0851996884.pdf

Laboratory rearing and field performance of

natural enemies

In view of all these obstacles, one of the first
conclusions is that it would be best to rear
the natural enemies in as natural a situation
as possible, a conclusion that is supported by
a number of researchers with experience in
mass production (see, for example, King and
Morrison, 1984; Bigler, 1989). Another impor-
tant conclusion based on recent information
about learning is that the host habitat and
the host should provide the same cues in
mass rearing as in the field, or, if this is not
possible, the natural enemies should be
exposed to these cues after rearing but before
being released in the field. The problems that
remain, even when rearing is done as natu-
rally as possible, are related to obstacles 3, 4,
5 and 8 in Table 1.4. Anyone starting a mass-
rearing facility should be prepared not only
to overcome these obstacles but also to rec-
ognize the conflicting requirements placed
on natural enemies in a mass-production
programme and during field performance
(Table 1.5).

Development and Implementation of

Quality Control

Natural enemies are often mass-produced
under conditions that are very different from
those found in commercial crops. Because of
these differences, most of the points listed in

Table 1.5 are applicable and must be consid-

ered in quality control programmes. The

development of quality control programmes

for natural-enemy production has been

rather pragmatic. Guidelines have been

developed for more than 30 species of

natural enemies (Chapter 19) and descrip-

tions of the development of various quality

control tests included in these guidelines can

be found in van Lenteren (1996, 1998) and

van Lenteren and Tommasini (1999). The

guidelines developed until now refer to

product-control procedures, not to produc-

tion or process control. They were designed

to be as uniform as possible so that they can

be used in a standardized manner by many

producers, distributors, pest-management

advisory personnel and farmers. These tests

should preferably be carried out by the pro-

ducer after all handling procedures just

before shipment. It is expected that the user

(farmer or grower) will only perform a few

aspects of the quality test, e.g. per cent emer-

gence or number of live adults in the pack-

age. Some tests are to be carried out

frequently by the producer, i.e. on a daily,

weekly or batch-wise basis. Others will be

done less frequently, i.e. on an annual or sea-

sonal basis, or when rearing procedures are

changed. In the near future, large cage tests,

flight tests and field-performance tests will

be added to these guidelines (Chapters 16

and 19). Such tests are needed to show the

relevance of the laboratory measurements.

Laboratory tests are only adequate when a

14 J.C. van Lenteren

Table 1.5.Conflicting requirements concerning performance of natural enemies in a mass-

rearing colony and under field conditions.

Natural-enemy features that are Natural-enemy features that are

valued in mass rearing important for field performance

1.Polyphagy (makes rearing on unnatural Monophagy or oligophagy (more specific

host/prey easier) agents often have a greater pest-reduction

capacity)

2.High parasitism or predation rates at High parasitism or predation rates at low

high pest densities pest densities

3.No strong migration as a result of direct Strong migration as a result of direct or

or indirect interference indirect interference

4.Migration behaviour unnecessary and Migration behaviour essential

unwanted, ability to disperse minimal

5.Associative learning not appreciated Associative learning appreciated