Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/1/2014
Publication Date: 10/1/2014
Citation: Smith, L. 2014. Prediction of the geographic distribution of the psyllid, Arytinnis hakani (Hemoptera, Psyllidae), a prospective biological control agent of Genista monspessulana, based on the effect of temperature on development, fecundity. Environmental Entomology. 43(5):1389-1398. doi: 10.1603/EN14086.
Interpretive Summary: French broom is a leguminous shrub from western Europe that has invaded rangeland, woodlands and rights-of-way in the Pacific western USA. The plant is toxic to livestock, and it produces thickets that displace native species and increase the risk and intensity of wildfire. Large quantities of seeds are produced which remain dormant until the soil is disturbed, which makes it extremely difficult to control. The USA, Australia and New Zealand have targeted the plant for biological control. Foreign exploration studies ranked the psyllid, Arytinnis hakani, as the prospective agent with the highest potential. However, it is important to evaluate the climatic requirements of a prospective agent to determine if it is likely to be effective in the introduced range of the weed. We measured the effect of temperature on survival, reproduction and development rate of this psyllid in laboratory experiments. The results help explain why the psyllid is not effective in hotter parts of Australia, where it is currently established. We predict that the psyllid is likely to be effective in coastal California, which is where French broom infestations are most severe, but less effective in the Sierra foothills, which have hotter summers and colder winters.
Technical Abstract: The psyllid, Arytinnis hakani, is a prospective biological control agent of Genista monspessulana (French broom), an invasive shrub originating from western Europe. It is a multivoltine species that is not known to diapause. The insect is established in Australia, where it appears to cause heavy defoliation and mortality of the target weed, except at warm sunny sites. This suggests that bright light or high temperatures may hamper the agent. We measured the effect of temperature on development rate, survival and fecundity of the psyllid to determine its suitable temperature range. Intrinsic rate of increase was highest near 22°C, and there was no population growth at the extremes of 5°C and 26°C. Net reproductive rate was highest at 16.5°C. Fecundity was highest at 22°C, and decreased to half at 16°C and at 27°C. Adult female longevity decreased with increasing temperature over the range studied. Nymphal survivorship was highest at 16°C and dropped to 0% at 5°C and 26°C. Eggs were able to complete development in 83 days at 5°C, but with only 20% survivorship vs. 78 to 95% survivorship at higher temperatures. For populations with a stable age distribution, only 2 to 3% of the population is in the adult stage. Climate modeling using CLIMEX indicated that the geographic distribution of the psyllid is constrained by high temperature stress in Australia. The psyllid is predicted to be suitable in coastal California but not in the Sierra foothills.