''Heterodera humuli'' is a plant pathogenic nematode, the hop cyst nematode. It is an obligate parasite and infests hop plants, ''Humulus lupulus''.

Description

The female hop cyst nematode is white and lemon-shaped with a body length of and a width of . The male is transparent and

vermiform Vermes (" vermin/vermes") is an obsolete taxon used by Carl Linnaeus and Jean-Baptiste Lamarck for non-arthropod invertebrate animals. Linnaeus In Linnaeus's ''Systema Naturae'', the Vermes had the rank of class, occupying the 6th (and last) ...

with a body length . The

eggs An egg is an organic vessel in which an embryo begins to develop. Egg, EGG or eggs may also refer to: Biology * Egg cell, the female reproductive cell (gamete) in oogamous organisms Food * Eggs as food Places * Egg, Austria * Egg, Switzerland ...

are oval, and the first two

instar An instar (, from the Latin '' īnstar'' 'form, likeness') is a developmental stage of arthropods, such as insects, which occurs between each moult (''ecdysis'') until sexual maturity is reached. Arthropods must shed the exoskeleton in order to ...

larva A larva (; : larvae ) is a distinct juvenile form many animals undergo before metamorphosis into their next life stage. Animals with indirect development such as insects, some arachnids, amphibians, or cnidarians typically have a larval phase ...

e are vermiform. The second instar larvae are mobile in damp soil and invade suitable roots. Here they develop further and become sedentary, burying their heads in cells and feeding on the cell sap. The central part of their bodies swells, and after moulting again they develop into bottle-shaped third instar larvae and then thicker lemon-shaped fourth instar larvae. At this stage they either become male or female depending on the food supply. The swollen larval bodies break out of the root and the mobile males travel through the soil while the females remain attached to the root tissues by their heads. After insemination, the females continue feeding and lay eggs. These remain inside the bodies of the females which die and turn into cysts. A single generation lasts 34 to 56 days depending on environmental conditions.AgroAtlas
/ref>

Distribution

The hop cyst nematode occurs in many European countries, the U.S., Canada, South Africa and New Zealand.

Biology

The optimal soil temperature for the development of this nematode in plant roots is about . It prefers heavy soils. The main host plant is the hop, ''Humulus lupulus'', but the nematode can also survive in the roots of the

stinging nettle ''Urtica dioica'', often known as common nettle, burn nettle, stinging nettle (although not all plants of this species sting) or nettle leaf, or just a nettle or stinger, is a herbaceous perennial flowering plant in the family Urticaceae. Or ...

, ''Urtica dioica''.Morphology and Biology of Hop Cyst Eelworm (Heterodera Humuli Filipjev 1934)
/ref> Infection with this nematode can lead to a poor quality crop and a decrease in yield of hops of 50%. Mortality in hop cuttings is higher in the presence of this nematode. In a research study in England, cysts of ''H. humuli'' were found in every sample taken in a hop garden. The largest number occurred in the top of soil but some were found at much greater depths. The numbers of second instar larvae fluctuated in a pattern which indicated that there were probably two or three generations in a growing season, each lasting about six weeks. Under controlled conditions of and a sixteen-hour day, the life cycle lasted forty days and this was the optimal temperature for development. Most second stage larvae invaded hop roots at but the egg hatch was greater at . In moist soil, the second-stage larvae survived for at least fifty four days and were still capable of invading roots and reproducing. It is uncertain how long the eggs remain viable in the cysts but in hatching trials using root diffusates of ''H. lupulus'', ''

Cannabis sativa ''Cannabis sativa'' is an annual Herbaceous plant, herbaceous flowering plant. The species was first classified by Carl Linnaeus in 1753. The specific epithet ''Sativum, sativa'' means 'cultivated'. Indigenous to East Asia, Eastern Asia, the pla ...

'', ''Urtica dioica'', ''

Urtica urens ''Urtica urens'', commonly known as annual nettle, dwarf nettle, small nettle, dog nettle, or burning nettle, is a herbaceous annual flowering plant species in the nettle family Urticaceae. It is native to Eurasia, including the Himalayan regions ...

'' and ''

Ficus ''Ficus'' ( or ) is a genus of about 850 species of woody trees, shrubs, vines, epiphytes and hemiepiphytes in the family (biology), family Moraceae. Collectively known as fig trees or figs, they are native throughout the tropics with a few spe ...

'' sp., only the diffusate of ''H. lupulus'' had any effect on the hatching rate of the larvae.

References

External links

Nemaplex, University of California - Heterodera humuli
{{Taxonbar, from=Q5747103 humuli Plant pathogenic nematodes Hop diseases Nematodes described in 1934