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cate the problem. Furthermore, results from
contamination checks throughout the course
of production can be used to show that
harmful pathogens have not entered the sys-
tem (see section on safety). A simple method
for contamination monitoring is to take sam-
ples of the medium/substrate (pre- and
postinoculation) and the inoculum itself and
to plate each sample on generalist agar
media, such as nutrient agar and Sabouraud
dextrose agar (SDA). These check plates
should be incubated (at approximately 25°C)
for 2–3 days and observed for the appear-
ance of bacterial and fungal contaminants,
respectively. Should contaminants appear on
any of the plates, the source may be identi-
fied by a process of elimination so that reme-
dial action can be taken. If contaminants
have entered the system, the batch should be
discarded. Clearing contaminated batches
soon after discovery reduces the risk of intro-
ducing high levels of contamination into the
production environment, which may persist
to affect subsequent batches.

Safety

The intrinsic safety of any microbial control
agent can be evaluated by carrying out the
appropriate mammalian and ecotoxicologi-
cal safety tests. These tests tend to be expen-
sive, but are a requirement of registration of
microbial agents in countries where registra-
tion of biological agents is enforced
(McClintock, 1999; Neal and Newton, 1999).
Use of microbial agents for biological control
cannot simply be assumed to be safe and
some degree of testing should be employed
in all cases.
Safety issues also arise in respect of micro-
bial contamination of the final product.
Standards for biological purity need to be set;
these should include a thorough assessment
of the production process to establish that
human pathogens are unlikely to enter the
system under normal operating procedures.
In addition to the standard contamination-
monitoring checks described in the previous
section, these precautions should be sufficient
evidence that harmful microorganisms are
unlikely to be present in the product.

Levels of contamination in unformulated

products can be quantified using a simple

dilution series plated on to a generalist agar

medium (Jenkins et al., 1998). In order to set

an acceptable level of contaminating organ-

isms, baseline levels of contaminants enter-

ing the system during downstream

processing and during formulation should

be established. Again, in-process contamina-

tion-monitoring records can be used as evi-

dence to show that contaminants have not

multiplied during the fermentation process.

The final aspect of product safety relates

to the genetic and phenotypic stability of

the organism being produced. Provided

that master cultures have been carefully

maintained, there should be no cause for

concern. Phenotypic stability should be

monitored during routine laboratory

manipulation of the isolate, so laboratory

personnel should become familiar with the

typical characteristics of the isolate and

should report any changes observed outside

the normal growing characteristics. If

doubts arise about fungal efficacy, checks

using baseline data from molecular charac-

terization should be carried out to ensure

that genetic change is not detectable,

although the sensitivity of many of these

techniques to detect small genetic changes

can be limited. Any changes in phenotypic

characteristics indicate a need to draw on

fresh material from long-term storage.

Efficacy

Efficacy is the most critical factor in ensuring

product performance and long-term accep-

tance. If a product has high viability and vir-

ulence/pathogenicity, the chances of field

efficacy are maximized. However, under-

standing the ecology and the effect of envi-

ronmental factors on the fungus is essential

to ensure reliable field performance of even

the highest-quality product.

Viability is easily measured in fungi; most

laboratories working with these agents have

an established method for assessing product

viability. For conidial products, a relatively

quick, and probably the most accurate,

method is to determine the percentage ger-

Quality Control of Fungal and Viral Biocontrol Agents 251