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The authors have declared that no competing interests exist.

Conceived and designed the experiments: MTM GLT MEO. Performed the experiments: MTM DHS. Analyzed the data: MTM MEO. Wrote the paper: MTM DHS GLT MEO.

Crop production is at risk for yield loss from both aboveground and belowground herbivores that can occur concurrently and interact through a shared host plant

Belowground plant-parasitic nematodes are important yield-reducing pathogens of all major field crops produced in the U.S.

Aboveground-belowground herbivore interactions are of particular importance for soybean,

Previous research observed that aboveground lepidopteran herbivores were capable of increasing

Research exploring the co-occurrence of

McCarville

Heeren

In a greenhouse, we manipulated the density of

For these experiments, a modified version of the Standard Cyst Evaluation-2008 (SCE-08) protocol was utilized

Cone-tainers were filled with 100 ml of a soil-sand mixture created by adding construction sand to ^{−1} of soil. This population density was selected to reduce the likelihood of competition among

Two soybean cultivars were used for the experiment, Kenwood 94 and Dekalb 27–52. Kenwood 94 is a

Aphid-density treatments were applied to whole plots when plants reached the first trifoliate or V1 stage

Cone-tainers in the 30-d group were harvested from each whole plot at 30 d after planting, and data were collected as described below. Plants assigned to the 60-d group were transferred with all the soil within their respective 125-ml cone-tainers to 650-ml cone-tainers (Stuewe & Sons, Tangent, OR) after 30 d. The new cone-tainers then were filled to 650 ml with the addition of

All

Data collected from the 30-d and 60-d groups of plants were analyzed separately using analysis of variance (ANOVA) with a mixed effects model. The model included the fixed effects of experimental run, block, aphid density, and soybean cultivar. The interactions of run*block, run*aphid density, block*aphid density, and aphid density*soybean cultivar were included as fixed effects. The whole-plot error term of run*block*aphid density was included as a random effect, along with the effect of subsample (i.e. plant nested within aphid density*soybean cultivar). This model allowed us to assess the effects of soybean cultivar, aphid density, and their interaction on the total number of ^{−1}.

The number of ^{−1} and eggs plant^{−1} were log transformed to meet the assumptions of ANOVA (non-transformed data are presented in all figures). These data were analyzed to determine if soybean cultivar, aphid density, or their interaction affected the number of

Based on the results of our initial analyses, we hypothesized that the effect of ^{−1} and eggs plant^{−1} data separately.

Mean ^{−1} (± SEM) among the ten-, five-, and zero-aphid density treatments were 278±24, 225±16, and 3±1, respectively for the 30-d group. Upon transfer of the 60-d group plants from the 125-ml cone-tainers to the 650-ml cone-tainers, there were only a few aphids on plants in the zero-aphid treatment. These aphids were removed before the nets were placed back over the buckets. At the conclusion of the 60-d group, ^{−1} and 99±14 aphids plant^{−1}, respectively.

Numbers of ^{−1} for the 30-d group varied significantly by experimental run (^{−1}. On the ^{−1} with ^{−1} varied significantly by experimental run (^{−1} increased as aphid density increased on the resistant cultivar, with a 28% increase in numbers of females between the zero-aphid density and ten-aphid density treatments (

Numbers of females are represented by bars with numbers of eggs represented by boxes above the bars. Note the difference in scales used for the two graphs. Three aphid density treatments were established by artificially infesting plants with zero, five, or ten ^{−1} 10 d after seed was planted. Letters represent significant differences among aphid densities (^{−1} and lower case letters assigned to females plant^{−1}.

The number of ^{−1} for the 30-d group responded similarly to the treatment effects as the number of females plant^{−1}. Eggs plant^{−1} varied significantly by experimental run (^{−1} varied significantly by experimental run (^{−1} decreasing with increasing aphid density (^{−1} varied by experimental run (^{−1} increasing with increasing aphid density. We observed a 34% increase in eggs on resistant plants initially infested with 10 aphids compared to those assigned to the zero-aphid treatment (

Numbers of ^{−1} were affected by cultivar (^{−1} produced with increasing aphid density (

Numbers of females and cysts are represented by bars and numbers of eggs represented by boxes above the bars. Note the different scales used for the two graphs. Three aphid density treatments were established by artificially infesting plants with zero, five, or ten ^{−1} 10 d after seed was planted. For the susceptible cultivar, aphid density significantly affected the number of ^{−1} and had a marginally significant effect on numbers of eggs plant^{−1}. Letters represent significant differences among aphid densities (^{−1} and lower case letters assigned to females and cysts plant^{−1}.

Results from the analysis of ^{−1} at 60 d were similar to those obtained from the analysis of females and cysts plant^{−1}. The number of eggs plant^{−1} varied significantly by cultivar (^{−1} on the susceptible cultivar varied marginally with aphid density (^{−1} decreased with increasing aphid density on the susceptible cultivar at 60 d (

Our data summary analyses of both numbers of ^{−1} and eggs plant^{−1} revealed that the effect of

The effect of ^{−1} and eggs plant^{−1} was calculated as the average of the ten-, five-, and zero-aphid treatment means.

In our experiment,

Aboveground lepidopteran herbivores are reported to affect belowground plant-parasitic nematodes in soybean

In more recent research, conflicting results concerning the effect of

McCarville ^{−1} in the 30-d and 60-d SCN-susceptible cultivar treatments, respectively, and the average end-of-season ^{−1} (maximum 34,975 eggs 100cc soil^{−1})

Heeren ^{−1} and <100 cumulative aphid days (i.e. <10 aphids plant^{−1} for <10 d) for some soybean lines.

Given the results of our current experiment and the previous results of McCarville ^{−1} (analysis not shown). Therefore, the effect of increased ^{−1}), where aphid feeding has no effect on

Going forward, it will be essential to determine under what range of field conditions

We thank Kayla Mills, Taylor Mordhorst, Tom Klunker, Cody Kuntz, and Adam Varenhorst for assistance with planting and estimating pest densities. We also thank Drs. Ian Kaplan and Scott Johnson for their helpful edits and suggestions, which improved this manuscript.