Canola Nutrition and Variety Affect Oviposition and Offspring Performance in the Generalist Herbivore, Mamestra configurata (Lepidoptera: Noctuidae)

Abstract

Bertha armyworm Mamestra configurata Walker (Lepidoptera: Noctuidae) is a generalist herbivore that feeds on several crops in different plant families. Canola Brassica napus L. (Capparales: Brassicaceae) is one of the most favored host plants making the bertha armyworm a significant insect pest in the Canadian Prairie Provinces. The performance of the bertha armyworm on canola may vary with the quality of the canola plant. We tested the impact of plant nutrition and canola variety on oviposition and subsequent larval development of the bertha armyworm. A range of fertilization levels (0.0, 1.0, 3.0, and 5.0 g/pot) were applied to three different canola varieties: Clearfield 5535 CL, Roundup Ready hybrid 6060RR, and Q2. The total number of eggs laid on plants in a no-choice experiment increased with fertilizer level but a similar number of eggs were laid on plants that received moderate and high fertilizer treatments. Larvae reared on plants that received the moderate fertilizer application yielded heavier pupae than those reared on plants with low and high fertilizer treatments. Most eggs were laid on the Q2 variety when compared to Clearfield 5535 CL and Roundup Ready 6060 RR. Bertha armyworm females preferred to lay eggs on plants that received moderate or high fertilization over plants with the low fertilizer treatment. Plant leaf tissue nutrient content and plant growth were highest in plants that received moderate and high fertilizer treatment. We conclude that bertha armyworm oviposition behavior and larval performance are influenced by fertilizer treatment and canola variety.

Influence of crop variety and fertilization on oviposition preference and larval performance of a generalist herbivore, the true armyworm, Mythimna unipuncta

“…Higher amounts or a broader range of fertilizer concentration may be necessary to observe a dose response in larval performance in M. unipuncta . For example, M. configurata larvae fed canola plants treated with 3.0 g of fertilizer per plant produced heavier pupae than those reared on canola plants at 1.0 g per plant (Weeraddana & Evenden, 2018). Fertilization rates used in the current study were adopted from industry recommendations for cereal production in Canada (Kryzanowski, 2002), and thus, M. unipuncta larvae are probably not exposed to higher fertilizer rates that may allow this pest to reach its maximum performance potential.…”

“…Nitrogen fertilization not only increases the nutrient content of host plants for larval development, but also enhances the host plant volatile profile (Chen et al, 2010; Veromann et al, 2013) and chlorophyll concentration in leaves (Fox et al, 1994; Garratt et al, 2010) and, thus, can augment host plant attractiveness to insects. Many female herbivores assess the nutrient content of host plants and preferentially oviposit on plants with higher nitrogen levels (Jauset et al, 1998; Jiang & Cheng, 2003; Prudic et al, 2005), including other armyworm pests like bertha armyworm (Weeraddana & Evenden, 2018) and beet armyworm (Chen et al, 2008). Fertilizer input supported tiller growth in the cereal crop varieties tested, and therefore, increased potential oviposition sites for M. unipuncta .…”

“…Environmental factors can also affect host plant quality and suitability for insect herbivores, which, in turn, can influence preference–performance coupling. Water stress or nutrient deficiency of a host plant may alter the herbivore larval performance, and adult females would benefit by differentiating plants grown under varying environmental conditions (Thompson, 1988; Weeraddana & Evenden, 2018). Augmentation of plant nutrition through fertilization results in host plants with a higher nitrogen content and biomass.…”

Herbivore‐induced plants do not affect oviposition but do affect fitness of subsequent herbivores on canola

“…Bertha armyworm females use host cues during oviposition, as the foliar glucosinolate sinigrin deters oviposition by BAW whereas different foliar glucosinolates enhance oviposition (Ulmer et al., ). Female BAW moths also lay more eggs on fertilized than on unfertilized canola plants (Weeraddana & Evenden, ). Larval feeding by DBM on canola induces the production of volatile glucosinolates (Renwick et al., ); however, in our experiment, female BAW moths laid a similar number of eggs on plants that were undamaged or damaged by DBM larvae.…”

“…In the Canadian Prairie Provinces, BAW adult females eclose in the early summer and lay eggs on canola plants during flowering (Ulmer et al., ). Bertha armyworm oviposition is influenced by foliar glucosinolates (Ulmer, ), the presence of conspecific eggs (Ulmer et al., ), and plant nutrients (Weeraddana & Evenden, ).…”