Pathogenicity of Metarhizium anisopliae isolates on Nezara viridula and Dichelops melacanthus in wheat crop

<div><p>ABSTRACT: Bugs such as Nezara viridula (Linnaeus) and Dichelops melacanthus (Dallas) are considered the main insect pests of wheat crop in Brazil. The use of the entomopathogenic fungus Metarhizium anisopliae (Metschnikoff) may be an alternative for the management of these insects in the crop. The objective of this work was to verify the pathogenicity of different isolates of M. anisopliae on adults of N. viridula and D. melacanthus under laboratory and greenhouse conditions. In the laboratory, isolates 05RA, 11RA, 08RA and 02RA were obtained from N. viridula and D. melacanthus infested with M. anisopliae. Also, a high pathogenicity (100% of mortality) of both species was recorded in a bioassay of the topical application 8 Days After Application (DAA). However, compared to the other isolates, the 08RA isolate showed the highest pathogenicity in a shorter time interval for N. viridula (Mean Time “MT” = 2.8 days) and D. melacanthus (MT = 4.0 days). Under greenhouse conditions, the 08RA isolate provided a mortality of 44.9% (N. viridula) and 35.7% (D. melacanthus) in the same evaluation period. However, at 14 DAA, the mortality was 100% for both species, with the MT values of N. viridula and D. melacanthus being obtained at 8 days and 10 days, respectively. The fungus M. anisopliae is a promising alternative for the control of adult N. viridula and D. melacanthus in wheat crop.</p></div

Comparison of fitness components of life stages of <i>S</i>. <i>frugiperda</i> strains reared on non-Bt corn.

<p>Within each development stage, bars with the same letter are not significantly different (LSD <i>t</i>-test; <i>P</i> > 0.05).</p

Survival of <i>S</i>. <i>frugiperda</i> on leaf discs of different Bt and non-Bt maize plants.

<p>Values represent means ± SE. A separate ANOVA (Tukey’s test, <i>P</i>≤0.05) was conducted for treatments within each column (means followed by the same letter in column are not significantly different).</p><p>^a Mean weight of survivors.</p><p>^b Weight reduction compared to control (non-Bt).</p><p>n.a. Not applicable</p><p>Survival of <i>S</i>. <i>frugiperda</i> on leaf discs of different Bt and non-Bt maize plants.</p

Geographic coordinates, total number of caterpillars sampled and date of sampling of field populations sampled for F₂ screen.

<p>Geographic coordinates, total number of caterpillars sampled and date of sampling of field populations sampled for F₂ screen.</p

Concentration-response and growth inhibition response (MIC₅₀ and EC₅₀; ng/cm²) of <i>S</i>. <i>frugiperda</i> in diet-overlay bioassays with purified Cry1A.105 and Cry2Ab2 proteins.

<p>^a MIC₅₀: Concentration that inhibits molting to second instar in 50% of individuals after 7 days.</p><p>^b<i>P</i> > 0.05 in the goodness-of-fit test.</p><p>^c Resistance Ratio = (MIC₅₀ or EC₅₀ of indicated strain)/(MIC₅₀ or EC₅₀ of SS strain).</p><p>^d EC₅₀: Effective concentration of protein required to cause 50% growth inhibition at 7 days.</p><p>Concentration-response and growth inhibition response (MIC₅₀ and EC₅₀; ng/cm²) of <i>S</i>. <i>frugiperda</i> in diet-overlay bioassays with purified Cry1A.105 and Cry2Ab2 proteins.</p

Distribution of populations of <i>Spodoptera frugiperda</i> used in F₂ screen.

<p>Distribution of populations of <i>Spodoptera frugiperda</i> used in F₂ screen.</p

Estimates of effective dominance, <i>D</i>_GIL (after [40]), for the Cry1A.105 and Cry2Ab2 resistance traits in the RR <i>S</i>. <i>frugiperda</i> strain compared with the laboratory-reared SS strain, based on growth inhibition at 508.7 and 1589.8 ng of Cry1A.105 or Cry2Ab2/cm² of diet, respectively.

<p>Estimates of effective dominance, <i>D</i>_GIL (after [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0140130#pone.0140130.ref040" target="_blank">40</a>]), for the Cry1A.105 and Cry2Ab2 resistance traits in the RR <i>S</i>. <i>frugiperda</i> strain compared with the laboratory-reared SS strain, based on growth inhibition at 508.7 and 1589.8 ng of Cry1A.105 or Cry2Ab2/cm² of diet, respectively.</p

Fertility life table parameters of <i>S</i>. <i>frugiperda</i> strains fed on non-Bt maize.

<p>Values within a column followed by the same letter are not significantly different for two-tailed <i>t</i>-tests for pairwise group comparisons (<i>P</i> > 0.05).</p><p>^a T = mean generation time; R_o = net reproductive rate; r_m = intrinsic rate of increase and λ = finite rate of increase.</p><p>Fertility life table parameters of <i>S</i>. <i>frugiperda</i> strains fed on non-Bt maize.</p

Survival of <i>S</i>. <i>frugiperda</i> larvae per plant (mean ± SE) on MON 89034 maize and non-Bt near-isoline in greenhouse trials.

<p>^a Values followed by the same letter are not significantly different (LSD <i>t</i>-test. <i>P</i> > 0.05).</p><p>Survival of <i>S</i>. <i>frugiperda</i> larvae per plant (mean ± SE) on MON 89034 maize and non-Bt near-isoline in greenhouse trials.</p

Number of two-parent families tested and positive lines of <i>S</i>. <i>frugiperda</i> (those with any offspring that survived on MON 89034 maize) identified using F₂ screen method.

<p>Number of two-parent families tested and positive lines of <i>S</i>. <i>frugiperda</i> (those with any offspring that survived on MON 89034 maize) identified using F₂ screen method.</p