Foliar

nematode The nematodes ( or grc-gre, Νηματώδη; la, Nematoda) or roundworms constitute the phylum Nematoda (also called Nemathelminthes), with plant-Parasitism, parasitic nematodes also known as eelworms. They are a diverse animal phylum inhab ...

s are

plant Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae exclud ...

parasitic roundworms in the genus '' Aphelenchoides''. The three most economically important species are ''

Aphelenchoides fragariae Strawberry foliar nematode, or strawberry crimp nematode, is a disease caused by ''Aphelenchoides fragariae'', a plant pathogenic nematode. It is common in strawberries and ornamental plants and can greatly affect plant yield and appearance, resu ...

'', ''A. ritzemabosi'', and ''A. besseyi''. Foliar nematodes are becoming a widespread and serious problem for the ornamental and nursery industries. ''A. fragariae'' causes damage on hundreds of different plants including

chrysanthemum Chrysanthemums (), sometimes called mums or chrysanths, are flowering plants of the genus ''Chrysanthemum'' in the family Asteraceae. They are native to East Asia and northeastern Europe. Most species originate from East Asia and the center ...

begonia ''Begonia'' is a genus of perennial flowering plants in the family Begoniaceae. The genus contains more than 2,000 different plant species. The Begonias are native to moist subtropical and tropical climates. Some species are commonly grown ind ...

, gloxinia,

African violet ''Streptocarpus'' sect. ''Saintpaulia'' is a section within '' Streptocarpus'' subgenus ''Streptocarpella'' consisting of about ten species of herbaceous perennial flowering plants in the family Gesneriaceae, native to Tanzania and adjacent so ...

cyclamen ''Cyclamen'' ( or ) is a genus of 23 species of perennial flowering plants in the family Primulaceae. ''Cyclamen'' species are native to Europe and the Mediterranean Basin east to the Caucasus and Iran, with one species in Somalia. They grow ...

, and a wide variety of bedding plants and

fern A fern (Polypodiopsida or Polypodiophyta ) is a member of a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. The polypodiophytes include all living pteridophytes except t ...

s, causing brown to black, vein-delimited lesions on leaf tissue, defoliation, and possible stunting of plants.

Biology

While many plant parasitic

s feed on plant

root In vascular plants, the roots are the organs of a plant that are modified to provide anchorage for the plant and take in water and nutrients into the plant body, which allows plants to grow taller and faster. They are most often below the sur ...

s, foliar nematodes live and reproduce inside the

leaves A leaf (plural, : leaves) is any of the principal appendages of a vascular plant plant stem, stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", wh ...

of plants. The nematodes live within the

epidermis The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and hypodermis. The epidermis layer provides a barrier to infection from environmental pathogens and regulates the amount of water rele ...

and mesophyll tissues of leaves, which causes necrosis and collapse of the palisade and spongy parenchyma tissues. Inside the leaves of plants female nematodes lay one or two eggs a day, with each female producing up to 25 to 30 eggs. The generation time from egg to adult is finished in 10-14 days, with eggs hatching in 3 to 4 days, and nematodes maturing after 6-12 days. This rapid generation time allows populations to quickly grow, sometimes reaching thousands of nematodes per leaf Adult foliar nematodes are able to overwinter by surviving in dried plant tissue in a dormant state. The nematodes can survive in this dead leaf material for several months. Foliar nematodes do not survive for very long in bare soil alone.

Dispersal

Foliar nematodes occur throughout the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...

greenhouse A greenhouse (also called a glasshouse, or, if with sufficient heating, a hothouse) is a structure with walls and roof made chiefly of Transparent ceramics, transparent material, such as glass, in which plants requiring regulated climatic condit ...

and nursery settings. Foliar nematodes travel in films of water, swimming up the stems of plants and entering leaf tissue through

stomata In botany, a stoma (from Greek ''στόμα'', "mouth", plural "stomata"), also called a stomate (plural "stomates"), is a pore found in the epidermis of leaves, stems, and other organs, that controls the rate of gas exchange. The pore is bor ...

. The nematodes are transmitted plant to plant by splashing, overhead

irrigation Irrigation (also referred to as watering) is the practice of applying controlled amounts of water to land to help grow Crop, crops, Landscape plant, landscape plants, and Lawn, lawns. Irrigation has been a key aspect of agriculture for over 5,00 ...

, rainfall, and other forms of dripping water. They can also be transmitted through infected vegetative nursery cuttings, and can be rapidly spread in new material if symptoms are not present during the propagation of cuttings.

Control

Presently, there are very few control options for plants infested with foliar nematodes. The current recommendations are to destroy infected plant material, and avoid using overhead irrigation to prevent the spread of nematodes to new plants.

References

{{reflist Aphelenchoides Agricultural pest nematodes