Monitoring Patch Expansion Amends to Evaluate the Effects of Non-Chemical Control on the Creeping Perennial Cirsium arvense (L.) Scop. in a Spring Wheat Crop

Abstract

The creeping perennial weed species Cirsium arvense (L.) Scop. occurs in patches. Expanding creeping roots allow these patches to increase their covered area. This characteristic has rarely been addressed when investigating the effects of control options in arable fields. We designed a three-year field experiment (2019–2021) in north-eastern Germany, accounting for existing patch patterns. The experimental setup included an untreated control, a competition treatment (cover crop, CC), two disturbance treatments by mouldboard ploughing (PL), root cutting (RC), and four combined applications (RC + CC, PL + CC, PL + RC, PL + RC + CC). Root cutting was performed by a prototype tillage machine produced by “Kverneland”. Plots were defined by the species growth pattern and mapped by GPS and UAV. The experiment investigates the thistle response variables: “Expansion”, “Density”, “Coverage”, and “Height”. Treatments including disturbance by ploughing (PL, PL + CC, PL + RC, PL + RC + CC) reduced “Density” by the factor 0.15 and “Expansion” by 0.25, while those without ploughing (CC, RC, RC + CC) only reduced “Density” by the factor 0.68 and “Expansion” by 0.71. Adding root cuttings or cover crops did not further increase the reduction effect of ploughing. Treatments with competition by cover crops impacted “Expansion” more clearly than “Density”. When cover crops were combined with root cutting (RC + CC), “Expansion” was almost additively reduced, resulting in a reduction comparable to that of ploughing. The “Height” of the shoots was significantly reduced in four treatments (PL, RC + CC, PL + RC, PL + RC + CC), while “Coverage” did not change significantly. UAV patch monitoring proved to be accurate enough for thistle “Expansion” but not for thistle “Density” within the patch. The results of this study demand innovative research when controlling patch-forming creeping perennial weeds. The need for patches will limit small-scale experimental set ups.