Diseases and Management of Crops under Protected Cultivation
Diseases and Management of Crops under Protected Cultivation
Diseases and Management of Crops under Protected Cultivation
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(<strong>Diseases</strong> <strong>and</strong> <strong>Management</strong> <strong>of</strong> <strong>Crops</strong> <strong>under</strong> <strong>Protected</strong> <strong>Cultivation</strong>)<br />
leaf spot, stem rot, Phytophthora blight, powdery mildew <strong>and</strong> grey mold respectively. Cucumber<br />
also attracts a considerable quantum <strong>of</strong> fungal pathogens. Out <strong>of</strong> which downy mildew<br />
(Pseudopernospora cubenses), Powdery mildew (Ersiphe cichoracirum <strong>and</strong> Sphacelotheca<br />
fuligena), Alternaria leaf spot (Alternaria cucumerina),Anthracnose (Colletotricum lagenarium) <strong>and</strong><br />
Damping <strong>of</strong>f (Pythium spp) are important. Survival <strong>of</strong> pathogen is also enhanced inside polyhouse<br />
due to availability <strong>of</strong> host because <strong>of</strong> longer growing season.<br />
Bacterial diseases<br />
Bacterial diseases are less frequent but <strong>under</strong> high moisture <strong>and</strong> poor irrigated condition<br />
may cause huge damage. Erwinia carotovora ssp. carotovora (Bacterial s<strong>of</strong>t rot) , Xanthomonas<br />
campestris pv. vesicatoria (Bacterial spot), Ralstonia solanacearum (Bacterial wilt). Pseudomonas<br />
syringae pv. lachrymans (Angular leaf spot), Erwinia tracheiphila <strong>and</strong> Ralstonia solanacearum<br />
(Bacterial wilt) are pronounced to name some.<br />
Viral diseases<br />
Tomato, cumcumber <strong>and</strong> capsicum are very sensitive to virus diseases <strong>under</strong> protected<br />
environment. It <strong>of</strong>ten spreads in the plantation by insect vectors such as whitefly, thrips <strong>and</strong><br />
aphids. The damage caused by the virus is usually much greater than the mechanical injury<br />
caused by the insect vector. Plant tissue damaged by a viral disease does not die immediately.<br />
The most important symptom <strong>of</strong> viral infections is the light (white or yellow) colour <strong>of</strong> the leaves, or<br />
a mosaic pattern <strong>of</strong> light <strong>and</strong> darker shades <strong>of</strong> green on the leaves. In many cases, viral disease<br />
leads to dwarfed growth, rosette formation or other strange stem, fruit <strong>and</strong> leaf deformations. The<br />
symptoms <strong>of</strong> viral infections are <strong>of</strong>ten not found everywhere in a cultivated field but rather in<br />
patches <strong>and</strong> also sometimes without symptoms. Viruses prevalent among greenhouse crops<br />
include Tobacco mosaic virus or tomato mosaic virus (TMV or ToMV), Cucumber mosaic virus<br />
(CMV), Tobacco etch virus (TEV), Potato virus-Y (PVY), Potato leafroll virus (PLRV), Tomato<br />
spotted wilt virus (TSWV), Alfa- Alfa mosaic virus, Pepper veinal mottle virus (PVMV), Pepper mild<br />
mottle virus(PMMY), Chilli veinal mottle virus (CVMV Or Chivmv), Tomato yellow leaf curl virus<br />
(TYLCV), Tomato Big-Bud mycoplasma (TBB)<br />
<strong>Management</strong> strategy<br />
Proper field sanitation is the one <strong>of</strong> most important management strategy, since once the<br />
build up <strong>of</strong> innoculum occurs inside polyhouse it is very difficult to manage it. So prevention is<br />
always better than cure. Use disease-resistant varieties. Reduced incidence <strong>of</strong> leaf wetness by<br />
staking plants providing ample spacing between plants to allow for good air movement, <strong>and</strong><br />
avoiding overhead irrigation. Judicious use <strong>of</strong> chemicals with least toxicity recommended specially<br />
for polyhouse cultivation shoud be done. Chemicals like chlorothalonil, cymoxanil <strong>and</strong><br />
azoxstrobulin are prohibited in polyhouse grown tomato <strong>and</strong> thus should be avoided. As for viruses<br />
scout fields for the first occurrence <strong>of</strong> virus disease. Where feasible, pull up <strong>and</strong> destroy infected<br />
plants, but only after spraying them thoroughly with an insecticide to kill any insects they may be<br />
harboring. Use reflective mulches to repel insects, thereby reducing the rate <strong>of</strong> spread <strong>of</strong> insectborne<br />
viruses. Monitor vector population early in the season <strong>and</strong> apply insecticide treatments<br />
when needed. Minimize plant h<strong>and</strong>ling to reduce the amount <strong>of</strong> virus spread mechanically.<br />
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