Foliar nematodes are plant

Plant

Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...

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

Aphelenchoides fragariae

Aphelenchoides fragariae is a plant pathogenic nematode....

, 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

Chrysanthemum

Chrysanthemums, often called mums or chrysanths, are of the genus constituting approximately 30 species of perennial flowering plants in the family Asteraceae which is native to Asia and northeastern Europe.-Etymology:...

, begonia

Begonia

Begonia is a genus in the flowering plant family Begoniaceae and is a perennial. The only other members of the family Begoniaceae are Hillebrandia, a genus with a single species in the Hawaiian Islands, and the genus Symbegonia which more recently was included in Begonia...

, gloxinia

Gloxinia

Gloxinia can refer to:*The genus Gloxinia of flowering plants in the family Gesneriaceae*The plant species Sinningia speciosa, formerly classified in the genus Gloxinia and still commonly known by that name, in the family Gesneriaceae...

, African violet, cyclamen

Cyclamen

Cyclamen is a genus of 23 species of perennials growing from tubers, valued for their flowers with upswept petals and variably patterned leaves...

, and a wide variety of bedding plants and fern

Fern

A fern is any one of a group of about 12,000 species of plants belonging to the botanical group known as Pteridophyta. Unlike mosses, they have xylem and phloem . They have stems, leaves, and roots like other vascular plants...

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

Biology

While many plant parasitic nematode

Nematode

The nematodes or roundworms are the most diverse phylum of pseudocoelomates, and one of the most diverse of all animals. Nematode species are very difficult to distinguish; over 28,000 have been described, of which over 16,000 are parasitic. It has been estimated that the total number of nematode...

s feed on plant root

Root

In vascular plants, the root is the organ of a plant that typically lies below the surface of the soil. This is not always the case, however, since a root can also be aerial or aerating . Furthermore, a stem normally occurring below ground is not exceptional either...

s, foliar nematodes live and reproduce inside the leaves

Leaves

-History:Vocalist Arnar Gudjonsson was formerly the guitarist with Mower, and he was joined by Hallur Hallsson , Arnar Ólafsson , Bjarni Grímsson , and Andri Ásgrímsson . Late in 2001 they played with Emiliana Torrini and drew early praise from the New York Times...

 of plants. The nematodes live within the epidermis

Epidermis (botany)

The epidermis is a single-layered group of cells that covers plants' leaves, flowers, roots and stems. It forms a boundary between the plant and the external environment. The epidermis serves several functions, it protects against water loss, regulates gas exchange, secretes metabolic compounds,...

 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

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 in greenhouse

Greenhouse

A greenhouse is a building in which plants are grown. These structures range in size from small sheds to very large buildings...

 and nursery

Nursery (horticulture)

A nursery is a place where plants are propagated and grown to usable size. They include retail nurseries which sell to the general public, wholesale nurseries which sell only to businesses such as other nurseries and to commercial gardeners, and private nurseries which supply the needs of...

 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

Irrigation may be defined as the science of artificial application of water to the land or soil. It is used to assist in the growing of agricultural crops, maintenance of landscapes, and revegetation of disturbed soils in dry areas and during periods of inadequate rainfall...

, 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.