1-Fungal diseases:         Verticillium wilt

The causal organism:   Verticillium Dahlia kleb

Symptoms:

Verticillium wilt caused by v. Dahlia kleb. Has been found almost in all pistachio growing areas of the many of country, and it is considered as the most common and damaging diseases of these crop .The diseases may kill young trees, while in fully grown trees usually only branches die. Trees of any age are subject to attack and hundreds die each year. The fungus, which attacks pistachios, also attacks cotton, tomatoes, melons, stone fruits and weed species, also serve as hosts, and these enable the pathogen to become established in non cultivated land.

The first symptoms of verticillium wilt are intervene patches of yellowing or scorching of the leaves on affected branches. Collapse of the branches with the first warm weather because root system that attacks of verticillium provide enough water, The classic symptom of verticillium wilt is rabid dry and death of one or more branches or whole tree, usually in late spring or early summer.

Xylem elements infected by verticillium become clogged by substances elaborated by the fungus and the tree these substances are darkly pigmented, and a cross-section of an infected root, trunk, or brunch reveals the pattern of verticillium infected in the new xylem: scattered black speckles or a more or less discontinuous black ring depending upon how many vessels are infected. The discolored xylem elements are non –functional and cannot transport water to the upper portions of the tree. The branches that die are these which are connected to the infected root and vascular system and no longer receive adequate water.

verticillium survives in soil the form of resting structures called microsclerotia. Each microsclerotia is approximately 30 dark-colored cells. They are extremely hardly and remain viable in soil for many years. Several hundred microsclerotia can be present in a cm^3 of soil and most microsclerotia are fount in the upper 15 cm of soil.

2-Root and Crown rot:

The causal organism:             Phtytophthora ssp.

Symptoms:

Phtytophthora ssp. is one of the most important phytopthological problems in pistachio areas. Above-ground symptoms of root rot usually develop slowly, and diseased trees show reduced growth, thinned canopy and early defoliation for several years .Trees with crown rot typically die within a year or two after inoculation. The bark and outer wood of infected roots and crowns are discolored, but the mycelium of Phtytophthora in the infected tissues cannot be seen by naked eye.

Phtytophthora infections on the trunk or scaffolds of trees from cankers in the bark, and the tree gums profusely.

3- Septoria leaf spot:

The causal organism  Septoria pistaciarum ( Mycospharella pistaciarum )

         In year with high diseases incidence S. pistaciarum may also attack the fruits. These species primary infections are produced by ascospores released from pseudothecia in over wintering leaves on the ground. These diseases are common and especially in years with rainy springs; they may cause heavy defoliant in late summer. Leaf spot from natural infection are round to irregular, 1-2mm diameter, with 1 to20 flaslike fruiting structures of the fungus (pycnidia).pycnidia measure 60-108 mm in diameter, pycnidiospore are colourness, curved to scale-shaped, and 44-85.5 x 3-3.9mm, with 3 to 9 septa.

4-powdery mildew:

 The causal organism:            phyllactinia guttata

Symptoms:

phyllactinia guttata  has been reported on Pistacia terebinthus L. the fungus grows superficially as white powdery mycelia masses. Later the mycelia die, leaving a brown scar. Similar symptom can be found on rachises, fruit stem, petioles, underside of leaf blades, and young shoots. The conidia of the fungus are produced in short chains and are hyaline, one celled and barrel shaped.

Symptoms:

           Aflatoxin has been found so frequently is pistachio nuts from countries in the Middle East, that it has created great concern about is possible presence in pistachios grown in California.

Several recent studies suggested pre-harvest contamination of pistachio nuts with. A.flavus was isolated both from pistachios containing aflatoxin .Aflatoxin was also detected on early split nuts, infested and non-infested by the navel orange worm.

The elimination of early split nuts after harvest would require extensive sorting before hulling. While such a sorting apparition would be very costly if done by humans, electronic color sorters could detect early split nuts after hulling by the distinctly dark surfaces .The shells of early split nuts usually have strains; a characteristic dark stain along the suture can help the identification and sorting of the nuts. Aflatoxin analyses of early split nuts shows that more than 99% of the  aflatoxin contamination is associated with early  split nuts .Therefore it is mandatory that these nuts are recognized and sorted out to reduce aflatoxin to non detectable.