How to identify common easily confused symptoms in rice

I. Several kinds of bacterial wilt

1. Purple sheath blight bacterial wilt. Mostly seen in the late stage of late rice, often occurring in clumps in the field, and also with several plants affected in one hill. The base tissue of the rice is soft-rotted, with dark brown lesions. Peeling open the basal leaf sheath and stem, many black sclerotia smaller than amaranth seeds can be seen.

2. Bacterial foot rot bacterial wilt. Occurs sporadically in the field, generally 1-3 plants affected in one hill; the base of diseased plants shows mouse-gray rot, the root system is sparse and decayed, and peeling open the basal stem reveals it is full of foul water, with no sclerotia.

3. Physiological bacterial wilt. The rice stem shrinks and dries, and when the base of the rice stem is pinched by hand it is shrunken and hollow, making the plant prone to lodging, resembling damage by brown planthopper sclerotia. But there is no insect body at the stem base, no lesions, and no sclerotia in the leaf sheath and basal stalk; it mostly occurs when late rice is near maturity, with patches and blocks of bacterial wilt and wilting.

II. Several kinds of dead heart

1. Borer dead heart. Insect holes or insect frass can be seen on the lower part of the rice plant, and the dead heart is easy to pull up.

2. Mole cricket damage dead heart. There are no insect holes and no insect frass on the rice stem, the dead heart is easy to pull up, and the stem base and roots are broken apart.

3. Stripe leaf blight dead heart. The central leaf of the diseased plant has yellow stripes and curls into the shape of a paper spill, bending and drooping to form a "false dead heart." There are no insect holes at the base, no rot, and the dead heart is not easy to pull up.

4. Wilting-type bacterial leaf blight dead heart. There are no insect holes on the rice stem, the basal stem nodes turn yellowish-white with bacterial ooze, with no foul odor, and peeling open the just green-curled central leaf often also reveals yellow bead-like bacterial ooze.

III. Several kinds of leaf spots

1. Rice blast leaf spot. In the acute type, the lesion begins as a clear brown small spot, then becomes oval, with gray-green mold-like material on the back of the leaf; in the chronic type, the lesion becomes diamond-shaped, reddish-brown at the sides, gray-white in the center, with a brown line running through the middle of the lesion. When humid, gray-green mold can be seen on the back of the lesion.

2. Sesame leaf spot. The lesion initially resembles a small needle-head-sized dot, then gradually forms an oval spot, shaped like sesame. At a rough glance the lesion is dark brown, darker than rice blast lesions; on close inspection the color is divided into 3 layers: a yellow halo on the outside, a relatively wide dark brown edge layer, and mostly yellow in the center. There is no necrotic line at the two ends of the lesion, and mold fuzz is hard to see on the diseased part.

3. Brown stripe leaf spot. The lesion is a short line-like stripe, brown, parallel to the leaf veins, mostly at the leaf tip, and the mold layer is hard to see. When the diseased part is broken and squeezed, a milky white juice flows out. Severely diseased plants rot at the lower part, giving off a foul odor, the diseased leaves have dead heart, and the central leaf dies inside the culm.

IV. Several kinds of yellow leaves

1. Bacterial leaf blight yellow leaves. On the leaf tip or leaf margin, yellow-green or dark green spots first appear, then expand along the leaf veins into streaks, appearing gray-white; the boundary between the diseased part and the healthy part is obvious, and yellow gum-like "bacterial ooze" is often present on the lesions.

2. Yellow dwarf disease yellow leaves. It first occurs at the leaf tip of the 1-2 leaves below the top leaf, then gradually develops until the whole leaf turns yellow, or becomes mottled mosaic; the plant is dwarfed with shortened internodes, the rice leaves droop and spread flat, there are many black roots and few new roots, and the plant often rolls longitudinally, turns yellow, dries up and dies.

3. Physiological premature senescence yellow leaves. It spreads from the bottom upward, and the diseased leaves mostly appear orange-yellow with a certain metallic luster, occurring in patches or throughout the whole field. There are no lesions on the yellow leaves and no bacterial ooze.

4. Fertilizer damage yellow leaves. Ammonium bicarbonate, ammonia water, pesticides, etc., if applied improperly, can cause poisoning, leading to blocks and patches of rice leaves being scorched into bright yellow or golden yellow, and sometimes there are scorched spots on the yellow leaves.

V. Several kinds of white heads

1. Yellow stem borer white heads. There are insect holes and insect frass on the rice stem, the white heads are easy to pull out, there is no lesion on the panicle neck, and the white head clusters in the field are obvious.

2. Rice neck blast white heads. There are no insect holes on the rice stem, the white heads are not easy to pull up, and dark brown lesions occur on the panicle neck, panicle rachis, and branch stalks. The panicle neck or branch stalks break easily, and when humid, gray-brown fuzzy mold grows on the diseased part.

3. Sheath blight white heads. On the leaf sheath, leaf blade, panicle neck, or stem, dark green spots first appear, then expand into oval cloud-patterned lesions; the lesion edge is brown, the center is light brown to gray-white, there are no insect holes on the stem, the basal tissue becomes soft, and the white heads lodge flat on the ground.

4. Bacterial foot rot white heads. Occurs sporadically in the field; the white heads do not lodge easily and do not break, the stem base and roots show gray soft rot with a foul rot odor, there are no insect holes on the stem, the roots are sparse and decayed, peeling open the basal leaf sheath and stem shows no sclerotia, and the white heads are not easy to pull out.