THE MONTHLY BULLETIN. 257 



branches. The disease has been distributed in tliis way to many sec- 

 tions of the State, and i)ro})al)ly will continue to be distributed so, 

 in spite of the utmost care that inspectors and horticultural commis- 

 sioners may take to g'uard auaiust it. Tiie disease does not cause 

 any serious etfects on the small tree, otlier than its dissemination, and 

 after the end of the .season has for the most part entirely died out. 



The germs live over in the bark and wood and pos.sibly the pith of 

 the diseased branches. I'robably llic infection from the fallen disea.sed 

 leaves is a ne,uli.iiil)le (piantity. The orjianism in the twig tissue is in 

 a rather dormant condition during the winter months, and probably 

 at this time many of the germs die. When .spring comes and the sap 

 begins to start, the l)acteria again become active and are given otV 

 from the old diseased lesions of the branches to the new growth. This 

 is the initial infection. From these, further infections under favorable 

 conditions take place. This secondary infection often occurs on a 

 large number of .small nuts and is i-ather sudden in its ai)pearanc(\ 



On the surface of the diseased tissue of both the branches and nuts 

 can often be observed a whitish substancf^ that accumulates during the 

 suiiniier, but at length gradually disappears. This is found to be 

 coni])osed of nuiiiei-ous bactei-iii and broken down plant tissu(\ and 

 cultures made from it give the walnut blight organisiu. Wlien wet 

 this white deposit absorbs watei- and becomes soft and guin-like. It 

 is thought that this substance attracts tlies and other insects which 

 cai-i-y the germs to other i)arts of the tree, i.arge nuts having the blossom 

 infection sometimes show gum-like streaks I'unning down over the nut 

 from the diseased portion. The organism is ((uite resistant to desicca- 

 tion and can live over in cloudy weather for .several days on the sur- 

 face of diseased niits. From e.xjKM-imental work, it ha.s been found 

 that the organism can withstand 20 to 50 days of drying before being 

 killed, if no germicidal action of the sunlight is present. 



Positive results are easily secured by atomizing the healthy nuts and 

 green twigs with sterilized water containing the disease producing 

 organisms. Puiu-tiu'e inoculations are somewhat more sure of results, 

 especially on the twigs. The disease will begin to show in about ten 

 days from inoculations. Successful infections have been made on 

 the following species of Juglans by puncture inoculation on the young 

 growth; Eastern Black walnut, J. nigra: Southern California Black, 

 /. calif ornica; Northern California Black, J. hindsii; Butternut. J. cine- 

 rea; Japanese walnuts, /. cordifonnis and J. sieboldiana; also on Para- 

 do.x and Royal hybrids. 



Losses from blight for the past ten years have been considerable, 

 in some cases being as much as 50 per cent. We know that during 

 the last decade the average has multiplied many times, yet the total 

 walnut crop has increased but little during this period. Possibly the 

 deterioration of the trees with age, or the blight, or both may be in 

 some measure to blame for this. 



CONTROL. 



Considerable experimental work has been done in an endeavor to 

 find a practical control for the disease. Extensive spraying experi- 

 ments were conducted by Mr. Newton B. Pierce with the Bordeaux 

 spray. Different growers at Mr. Pierce's suggestions continued the 



