DISEASES AND INSECT PESTS. 



The following short account of the diseases and insect pests is not intended to be exhaustive, 

 and is only intended to refer to the raisin districts of our State. I have not included accounts of 

 the phylloxera nor of other insects or fungi which do not exist in these districts, but which may 

 be troublesome in other parts of the State. Strictly scientific descriptions have purposely been 

 left out, but I have endeavored to make the popular account as correct and as condensed as 

 possible. Of insects and fungi I have only enumerated those which are of importance through 

 the damage they occasion from time to time. Those which prey on the vines, but which cause no 

 great damage, and which the grower need not prepare himself to fight, have here been left out 



POWDERY MILDEW OR UNCINULA. 



General Notes. This disease of the grapevine is caused by the 

 growth of parasitic fungus known in Europe as Oidium Tuckeri^ 

 and in this country as Uncinula spiralis or powdery mildew. I am 

 satisfied the two names signify the same fungus, only the European 

 form has never been found as highly developed as the American one, 

 which has on that account received a name of its own. If the two are 

 identical, then the European Oidium, which for many years caused 

 the destruction of the transatlantic vineyards, was imported to that 

 country from this. The Uncinula spiralis is undoubtedly native on 

 our indigenous vines. 



Characteristics. The mildew appears in two different stages, one in 

 the spring when the vines are in blossom, the other again later in the 

 summer when the fruit is more advanced. The first stage of the 

 mildew resembles a fine cobweb spun between the flowers of the bunch. 

 If allowed unrestricted sway, the flowers will drop off, the fruit will 

 never set, or set only imperfectly, and the crop will be a great loss or 

 even a total failure. Generally the inexperienced vineyardist does not 

 perceive the mildew until too late. A slight touch to the vine will 

 then bring down all the young fruit or blossoms like a shower, and 

 the stem of the bunch will be seen tp be entirely bare, or with only a 

 few scattered berries. This form of the Uncinula mildew has not 

 been as scientifically investigated as would be desirable, and nothing 

 is known as regards its development It is possibly a primary genera- 

 tion and early stage of the later Uncinula. I believe this form of 

 the mildew is identical with the disease which is called Colure by the 

 French, and which is characterized by the dropping of the young, 

 undeveloped grapes. The first appearance of this mildew is always 

 accompanied by white, salty excrescences on the edges of the grape 

 leaves. Whether they are directly or indirectly connected with the 

 fungus is not known. 



The later form, the powdery mildew, and the form which has given 

 this mildew its name, appears later in the season, when the grapes are 

 half grown or more. It then takes the shape of fine powder-like 

 patches or blotches on the upper side of the leaves, stems or berries. 

 These spots are of a dull gray or whitish gray color, and smell strongly 

 of mold or mushrooms. If these mildew spots when young are 



