Strawberry aphelenchoides: symptoms of pest damage and methods of nematode control
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5 р \. Aphelenchoides fragariae [pathogen. A Y t —
II. ^ -: = I R Y | E - < E | | 'Trote, 1961). Legend: A — sexually mature female; B — head end; C — tail end of female; sb | D — tail end of male; E — spicule; s.b. — median esophageal bulb; st. — stylet; m. — mucro; v. — vulva. d |. `ch ‹ A < 1 < “A EE! A TS. A 1“ | i \ \ / 7 = m #4 2.16.5. Nematodosis Strawberry nematode (aphelenchoidosis)
Pathogen — Aphelenchoides fragariae (Ritzema Bos) Christie.
Harmfulness. Infects about 300 plant species from 50 families, including 70 fern species. In greenhouses, it also affects ornamental plants: Amaryllidaceae, Liliaceae, Geraniaceae, Begoniaceae, Violaceae, Rosaceae, many members of the Asteraceae family, and others.
Symptoms. The main signs of infection are yellowish-brown or reddish spotting of leaves and deformations of shoots and reproductive organs.
Strawberry aphelenchoidosis: pest biology and control measures
Strawberry aphelenchoidosis is caused by microscopic nematodes that parasitize inside and outside plant tissues. Pests are located mainly on leaves, in buds, and in the primordia of reproductive organs. Their vital activity leads to the deformation of plant organs, stunted growth, and a significant decrease in yield. The development of one generation of the pest occurs rapidly, which requires prompt control measures from the agronomist.
For accurate identification of the nematode in the laboratory, its morphometric parameters are evaluated. The pest's body is thin and highly mobile. Females are 0.45–1.00 mm long and 15–23 μm wide, with a stylet 10–11 μm long, a vulva at 64–72% of the body length, and a posterior uterus about 8 body diameters long. Males are somewhat smaller: their length is 0.60–0.80 mm with a width of 13–21 μm, spicules reach 17–21 μm, and the stylet is 8–10 μm.
The basis of control against aphelenchoidosis is careful preparation of planting material. Thermal disinfection allows for the effective destruction of nematodes at all stages of development without damaging the plants themselves. Also, when preparing transplants and for the protection of nursery plots, the application of systemic nematicides is permitted. Timely prevention prevents the spread of the dangerous parasite throughout the planting area.
- Generation development — 2–3 weeks
- Female length — 0.45–1.00 mm
- Male length — 0.60–0.80 mm
- Water temperature for treatment — 46–47 °C
- Thermal treatment time — 10–15 minutes
- Perform thermal treatment of the planting material by immersing the transplants in hot water.
- Keep the plants in water for a strictly defined time, observing the temperature regime.
- Use systemic nematicides for treating nursery plots and preparing clean planting material.
Diagnosis of non-pathogenic disorders and nutrient deficiencies
Improper care of plantings often provokes the appearance of symptoms that are easily confused with infectious diseases. Physiological disorders can manifest as wilting, spotting, or changes in leaf coloration. It is important for the agronomist to remember that visual assessment does not always yield an accurate result. Any preliminary diagnosis must be confirmed by laboratory analysis of plant samples for the absence of pathogens.
Symptoms of non-infectious disorders often coincide with signs of dangerous diseases. Do not start chemical treatments with fungicides or bactericides until you receive laboratory test results confirming the absence of pathogenic microorganisms in the samples.
Most non-pathogenic disorders can be corrected upon timely detection and elimination of the causes of stress. The agronomist must regularly monitor the condition of the foliage and shoots for deviations. To quickly determine the causes of plant condition deterioration, use the table of indicative symptoms provided below.
| Symptom | Possible cause of the disorder |
|---|---|
| Leaves retain turgor but turn yellow | Growing in calcareous soil or watering lime-intolerant plants with hard water |
| Dry brown dots or spots | Lack of soil moisture (insufficient irrigation) |
| Soft dark-brown spots | Watering with cold water, moisture on leaves, burns from sunlight or aerosols, pest damage |
| Leaves curl and fall off | Sudden temperature changes, cold drafts, sharp increase in light intensity during the day, or severe soil drying |
| Simultaneous leaf drop without loss of turgor | Overwatering or the development of an infectious disease |
| Drying of leaf tips | Low humidity (dry air) |
| Yellowing, drying, or wilting of leaf edges | Soil drying or overwatering, excess light (regular drooping at noon), excessively high temperature, lack of light, or nutrient imbalance |
| Stunted growth of the aerial part | Insufficient lighting, excess or deficiency of nutrients, dry air |
| Stretched stems | Insufficient lighting |
Nutrient deficiency also causes characteristic changes in the appearance of plants. Symptoms of element deficiency can be localized both on old leaves and on young growing tissue. Understanding this specificity allows for a quick adjustment of the top dressing schedule in field conditions or in a greenhouse. Below is a guide for non-pathogenic disorders for key elements of mineral nutrition.
Pay attention to the soil acidity in your plot. Iron and manganese deficiency usually manifest in alkaline and limed soils, whereas magnesium starvation is characteristic of acidic soils.
Diagnostic keys have been developed for the precise identification of specific nutrient deficiencies. They take into account the localization of the first signs of starvation on the plant and the nature of tissue changes. A summary table will help to quickly determine the missing element and adjust the nutrition program.
| Nutrient | Localization of symptoms | Characteristic signs of starvation | Conditions for deficiency manifestation |
|---|---|---|---|
| Iron | Young leaves (initially only between veins) | Light yellow color, transitioning to yellowing of the entire leaf. Necrosis and tissue death are usually absent. | Alkaline or heavily limed soils |
| Manganese | Initially on young leaves between veins, then on older ones | Interveinal chlorosis (veins remain green even during severe starvation). Chlorotic tissue turns brown or becomes transparent, gradually undergoing necrosis. | Predominantly alkaline or excessively limed soils (also occurs in acidic ones) |
| Zinc | Young leaves | Leaves are abnormally small, covered with yellow spots or uniformly chlorotic. Necrosis and tissue death are characteristic. | — |
| Potassium | Old leaves in the lower part of the plant | Greyish-green color of leaves transitions to bronze or yellow-brown, edges turn brown. Spots along veins, tissue decay and death. Roots are weak, brown. Stems are thin and lignifying. | — |
| Magnesium | Old leaves | Interveinal chlorosis (veins remain green). Leaves are brittle, edges curled upwards. Chlorotic tissue turns brown and dies. Purple-red pigmentation is possible on individual leaves. | Predominantly acidic soils |
| Molybdenum | Old leaves (then young ones as growth progresses) | Clearly defined mottling with light green veins. Areas of chlorotic tissue swell, leaf edges curl inward. Necrosis develops along the edges and tips. | — |
| Calcium | Growing tissues of roots and stems, young leaves | Thick woody stems, stunted growth. Root tips die and disintegrate; small spherical swellings form on the surviving ones. New leaves are chlorotic (old ones remain green). New shoots lose turgor; in cases of acute deficiency, terminal buds die. | — |
Diagnosis of nutrient deficiency based on external signs
It is important to recognize signs of nutrient deficiency in plantings in a timely manner. A lack of boron, copper, nitrogen, or sulfur directly affects the development of the above-ground part and the root system. Timely diagnosis allows for the accurate determination of the cause of plant suppression and the adjustment of the nutrition scheme.
Symptoms of nutrient deficiency are easily confused with infectious diseases, therefore always evaluate the signs in combination.
Boron deficiency manifests as distinct deformation of above-ground organs. Newly formed leaf buds and leaf stalks are light in color, brittle, and often malformed. Internodes are shortened, and leaf rosettes form at the tips of shoots. With prolonged starvation, terminal buds die, and new shoots develop from lower buds. Root growth is significantly slowed.
Symptoms of boron deficiency are also clearly visible in other crops. Dark-colored areas of corky tissue appear on the surface of radish roots and other plants. The formation of hollow stems is characteristic of head cabbage and cauliflower. In celery, the stems crack when this element is in short supply.
When diagnosing boron deficiency, use the following symptom patterns as a guide:
- growth slows down, chlorosis appears on leaves;
- growth is slowed, there is no leaf chlorosis.
Copper deficiency leads to leaf tissues losing turgor, and the blades themselves look as if they have been bleached. Pronounced chlorosis develops on the plants. At the same time, overall growth is significantly slowed.
Copper starvation is usually observed in soils rich in organic matter.
Nitrogen deficiency is expressed by the slowing of plant growth, while their stems become thin, fibrous, and hard. Large yellow-green spots appear on the leaves, and in cases of acute starvation, the entire plant may turn yellow. At the onset of nitrogen starvation, the root system develops better than the above-ground organs. However, as the deficiency increases, root growth ceases, and they turn brown and die.
Sulfur deficiency is manifested by a change in the condition of lower leaves—they become thick, hard, and gradually acquire a yellowish-green color. The stems are hard, woody, abnormally elongated, and spirally twisted. The root system remains highly developed during sulfur starvation.
In another type of starvation, plant stems become thin and woody, while leaves become smaller and acquire a darker color than normal. In many vegetable crops, characteristic purple-violet shades appear on the lower surface of the leaves. Under such symptoms, roots are very poorly developed. The processes of fruit set and maturation are significantly delayed.
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