Semiochemicals

The European strategy for the sustainable use of pesticides focused the attention on means for crop protection, alternative to chemical insecticides where, among others, the semiochemical substances find their own place. Given the particularity of the semiochemicals compared to the traditional active substances and to the other biological control means, it became necessary to draw up a guidance document to define the key points of the registration process for their use in agriculture.

Semiochemical substances are produced naturally from vegetable and animal beings and they are functional to signal transmission among individuals of the same species (pheromones) and of different species (allelochemicals). Semiochemicals take part in the interactions among living organisms and their use may alter the usual communication causing, for example, behavioral changes on target organisms.

Pheromones are highly complex mixtures of chemical substances whose composition and concentration strictly depends on the species. Pheromones include, among others, sexual pheromones (coupling regulation), aggregation pheromones (inducing a large number of individuals to be located near the emission source) and the dispersion pheromones (limiting the aggregation events). Allelochemicals are chemical substances released by insects to take direct benefit for themselves, as example, the substances which solicit the departure of the species different from the emitting ones. Allelochemicals are also substances, released from several sources, beneficial for the receiving organisms such as the plants which attract pests. Lastly, allelochemicals are also those substances released for the beneficial of both the emitting and the receiving organism, like the smell issued by flowers which attracts the insects (while they foraging they perform pollination service and allow plants to reproduce).

Semiochemicals are active at very low concentrations, these concentrations are usually comparable to the so named "natural exposure level” so their environmental impact is considered negligible making easier the registration procedure. It’s clear that also the other aspects as the identity, the chemical-physical properties and the efficacy of the plant protection products containing semiochemicals should be approached in a different way. For the efficacy, it should be considered the decrease in crop damages rather than the target organism mortality and the higher performance variability compared to the traditional chemical substances. The future guidance document will surely help to clarify all these specific aspects.