Extended Summaries: IUPAC Conference
but has additional wheat tolerance. Penta¯uoroethyl
reduces activity notably.
Semiochemical modulation of oviposition
behaviour in the gregarious desert locust
Schistocerca gregaria
3.1.3 Combining ¯uorinated benzenesulfonamide with di-
¯uoromethyltriazine (Fig 8)
Baldwyn Torto,* Yousif OH Assad, Peter GN Njagi and
Ahmed Hassanali
International Centre of Insect Physiology and Ecology, PO Box
After variation of the heterocyclic moiety from
tri¯uoromethylpyrimidine to di¯uoromethyltriazine,
tri¯uoromethyl as side chain on the benzenesulfon-
amide again leads to more active compounds than
di¯uoromethyl. Both show good wheat selectivity.
30772, Nairobi, Kenya
Abstract: Bioassays have shown that sand freshly
contaminated by ovipositing females of the gregar-
ious desert locust Schistocerca gregaria (Forskal) is
more effective in inducing further oviposition from
conspeci®cs than contaminated sand stored for
three or six months, which contrasts with results
obtained previously with Locusta migratoria
(Reiche & Farmaire). The activity of contaminated
sand correlated with the levels of three unsaturated
aliphatic ketones, (Z)-6-octen-2-one, (E,E)-3,5-
octadien-2-one and its geometric isomer (E,Z)-3,5-
octadien-2-one present in the volatile emissions
from the sand.
3.1.4 In¯uence of new triazine substituents: CCIF2 vs CF3
(Fig 9)
However, chlorodi¯uoromethyl- and tri¯uoromethyl-
triazine are different, in that each combines better with
an aromatic ester than with the ¯uorinated side chain.
Selectivity in wheat is common to all.
Keywords: Schistocerca gregaria; (Z)-6-octen-2-one;
(E,E)-3,5-octadien-2-one; (E,Z)-3,5-octadien-2-one;
oviposition; seimiochemical; locust
4
CONCLUSION
Side-chain-¯uorinated pyrimidines, triazines and
benzenesulfonamides are ideal building blocks for
the research chemist. They offer chemical and
biological ¯exibility for new sulfonylureas as post-
emergence herbicides. Selectivity in wheat and cotton
is observed, best herbicidal activity being obtained up
to the three- to four-leaf stage of the weeds. Selected
compounds are undergoing broad ®eld tests in wheat.
Gregarious females of the desert locust Schistocerca
gregaria (Forskal) and Locusta migratoria (Reiche &
Farmaire) produce pheromones during oviposition
which attract conspeci®cs to lay their eggpods at
common sites.1±4 In L migratoria, repeated layings by
females increase the preference of the sand for further
oviposition.3,4 Of the two locust species, pheromone
identi®cation has been carried out for S gregaria in
recent work from our laboratory. Two aromatic
compounds, acetophenone and veratrole were identi-
®ed from the volatiles emitted by the froth plug of the
eggpod as oviposition pheromone components.5,6 In
the present study, the oviposition response of females
of S gregaria to sand in which conspeci®cs had laid
previously, but without the froth or eggs, was
compared to that of clean sand. On average, about
75% of the eggpods deposited by females were laid
into moist sand contaminated by conspeci®cs com-
pared to 25% into clean moist sand. However, much
of the activity of contaminated sand was lost after long
storage at room temperature, dropping to 56% after
three months, with a total loss of activity after six
months. These results contrast with those obtained
previously for L migratoria for which the activity of
contaminated sand can last for as long as six months.4
Gas chromatographic-electroantennographic detec-
tion (GC-EAD) analysis revealed the presence of
three candidate oviposition pheromone components in
the volatiles of freshly contaminated sand. These were
identi®ed by GC-MS as (Z)-6-octen-2-one, (E,E)-3,5-
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* Correspondence to: Baldwyn Torto, International Centre of Insect
Physiology and Ecology, PO Box 30772, Nairobi, Kenya
E-mail: btorto@icipe.org
Contract/grant sponsor: IFAD
(Received 25 June 1998; accepted 16 December 1998)
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Pestic Sci 55:566±614 (1999)