II. Rose
Rose is an ornamental shrub grown for its beautiful pleasantly smelling flowers of various hues in the gardens but its commercial cultivation is done for its flowers and rose oil in the states of Uttar Pradesh, Tamil Nadu, Karnataka, Rajasthan and Punjab.
Of the nearly 15 nematode species associated with rose, most common and damaging are Meloidogyne spp, Xiphinema diversicaudatum, Hoplolaimus galeatus, Pratylenchus spp., Tylenchorhynchus dubius, etc.
a. Root Knot Nematode (Meloidogyne spp.):
Though M. hapla, M. arenaria, M. incognita and M. javanica have been mentioned as rose pests in the countries like USA, Russia, Israel and Poland only latter two have been reported from roses in India. Damage is at its worst in warm sunlit sandy soils that remain moist.
Nature of Damage:
- Sedentary endoparasites in which J2s preferably invade the roots near root cap.
- The parasitic nematodes suck and drain the fine hair like rose roots and create knots in the smaller roots thus, limiting the development of the root system.
- These tiny swellings (galls) appear all over the mass of the rose roots.
- The damaged roots can no longer take up water or nutrition into the upper parts of the plant.
Symptoms:
- Weak, stunted plants, don't have normal healthy green coloration.
- Flowering is sparse.
- The overall life span of the nematode affected rose is shortened greatly.
Management:
- Marigolds or Alliums as under plantings repel nematodes.
- Nematodes can be controlled by planting nematode-free plants into parts of the garden where nematodes haven't been a problem previously.
b. Dagger nematode (Xiphinema diversicaudatum):
- It is a major pest of roses in countries like USA, Russia, Canada, Australia, New Zealand, India etc.
- Its wide host range includes strawberry, raspberry, grapevine, apple, asparagus, cabbage, carrot, cherry, peach, hops etc. But it is most serious on rose and strawberry.
- It is a migratory ectoparasitic nematodethat mainly infects the root tips.
- It causes galling of root tips in roses. Besides, malformation, chlorosis and dwarfing of roses are recorded.
- Life cycle may take three years to complete.
- Females survive for more than five years and mate several times during this period with males which are as abundant as females.
- It can survive in the soil devoid of higher plants for up to three years.
- Eggs are killed at 5oC, but juveniles and adults survive this temperature.
- Fallowing and crop rotation are practically not feasible against this nematode due to its vast host range.
- This nematode poses more threat as a virus transmitting agent.
 Galling on rose roots caused by Xiphinema diversicaudatum
c. Lesion nematode (Pratylenchus spp.):
- Important species are P. vulnus, P. pratensis and P. penetrans.
- Root symptoms appear in the form of dark lesions, reduced root system and death of feeder roots.
- Above-ground symptoms appear in the form of malnutritioned stunted plants showing leaf chlorosis and sparse flowering.
- Interculturing with marigold and post-planting drenches with DBCP (nemagon) controls the nematodes.
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