Exceptional successes with biological control of invasive cacti in the north-western grasslands

Helmuth Zimmermann & Hildegard Klein

Helmuth Zimmermann & Associates (Central) Plant Protection Research Institute, ARC, Pretoria Contents

• Introduction to invasive alien plants in the north-western grasslands • The invasive cacti • History of control • Recent biological control successes  Cochineal biotypes and the new association effect Before-and-after results of using new biotypes of Dactylopius species • Dealing with new emerging cactus invaders • Conclusion Invasive alien plants in the north-western grasslands

Western North West Province Northern Cape North-east Western Cape North-west Free State North-western grasslands Transformer invasive alien plants in the north-western grasslands

• Cactus species •Prosopis species and hybrids •Tamarix species The main invaders Prosopis hybrids Tamarix spp The main invaders: the Cacti The cactus species

Important species Opuntia Chollas Others Opuntia ficus-indica Cylindropuntia fulgida var. fulgida Tephrocactus auriculata Opuntia stricta Cylindropuntia fulgida var. mamillata Trichocereus schickendantzii Opuntia humifusa Cylindropuntia imbricata Harrisia martinii Opuntia aurantiaca Cylindropuntia pallida Opuntia engelmannii Cylindropuntia leptocaulis Emerging species Cylindropuntia spinosior Opuntia elata Trichocereus pachanoi Harrisia tortuosa The main invaders: cactus species

Cylindropuntia pallida Cylindropuntia fulgida var. fulgida The main invaders: cactus species

Cylindropuntia fulgida var. mamillata Cylindropuntia imbricata The main invaders: cactus species

Opuntia engelmannii Opuntia stricta The main invaders: cactus species

Opuntia humifusa Opuntia aurantiaca Chemical control: effective but VERY costly and a serious hazard to the environment. Two Biological Control Agents 1. Cactoblastis cactorum. This biological control agent is important in the biocontrol of Opuntia species. It is effective against small plants. It played a major role in the biological control of prickly pear: Opuntia ficus indica. Biological control agents: the Cochineals 2. Dactylopius opuntiae • Biotype “ficus-indica” Biotypes and the NEW ASSOCIATION effect This entails using biocontrol agents that have • Biotype “stricta” not shared a recent history of intensive 3. Dactylopius tomentosa interaction in evolutionary time with their • Biotype “imbricata” host. • Biotype “cholla” 4. Dactylopius austrinus

The case of Dactylopius tomentosa and the biocontrol of Cylindropuntia fulgida

Dactylopius tomentosus collected from Cylindropuntia fulgida in its native range in Mexico was ineffective. The case of Dactylopius tomentosa and the biocontrol of Cylindropuntia fulgida (cont.)

…. but the same cochineal species from a related but geographically separated cactus species achieved spectacular control of C. fulgida = New Association effect.

Dactylopius tomentosus (“cholla” biotype) on Cylindropuntia cholla in Baja California (Mexico) The results……… (Chollas) Before (2013)

Dactylopius tomentosus “cholla” biotype

Boxing glove cholla After 2015 Monitoring the decline of the boxing glove population Monitoring the effect of biocontrol : Results A. Groblershoop (Grassland)

300 3500 450

400 3000 250

350 2500 300 200

2000 250 150 Feb.2015 200 1500

150 100 July.2015 1000 100 50 Dec.2015 500 50

0 0 0 Number of plants in 200 m² m² 200 in plants of Number Isolated Medium Large plants cladodes Size Plants and small plants 90% decrease 99% decrease 86% decrease Further results …

Heuningvlei, 100 kn NE of Kuruman: 2015 Further results The results……… Before 2008

After 2011

Chain fruit cholla Cylindropuntia fulgida. var. fulgida From this …… to this in 2 years The results……. Cylindropuntia imbricata Using Dactylopius tomentosa biotype “imbricata” The results…….

Cylindropuntia leptocaulis using Dactylopius tomentosa biotype “imbricata” The results……. (prickly Pears: Opuntia spp)

Opuntia ficus-indica

1932

Dactylopius opuntiae “ficus” biotype

1935 The results……. (cont.) Dactylopius opuntiae “stricta” biotype

Opuntia stricta: 2012 2014

Heuningvlei Opuntia stricta in the KNP 1997 2002

Monitoring progress Cochineal – Dactylopius opuntiae “stricta” + biotype

50 8 7 40

2 2 6 - 30 5 4 20

Cladodes m Cladodes 3 2 abundance cochineal 10 1 0 0 The results……. (cont.)

The “stricta” biotype was also used to control other Opuntia humifusa. The results……. (cont.)

Biological control Dactylopius austrinus Opuntia aurantiaca

Vaal River between Warrenton and Schmidtdrift 1980 The results……. (Harrisia martinii)

20 km South-east of Kimberley Hypogeococcus festerianus

About 1988 Unresolved Problems

Opuntia engelmannii Douglas, Prieska, North-western Freestate

Groblershoop New emerging invaders: Early Detection & Rapid Response Programmes

Opuntia elata

Beaufort West Graaff-Reinet New emerging invaders: Early Detection & Rapid Response Programmes Harrisia tortuosa Tephrocactus articulatus

Douglas Far Northern Cape New emerging invaders: Early Detection & Rapid Response Programmes

Cylindropuntia spinosior Cylindropuntia pallida Cylindropuntia spinosior Cylindropuntia pallida

Flinders Range Queensland, Australia Southern Australia

Q Conclusions • Biological control does offer inexpensive and lasting solutions to most of our cactus invasions. • However, the chances for biological control of invaders in the Opuntioideae are compromised by the importance of commercially cultivated cactus pear. • Early detection of new invaders and their immediate control is the most cost-effective method to prevent future disasters. • But many new invaders are just waiting to escape! Thank you.