Preliminary Evidence of Foliar Spray Effectiveness Against the Invasive Cactus Cylindropuntia pallida (Rose), F.M. Knuth in South Africa

Using the biometric differences (i.e., plant physical characteristics) between the C. pallida populations previously treated with herbicide and those of the untreated populations, we tested the prediction that herbicidal treatment suppresses C. pallida plant growth in South Africa, where invasive cacti display high resilience to herbicide treatment. We also determined whether the surrounding communities knew of C. pallida invasion and whether they experienced any negative impacts. Overall, biometric analyses supported the study’s prediction because C. pallida plant height in treated populations was significantly lower than in untreated populations and before treatment. The average plant height of populations not treated with herbicide (i.e., experimental control) and those measured before treatment were not significantly different, but both were significantly greater than the heights of populations previously treated with herbicide. Similarly, the mean number of fruits, cladodes and juveniles per C. pallida plant treated with herbicide was significantly lower than in the untreated populations. We found a significant positive correlation between all measured parameters and C. pallida plant height. Out of 39 participants, 16 (41.0%) confirmed C. pallida presence in and around their properties, with 21 (53.9%) participants having experienced negative impacts directly and indirectly through fatal injuries on pets and livestock in the sampled sites. We confirmed the effectiveness of herbicide in suppressing the invasion of C. pallida and that people experience substantial negative impacts in areas where the species has established.