Diseases and Management of Crops under Protected Cultivation

(Diseases and Management of Crops under Protected Cultivation)
slow pace in the beigning but offers longer term management than the more traditional technology
areas and the cost for control is lower relative to more traditional control procedures. Typically,
biocontrol agents are released in relatively low numbers for only a short time in the beginning of
the program unlike more traditional methods of control which are used continually over many
years.
To ensure the success of any biological control programme it should be be used
preventatively when the pest populations are still low. A regular monitoring programme is needed
for early detection of pest. In case of spidermites they should be introduced at hotspots as soon as
the pest is detected .Delaying the introduction is a major factor in programme failure.
Natural enemies of insects and mites:-
From the economic standpoint, an effective natural enemy is the one which is capable of
regulating the population density of the pest, maintaining it below the economic damage level
established for a given crop. In general the natural enemy should present the following
characteristics; it should comply with environmental physical conditions changes, should be
specific to the host; should have a high searching capacity, especially at low densities of host,
should have seasonal synchronization with host and should be able to survive in absence of host.
In case of pest insect and mite control, the major natural enemies are the insects, known
as entomophaghus. The entomophaghus group is represented by predators and parasitoids.
Parasitoids: - are insects that develop on or within the host. They require only one host to
complete their life cycle from egg to adult and kill the host when their cycle is completed. The
parasitoids are the most effective natural enemies for biological control. Parasitoids are found in
different insect orders however in Diptera and especially in Hymenoptera this group has become
abundant. The great host diversity in different habitats makes the hymenoptera parasitoids one of
the most important groups for biological control.
Predators: - A predator is an organism that lives by preying on other organisms and destroys it for
its own gain. Several insects and mites are predators during their whole lifecycle. A predator
usually hunts the most abundant insects that they can find in any environment.Phytoseiulus
persimilis and Amblyseius californicus belonging to family Phytoseiidae are two important
predatory mites used for the control of spidermites,besides this a predatory bug Macrolopus
caliginosus is also an efficient biocontrol agent
Natural enemy/Predatory Mites, Phytoseiulus persimilis
This mite is a natural predator of spidermites and was one of the
first greenhouse biological control agents available commercially. It
is red shiny pear shaped mite with long legs, slightly larger than its
prey and moves very fast. It is an indigenous species of
Mediterranean region which was accidentally introduced from Chile.
Photo by Naved Sabir
The eggs of P. persimilis are oval and orange in colour. Larvae and nymphs are pale and
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