Page 14 - Volume 2,Issue 2, July 2009

Albano

et al.

58

ies have shown the importance of pollinat-

ing insects for the improvement of strawber-

ry crop production, in terms of fruit quality

(size, weight and shape) (1, 4, 8, 9, 24).

In Québec, the CRAAQ (Centre de Réfer-

ence en Agriculture et Agroalimentaire du

Québec) recommends strawberry grow-

ers to apply the fungicide chlorothalonil

at

the vegetation and two other sprays of oth-

er registered fungicides for grey mould dur-

ing flowering. As a consequence, only those

flowers that are open during that moment

become protected. After flowering, the fun-

gicide labels recommend several applica-

tions at 7- to 10-day intervals or at 5-day in-

tervals if conditions are favourable for the

spread of the disease. Although some stud-

ies point out the negative consequences of

some fungicides on strawberry pollen ger-

mination (13), these products are most of-

ten used without the knowledge of this

fact. Furthermore, the repulsive behaviour

of those fungicides to pollinators has appar-

ently never been examined. Another identi-

fied problem is the development of resistant

forms of

B. cinerea

to some fungicides used

in strawberry plantations (12).

The present study is part of a wid-

er framework that aims at reducing the

amount of fungicides used to fight the grey

mould fungus, bringing down production

costs and increasing the treatment efficacy

by dispersing selected fungicides that are

non-toxic for pollen and non-repulsive for

pollinators, such as honey bees and bum-

ble bees. This project is pioneering in the

sense that it included the testing of the dis-

persion of a biofungicide and synthetic fun-

gicides in its global scope, using dispensers

that are adapted either to the hives of honey

bees or those of bumble bees. Previous tests

were performed in order to select the non-

toxic and non-repulsive fungicides both for

strawberry pollen and pollinators, respec-

tively. Among these fungicides the biofungi-

cide Rootshield®, a commercial formulation

of the antagonist

Trichoderma harzianum

Ri-

fai, and several synthetic fungicides were se-

lected (10).

T. harzianum

is an antagonistic fungus

of a wide range of pathogens including

B.

cinerea

that is responsible for grey mould

on strawberry (3, 15). There is a diversity of

mechanisms available to

Trichoderma

spp.

for pathogen suppression, including (i) the

production of

antifungal metabolites, (ii)

mycoparasitism, and (iii) competition with

the pathogen for nutrients and space. These

features make this fungus attractive as a bio-

control agent (26).

The scope of the present study includ-

ed the need to demonstrate the efficiency

of the dispersion of fungicides by pollinators

that pass through the dispenser to the flow-

ers that they visited. Because this task is easi-

er and cheaper to achieve using conidia of

T.

harzianum

that can be grown on agar medi-

um, than synthetic fungicides which require

costly analysis, this validationwas performed

only with the Rootshield® biofungicide.

The main purpose of this study - which

intends to satisfy one of the tasks of the wid-

er project that was mentioned above – was

therefore to determine the effectiveness of

honey bees and bumble bees in transmit-

ting the powder formulation of

T. harzianum

from hives-mounted dispensers containing

the biofungicide Rootshield® to flowers in

open field and greenhouse assays.

Materials and Methods

1. Dispensers

The construction of the first dispenser

model for honey bees was based on works

by Gross

et al.

(16) and Kovach

et al.

(17).

Modifications were made to this model by

Emile Houle. After several tests, the original

model was gradually improved before a final

model, now called the Houle-dispenser, was

attained (Figure 1). This later model is entire-

ly made of folded sheets, providing the po-

tential for its fast and easy construction. Fur-

thermore, several holes were incorporated

on the sides in order to avoid internal wa-

ter condensation. The new design allows

the dispenser to be adjusted to the beehive

entry without difficulty. The dispenser has a

system that makes bee entries and exits in-