0851996884.pdf

dry conditions. Applying equations and
experimental protocols used for estimating
seed longevity (Ellis, 1988; Roberts and Ellis,
1989; Dickie et al., 1990), it is possible to
define constants for conidia of individual
species of mitosporic fungi and thus predict
the longevity of fungal products in storage
(Hong et al., 1997, 1998). When packaged in
hermetically sealed, foil-lined sachets at low
moisture content (5%), conidia of M. aniso-
pliaevar. acridumcan be stored for up to a
year at 30°C and 6 years under refrigera-
tion. Further, it is possible to predict shelf-
life under more practical fluctuating
temperature conditions, using a modification
of the predictive model (Hong et al., 1999).
Recently, these models have been applied to
data for conidia of B. bassiana(Hong et al.,
2002), showing that, although conidia of dif-
ferent fungal species can vary in their
absolute longevity (M. anisopliaevar. acridum
has greater conidial longevity than B.
bassiana), the relative effect of moisture con-
tent and temperature on the lifespan of coni-
dia is similar between species. Thus, it is
possible to harness these models to give
clear estimates of the likely shelf-life of a dry
conidial product when stored under a range
of conditions. For other product types (blas-
tospores, dried mycelium, aqueous formula-
tions, etc.) no such models exist, but data
obtained during optimization of the harvest-
ing or drying process can and should be
used to clearly indicate the expected shelf-
life of the product.
Most important with regard to shelf-life
is that each batch of product should per-
form similarly to the next during long-term
storage. To ensure that this is the case,
nutritional conditions, method of down-
stream processing, final moisture content of
the product and packaging should be stan-
dardized. Provided these parameters are
consistent for all batches, storage tempera-
ture becomes the primary factor in deter-
mining likely shelf-life (Hong et al., 2000).
As much information as possible on the
effects of storage temperature on shelf-life
should be given on the packet. Clear
labelling can help to take the mystery out of
the use of mycopesticides and help to
increase user confidence.

Specifications

Specifications over and above the standards

laid out above include information such as

the amount of active ingredient (ai) per gram

or millilitre of product (e.g. conidia g^1 or

ml^1 formulation). Further specifications

might include particle-size spectrum, which

is critical for many application techniques,

and other physical properties related to the

formulation, such as suspensibility, wettabil-

ity, flowability and emulsion stability.

Recommended minimum quality control for

fungi

Careful culture maintenance and preservation

• Accurate identification and characteriza-
  tion of the fungal strain by a recognized
  taxonomist.


• Use of established long-term storage
  methods for the isolate obtained from the
  original isolation.


• Use of single-spore (ss) isolation to reduce
  genetic drift.


• For production, use of stock culture mate-
  rial bred from the ss isolation and kept in
  long-term storage.

In-process contamination monitoring

• Take subsamples at critical stages through-
  out the course of production for the detec-
  tion of contaminants entering the system.

Total contaminating-organism count

(assuming prior screens for human pathogens

are clear)

• Measured by dilution plating on to gener-
  alist media. The acceptable level of conta-
  mination will be product-specific, but
  should always be backed up with results
  of in-process contamination monitoring to
  show that contaminants have not entered
  during the production process and have
  not multiplied with the production fungus.
  Under ideal conditions, a typical limit for
  an unformulated fungal product could be
  as low as 1 × 106 cfu g^1 in pure conidia
  powder containing 5 × 1010 conidia g^1.

Quality Control of Fungal and Viral Biocontrol Agents 253