Plasmodium's ancestors lost the ability to photosynthesize a long time ago. But they still hold onto some of the ancestral enzymes from the bacteria that their forebears swallowed 1.3 billion years ago. As a result, Plasmodium is weirdly similar to flowers and trees. Some scientists have even taken advantage of this evolutionary kinship by looking at weed-killers as potential drugs for malaria.
This ancient heritage also explains why Plasmodium can smell like lemons. Odom and her colleagues found that the parasite make pinene and limonene using enzymes that are related to the ones that plants use to make these chemicals.
There are reasons to think that the parasite are using these chemicals to lure mosquitoes. While we're painfully aware of the appetite mosquitoes have for blood, the fact is that mosquitoes also feed on flower nectar. They depend on the nectar for sugar they need to fuel their flights. Many insects are keenly sensitive to certain colors and odors that flowers produce, which guide them reliably to their next meal of nectar. Odom and her colleagues found that the antenna of malaria-carrying species of mosquitoes are exquisitely sensitive to pinene and limonene. If you want to attract mosquitoes, it makes sense to make those chemicals.