Page 20 - Volume 2,Issue 2, July 2009

Albano

et al.

64

Advantages and limitations of dispens-

ers

The Houle-dispensers for honey bees,

when loaded with

T. harzianum

and used as

in this study, had some of the requisites that

distinguish efficient dispensers: (i) by avoid-

ing the transfer of inoculum to the hive’s in-

terior by having separate entrances and ex-

its, (ii) by assuring that insects get dusted

while exiting the hives-mounted dispensers,

and (iii) by not having negative impacts on

the health of honey bee colonies. This latter

point was shown by an extensive study on

honey bee colony development and honey

production in relation to the use of the in-

oculum loaded dispensers placed on hives

during the three week strawberry flowering

period (10). Nevertheless, in an open field

situation some technical problems were de-

tected after a long-term use of the dispens-

er for honey bees. The main limitation found

was related to the maintenance of the bio-

control agent in good condition for its dis-

persal. According to our observations, some

water condensation in the interior of the dis-

pensers was observed, which resulted in al-

terations in the properties of the biocontrol

agent (cluster formation) that obviously af-

fected the efficacy of its dispersion by pol-

linators. What happens is that the humidi-

ty formed inside the hive during the night

turns out to be more difficult to evaporate

due to the presence of the dispenser in the

hive entrance. This problem was partial-

ly solved by drilling holes in the sidewalls

of the dispensers. Other practical recom-

mendations to minimize this problem are

to place the hives in early morning sun lo-

cations and to replace the biofungicide on a

daily basis after cleaning the dispensers.

Regarding Houle-dispensers for bum-

ble bees, the most important advantage

was to have entries and exits independent

from each other. This was an important im-

provement when compared with previous

dispensers (17) allowing less impact on hive

tunnel traffic and avoiding the transfer of in-

oculum into the hive. As in the Houle-dis-

penser for honey bees, the major limitation

detected was related to the maintenance of

the biocontrol agent in good condition for

its dispersal. In this case, the main problem

was bumble bees letting their liquid excre-

ments over the powder formulation, which

causes it to be no longer available for dis-

persion. Maccagnani

et al.

(21) identified the

same problem with their SSP-dispenser.

Further investigation should be directed

towards increasing the dispensers’ efficien-

cy, which necessarily implies the optimis-

ation of the existing models and eventual-

ly the creation of new models. As such, we

agree with Bilu

et al.

(5) that stressed the

need for comparing different kinds of dis-

pensers, using standard methodologies in

order to establish an adequate dataset for

correctly assessing the technique for the

dispersion of biocontrol agents by bees.

The authors are grateful to Les Fraises de l’Île

d’Orléans inc., especially Louis Gauthier for

his assistance during all the fieldwork, and to

other producers for the use of their strawber-

ry fields, Misters Plante, Gosselin and Pouliot.

We are also grateful to other project members

such as Éric Cadorette and Jocelyn Boulianne

for their help on the laboratory and field work,

respectively. Financial support for this research

was provided by Fundação para a Ciência e a

Tecnologia (co-financed by POCI 2010 and the

European Social Fund) with a doctoral grant

to S. Albano and by le Conseil pour le dével-

oppement de l’agriculture du Québec (CDAQ).

We dedicate this work to Pierre Thibodeau,

who passed away before its publication.

Literature Cited

Albano, S., de Oliveira, D., Salvado, E., Quares-

1.

ma, M., Borges, P. and Mexia, A. 2005. Avaliação

da importância dos insectos polinizadores na

melhoria da produção na cultura do morango.

Actas da Associação Portuguesa de Horticultu-

ra, II Colóquio Nacional da Produção de Moran-

go e Pequenos Frutos, São Teotónio: 121-129.

Al-mazra’awi, M.S., Shipp, L., Broadbent, B. and

2.

Kevan, P. 2006. Biological control of

Lygus line-

olaris

(Hemiptera: Miridae) and

Frankliniella oc-

cidentalis

(Thysanoptera: Thripidae) by

Bom-

bus impatiens

(Hymenoptera: Apidae) vectored