Foliar disease on som alone costs roughly 12,900 kg of leaf per hectare per year across the four principal diseases — against a mature yield of 18,000–20,000 kg. Leaf lost to disease is rearing capacity lost, so plant protection here is silkworm protection at one remove.
Som
| ৰোগ | কাৰক জীৱ | Peak | Leaf loss | Control |
|---|---|---|---|---|
| Leaf spot | Phyllosticta perseae | Year-round; peak Jun–Aug | 3,214 kg/ha/yr (16.07 %) | 0.1 % Indofil M-45 twice at 15-day intervals before peak; use S3 som |
| Anthracnose | Colletotrichum gloeosporioides | July (60 %) | 2,932 kg/ha/yr | Pluck and burn infected leaves early; Indofil M-45 as prophylactic |
| Grey blight | Pestalotiopsis desiminata | May–Aug | 3,705 kg/ha/yr | 0.1 % Bavistin twice at 15-day intervals |
| Red rust | Cephaleuros parasiticus | — | 3,022 kg/ha/yr | Prune and pluck infected parts; 1 % Bordeaux mixture |
Leaf spot: circular to irregular brown spots with yellow margins, coalescing until the lamina dries and falls. Anthracnose: brown round to oval spots, infected areas drying brown to black, branch tips withering. Grey blight: ash-grey spots enlarging, collapsing and malforming. Red rust: yellow-green to orange hairy pustules with chlorotic halos, branches stunted.
Soalu
| ৰোগ | কাৰক জীৱ | Peak | Leaf loss | Control |
|---|---|---|---|---|
| Brown blight | Colletotrichum gloeosporioides | Sep–Oct | 3,142 kg/ha/yr | Pluck and burn; copper oxychloride (Fytolan / Blitox-50) @ 3 g/L at 15-day intervals |
| Grey blight | Pestalotiopsis spp. | Feb–Mar; Oct–Dec | 3,801 kg/ha/yr | Pluck and burn; copper oxychloride @ 3 g/L as prophylactic |
| Red rust | Cephaleuros | — | — | As for som |
Castor
| ৰোগ | কাৰক জীৱ | Season | Control |
|---|---|---|---|
| Seedling blight | Phytophthora parasiticus | End June – September | Fytolan / Blitox-50 @ 3 g/L at 15-day intervals |
| Alternaria blight | Alternaria ricini | Rains; heaviest Apr–Jul | Fytolan / Blitox-50 @ 3 g/L at 15-day intervals |
| Cercospora leaf spot | Cercospora ricinella | May – August | Dithane Z-78 or Ziram @ 2 g/L |
| Powdery mildew | Leveillula taurica | November – March | 0.2 % wettable sulphur at 15-day intervals in dry weather |
| Fusarium wilt | Fusarium oxysporum f. sp. ricini | Rainy season | Seed treatment with Thiram @ 3 g/kg or Carbendazim @ 2 g/kg; soil drench with Carbendazim @ 2 g/kg |
Safety period before feeding. Seven days after Fytolan or Blitox-50;
one month after wettable sulphur. Leaf sprayed inside these windows must not go to worms.