accompanied by the secretion

of brown viscid liquid with a characteristic

bitter smell), crown or frondloss and appear-

ance of a dried off shoot are usually only

visible long after the palm has become in-

fested. Secondary infections of opportunis-

tic bacteria and fungi may occur within in-

jured tissues, accelerating the deterioration

of palms.

As mentioned above, early detection of

infested palms is very difficult but it is essen-

tial to ascertain the first symptoms as soon

as possible in order to take appropriate mea-

sures. Currently, the use of bioacoustics and

infrared systems or even the use of dogs can

be employed with the aim of detecting early

infestations (Faleiro, 2006). Future develop-

ments are expected and urgently needed.

3.2. Control

Because it is difficult to detect damage

by

R. ferrugineus

during the early stages of

infestation, emphasis is generally focused

onpreventive measures mostly relying on

chemical applications. Control methods

against

R. ferrugineus

range from gener-

al dusting of the leaf axils with insecticides

after pruning, or spraying of the palm tree

trunk, to localized direct injections of chem-

icals into the trunk (Faleiro, 2006). All these

treatments are often complemented with

cultural and sanitary methods that include

early destruction of infested plant material

(Kurian and Mathen, 1971) and prophylactic

treatment of cut wounds (Pillai, 1987). Dur-

ing the latest years, in the Region of Valen-

cia, an integrated pest management (IPM)

strategy has been implemented. This strat-

egy includes (a) plant quarantine and plant

certification, (b) mass trapping of adult wee-

vils using ferrugineol-based food baited

traps (Hallett

et al

., 1993), (c) crop and field

sanitation, (d) preventive chemical treat-

ments of gashes,(e) filling frond axils of

young palms with a mixture of insecticides

and (f) curative treatments of infested palms

in the early stages of attack, eradicating se-

verely infested palms. These palms should

be removed and destroyed by shredding.

Burning is not recommended as destruc-

tion means because palms do not burn easi-

ly and complete destruction of

R. ferrugineus

cannot be guaranteed in this case.

3.2.1. Chemical control

The most common and practical mea-

sure in chemical control is mainly based

on the repeated application of large quan-

tities of synthetic insecticides employed in

a range of preventive and curative proce-

dures designed to contain the infestation.

These procedures have been developed

and refined since commencing in India in

the 1970’s when work on application of or-

ganophosphates and carbamates ensured

these chemicals to become the mainstay of

the chemical approach to control

R. ferrug-

ineus

(Murphy and Briscoe, 1999). In Spain,

a minimum of 8 preventive treatments per

season (from March to November) are rec-

ommended by the Valencian Department

of Agriculture. However, only 4 active sub-

stances are nowadays authorized in palms

against

R. ferrugineus

. These are Chlorpyri-

fos, Imidacloprid, Phosmetand Thiamethox-

am (MARM, 2011). Some of these pesticides

can be applied as spray on the stipe, inject-

ed into the trunk, or as a drench.

3.2.1.1. Systemic insecticides

Imidacloprid is a chloronicotinyl ni-

troguanidine systemic insecticide that has

both contact and ingestion activity and

works by disrupting the transmission of im-

pulses in the nervous system of insects. It

appears in the MARM list (MARM, 2011) un-

der two different formulation categories,

soluble concentrate (SL) and oil dispersion

(OD), and it can be applied by spraying, in-

jection or irrigation. The formulation, imida-

cloprid SL, was successfully tested by Kaakeh

(2006), in laboratory and semi-field assays

against

R. ferrugineus

. The OD formulation

was recently tested by our group (Dembil-

io

et al

., 2010a; Llácer

et al

., 2012). Preventive

and curative semi-field trials with imidaclo-

prid OD applied by soil injection to

P. canar-

iensis

showed 100 % and 94 % efficacies, re-

spectively (Llácer

et al

., 2012). Furthermore,

preventative treatments had high efficacy