Data for: A diverse parasite pool can improve effectiveness of biological control constrained by genotype-by-genotype interactions

<p>The outcomes of biological control programs can be highly variable, with natural enemies often failing to establish or spread in pest populations. This variability has posed a major obstacle in use of the bacterial parasite <em>Pasteuria</em> <em>penetrans</em> for biological control of <em>Meloidogyne</em> species, economically devastating plant-parasitic nematodes for which there are limited management options. A leading hypothesis for this variability in control is that infection is successful only for specific combinations of bacterial and nematode genotypes.  Under this hypothesis, failure of biological control results from the use of <em>P</em>. <em>penetrans</em> genotypes that cannot infect local <em>Meloidogyne</em> genotypes. We tested this hypothesis using isofemale lines of <em>M</em>. <em>arenaria</em> derived from a single field population and multiple sources of <em>P</em>. <em>penetrans</em> from the same and nearby fields. In strong support of the hypothesis, susceptibility to infection depended on the specific combination of host line and parasite source, with lines of <em>M</em>. <em>arenaria</em> varying substantially in which <em>P</em>. <em>penetrans</em> source could infect them. In light of this result, we tested whether using a diverse pool of <em>P</em>. <em>penetrans</em> could increase infection and thereby control. We found that increasing the diversity of the <em>P</em>. <em>penetrans</em> inoculum from one to eight sources more than doubled the fraction of <em>M</em>. <em>arenaria</em> individuals susceptible to infection and reduced variation in susceptibility across host lines. Together, our results highlight genotype-by-genotype specificity as an important cause of variation in biological control and call for the maintenance of genetic diversity in natural enemy populations.</p>