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 parasitic roundworms in the genus ''

Aphelenchoides ''Aphelenchoides'' is a genus of mycetophagous nematodes. Some species are plant pathogenic foliar nematodes. Taxonomy In 1961 Sanwal listed 33 species and provided a key. The most important species of these are ''Aphelenchoides ritzemabosi'' ...

''. The three most economically important species are '' Aphelenchoides fragariae'', ''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, gloxinia, African violet, cyclamen, and a wide variety of bedding plants and ferns, 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 roots, foliar nematodes live and reproduce inside the leaves 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 Subcutaneous tissue, hypodermis. The epidermis layer provides a barrier to infection from environmental pathogens and regulates the ...

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 U.S. state, states, a Washington, D.C., federal district, five ma ...

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 material, such as glass, in which plants requiring regulated climatic conditions are grown.These ...

and nursery settings. Foliar nematodes travel in films of water, swimming up the stems of plants and entering leaf tissue through stomata. 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 crops, landscape plants, and lawns. Irrigation has been a key aspect of agriculture for over 5,000 years and has been dev ...

, 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