Effects of nitrogen fertilization on insect pests, their parasitoids, plant diseases and volatile organic compounds in Brassica napus

The potential of crop management practices to reduce pollen beetle damage in oilseed rape

“…Despite these soil quality effects, Zaller et al (2008b) observed no direct influence of variation in nitrogen fertiliser rates (range 45-143 kg ha −1 ), perhaps because applications may not have accurately reflected soil nitrogen availability. By contrast, Culjak et al (2011) found greater pollen beetle abundance on plants treated with lower and higher N rates (of 69 and 115 kg ha −1 respectively) than on those treated at medium rates (92 kg ha −1 ), and Veromann et al (2013) were also able to demonstrate an influence of nitrogen fertiliser, with increased beetle infestations occurring on both low (60 and 80 kg ha −1 N) and high (160 kg ha −1 ) rate nitrogen-treated plots, compared with zero and medium (100, 120 and 140 kg ha −1 ) rate treatments. In this case, there was some evidence that differences in infestation rates were mediated through quantitative changes in plant volatile profiles which differed according to nitrogen application rates.…”

“…There is little evidence in the literature of direct crop nutritional status effects on pollen beetle natural enemies; rather, pollen beetle parasitism rates appear to be influenced indirectly through host density-dependence effects (Zaller et al 2009b;Veromann et al 2013). Similarly, the activitydensity of Amara similata (Carabidae) females was found to be negatively correlated with soil index (Haschek et al 2012), and this is most likely related to prey and/or weed seed abundance; on more productive soils, readily available food resources lead to satiated beetles that are relatively inactive and less likely to be trapped (Lenski 1984).…”

Potential for oilseed rape resistance in pollen beetle control

“…However, a number of studies have compared life history traits of adults and larvae of this pest among different brassicaceous species Charpentier 1985;Borg and Ekbom 1996;Ekbom and Borg 1996;Hopkins andEkbom 1996, 1999;Ekbom 1998;Hopkins et al 1998;Billqvist and Ekbom 2001;Bartlet et al 2004;Cook et al 2007;Veromann et al 2012Veromann et al , 2014Kovács et al 2013;Kaasik et al 2014a, b). These results are summarized in Fig.…”

“…Since pollen beetle resistance to pyrethroids, the main insecticides used against this species, has been increasing in natural populations over the last 40 years (Lakocy 1977;Hansen 2003;Slater et al 2011;Heimbach and Müller 2012;Wrzesińska et al 2014;Zimmer et al 2014), research has been ongoing in order to develop a number of alternative control strategies within the framework of integrated pest management. Strategies tested include trap cropping using early-flowering plants (Cook et al 2004a(Cook et al , 2006(Cook et al , 2007Nerad et al 2004;Nilsson 2004;Frearson et al 2005) or companion plants (Veromann et al 2012;Kaasik et al 2014a, b), enhancement of biological control through the attraction of larval parasitoids (Büchi 2002;Scheid et al 2011;Kovács et al 2013;Kaasik et al 2014a, b) or spraying of entomopathogenic fungi (Hokkanen 1993;Husberg and Hokkanen 2001) or nematodes (Nielsen and Philipsen 2005), adapting agronomical practices (Valantin-Morison et al 2007;Valantin-Morison and Meynard 2008;Veromann et al 2009Veromann et al , 2013, diffusing repellent volatile compounds (Mauchline et al 2005(Mauchline et al , 2008(Mauchline et al , 2013Pavela 2011) or using botanical insecticides (Pavela 2011;Dorn et al 2014).…”

Prospects for improved off-crop habitat management for pollen beetle control in oilseed rape

“…These include efforts to reduce prophylactic insecticide applications through improved pollen beetle forecasting (Johnen and von Richthofen 2013;Ferguson et al 2016), and monitoring Skellern et al 2017), and determination of more accurate control thresholds (AHDB-HGCA 2012; Ellis and Berry 2012;Ramsden et al 2017). Other strategies aim to reduce pest numbers to below economic threshold levels; these include the use of plant-or insect-derived semiochemicals or 'signal chemicals', enabling behavioural manipulation of pests or their natural enemies (Cook et al 2007a;Mauchline et al 2008Mauchline et al , 2013Pavela 2011; reviewed by Mauchline et al in press), botanical insecticides or other natural products such as silicate dusts as alternatives to synthetic insecticides (Pavela 2011;Daniel et al 2013;Dorn et al 2014), modification of crop management practices (Valantin-Morison et al 2007;Veromann et al 2009Veromann et al , 2013; reviewed by Skellern and Cook in press), breeding for OSR resistance to the pest (reviewed by Hervé and Cortesero 2016;Hervé 2017), and inundative biological control via the application or release of natural enemies such as entomopathogenic fungi (e.g. Hokkanen 1993;Husberg and Hokkanen 2001; reviewed by Hokkanen and Menzler-Hokkanen 2017) or nematodes (Menzler-Hokkanen and Hokkanen 2005).…”