Paralongidorus maximus

Adult individuals possess a characteristic elongated, thread-like body of a whitish color. The body length can reach several millimeters, making them visible to the naked eye upon careful examination of soil samples.

A key morphological feature is the presence of a very long and thin stylet (odontophore), which is used for piercing plant tissues. This structure allows the nematode to penetrate deep into root tissues.

Systematically, this species belongs to the kingdom Animalia, phylum Nematoda. Unlike many other plant-feeding nematodes, P. maximus is an ectoparasite, meaning it feeds on the root surface without fully entering the internal tissues.

The life cycle includes an egg stage and four larval stages, each followed by a molt. Development occurs slowly, and the entire life cycle can last more than one year depending on environmental conditions.

Paralongidorus maximus is a polyphagous pest that damages a wide range of crops. The greatest economic damage occurs in nurseries, orchards, and fields growing vegetable crops.

Key host plants include strawberries, raspberries, and various species of coniferous and deciduous trees. Additionally, the nematode can parasitize many weed species, allowing it to survive in the soil for long periods.

Damage manifests as a result of direct mechanical injury to root cells caused by the stylet. This leads to the formation of specific galls (swellings) on the root tips, which halts their normal growth.

The damaged root system loses its ability to effectively absorb water and mineral nutrients. The plant experiences constant stress, which is exacerbated during drought periods.

In addition to direct damage, secondary infections—such as pathogenic fungi and bacteria—enter the plant through the microscopic wounds caused by the nematode, leading to root rot and plant mortality.

Nematode activity is directly dependent on soil temperature and moisture levels. The most favorable conditions are moderate temperatures ranging from +15 to +22 degrees Celsius.

In open-field conditions, the period of maximum damage typically occurs during spring and autumn when the soil is sufficiently moist and plant roots are actively growing, releasing attractants.

During hot summer months, when the soil dries out, nematodes may migrate to deeper soil layers where moisture persists or enter a state of anabiosis.

The parasite spreads across a field through the movement of infested soil attached to agricultural machinery, tools, or footwear. Nematodes can also be transported with nursery planting material.

The survival duration of the population without host plants is limited; however, the presence of weeds ensures the stability of the pest population within the field.

Above-ground symptoms of P. maximus infestation are not strictly specific, which often complicates diagnosis. Plants exhibit stunted growth and look suppressed and chlorotic.

A key sign is the uneven development of plants in the field: the emergence of "patchy" areas where crops look significantly weaker or are dying.

Upon digging up the plants, root deformation is observed. Root tips may be crooked, branched, or possess visible galls resulting from the disruption of the apical meristem.

During drought periods, infested plants are the first to wilt, as they cannot compensate for water loss due to an impaired root system.

Accurate diagnosis requires a phytohelminthological analysis of soil and root samples in a specialized laboratory using nematode extraction methods.

Control of P. maximus is difficult due to the deep migration of individuals in the soil and the lack of highly effective selective nematicides for most crops.

The primary control method is the implementation of crop rotation. Excluding susceptible crops from planting for 3–5 years can significantly reduce the nematode population density in the soil.

It is important to thoroughly clean agricultural machinery and tools before moving from infested fields to clean areas to prevent the spread of the pest.

The use of sanitized, certified planting material grown in sterile substrates is a key condition for preventing the infestation of new areas.

The use of green manure crops with phytosanitary properties (e.g., certain varieties of mustard or oilseed radish) helps suppress nematode populations in the soil through the release of toxic alkaloids.