HIPV emission is widespread in nature and lack of response
to herbivory may be rare in wild plants [16]. It has
been shown [17] that HIPV-silenced Nicotiana attenuata
plants had reduced fitness due to increased herbivory by
Manduca spp. resulting in a twofold decrease in bud and
flower production. Furthermore, Zakir et al. [18] found a
significant reduction in oviposition by Spodoptera littoralis
on undamaged plants adjacent to herbivore-damaged cotton plants under both field and laboratory conditions. Heil
[9] discussed use of HIPVs as tools in biocontrol and
challenges faced in their application in agriculture. These
include a lack of field studies, possible slower growth but
increased damage by parasitised insects, attraction of
hyperparasitoids or herbivores, lack of reward for attracted
natural enemies and insufficient levels of natural enemies
in the environment. These are important points that require
further study, especially in outdoor field conditions
and possible adjustment of agronomic practices, for example, conservation biocontrol to boost natural enemy populations and provide a suitable environmental context for
the crops that ‘cry for help’.