THE MONTHLY BULLETIN. 373 



however, which tend to indicate both the safety and value of such 

 treatment sufficiently to strongly endorse it for the limited purpose 

 suggested above. Among these may be mentioned, as important for 

 consideration, the more uniform moisture and temperature conditions 

 ol)tainable, the avoidance of having to work the groimd too wet, the 

 elimination of the tendency to form plow sole and the permitting of 

 roots to feed in that part of the soil near the surface where a large 

 portion of available nitrogen is concentrated. Recent moisture deter- 

 minations comparing this system with clean culture show that less water 

 is required to maintain a given moisture content. Mulching of the 

 entire ground has proven of great value in Florida, Cuba, and else- 

 Avhere. and we believe that in the limited form suggested it is applicable 

 to our conditions and will prove a real benefit.— R. S. Vaile, Citrus 

 Experiment Station. 



The Citricola or Citrus Gray Scale The citrus gray scale. Coccus 



citricola, is of peculiar interest to citrus growers in our State. This 

 scale was not known in California before 1907 and was first discovered 

 at Claremont. Los Angeles County, in old orchards which were in full 

 bearing. Although of recent introduction, it is now almost as wide 

 in its distribution in the citrus groves of the State as is the well known 

 black scale, Saissetia olecc. It is a rival also of this latter scale in its 

 destructiveness. It sucks from the sap and thus robs the trees which 

 it infests of their vitality. The mischief is aggravated by the large 

 amount of honey dew which the scale secretes. This secretion prob- 

 ably injures the trees in two ways : it must come from the trees, although 

 of course modified by the insect, and in attracting the black smut fungus 

 does further injury. This fungus not only stops the breathing pores 

 and lessens the vigor of the foliage, but it also stains the fruit, which 

 often must be washed. The fungus is also a sore disfigurement to the 

 trees. This scale closely resembles the soft brown scale, Coccus hesperi- 

 dum, but differs in being generally oviparous, or egg laying, while the 

 young of the soft brown scale are born alive. 



The gray scale is very prolific. Fifteen hundred eggs may be pro- 

 duced by a single scale. Unlike the soft bro^ra scale, it infests old 

 trees as much as young ones— if not more — in orchards where I have 

 observed its work, and it also works on all parts of the trees but is 

 always most abundant on the north side. Also unlike the soft brown 

 scale, it is very free from effective parasites or predators. I think all 

 experience to the present time proves that fumigation is the onlv 

 reliable remedy, but the time for this seems to be quite limited, the 

 experiments of Mr. Kell at Claremont showing that this scale is best 

 controlled by fumigating from July fifteenth to September fifteenth, 

 while the black scale can be fumigated from the first of August until 

 the first of January with good effect. In this connection I am very 

 pleased to call attention to an excellent bulletin. No. 255, on this citrus 

 gray scale, prepared by Prof. H. J. Quayle of the University of Cali- 

 fornia. This bulletin is beautifully illustrated and is marked with the 

 characteristic thoroughness which is peculiar in all the admirable pub- 

 lications which we have received from Professor Quayle. All of the 

 county horticultural commissioners should write at once for this valu- 

 able bulletin, especially if they are stationed in a citrus region. 



