Increased nutrient availability decreases insect resistance in cranberry

Abstract

1 Herbivorous insects are considered to be a major problem in cranberry (Vaccinium macrocarpon Ait.) production. Spraying chemical pesticides is common practice, although beneficial insects could also be affected. 2 We aimed to strengthen the resistance mechanisms that cranberry plants themselves use to combat insect pests by manipulating available nutrient levels. We hypothesized that cranberry genotypes respond differently from nutrient availability with regard to growth and defence against multiple herbivores. 3 In the present study, six cranberry varieties (i.e. genotypes) were subjected to four different fertilizer rates. In a greenhouse setting, we assessed soil and leaf nitrogen concentrations; weight gain of the native pests spotted fireworm (Choristoneura parallela Robinson), sparganothis fruitworm (Sparganothis sulfureana Clemens) and the invasive pest gypsy moth (Lymantria dispar L.); levels of leaf proanthocyanidins (PACs); and plant growth. 4 The results obtained showed that cranberry varieties differ in their insect resistance qualities, although this depended on the insect species identity; genotypic variation was observed in resistance against the invasive pest L. dispar but not against the two native insect pests. Overall, increased nutrient availability decreased plant resistance to the three herbivores (i.e. increased larval weight gain and reduced PAC levels), regardless of the cranberry genotype. Nutrient availability correlated negatively with PAC levels and positively with herbivore weight gain and plant growth, indicating a potential trade-off between growth and defence. 5 Fertilization management to strengthen insect resistance in cranberry may contribute to the development of more sustainable pest management practices, especially for organic production.

Defensive Responses of Tea Plants (Camellia sinensis) Against Tea Green Leafhopper Attack: A Multi-Omics Study

“…For instance, a study has shown that free amino acid pools and excretion of amino N in silverleaf whiteflies Bemisia tabaci, a major agricultural pest and a phloem feeder, could be rapidly altered by the N status of cotton leaves (Crafts-Brandner, 2002). Many other studies also suggest that increased nutrient availability positively benefits the performance of herbivorous insects with various feeding modes while negatively affecting plant specialized metabolism and thereby lowering plant resistance (Chow et al, 2009;Larbat et al, 2016;de Lange et al, 2019). Therefore, such a great reduction in amino acid and glutathione concentrations in tea leaves would presumably exert a large negative impact on insect performance and might deter further feeding.…”

Does enhanced nutrient availability increase volatile emissions in cranberry?

“…In a previous study, we showed that increased availability of N, phosphorus (P), and potassium (K) decreased resistance to herbivores in terms of reduced levels of leaf proanthocyanidins, important defensive compounds, and increased weight gain of the leaf-chewing herbivores gypsy moth (Lymantria dispar, Lepidoptera: Erebidae), Sparganothis fruitworm (Sparganothis sulfureana, Lepidoptera: Tortricidae), and spotted fireworm (Choristoneura parallela, Lepidoptera: Tortricidae). 14 To assess whether NPK availability also affects HIPV emissions, we studied HIPV emissions in cranberry in response to four different fertilizer regimes. Plants were induced with methyl jasmonate (MeJA), a derivative of jasmonic acid that induces HIPVs emissions and other defenses in cranberries, [15][16][17] or were noninduced, to assess inducible and constitutive emissions of plant volatiles, respectively.…”

“…Plant varieties and growing conditions are described in detail elsewehere. 14 In brief, plants were supplied with different amounts of Osmocote 14-14-14 NPK Controlled Release Fertilizer (Everris NA Inc., Dublin, OH, USA). Four fertilizer regimes were applied: 2×, 1×, ¼×, and 0×, corresponding to 4 g, 2 g, 0.5 g, and 0 g fertilizer, respectively.…”

“…15 These four fertilizer regimes lead to differential N concentrations in cranberry soil and leaves. 14 MeJA-induction was realized by spraying the plants with 1 mL of a 1 mM MeJA (Sigma-Aldrich, St. Louis, MO, USA) solution dissolved in 0.1% Tween 20 (Sigma-Aldrich), ca. 16 h before volatile collections.…”

“…This study demonstrated that under greenhouse conditions, enhanced NPK fertilizer applications increased total HIPV emissions in cranberry, regardless of the variety. This increase could be attributed to an increase in plant fresh weight, 14 since it was no longer visible when correcting total volatile emissions for the increased plant biomass. Both quantitative and qualitative changes in volatile emissions were observed.…”