Western corn rootworm adult captures as a tool for the larval damage prediction in continuous maize

Abstract

Continuous maize production in Croatia and Central Europe is at serious risk from western corn rootworm (WCR) (Diabrotica virgifera virgifera, LeConte) activity. When alternatives to sowing continuous are not feasible, farmers will need a reliable tool that will allow them to choose fields for continuous cultivation. The decision could be based on assessing the adult populations in fields from the previous year. Non-baited yellow sticky traps [Pherocon AM (PhAM)] could be utilized as a practical tool for sampling. The main objective of this study was to determine which WCR adult population data collected by PhAM traps could most reliably predict the subsequent WCR larval population and damage. Adult WCR population densities in 30 cornfields were determined weekly over a 74 day period each year (24th to 35th week) from 2006 to 2009. In addition to root damage and plant lodging measurements, soil and root sampling were conducted to measure the WCR larval population in continuous maize fields. Larval infestation is best predicted by maximal weekly capture (MWC) but, root damage is better predicted by capture of adults in the 31st week of previous year. For the prediction of plant lodging, MWC, average daily capture (ADC) and the capture of adults in 29th week were found to be equivalent. To save money and to shorten the sampling period, farmers should employ PhAM traps between the 29th and 32nd week. The estimated WCR adult capture that could cause significant larval infestation is ! 22 adults/trap in the 29th week. Significant future root damage is predicted if ! 41 adults/trap are captured in the 31st week. Plant lodging is predicted if ! 36 adults/trap (for 90% of upright plants) or ! 32 adults/trap (for 10% of partially lodged plants) are captured in 29th week. Findings will help to develop economic threshold models and improved decision-making for WCR management.

Alternatives to neonicotinoid insecticides for pest control: case studies in agriculture and forestry

“…Both USA and European authors have demonstrated that there is a correlation between the number of adults captured by yellow sticky traps (i.e. PhAM) and plant damage the following year (Blandino et al 2014 ; Boriani 2006 ; Hein and Tollefson 1985 ; Kos et al 2014 ). The US authors stated that economic thresholds would be exceeded when more than 40 beetles/PhAM trap/week (6 beetles/PhAM trap/day) were caught the previous year in one period (ca.…”

“…In Italy, the threshold was 42 beetles/PhAM trap/day on average over a 6-week period after the beginning of adult flights (Boriani 2006 ; Blandino et al 2014 ). In Croatia, the threshold was estimated at 41 adults/ PhAM trap in week 31 (Kos et al 2014 ). Economic thresholds can greatly vary with climatic/agronomic conditions and prices of maize and insecticides (Oleson et al 2005 ).…”

Non‐target effects of insecticides, entomopathogenic fungi and nematodes applied against western corn rootworm larvae in maize

“…Instead, European maize growers in highly infested areas began to apply insecticides against D. v. virgifera larvae to prevent yield losses. Various traps can be utilized for sampling WCR adults to determine the previous year's adult population and to take action based on established thresholds (Kos et al 2014). Foliar insecticides targeting the adult beetles are only occasionally applied, mainly because of high costs and limited efficacy but also because they could interfere with integrated and biological-based management options already in place against other European maize pests, for example the European corn borer.…”

An update of the Worldwide Integrated Assessment (WIA) on systemic pesticides. Part 4: Alternatives in major cropping systems

“…Thresholds have been defined for wireworms (Furlan 2014 ), brown planthopper (Zheng et al 2007 ) and for different cotton pests, including A. gossypii (Silvie et al 2013 ; Sequeira and Naranjo 2008 ). Data input for DSS are regularly collected through field-level monitoring: WCR and wireworms can be monitored using sticky traps, pheromone traps or bait traps (Sufyan et al 2011 ; Vuts et al 2014 ; Benefer et al 2012 ; Parker 1994 , 1996 ; van Herk and Vernon 2013 ; Tóth et al 2002 ; Tóth et al 2007 ; Vuts et al 2012 ; Tóth 2013 ; Tóth et al 2015 ; Furlan et al 2017a , 2017b ; Bažok et al 2011 ; Kos et al 2014 ). In Northern Italy (Emilia-Romagna region) a monitoring net for two wireworm species has been employed in 2017 and 2018 using about 1100 pheromone traps per year, providing provisional threshold to alert farmers on infestation risk.…”