Diseases and Management of Crops under Protected Cultivation

(Diseases and Management of Crops under Protected Cultivation)
water after one week or 10 days till flowering.
Diseases:
Die-back: This is the most serious of the rose disease in India. Earlier reports suggest that this
disease was caused by fungus Diplodia rosarum Fr.
As the term die-back implies, the disease causes the death of the plant from top
downwards. The disease starts from the pruned surface of the twigs. Initially it may be observed to
the extent to a few centimeters below the pruned end, but in the severe cases, the disease
spreads further and kills the entire plant.
Soil drenching with 2 g/l bavistin, benomyl or demosan, has also been reported to control
the disease. Spraying with 0.2% captan or 0.2% mancozeb or 0.2% copper oxychloride
immediately after pruning and then twice at 10 days interval is also effective for controlling die
back of rose
Black spot: This disease is caused by Diplocarpon rosae Wolf.
This disease is also called leaf blotch, leaf spot, blotch and star sooty mold. Characteristics
black spot 2-12 mm in diameter develops on upper leaf surfaces. These leaf spots are circular or
irregularly coalescent with characteristic feathery, radiate, fibrillose margins of sub-cuticular
mycelial strands.
The infected leaves as they are observed should be clipped off and burnt. Preventive
sprays of ferbam (0.1%) at fortnightly intervals, benlate or bayleton (0.1%) applied just before the
appearance of the spots helps in managing the disease. Bavistin (0.1%) was found most effective
fungicide against leaf spot caused by Diplocarpon rosae.
Powdery mildew: It is a major disease of the rose all over the world caused by Sphaerotheca
pannosa var. rosae (Wallr) Lev.
The disease affects all the aerial parts of the plant, though the leaves are found to be
affected more. The younger leaves get curled, exposing the lower surface and such leaves are
likely to be purplish than the normal leaves raised blister like areas develop in these leaves, which
becomes coated with the white powdery growth of the fungus.
Insect:
Mites: These are minute, polyphagous pests found in large colonies on the underside of the
leaves covered with fine silky webs. Due to their feeding, white specks appear on the leaves and
these specks coalesce and appear as white patches. Ultimately, affected leaves become mottled.
Abamectin (0.5 ml/l) or difenthiuron (Polo) should be sprayed.
Aphids: Large, dark green or pink brown aphids Macrosiphum rosae feed on buds, shoots and
leaves. Colonies may persist throughout the year but are most numerous and troublesome in late
spring and early summer. Foliage of infested plants is fouled with sticky honeydew and sometimes
with sooty molds and growth may be checked. Aphid populations tend to increase most rapidly on
soft and sappy growths. Use of nitrogenous fertilizers should be restricted. Systemic insecticides
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