6 BULLETIN 746, U. S. DEPARTMENT OF AGRICULTURE. 



The "dead hearts " due to the moth borer are caused in the fol- 

 lowing manner: The adult moths emerge in the spring, when the 

 cane plants are small, and deposit clusters of eggs on the leaves of 

 the young plants. The eggs hatch, and the small larva? feed here 

 and there on the tender whorls, rolls of holes appearing on the leaves 

 as they expand. Many of the larva) seem to perish during this 

 period, partly because of their cannibalistic habits. Not more than 

 three larvae, usually only one, seem to find their way to the interior 

 of a young cane plant. When about half grown a larva crawls down 

 the outside of the stem to a point near or even below the surface of 

 the ground. Gnawing a hole through the outer layer of the stem it 

 works its way to the interior of the plant, cutting the tender inner 

 shoot and forming a " dead heart." The inner shoot does not dry 

 up immediately, so that the larva has some time to work before the 

 injury can be noticed. Tunneling within the plant the insect reaches 

 its largest size, pupates, and finally leaves the plant as an adult moth. 



During a year when few plants were killed in this way it was 

 estimated that there were about 10 " dead hearts " per acre. In other 

 3'ears as many as 100 " dead hearts " have been counted per acre. 



EFFECT ON MATURE CANE. 



While the work of the larvae on the small plants kills the plants, 

 larger stalks usually do not die. In these the larvae burrow up and 

 down, sometimes gnawing their way out through the hard rind and 

 reentering at another point. Frequently a mature stalk will harbor 

 two or three larvae which work in different parts of the cane from the 

 top to the bottom. Three sections of infested cane are illustrated in 

 the frontispiece. 



A red coloration, showing dark in the canes illustrated in the fron- 

 tispiece, usually is observed in the pith along the tunnels. This is the 

 disease " red rot," which is caused by the fungus CoUetotrieliiim fal- 

 caturn. "By far the largest number of stalks become infected [with 

 red rot] through the burrows made by the cane borer," writes Dr. 

 C. W. Edgerton (50), who sums up the injury due to red rot as 

 follows : " First, the loss in stand ; second, the killing of the young 

 plants; third, the injury to the leaves; fourth, the loss in per cent 

 of sucrose with a corresponding increase of glucose." " Knowing 

 that a large per cent of the red-rot infection in cane is by means 

 of borer channels," Dr. Edgerton continues, " a greater effort should 

 be made to control the insect." 



The spores of other fungi, as well as bacteria, 1 also gain entrance 

 through the borer holes. Cane badly bored is found to be hard and 

 dry, making it more difficult to grind. The growth is checked, and 



1 Prof. Wm. L. Owon (119), formerly bacteriologist of the Sugar Experiment Station 

 at Audubon Park, New Orleans, La., has studied and described a bacterium which he 

 found in the tunnels made by the moth borer in sugar cane. lie has given it the name 

 of Bacillus saccharalis. 



