To investigate the potential of both native and non-native Solanum species as PCN trap crops

Effectiveness of control of PCN was assessed by calculating the mean initial (Pi) and final (Pf) number of PCN eggs/gram soil in pot trials. In year one, seven potential trap crops (2 samples of black nightshade, 2 samples of sticky nightshade, thorn-apple, woody nightshade, and a Solanum species (species name yet to be confirmed and referred to as “unspecified Solanum spp” throughout the project/ report) were compared.  In year two this was reduced to black nightshade, sticky nightshade and the unspecified Solanum spp. In the final year only black nightshade and the unspecified Solanum spp were studied.

Over three years of the project black nightshade and the unspecified Solanum spp were most effective at controlling PCN. The optimum period for sowing trap crops appeared to be in the period from late April to mid-July. In the experimental set-up used, later sowings (August and September) were prone to failure. 

It was not possible to demonstrate differences in PCN control based on either one or six plants per pot.  The effect of the higher plant population was to reduce dry weight per plant as a result of plant-to-plant competition.  Field work is required to determine the optimum established plant population for maximum PCN reduction.

Soil type had a significant effect on the phytotoxicity of the herbicides tested.  Both black nightshade and the unspecified Solanum spp were killed to a greater extent when grown in the loamy sand and sandy loam soils than in the silt loam.

In practical terms, although black nightshade was most effective at reducing PCN levels it may be that other species are better candidate trap crops as their establishment is more reliable and their canopies are more vigorous and give better weed suppression. 

All the experiments in the project were done in pots and further studies at the field scale are needed. The risks associated with deployment of the novel trap crops, such as their potential as hosts for potato pests and diseases, also need to be evaluated.