0851996884.pdf

Poor shipping conditions frequently led
to natural enemies arriving either dead or in
poor condition. Difficulties in shipping can
be considerable in countries where crops
with the same target pest are not concen-
trated together and where distances are
large. Most transport is still by truck,
although an increasing quantity is sent by
aircraft. Intercontinental transport problems
are caused less by containerization than by
the sometimes excessively long handling
time at customs, which leads to high mortal-
ity or decrease in fitness. The logistics of
shipments remains one of the main problems
for the commercialization of biological con-
trol. Examples of the different techniques for
collecting, counting, packaging and shipping
of natural enemies are given in Table 12.2.

Release of Natural Enemies

Developmental stage at which organism is

released

Entomophagous insects can be brought into
greenhouses or the field in different stages of
their development (see also Table 12.2):

• eggs (e.g. Chrysoperla);


• larvae or nymphs (e.g. Chrysoperla,
  Phytoseiulus, Amblyseius, Orius);


• pupae or mummies (e.g. Aphidius,
  Trichogramma, Encarsia);


• adults (e.g. Dacnusa, Diglyphus, Orius,
  Phytoseiulus);


• all stages together (e.g. Phytoseiulus,
  Amblyseius).

The stage in which the beneficials are intro-
duced depends mainly on the ease of trans-
port and manipulation in the field, but it is,
of course, also important to release the nat-
ural enemy at a stage when it is most active
at killing the pest. Usually the stage that is
least vulnerable to mechanical handling is
chosen and therefore a non-mobile stage,
often the egg or pupa, is most suited for
transport and release. In situations where it
is difficult, but essential, to distinguish the
natural enemy from the pest, the only solu-
tion is to introduce adults. Adult releases for
parasitoids are advised only when younger

natural-enemy stages cannot be distin-

guished or separated from the pest insect:

the handling and releasing of delicate adult

parasitoids is very difficult and often a large

reduction of fertility is observed compared

with the fertility of parasitoids when

released as immatures. When the natural

enemy is released in one of the developmen-

tal stages that do not prey upon or parasitize

the host, the timing should be such that the

active stage emerges at the right moment of

pest population development. For some nat-

ural enemies the stage of release depends on

pest development: when pest density is low,

release of first-instar C. carneasuffices; when

the infestation with the pest organisms is

already relatively high, it is better to release

second-instar larvae, which have a much

higher predation capacity.

Methods of introduction

Beneficials are introduced into the field in

many ways (Table 12.2). Eggs and pupae are

either distributed over the field on their nor-

mal substrate (leaves of the host plant, e.g.

Chrysoperla and Encarsia) or glued on

paper/cardboard cards (e.g. Encarsia,

Trichogramma). These stages of the natural

enemies can also be collected and put into

containers, which are then brought into the

field (e.g. Trichogramma).

The mobile stages of natural enemies, lar-

vae or nymphs and adults, can be put into

the field in containers from which they

emerge (e.g. many adult parasitoids and

predators) or the grower can distribute nat-

ural enemies in these stages over the crop,

for example by ‘sprinkling’ them on to the

plant. In this case, the use of dispersal mater-

ial (e.g. buckwheat, vermiculite) is often nec-

essary in order to obtain a homogeneous

distribution of small natural enemies. When

natural substrates (e.g. buckwheat or wheat

bran) are used as dispersal materials, they

must be free of pesticides.

Instead of introducing the predator or

parasitoid by itself, one can also introduce a

whole ‘production unit’, e.g. ‘banker-plants’

containing the host insect and its natural

enemy can be brought into a crop. When the

Mass Production of Natural Enemies 187