74 



THE AGRICULTUBAL NEWS. 



March 4, 1911. 



INSECT NOTES. 



THE MOTH BORER OF THE SUGAR- 

 CANE AS A PEST OF INDIAN CORN. 



The moth liorer of the sugar-cane {Diatraeit lacchaiulis) 

 has long been known as a serious pest in all parts of tropical 

 America where sugar-cane is grown. Among the early 

 entomological work carried on by the Imperial Department of 

 Agriculture was an extensive study of this insect, as a result 

 of which its life-history and habits became known. A paper 

 entitled ' The Jloth Borer in Sugar-cane ' appeared in the 

 West Indian Bulletin, Vol. I, p. 327, and subsequently 

 the moth borer has been included in all accounts of the 

 insect pests attacking this crop. In the Agricultural News, 

 also, mention has from time to time been made of the work 

 of this insect, and of the methods used for its control. 



The moth borer is not recognized in the West Indies as 

 a serious pest of Indian corn, although it has been observed 

 to attack this crop in several instances. I'l the southern 

 part of the United States, however, it is commonly known as 

 the larger corn-stalk borer, which would indicate that it is 

 best known as a pest of Indian corn, in spite of the fact that 

 it is a serious pest of sugar-cane in those portions of the 

 Southern States where this crop is cultivated. 



A circular (No. 116) recently issued by the United 

 States Department of Agriculture, Bureau of Entomology, 

 entitled The Larger Corn-Stalk Borer (Diatraea saccharal- 

 is, Fab.) presents a considerable amount of information 

 which may be of interest to readers of the A(/ricultural JVews. 



It is believed that Diatraea saccharalis was introduced 

 into the United States from the West Indies or Central or 

 South America with importations of sugar-cane cuttings, 

 many years ago. It occurs at the present time in localities 

 considerably further north than those where sugarcane is 

 cultivated. 



Corn is damaged in two ways by the larvae of the stalk- 

 borer, which, in the latitude of South Carolina, has two 

 brood.s, or generations, a year. The eggs are laid in .spring 

 (April and May) on the leaves of the young corn plants. The 

 young cater()illar crawls down the leaf into the centre or 

 throat of the plant, where it feeds for a time, tunnelling 

 through and through the rolled-up, tender leaves. Later in 

 the season, it descends on the outside of the plant, and 

 attacks the stalk near the surface of the ground. A hole is 

 cut through the outer wall of the stalk, by means of which 

 the caterpillar is able to enter the central pith. The soft, 

 central portion of the stalk furnishes food for the remainder 

 of the larval life of the insect: this, when fully grown, tunnels 

 upward a short distance, turns to one side, and cuts a circular 

 hole through the outer wall. A few loose threads are spun 

 across this opening, and the larva retreats into its burrow 

 and transforms to the pupal stage. 



The length of time required for the development of the 

 larvae in the spring is about twenty or thirty days. The eggs 

 hatch in from seven to ten days; the pupal stage occupies 

 from seven to ten days, after which time the adult moths 

 emerge, and egg-laying for the next generation commences 

 almost at once. The time occupied for the first generation, 

 including egg, larva, pupa, and adult, is from thirty-four to 

 fifty-two days. 



The eggs for the .second generation are laid on the leaves, 

 and the larvae proceed, after feeding there a short time, to 

 attack the stalk of the corn near the ground. Those caterpil- 

 lars do not injure the plant by entering the centre, in the 

 manner of the larvae of the first brood. The larvae of the second 



live in the pith of the cornstalk, like those of the first 

 but when fully grown they turn downward, and pene- 

 trate to the extreme base of the stem, where they pass the 

 winter in the larval condition. 



The over-wintered larvae change to pupae in the spring, 

 and the adult moths emerge and fly about in search of young 

 corn on which to deposit eggs. 



This liorer has been reported as attacking Sorghum {Sorg- 

 hum vulgart), Johnson grass (Sorghum halejjense), Guinea 

 corn (Andropo(/on Sorffhum, var. vnlr/aris), and Grama grass 

 {Tripsacum dactyloidei), in addition to Indian corn and 

 sugar-cane. 



In South Carolina, Diatraea saccharalis is stated to have 

 Vjut few natural enemies. The minute Hymenopterous egg 

 parasite (Trichoi/ramma pretiosa) has lieen found in a few 

 instances, living in and destroying the eggs. The larva of 

 a brown, velvety beetle Chauliognathus piennsylvanicus is 

 a valuable natural enemy, from its habit of entering the holes 

 in the stubble after the corn is cut and devouring the borer 

 larvae. The termites or white ants {Termes JJai'ipes) some- 

 times destroy the borers in the stubble in the winter. Fungi 

 have been observed to attack and kill the larvae, but none of 

 these agencies is thought to exert any great influence in 

 checking the pest. 



Rotation of crops is considered a very efhcient means of 

 combating the larger cornstalk borer, for it has been proved 

 that where corn follows corn m the same field, in successive 

 years, the attacks are worse than when other crops intervene. 

 The complete destruction of all stubble in the field during 

 the winter is perhaps the best method to employ against 

 this insect. 



It may be well briefly to review the situation in the 

 West Indies with regard to Diatraea saccharalis. This insect 

 is commonly known as the moth borer — the principal insect 

 pest of the sugar-cane. It occasionally attacks Indian corn 

 as a stalk-borer, but no observations seem to have been 

 recorded as to the habit of this insect of feeding on the corn 

 leaves and tunnelling in the rolled-up leaves in the throat of 

 the plant. The leaves of Indian corn are attacked in this 

 manner by another insect, the corn ear- worm {Laphi/gma 

 frugiperda). 



The moth borer's eggs are laid on the leaves of the sugar- 

 cane; the larvae enter the cane at the axis of the leaves, and 

 most of the larval life is spent in the stem of the plant. The 

 time required for the life-cycle is about fiftj- days. Breeding 

 is probably continuous, one brood or generation following 

 another. The greatest abundance of adult moths, and con- 

 sequently the most rapid rate of egg-laying, occurs in Febru- 

 ary and March. 



In addition to its direct effect, the moth borer has 

 a very great influence on the welfare of the sugar cane as 

 a result of the easy access to the interior of the plant which 

 is afforded to disease-producing fungi by means of the 

 tunnels of the insect. 



The remedies recommended and in use for the control of 

 the moth borer, are: (a) collecting the eggs, (b) cutting out 

 dead hearts. Parasites exenise a considerable influence in 

 destroying numbers of eggs. Eggs of the moth borer should 

 be kept a few days away from the fields, to allow the 

 egg parasite to emerge. These, being able to fly, will find 

 their way back to the cane fields, while it will not be possible 

 for the young larvae that hatch to return in this waj'. 



The collecting of eggs is not a diflicult matter. The flat 

 scale-like eggs are laid on the leaves of the cane, and 

 children can easily be taught to find them. Dead hearts, the 

 young cane shoots which are dead or dying as a result of the 

 feeding of the liorer at the growing point, should be cut out, 



