Porphyric Insecticides - Chlorophyll Biosynthesis and Technological Applications - page 418

third instar H . zea larvae in each cell of a 20 cell plastic tray. The tray was sealed
with a glass plate to prevent the escape and/or desiccation of the larvae. For both
species, treatment was replicated three times. After 17 h of dark incubation at room
temperature, the control and treated insects were placed in the growth chamber at
28 C, [about 21.1 mW·cm 2 of white light (metal halide)] under a 14 h light-10 h
dark photoperiod. After 6 h in the light, untreated diet was added to each treatment.
The untreated food was replenished daily. Insect death was monitored over a
6-day period.
Anthonomus grandis were obtained from a colony maintained at the Boll Weevil
Research Laboratory, USDA, SEA, Mississippi State, Mississippi. A single tray of
eggs dispersed on boll weevil diet was received weekly and held at room tempera-
ture until adults emerged. ALA and a modulator were added to liquefied, warm, boll
weevil diet (BioServe Inc.) to a final concentration of 8 mM of ALA and 6 mM
modulator. The mixture was blended for 2 min in a Sorval Omnimixer. Treated and
control diets (the latter lacking ALA and modulators) were poured into 12 ml
plastic molds and allowed to cool down and solidify before storage in a refrigerator
at 4 C. Treatment consisted of placing 15 adults and a block of control or baited
food in a cardboard carton (9 cm h

10 cm diameter) sealed with a plastic lid.
In order to minimize desiccation, a small petri dish (about 2.5 cm in diameter)
containing cotton moistened with water was placed in the bottom of each carton.
The baited food was replenished daily for the duration of the experiment.
Dark incubation, exposure to light and evaluation of mortality was as described
for T . ni and H . zea .
Blattella germanica were obtained from a colony maintained in a Biotronette
Mark III Environmental Chamber at 28 C, and 50 % relative humidity. The
chamber was set for an 8-h light-16-h dark photoperiod. The colony was initiated
from egg cases purchased from Carolina Biological Supply and was maintained on
a diet of dog food and water. Sub-colonies were established weekly in separate
42-cm 27-cm plastic animal cages. Waldbauer's medium was prepared exactly

as described for T . ni . However concentrations of ALA and modulator were raised
to 24 and 16 mM, respectively. Treatment consisted in placing a 12 ml baited block
of food and 15 adults in a cardboard carton sealed with a plastic lid. As was
described for A . grandis , a small petri dish containing moistened cotton was placed
in the bottom of the carton. Control and treated containers were then placed in
darkness at room temperature for 40 h. After dark-incubation the cartons were
placed under subdued light (20-40 ft. candles) for the duration of the experiment.
The baited diet, and water in the cotton dish, were replenished daily. Mortality was
recorded over a 6-day period.
The results of the screening effort are described in Table 18.11 . Thirty six
compounds belonging to ten different chemical families (templates) were effective
(

70 % mortality) against at least one insect species. T . ni was generally more
susceptible than the other species. Structure-activity studies of some of these
compounds are described below.

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