Pecan nut Diseases A

Lecture To ToT trainees ( FFS)

By Mr. Allah Dad Khan

Provincial Coordinator IPM KPK

MINFAL Pakistan

Pecan Nut Scab Small, rough or velvety olive green to black spots on leaves, green twigs or

fruit; lesions may coalesce to form large dark areas with an irregular shape; leaflets may drop from plant if they are infected at the base of the petiole; lesions on young leaves may dry out and crack, resulting in a "shot hole" appearance as the leaves expand; lesions on shucks are virtually identical to those on the leaves ; severe infection of fruit can cause fruit to stop developing

ScabScab lesions on pecan foliage

Scab symptoms on pecan shucks

ScabScab symptoms on pecan shucks

Scab symptoms on pecan shucks

Pecan nut casebearer Acrobasis nuxvorellaSymptoms

Holes in nutlets at base which usually is associated with black frass that protrudes from the hole; frass and damaged nutlets are held together by silken thread; adult insect is a small, light gray moth; larvae are initially white with a brown head and mature to olive or jade green

Bacterial leaf scorch Xylella fastidiosa

Symptoms Bacterial leaf scorch symptoms on pecan

Tan to brown necrotic lesions with distinct dark brown line separating the diseased tissue from healthy; lesions occur on leaf margin or apex; entire leaves becoming necrotic; leaflets may drop from tree; symptoms may be confined to one limb or scattered throughout canopy

Bacterial leaf scorch

Bacterial leaf scorch symptoms on pecan

Bacterial leaf scorch symptoms on pecan

Bacterial leaf scorch

Bacterial leaf scorch symptoms on pecan

Bacterial leaf scorch symptoms on pecan

Sooty Mold

SymptomsFigure 27. Sooty mold.

Sooty mold is a conspicuous black, sooty fungus found on leaves (Figure 27) and nuts of pecans. This fungus is not pathogenic on plants and can easily be removed by rubbing with a clean cloth. It grows on honeydew produced by insects. The direct damage to plants is minimal; however, severe infestations will reduce the amount of light reaching the leaf surface, thus reducing the production of carbohydrates in the tree. Controlling aphids and other honeydew-producing insects should help to control sooty mold.

Anthracnose Colletotrichum gloeosporoides

Symptoms Shiny, dark brown

sunken lesions on green fruit which may coalesce to cover the whole fruit; may be pink colored fungal masses on lesions during wet weather; yield may be reduced

Downy spot Pseudocercosporella caryigena

Symptoms

Circular, pale yellow spots on lower surface of leaves; spots may be covered with fuzzy white growth during wet; lesions develop through leaves and become visible on upper leaf surface; lesions on upper leaf surface yellow-brown; leaflets may drop from tree; nut yield may be reduced die to defoliation

Shuck and kernel rot Phytophthora cactorum

Symptoms Rotting fruit with rot

starting at stem end of fruit; dark brown rot with light brown margin spreading to cover entire fruit; kernels have a dark seed coat and bitter taste.

Powdery mildew Phyllactinia guttata

Symptoms

Small, powdery white spots on leaves and fruit; spots spread to cover entire leaf; small black fungal fruiting bodies may be visible in the white growth; young leaflets may crinkle as they mature

Vein spot Gnomonia nerviseda

Symptoms

Dark brown to black lesions associated with vascular tissues e.g. along leaf veins or leaf midribs; leaves may fall from trees

Crown Gall

Symptoms Crown gall is a disease that results

in round to irregular swollen tumors or galls, usually found at or near the soil line on the trunk or roots. Infected trees show a lack of vigor, foliage lacks normal green color, and occasionally the tree may die. To prevent crown gall, plant disease-free trees. For individuals with a small pecan nursery, it is important not to locate a nursery in an area where crown gall has been observed previously. As a preventative control measure, it would be advisable to treat the seed with Galltrol-A before planting

Crown Gall

Zonate leaf spot Grovesinia pyramidalis

Symptoms Zonate leaf spot lesions on pecan leaflet

Lesions with concentric rings on leaves which are tan to light brown on the leaf underside and gray-brown on the upper leaf surface; a crystalline substance may be present on the surface of the lesion; infected leaves dry out by late summer and drop from the tree prematurely; defoliation may be severe

Zonate leaf spot

Zonate leaf spot symptoms on pecan leaf

Close-up of zonate leaf spot lesions on pecan leaflet