Infecting Organism

Diagnostic Symptoms

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Alternaria alternata

Light brown small circular spots that turn dark brown to grey and are circular to irregular in shape with concentric rings. Spots may coalesce forming large areas of necrosis.

Sclerotinia sclerotiorum

Wilting, chlorotic leaves, necrotic leaves at the base of the stem, and bleached stems. Symptomatic plants often have tufts of white hyphae present on stems and large, irregularly shaped 2 to 8mm black sclerotia on the base of the stem.

Sclerotium rolfsii

Yellowing and wilting of leaves, bleached stems, and eventual plant necrosis. White cord-like mycelia growth is visible at the base of stems, especially early in the morning. Mycelium is accompanied by the formation of brown sclerotia 0.5-2mm in diameter.

Septoria steviae

Shiny olive-gray foliar lesions, that are depressed and angular. Lesions often have a chlorotic halo and rapidly coalesce, turn necrotic, and leaves fall from the plant. Up to 50% of the foliage can become necrotic in severe cases.

Rhizoctonia sp.

Sunken reddish spots, gradually expand to kill the plants. Reddish-brown to brown collar rots and root rots are common in young plants. These rots inhibit normal growth and cause stunting or plants with poor vigor. Callus formation and thickening of the collar area also occurs.

Fusarium oxysporum

Wilting, chlorosis, necrosis, premature leaf drop, browning of the vascular system, stunting, and damping-off. Fusarium wilt starts out looking like vein clearing on the younger leaves and drooping of the older lower leaves, followed by stunting of the plant, yellowing of the lower leaves, defoliation, marginal necrosis and death of the plant.

Insect Pest

Description

Control Measure

Cutworm

Cutworms are moth larvae that hide under litter or soil during the day, coming out in the dark to feed on plants. A larva typically attacks the stem, and consequently cuts it down; hence the name cutworm. Cutworms are not worms, biologically speaking, but caterpillars.

Biological

Use Bacillus thuringiensis var. Kurstaki inoculants either as spray or with baits.

Chemical

Soil application of Carbofuran 3G or Phorate 10G followed by an irrigation.

Aphids

White fly

Aphids are small, soft-bodied insects with long slender mouthparts that they use to pierce stems, leaves, and other tender plant parts and suck out fluids.  Many aphid species are difficult to distinguish from one another; however, management of most aphid species is similar.

Whiteflyis a sap-sucking insect that is often found in thick crowds on the undersides of leaves. When infested plants are disturbed, great clouds of the winged adults fly into the air. Both nymphs and adults damage plants by sucking the juices from new growth causing stunted growth, leaf yellowing and reduced yields. Plants become weak and susceptible to disease.

Biological

Use Mineral oil + soap emulsion or Neem oil based insecticides

Chemical

Apply synthetic pyrethroids like permethrin or conventional insecticides like Imidacloprid, malathion, and acephate

Biological

Use Mineral oil + soap emulsion or Neem oil based insecticides

Ues yellow sticky traps

Chemical

Apply dichlorovos, imidacloprid or synthetic pyrethroids

Red spider mites

Red spider mites feed on the content of plant leaf cells by piercing them with their mouthparts. This results in a fine brown speckling effect on leaves where the cells have died. Adult mites also spin a fine silk webbing over leaf surfaces. With heavy infestations this can cover most of the plant

Biological

Use Mineral oil + soap emulsion or Neem oil based insecticides

Wash the plants to physically remove the nites

Chemical

Apply dicofol, dinocarp, abamectin, bifenazate, hexythiazox, or spiromesifen based spray pesticides

Thrips