Challenges Inherent in Controlling Prickly Pear Species; a Global Review of the Properties of Opuntia stricta, Opuntia ficus-indica and Opuntia monacantha

Abstract

Opuntia species (prickly pear) were deliberately introduced to many countries around the world for fruit, cochineal dye production, living fencing or as ornamentals. They are now some of the world's most significant weeds, particularly in regions with warm and or dry climates, as they pose threats to economic and environmental assets. In addition, they can cause considerable health issues for humans and animals. Opuntia spp. have prolific reproduction abilities, being able to reproduce both vegetatively and by seed. They have generalist pollination and dispersal requirements, which promotes their establishment and spread. Opuntia stricta, O. monacantha and O. ficus-indica are the most globally widespread of the Opuntia spp. In many countries, biological control agents, particularly the cactus moth (Cactoblastis cactorum) and various cochineal insects from the Dactylopius genus, have successfully reduced land-scape scale populations. On a smaller scale, controlling these weeds by either injecting or spraying the cladodes with herbicides can provide effective control. Care must be taken during herbicide treatments as any untreated areas will regenerate. While biological control is the most cost and time effective control method for landscape-scale infestations, further research into the combined efficacy of herbicides, fire, grubbing and pre-burial techniques would be beneficial for land managers to control small-scale and establishing populations. It would also be useful to have greater knowledge of the potential seedbank longevity and seed ecology of these species so that integrated management strategies can be developed to not only deal with initial populations but also the subsequent seedling regrowth.

Keywords: Opuntia ficus-indica; Opuntia monacantha; Opuntia stricta; biological control; invasive Opuntia species; prickly pear management; weed managemnet.

Figure 1

Photographs of Opuntia stricta. (a) depicts an image of the cladodes and growth form; (b) shows a close up of the fruit; and (c) is an image of the flower. Photographs provided by the Queensland Government (personal communication, 5 October 2022).

Figure 2

Photographs of Opuntia monacantha. (a) shows the growth form of a single plant; (b) shows a close up of the flowers; (c) shows a close up of a cladode with fruit and spines; and (d) highlights the narrow cladode attachment point. Photographs provided by the Queensland Government (photos b and d, personal communication, 5 October 2022) and Sheldon Navie (photos a and c, personal communication, 11 October 2022).

Figure 3

Photographs of the cladodes with emerging flowers (a), and fruit (b), as well as the growth form of Opuntia ficus-indica (c). Photographs provided by Queensland Government (photo c, personal communication, 5 October 2022) and Sheldon Navie (photos a and b, personal communication, 11 October 2022).

Figure 4

A photograph of the cochineal insect feeding on O. ficus-indica cladodes. The white, waxy coating produced by Dactylopius spp. is evident. Photograph provided by Sheldon Navie (personal communication, 11 October 2022).