Initially described using existing genera in the family Trypanosomatidae, such as Trypanosoma or Leishmania, the nomenclature of Phytomonas was proposed in 1909 in light of their distinct hosts and morphology.

[3] Phytomonas is believed to have arisen from a single monoxenous lineage of insect parasitizing trypanosomatids some 400 million years ago.

[5] After this divergence, a heteroxenous lifestyle was developed, and most Phytomonas species are transferred between plant hosts by insect vectors in the Heteroptera suborder as a form of dixenous parasitism.

First proposed by Donovan in 1909, the term Phytomonas describes the relationship the genus has with plants compared to closely related organisms in Trypanosomatida.

[2] Since 1909, trypanosomatids were reported to infect plants from around the planet, but initially, there was little scientific interest in the genus, aside from possible relations to disease-causing organisms in animals and humans.

[7][6] In the 1970s, scientific interest was revitalized due to increasingly devastating problems caused by the parasites in even more economically significant crops, namely coconut (Cocos nucifera) and oil palm (Elaeis guineensis).

[7][6] Finally, in 1982, Dollet successfully cultivated trypanosomatids in vitro, which allowed for the isolation of Phytomonas in 24 different plant families from across the globe.

Having a monoxenous lifestyle, the species was not observed in plants, but was categorized as Phytomonas due to features that were similar to other phytomonads, namely long twisted promastigotes and flagellated stages in the salivary glands of bugs.

[3] Within host plants, Phytomonas species have been observed in multiple tissue types, including phloem, seeds, fruits, flowers, and latex ducts.

[4] Notable examples include Phytomonas serpens in tomato, P. staheli in coconut and oil palm, and P. leptovasorum in coffee.

[9] Because the term Phytomonas was not founded on any strict criterion other than being flagellated protists in plants, the nomenclature fails to reflect the wide range of lifestyles of the various species in the genus.

[3] Within the plant, the organisms can be in several flagellated stages: mostly promastigote with some paramastigotes in the phloem and lacticiferous tubes, and amastigote form in the latex.

[6] However, most of the species are mainly observed in the promastigote form, with an elongated body and a single 10-15 μm long flagellum emerging from the anterior flagellar pocket.

[4] Also like other trypanosomatids, Phytomonas does not have a cell wall, but instead are protected from host responses and environmental conditions by membrane-anchored proteins and glycoinositol phospholipids.

[3] A paraxial rod also runs parallel to the axoneme of the single flagellum on one side, giving the flagella increased thickness, robustness, and strength.

It has been found that the endoplasmic reticulum (ER) of some species form subpellicular sheets that run parallel to the longitudinal axis.

[6] Depending on the species and isolates in question, the endoplasmic reticulum (ER) may also have ribosomes in paracrystalline array and incredibly thin intracisternal space.

[3] For example, in Phytomonas serpens, cells do attach to the interior of salivary glands, which indicates a true developmental stage within the insect host in some species.

[3] Vermeulen also suspected a Hemipteran insect, due to the presence of flagellate protists in the midgut of certain bugs often found on coffee plant roots.

The two forms differ in the amount of foliage loss and killing time, but both cases involve the browning and death of the roots.

[3] After ten weeks, the plant dies, and a foul odor arises due to secondary infection by bacteria and fungi.

Trypanosoma cruzi is the causative agent of Chagas' disease, and as a member of the family Trypanosomatidae, is related to organisms of the genus Phytomonas.

[13] Though more research is required, the phytomonads could potentially be used as vaccine agents to prime defense responses to T. cruzi antigens in order to interfere with the development of Chagas' disease in humans.