However, the issue of detecting potential
human pathogens in the final product
requires further investigation.Viability- Greater than 80% viable using a direct
counting method, e.g. counting germi-
nated spores under the microscope (up to
advised product expiry date when kept at
recommended temperature).
Virulence/potency- This aspect of quality control requires fur-
ther study before defined procedures and
limits can be set. In principle, a standard
bioassay appropriate to the agent in ques-
tion should be developed and the perfor-
mance of product batches compared with
a fungal standard at appropriate inter-
vals. Product performance should be
compared with that of the standard and a
tolerance limit set beyond which batches
are retested to confirm loss in efficacy and
discarded on second failure. The difficul-
ties of setting up such a system for micro-
bial inoculants have been discussed in the
section on efficacy above.
Other checks appropriate to specification- Moisture content.
- Quantity of active ingredient per gram
product. - Particle-size distribution as established by
the producer and indicated on the label
(e.g. for stable ultra-low-volume (ULV)
formulations, all particles should be
100 m, 99.9% should be 60 m and
80% 10 m).
Production and Quality Control of
Baculoviruses
Production technologyThe mass production of insect viruses, pri-
marily BV, such as nucleopolyhedroviruses
(NPV) and granuloviruses (GV), for use as
insecticides is currently exclusively by in vivo
propagation, although significant efforts are
under way to make mass production in cell
culture both practicable and cost-effective
(Reid and Weiss, 2000).
A virus is produced in vivoby infecting
larval stages of a susceptible host insect and
then rearing the insects to allow the virus to
multiply and complete its replication, before
harvesting the infected insects in order to
extract the propagated virus. The physical
facilities and systems employed for in vivo
production range from simple low-technol-
ogy methods, involving the use of wild-col-
lected larvae being reared in situor in simple
rearing units (Moscardi, 1999), to automated
mass-production facilities (Guillon, 1997).
High-technology facilities use insect larvae
specially reared in near-sterile conditions
involving capital equipment and a level of
sophistication comparable to anything else-
where in the biotechnology industry.
Low-technology, field propagation of BV
has been regarded as a viable option for
developing countries (Prior, 1989).
Commercial production of Anticarsia gem-
matalisNPV is carried out in Brazil using this
approach (Moscardi, 1999). However, pro-
duction of BV is most commonly a labora-
tory-based production system, using insects
that are reared in a specialized facility or col-
lected from the field, or a mixture of the two.
To inoculate the larvae, these are put on a
substrate of either fresh natural food or arti-
ficial diet that has been sprayed with BV or
has BV incorporated into it. The larvae are
then reared until virus propagation has been
completed or the larvae die of infection. In
some systems larvae are harvested alive just
prior to death (a step that may reduce pro-
ductivity but also reduces bacterial contami-
nation), though more usually they are
harvested when dead (Grzywacz et al., 1997).
The harvested larvae are generally frozen
prior to processing. Larvae are then
processed by macerating in water and fil-
tered to remove integument, mandibles and
other hard parts that might block sprayers.
Most current formulations used in develop-
ing countries are simple suspensions of
unpurified BV, although commercial formu-
lations can be quite sophisticated and may
contain synergists, phagostimulants, struc-254 N.E. Jenkins and D. Grzywacz