Agri 41. PlantPath

Pyricularia oryzae

Rice blast

Symptoms:

• Elliptical lesions resembling a spindle shape, which tapers towards each end.

• Center of the spot is whitish to gray with brown to reddish brown margin.

Description :conidia are hyaline to pale olive, bicelled (two-septate), with pyriform to obclavate shape.

Rhizoctania solani

Rice Shealth blight

Symptoms:

• initial oval to ellipsoidal greenish gray lesions on leaf sheath.

• older lesions coalesce with grayish white centers with tan to dark brown irregular borders.

Descriptions:

• hyphae are solely produced; septate, dark brown, branched at right angles.

• plate culture below shows the sclerotial bodies that are brown and irregularly shaped.

Bipolaris maydis

Corn Leaf Spot

Symptoms:

• begin as small diamond-shaped lesions.

• develops into elongated or rectangular brown spots.

Descriptions: conidia are curved, fusiform, pale to golden brown, distoseptate,

multiseptate, lunate with round ends, smooth, and with distinct basal scar.

Cercospora arachidicola

Peanut Leaf spot

Symptoms:

• dark brown to black spots on leaves.

• usually with yellow halo.

Descriptions:

• conidiophores are in fascicle (in group) and brown and septated.

• conidia are elongated, smooth, multiseptated, and hyaline.

Puccinia arachinidis

Peanut Rust

Symptoms:

• pin-head size, brick-red pustules on underside of the leaf.

Descriptions:

• uredospores are subglobose, ellipsoidal or obovoid, aseptate (no cross walls), smooth, and cinnamon brown.

Fusarium oxysporum f. sp. cubense

Panama Wilt of Banana

Symptoms:

• Yellowing of the older leaves.

• Pseudostem has brick red to brown streaks.

• Wilting of leaves at the petiole base.

Descriptions:

• microconidia are ellipsoidal, oval or kidney-shaped.

• have either a single septum or none.

Puccinia polysora

Corn Rust

Symptoms:

• round, cinnamon brown pustules on underside of the leaf.

Descriptions:

• uredospores are subglobose, rough-walled, yellow to orange, and aseptate (no cross walls).

Colletotrichum gloeosporiodes

Mango anthracnose

Symptoms:

• circular brown spots on leaves, collapsed spots, sometimes resulting to shot-hole.

• black rot on fruit skin or surface.

Descriptions:

• conidia are one-celled, ovoid to oblong, smooth, and slightly curved.

• conidia are hyaline (photo below shows conidia stained with cotton blue).

Lasodiplodia theobromae

Stem End Rot of Mango

Symptoms:

• dark brown to black rot develop from the stem end of the fruit.

Descriptions:

• conidia are bicelled, dark brown to black, obovoid, smooth.

Cercospora abelmoschi

Okra leaf mold

Symptoms:

• black moldy growths appear on the lower leaf surface.

• reddish discoloration is observed on the upper leaf surface.

Descriptions:

• conidiophores are in fascicle (in group), brown, and septated.

• conidia are multiseptate, smooth, and elongate.

Alternaria porri

Purple Blotch of Onion

Symptoms:

• starts with water-soaked lesions with white center on the leaves.

• progress as brown lesions with purple margin.

Descriptions:

• conidia are multiseptate, obclavate, catenate, with short to long beak, and smooth.

Phythium spp.

Damping-Off of Seedlings

Symptoms:

• water-soaked rot of root and stem.

• above soil plant parts topple down or wilt.

Descriptions:

• sporangia are globose, hyaline, smooth, and unicellular.

Peronosclerospora philippinensis

Corn Downy Mildew

Symptoms:

• white to yellow chlorotic streaks or stripes along leaf veins.

• white growth of structures associated with fungi is seen at the underside of the leaf.

• systemic disease.

Descriptions:

• finger-like sporangiophore.

• sporangia are hyaline, ellipsoidal, and unicellular.

Phytophthora colocasiae

Gabi (Taro) Leaf Blight

Symptoms:

• circular, zonate, brown to purplish brown lesions on leaves.

Descriptions:

• sporangia are obovoid, with papillum, unicellular, and smooth.

Albugo sp.

White Rust of Kangkong

Symptoms:

• white or yellow-creamy pustules on stems, flowers, or lower leaf surface.

• affected parts may curl.

Signs:

• catenate (in chain), hyaline, cylindrical, and smooth sporangia.

• sporangia are connected with disjunctor cells.

Ralstonio Solanacearum

BACTERIAL WILT OF SOLANACEOUS CROPS

Symptoms:

• rapid wilting and death of plants.

• lower leaves turn yellow, sometimes on one side of the plant or one side of a branch. This is followed by leaf and stem wilting.

Descriptions:

• gram-negative , rod-shaped, motile with a single polar or peritrichous flagella, 0.5-0.7 x 1.5-2.0 μm in size.

• colonies white or cream colored, irregularly round, fluidal and opaque.

Xanthomonas oryzae pv. oryzae

BACTERIAL BLIGHT OF RICE

Symptoms:

• lesions develop as water-soaked to yellow-orange stripes on leaf blades or leaf tips with wavy margin and progress toward the leaf base.

• old lesions turn yellow to grayish white with black dots

Descriptions:

• gram negative short and straight rods with round ends ((0.4-0.7 x 0.7-1.8μm), motile by a single polar flagella.

• colonies circular, convex and viscid, whitish yellow to straw yellow in color, have smooth surface, an entire margin, glistening, extremely mucoid.

Pectobacterium carotovorum

SOFT ROT OF VEGETABLES

Symptoms:

• water-soaked lesions which rapidly spread and develop into deterioration of the

tuber (or fruit) into a slimy, foul-smelling mass.

Descriptions:

• gram negative, straight rod (0.5-1.0 BACTERIAL BLIGHT OF ANTHURIUMx 1.0-3.0μm), motile by means of peritrichous flagella.

• colonies are whitish and umbonate.

Xanthomonas axonopodis pv. dieffenbachiae

BACTERIAL BLIGHT OF ANTHURIUM

Symptoms:

• yellowed (chlorotic), water-soaked lesions along the leaf margins that grow rapidly to form dead (necrotic) V-shaped lesions.

Descriptions:

• gram negative, aerobic rods with one polar flagellum, and produce yellow xanthomonadin pigment.

Xanthomonas citri

Cintrus canker

Symptoms:

• blister-like lesions on leaves and fruit darken to tan or black and develop a water-soaked margin with a yellow halo surrounding it.

• lesions may appear raised and corky or scabby surrounded by a water- soaked margin.

Descriptions:

• gram-negative, straight, rods (1.5-2.0 x 0.5-0.75 μm), motile by means of a single, polar flagellum.

Candidatus Liberibacter

Huanglongbing / Citrus Greening

Symptoms:

• blotchy mottle leaves

• reduced fruit size • stunted growth

• root decline and dieback • yellow shoot

Descriptions:

● originally grouped with mycoplasma-like organisms (MLOS) but subsequent studies revealed presence of a cell wall of Gram- negative type.

● cannot be isolated in pure culture.

● found in phloem sieve elements of infected plants.

Candidatus Phytoplasma

Rice Orange Leaf

Symptoms:

● Orange-colored leaves which later roll inward and desiccate.

Description:

● pleomorphic shape phytoplasmas in sieve tubes of infected cell.

Candidatus Phytoplasma

Cassava Witches Broom

Symptoms:

• shortening of nodes with dense clumping of

stunted leaves, resembling a witch's broom.

Meloidogyne incognita

Meloidogyne incognita

Symptoms:

• aboveground: stunting and chlorosis.

• belowground: numerous enlarged roots termed as galls or knots.

Descriptions:

• sedentary endoparasitic nematodes (migrate/feed inside the root tissue and establish a fixed feeding site).

• infective juveniles are vermiform while adult females are saccate/globose.

Radopholus similis

Toppling/Blackhead Disease of Banana

Symptoms:

• aboveground: uprooting (toppling) of banana, especially when fruiting or during

strong winds, because of destroyed anchor roots.

• belowground: black, circular lesions on rhizomes or roots.

Descriptions:

• vermiform migratory endoparasitic nematodes (migrate/feed inside the root tissue all throughout their life).

Pratylenchus spp.

CORN ROOT LESION

Symptoms:

• above ground: stunted growth and leaf chlorosis.

• below ground: lesions and necrosis.

Descriptions:

• vermiform migratory endoparasitic nematodes (migrate/feed inside the root tissue all throughout their life).

Tobacco mosaic virus (TMV)

TOBACCO MOSAIC

Symptoms: Mosaic

• intermingled pattern of light green and dark green areas on leaves with distinct boundaries between the yellow light and green

Description:

• rod shape virus particles

Rice tungro bacilliform virus (RTBV) and Rice tungro spherical virus (RTSV)

Rice Tungro

Symptoms:

• stunting and reduced tillering

• yellow-orange leaf discoloration

Descriptions:

• bacilliform shape and spherical shape virus particles

Banana bunchy top virus (BBTV) or Abaca bunchy top virus (ABTV)

ABACA/BANANA BUNCHY TOP

Symptoms: bunchy top

● stiff, narrow, short upright or erect leaves that crowd together at the apex of stems or pseudostems

● dark green streaks on leaf veins

● chlorotic edges on the leaves

Description:

• Spherical shape virus particles

Papaya ringspot virus (PRSV)

Papaya ring spot

Symptoms:

● mosaic on the leaves: intermingled pattern of light green and dark green areas on leaves with distinct boundaries between the yellow light and green.

● ringspot on the fruit: concentric rings or irregular almost circular chlorotic or dark green lines on fruits.

Descriptions:

• Flexuous rod shape virus particles.

Tomato leaf curl Philippines virus (ToLPV)

TOMATO LEAF CURL

Symptoms:

• Upward or downward curling of leaves.

• Stunted growth.

Descriptions:

• Geminivirus with twin-shaped particle (geminate).

Rice grassy stunt virus (RGSV)

Rice Grassy Stunt

Symptoms: Grassy appearance

• narrow, stiff and pale yellow leaves.

• profuse tillering.

Description:

• filamentous shaped virus particles

Citrus tristeza virus (CTV)

Citrus Tristeza

Symptoms:

• die-back.

• stem pitting.

• yellowing of leaves.

Description: flexuous-rod shape virus particles.

Potato spindle tuber viroid (PSTVd)

Potato Spindle TUber

Symptoms:

• severely reduced growth of infected plants.

• tubers are small, elongated, and cracked.

• ‘eyes’ are more pronounced than normal.

Descriptions:

• highly-structured, rod-like native

conformation that is 37±6 nm in length.

Coconut cadang-cadang viroid (CCCvd)

CADANG-CADANG DISEASE OF COCONUT

Symptoms:

• non-necrotic yellow spots on leaves.

• ‘brooming’ symptom caused by limiteddevelopment of the lamina in palms.

• rounding of nuts and reduction in the husk.

Descriptions:

• similar with PSTVd

Loranthus philippinensis

PHANEROGAM

● hosts are cultivated trees particularly mango.

● Loranthus species may also parasitize neem,

avocado, sapota trees, among others.

Characteristics:

• Hemiparasite or partial stem parasite.

• With leaves but lacks true roots.

Cuscuta sp.

PHANEROGAM:

● has a wide-host range which may include tomato, tobacco, legumes, trees, and shrubs.

Characteristics:

• True parasite.

• Yellow to orange leafless vinestrands around the host.

• Stem winds itself around host.