MSc

Mass production techniques, biology, predatory potential and prey
preference of predatory mites and the chrysopid predator, C. earn ea preying
T. ludeni in cowpea and P. latus in chilli were studied. Further, the effect of
pesticides on these bioagents and the role of these predators in the
management of T. ludeni and P. latus were also assessed.
A.longiyfspinosus was identified as the major predator of T. ludeni.
Another species of Amblyseius (unidentified)was the major predator of P
.latus in the field. In the laboratory a macrocheylitid mite, M. merdarius
found in rice bran was also observed as an efficient predator of P. latus.
Techniques were developed to mass multiply both species of
Amblyseius and their hosts, T. ludeni and P. latus in excised leaves of
cowpea. Using this technique, within a week a two fold increase of the
predator was seen. Techniques were developed to multiply another predatory
mite of P. latus, M. merdarius in storage mite, Tyrophagus sp. From 109
rice bran containing Tyrophagus sp., 410 M. merdarius were produced within
a month.
A. longispinosus when fed with pollen of A. auriculiformis and H.
rosa-sinensis , survived in the diet and laid eggs. The larvae that emerged
from the eggs completed development on pollen diet where .as in artificial
diet , though the gravid females survived and laid eggs, the larvae that
emerged from eggs did not reach adulthood. Studies on the biology of
predatory mite!.A.longispinosus and Amblyseius sp preying on T. ludeni and


P. latus respectively revealed that the predators completed its development
within a week.
In order to identify suitable hosts for mass rearing C. carnea, the
predator was reared on different hosts and it was observed that developmental
period was shortest when reared on Corcyra eggs. The fecundity and
longevity was maximum when reared on Corcyra eggs.






An assessment of predatory potential of A. longispinosus revealed that
the predator fed on all stages of T. ludeni. Among the different stages of the
predator ,adult was the most voracious and the most preferred stage of the
prey was eggs. In the case of Amblyseius sp. preying on P. latus the larvae
of the predator consumed all stages of prey mite except adult. The predatory
potential of M. merdarius on P. latus was higher than that of Amblyseius sp.
An assessment of predatory potential of C. carnea revealed that it was
a voracious feeder of A. craccivora as well as T. ludeni, The mean daily
consumption was highest for the third instar larvae in both the cases.
The prey preference of the predators was assessed through multiple
choice and single choice tests. Among the prey tested viz. T. ludeni , P. latus
and Tyrophagus sp, maximum preference was shown towards T. ludeni. The
broad mite, P.latus was also found to be preyed upon by the predator in both
multiple and single choice tests, but total avoidance was shown towards bran
mite Tyrophagus sp.
The prey preference of C. carnea assessed through multiple choice and
single choice tests revealed that A. craccivora was the most preferred prey and
it was followed by T. ludeni. Spiralling white fly was the least preferred one.





Effect of pesticides on predators assessed by exposing them to dry
films of pesticide showed that triazophos 0.05 per cent was the most toxic
chemical against A. longispinosus . In all the chemical pesticides tested none
of the predators survived after 24 hours. Though 10 percent emulsified extract
of A. panieulata, H.suaveolens and neem garlic emulsion 2.5 per cent were
found significantly safer than chemical pesticides, mortality of the predator
was observed in these treatments also indicating that negative impact of
botanical pesticides on natural enemy cannot be overlooked. Similar response
was shown by C. earn ea towards these pesticides, except in dicofol 0.05
percent which imparted lower mortality to the larvae.
Field experiments conducted in cowpea to study the effect of bioagents
and botanicals on T. ludeni, predators and yield showed that, application of
neem oilS percent was the best treatment for management of T. ludeni. This
was followed by application of neem garlic emulsion 2 percent, Fish oil
insecticidal soap 2.5 percent and garlic emulsion 2 percent taking into
consideration the benefit cost ratio.
Comparatively high population of predatory mites was observed in
plants released with A. longispinosus. The population of the predatory mite
increased steadily and within a month the population of the predator and prey
became almost equal. Though the predatory mite could check the population
of T.ludeni, the treatment was uneconomical.
The general predator, C. earnea could not bring spectacular reduction
in population of T. ludeni which may be due to the polyphagous nature of the
predator.

Field experiments conducted on chilli showed pronounced effect of
Amblyseius sp on P. latus from tenth day onwards at both the levels tested.
The release of the predator C carnea @5 and 10 per plant, and fish oil
insecticidal soap 2.5 percent was not effective in checking P. latus. Garlic
emulsion 2 percent gave substantial reduction immediately after first
application. Subsequently, the population increased but with repeated
application significant reduction in population was noticed.
There was no significant difference in the yield of chilli 111 the
different treatments. However based on benefit cost ratio, it is concluded that
application of nee m oil 5 percent, neem garlic emulsion 2 percent, garlic
emulsion 2 percent, fish oil insecticidal soap 2.5 percent and release of
Amblyseius @ 10 and 20 per plant are economically viable for management of
P. latus in chilli .