0851996884.pdf

control maintains consistency of production
output. Process control tells how the manu-
facturing processes are performing. These
elements of quality control are seldom
applied to arthropod mass-rearing pro-
grammes.
Mass rearing, usually done by small pri-
vate companies, is developed by trial and
error. Knowledge of mass-rearing techniques
is often limited in such organizations and the
time or money for extensive experimentation
is lacking. If success is to be obtained, quality
control of the end-product is essential, but
producers are generally more than happy if
they can meet deadlines for providing cer-
tain numbers of natural enemies. Although
most experts on quality control have
adopted tools and procedures needed to reg-
ulate the processes of arthropod production
so that product quality can be assured
(Chambers and Ashley, 1984), such tools and
procedures are not yet widely used by the
many small companies that compose 95% of
all producers. The main reason most of the
small companies do not develop and use
such product, process and production con-
trols is that they lack the extra financial
resources that are required. This limitation
can be a serious constraint for starting pro-
ducers.
Quality control seems to be developed
best when mass rearing is done in large
governmentally supported units. Chambers
and Ashley (1984) state that entomologists

often concentrate too much on production

control, while they are at best only partially

controlling production processes and

products. Quality control is frequently, but

wrongly, seen as an alarm and inspection

system that oversees and intimidates

production personnel.

Difficulties Encountered When

Developing Quality Control

Obstacles in mass rearing of arthropods

Artificial selection forces in mass rearing

may lead to problems related to performance

of natural enemies in the field if rearing con-

ditions differ strongly from the situation in

which natural enemies are to be released

(Table 1.4). For example, if temperature in

the mass-rearing facility differs considerably

from the field situation, synchronization

problems between natural enemy and pest

insect can be expected. Also, rearing on non-

target hosts or host plants (Chapter 9) can

create problems with natural-enemy quality

or recognition by natural enemies of essen-

tial semiochemicals.

Any of the obstacles mentioned in Table

1.4 may be encountered in mass-production

programmes. One of the main obstacles to

economic success seems to be the difficulty

to produce qualitatively good natural ene-

mies at a low price. But, with a strongly

Need for Quality Control of Biocontrol Agents 11

Table 1.4.Obstacles in mass rearing of natural enemies.

1.Production of good-quality natural enemies at low costs may be difficult (Beirne, 1974;

Chapters 11 and 12)

2.Artificial diets are often not available for natural enemies (Beirne, 1974; Chapter 9)

3. Techniques that prevent selection pressures leading to genetic deterioration are usually
   lacking (Mackauer, 1972, 1976; Chapters 6 and 7)
   4.Cannibalism by predators or superparasitism by parasitoids generally occurs (Chapter

9. 5.Rearing on unnatural hosts/prey or under unnatural conditions may cause behavioural
   changes in preimaginal and imaginal conditioning (Morrison and King, 1977; Vet et al.,
   1990; Chapters 3, 4 and 9)
   6.Reduced vigour can occur when natural enemies are reared on unnatural hosts
   (Morrison and King, 1977; Chapter 9)
   7.Reduced vigour can also be the result when natural enemies are reared on hosts that
   are reared on an unnatural host diet (Morrison and King, 1977; Chapter 9)
   8.Contamination of the rearing by pathogens may occur (Bartlett, 1984b; Chapter 10)