Costs and benefits of insecticide and foliar nutrient applications to huanglongbing-infected citrus trees.

BACKGROUND: The Asian citrus psyllid (ACP), Diaphorina citri Kuwayama (Hemiptera: Psyllidae), vectors Candidatus Liberibacter asiaticus, which causes huanglongbing (HLB). In Florida, HLB incidence is approaching 100% statewide. Yields have decreased and production costs have increased since 2005. Despite this, some growers are maintaining a level of production and attribute this in part to aggressive psyllid control and foliar nutrition sprays. However, the value of these practices is debated. A replicated field study was initiated in 2008 in a commercial block of 'Valencia' sweet orange trees to evaluate individual and combined effects of foliar nutrition and ACP control. Results from 2012-2016 are presented. RESULTS: Insecticides consistently reduced ACP populations. However, neither insecticide nor nutrition applications significantly influenced HLB incidence or PCR copy number in mature trees. In reset trees, infection continued to build and reached 100% in all treatments. Greatest yields (kg fruit ha-1 ) and production (kg solids ha-1 ) were obtained from trees receiving both insecticides and foliar nutrition. CONCLUSION: All treatments resulted in production and financial gains relative to controls. However, material and application costs associated with the nutrition component offset these gains, resulting in lesser benefits than insecticides applied alone. © 2016 Society of Chemical Industry.

Flight activity and dispersal of the cabbage seedpod weevil (Coleoptera: Curculionidae) are related to atmospheric conditions.

The cabbage seedpod weevil, Ceutorhynchus obstrictus (Marsham) (Coleoptera: Curculionidae), is an invasive pest of canola (Brassica napus L. and Brassica rapa L.) in western Canada. Under current climatic conditions, C. obstrictus is spreading from established populations in southwestern Alberta at ≈ 55 km/yr. We studied the influence of climatic conditions on C. obstrictus flight behavior in 2007 and 2008 and eastward dispersal from the western border of Saskatchewan from 2002 to 2007. Positive linear relationships between increases in mean temperature and flight height and between greater mean maximum temperature and expanded dispersal distances were significant. Increases in relative humidity were associated with reduced flight heights and dispersal distances. We developed models that predict the relationships of temperature and relative humidity with flight height and with dispersal distance. We also discuss implications for C. obstrictus dispersal under current climatic conditions and in the context of predicted climate change.