Foliar

nematode The nematodes ( or ; ; ), roundworms or eelworms constitute the phylum Nematoda. Species in the phylum inhabit a broad range of environments. Most species are free-living, feeding on microorganisms, but many are parasitic. Parasitic worms (h ...

s are

plant Plants are the eukaryotes that form the Kingdom (biology), kingdom Plantae; they are predominantly Photosynthesis, photosynthetic. This means that they obtain their energy from sunlight, using chloroplasts derived from endosymbiosis with c ...

parasitic roundworms in the genus '' Aphelenchoides''. 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 in the Asteraceae family. They are native to East Asia and northeastern Europe. Most species originate from East Asia, and the center of diversity is in China. Co ...

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 ...

, gloxinia, African violet, cyclamen, and a wide variety of bedding plants and

fern The ferns (Polypodiopsida or Polypodiophyta) are a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. They differ from mosses by being vascular, i.e., having specialized tissue ...

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 plant organ, 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 bel ...

s, foliar nematodes live and reproduce inside the

leaves A leaf (: leaves) is a principal appendage of the stem of a vascular plant, usually borne laterally above ground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, stem, ...

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 epidermal 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 (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

greenhouse A greenhouse is a structure that is designed to regulate the temperature and humidity of the environment inside. There are different types of greenhouses, but they all have large areas covered with transparent materials that let sunlight pass an ...

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 (: stomata, from Greek ''στόμα'', "mouth"), also called a stomate (: stomates), is a pore found in the epidermis of leaves, stems, and other organs, that controls the rate of gas exchange between the internal air spa ...

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

irrigation Irrigation (also referred to as watering of plants) 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 bee ...

, 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