Semiochemistry of Pentatomoidea 713
have been developed to manage or augment these natural enemies to improve the biological control of
stink bugs. However, for a related coreoid bug species, Alim and Lim (2011) used the aggregation phero-
mone of the soybean pest Riptortus pedestris to trap the adult bugs. They also used the same pheromone
to attract parasitoids, particularly Ooencyrtus nezarae Ishii (Hymenoptera: Encyrtidae), to host egg
masses, that were attached to the trap within screening that allowed parasitoids to freely enter and exit.
The design prevented the entrapment of the parasitoids that were attracted, which can be a problem with
less selective trap designs. Treated plots showed higher egg parasitism, marginally lower bug numbers,
and significantly lower bug damage to soybean pods (Alim and Lim 2011).
15.5.3 Future Directions in Research and Applications
The proper identification of semiochemicals and natural semiochemical blends requires the sequential
application of:
(1) rigorous analytical chemistry to identify all of the components in the volatiles released by the
target species;
(2) stereospecific syntheses to produce libraries of pure compounds for verification of identifica-
tions and for bioassays testing blends of precisely known compositions; and
(3) laboratory and field bioassays to work out the minimum blend of components that is both nec-
essary and sufficient to elicit the same behavioral responses as the natural pheromone.
Because of the cost and difficulty associated with production of multigram or larger quantities of
single isomers of semiochemicals with relatively complex structures, it may not be possible to use pure
isomers for practical applications or even for experimental trials. However, if less expensive mixtures of
isomers are to be used, they must be rigorously tested under field conditions to ensure that the unnatu-
ral isomers and other components present in the mixtures do not antagonize the desired behavioral
responses. For at least some pentatomoids, ratios of pheromone components and even the presence of
multiple unnatural isomers and other components have not proven critical to obtaining good responses
in the field. However, in other cases, pheromones of different species may interfere with each other
(Millar et al. 2010).
The conservation of the basic biosynthetic pathways that produce classes of compounds such as
terpenoids and acetogenins in insects and other organisms may provide opportunities to use engi-
neered organisms to produce pentatomid and other insect semiochemicals. Synthetic chemists already
exploit chiral phytochemicals such as citronellal as building blocks to synthesize semiochemicals.
Genomic and transcriptomic research on stink bugs (i5K Consortium 2013, Sparks et al. 2014) will
help to elucidate the details of semiochemical biosynthesis and also may provide the opportunity to
use genetically transformed organisms such as yeasts or plants as “factories” for pheromone produc-
tion (e.g., Ding et al. 2014). Such transformed plants also could be deployed in the field as possible
dead-end trap crops, as Møldrup et al. (2012) demonstrated with a Nicotiana sp. that was attractive to
ovipositing female diamondback moths (Plutella xylostella (L.)(Lepidoptera: Plutellidae) but lethal
to their offspring.
Regardless of the methods used to produce pentatomoid semiochemicals, to paraphrase Millar (2007,
2014), the devil is in the deployment. Use in large scale, real-world pest management will require easy-
to-use and effective tactics – be it monitoring, mass trapping, attract-and-kill, or trap-cropping – to
deploy pheromones or other semiochemicals for stink bug management. Furthermore, these methods
must be economically competitive with alternative methods that are available for managing a particu-
lar pest in order to have any chance of being adopted for commercial use. Effective, environmentally
friendly pest management takes place in the context of the agroecosystem and its surroundings, with
one being conscious of the diverse and mobile nature of Pentatomoidea and other pest and beneficial
species. Special attention must be paid to the known and powerful attraction of natural enemies to
stink bug semiochemicals that, depending on the exact method of deployment, could have effects rang-
ing from effective augmentation to severe depression of natural enemies that help to control stink bug
populations.