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PROCEEJ:)INGS OF HAVANA CONFERENCE

SECTION II.

Insect Pests of Sugar Cane (Including Utilization of Parasites).

D. L. Van Dine; Chairman. H. T. Osborn, Secretary.

Sugar Cane Stalkborers-a Discussion.Cutting out "Dead Hearts" for Control. By H. K. Plan/{.Control of Stalkborer by Dusting. By W. E. Hinds.Airplane Dusting for Insect Control: (Illustrated by motion picture). By> C. E.

Woolman.Corn as a Trap-Crop for Stalkborer Control, By W. E. Hinds.Parasites of the Stalkborer in Louisiana. By T. E. Holloway.Cuban Parasites of the Stalkborer. By H. K. Plank.Losses from the Moth Stalkborer. By J. T. Crawley.Grass Hosts of the Moth Stalkbor~r.· By H. K. Plan/{. .Control of Sugar Cane Insects by Parasites in Hawaii. By H.P. Agee..Parasite Exploration Work for Hawaii . .ByO. H.Swezey.Cooperative Explorational Work for Parasites; (Presented by .A. H. Rosenfel~f

. 13Y H. ~. Box .. Parasite Introductions into Formosa. By Miga/{u, Ishida.

SECTION II.

InsectPe.stsof Sugar: Cane (Including Utilization of Parasites)

A preliminary.' meeting .of the Committee'for •the.Section on Insect Pests','ofSugar,Cane was,helcl ~n the afte;~o~nof March 14th. ,The. discussions at this .meet­ing d~velqpedthat there wasa .great' deal of'interest in the subject of stalkborersofsugarcane. It was agreed to make the subject of stalkborersthe main topicat thegeneral session for-the following day, including the general subject of the, utilizatIonof parasites in the control of sugar cane insect pests. It was .also agreed that' thesubject of the insect transmission of the mosaic disease be referred to the Sectionon Sugar Cane Diseases for discussion in connection with the disease mosaic arid,further, that the question of such soil animals as snails, centipedes and nematodesbe left to the Section on Diseases in connection with root disease conditions.

General Session, March 15th, 2 :00 P. M..The subject of stalkborers of sugar cane was opened by Mr. T. E., Holloway

of Lquisiana. Mr. Holloway said:

'Those of you who. saw the pictures this morning will realize the immense lossdue to a larva boring thru the stalks of sugar cane. In cooperation with the Bureauof Agricultural Economics, we of the Bureau of Entomology have calculated anaverage 10ssinLouisiana of 19 or 2070 of the full crop with an occasional loss of30%:' .

Proceeding to seasonal history, the moth borer (Diatraea Saccharalis Fabr.)hibernates in planted seed cane, in sugar cane stubble to some extent and in largegrasses: It also hibernates in rice stubble. Old corn stalks have been found freeof hibernating borers as corn is ordinarily grown on Louisiana sugar plantations,that is, the corn being planted fairly early and drying out by midsummer and be'

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coming unattractive as' a food plant. The moths emerge from their hibernatingplaces about the last of April, ordinarily, With the deposition of eggs on youngcane plants the first generation commences. The young plants are completely killed,but as the cane becomes larger the work' of the borer does not kill the plants. Thereare from four to :five generations during the year, the, time of a generation vary­ing from about 45'daysto a much longer period depending on the temperature.

Going on to artificial control, I might say that while Hawaii is ideally situatedfor parasite introduction, or, biologic control, conditions in Louisiana' are excellentfor artificial controL We believe 'that by, eliminatingjbeavy grasses, by cutting thecane with a. machine' of some kind so as to avoid leaving tall stubble in which thelarvae hibernate, and by treating the seed cane to destroy the hibernating borers,that is, by following these measures the borer in Louisiana could be controlled.

There are two treatments of seed cane-s-with hot water and with water ofordi­nary temperature. Seed cane can be treated with cold water or water of ordinarytemperature-soaking the cane for seventy-two hours-s-and all the borers- in thecane will be killed, while the germination will be stimulated. There is no doubt thatthis is an effective measure. A plantation which was flooded -for some time, due tohigh water, was found afterwards to have very few borers. In the same way,thebadly drained portions of a plantation are less infested than the well drained portions.

A Louisiana planter treated the seed for a portion of his plantation some. yearsago, and found that due to the increased germination, the work really cost himnothing at all. However, the treated cane was planted in the midst of untr~ated

fileds, and the year was one in which practically every stalk of cane in Lousia:{i,i wasbored. No evidence of bene:fit was observed in regard to the infestation.

Weare now making an arrangement with a Louisiana sugar planter to reimbursehim for the entire cost of treating all, his seed cane. It is hoped that in this waydefinite results can be. obtained on the efficiency and cost of the method on a planta­tion scale. Quite a long time ago the egg parasite, Trichogramma minutum,wasfound on Louisiana' plantations. It occurred to me that we might try to preservethis parasite, and my idea was not to burn the leaves and tops-i-the "trash"-lefton the fields after cutting. Mr. ,W. G. Taggart, of the Louisiana Experiment Station,worked out a method of cultivating the soil so that this vegetable matter wouldbecome part of the soil.

We have found a reduction in borer infestation of 5'0% and the soil:is benefited.To close these introductory remarks, I want to point out the various factors

which influence borer abundance; Mr. W. E. Haley and myself, in "Facts aboutSugar" for January 8, 1927, listed:fifteen of these factors. (Mr. Holloway drawssketch on blacks board).

The "front" of a Louisiana plantation is on a water course, and here is thewell drained land. The plantation runs back to a swamp, and the closer one getsto the swamp, the poorer is the drainage. The front of a plantation is always moreheavily infested than the back, where the borer is drowned out-s-as it could be every­where by the water treatment.

A person of little, experience can easily make a mistake in 'conducting experi­~entson the borer. If you take two cottom fields and plant them with good seedyou can: obtain two comparable fields. But not so with sugar cane. You plant thestalks of the cane, and in planting the seed cane cuttings you are also planting borers.Under Louisiana conditions-not tropical ones-the whole effect of the early culti­vation is to provide for the emergence of the moths from the seed cane. The soil

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is partly removed so that the warmth of the sum will reach, the planted stalks, andthe soil is pulverized. If you plant cane containing live borers, you "seed" theplantations' with borers as well as with cane.

, Even if you plant two fields with cane having a hirer infestation of 20% youcannot tell whether your fields are comparable. In one field many of the stalks maycontain borers while in the other many of the borers may have left the stalk before

planting.The situation of,·a field on" the plantation, its surroundings, whether it is a

plant cane field or a stubble cane field-s-all these and many more factors influence

thesubsequent infestation.It is, therefore, as I said, easy to make a mistake in control experiments.Mr. Chairman, I believe that these remarks .will be sufficient to open the

discussion.At. the conclusion of Mr. Holloway's remarks, the Chairman called upon

various men of different countries for remarks on the stalkborers.Dr. Jeswiet from Java mentioned a borer of importance there (Diatrea striatalis).

He said that it was formerly a practice to cut out dead hearts as a control measure,also to collect eggs and hatch out the parasites for return to the field. This hasbeen discontinued as a field practice, but is being tried experimentally again.

Dr. Van Harreveld of Java stated that large sums of money had been spentin the past in artificial control of borers in Java but that no practical results has beenobserved. In his opinion the best practice is maximum agricultural production,particularly with varieties producing, a large number of shoots. He stated also thatthere is ,a natural weeding out of shoots from about 70,000 down to 25,000 peracre and that the destruction of many shoots by the borer does not affect the final

yield,In answer to a question by Mr. Matz of Porto Rico, Dr. Van Harreveld stated

that the percentage of infestation ran from 20 to 100% of the ,stalks,that a mi­nimum of20ro was always present. Mr. Matz also raised the question regardingthe losses in the mature' cane at the harvest time as distinguished from losses of shoots

before they mature.Mr. Rosenfeld of L~uisiana, speaking from experience in Tucuman, questioned

whether Dr. Van Rarreveld's .statement would apply in a locality with a short grow:ing season. In Tucuman the older shoots are attacked by borer, leaving the laterdeveloped shoots to produce the crop, thus shortening an already short period for

the growth of the cane.The 'question' was brought up by Mr. Lopez Dominguez of Porto Rico as to

the effect of deep .planting on borer infestation.Mr. Menendez Ramos stated that from his observations deep planting was a

solutioh,of theborer'~problem in the tropics.Mr. Earle Drought out the fact that in Cuba the question of,clean seed (em­

ph<j-siz;ed as one of the most important control measures in Louisiana by Mr. Hollo­V'lay)IS of' minor importance since in some localities in Cuba a planting may lastfor twentw years. Dr. Hinds asked as to the amount of seed necessary to give aperfect stand in Louisiana.' Mt., Taggert answered: four tons on the average.

Mr. Agee of Hawaii mentioned the weevil borer (Rhabdocnemis obscurus) pro­Hem in: Hawaii, and stated 'that the discussion of parasites would be deferred to alater time. Dr. Storey' from Natal, South Africa, mentioned a stalkborer ' in maize

that does not attack cane.

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Mr. Clarke from Fiji stated that the weevil borer, (Rhabdocnemis obscurasu Boisd)is a very serious pest but has been reduced in late years from an infestation of .30%in 1911 to 6% at present, due probably to various. factors working together. Thesefactors include a change of varieties, the burrJ:ing of the cane before cutting anel theintroduction of the tachinid fly parasite from Hawaii.

>Resistance of varieties to injury

Mr. Rosenfeld called attention to th~ conditions in Louisiana and the Argentine~the new PO] and Uba canes in Louisiana appear much more severely attackedthan the old-canes: '

Inthe Argentina (Tucuman) when first spread out in small plots, the varietiesPO] 213 and 36 showed very heavy infestation from borer. This lasted for acouple of years. Later, in 1919, when these varieties had been widely .planted,the borer ceased to exist as a problem. Last year for the first time the borer againdid some damage to the PO] canes. (This information is contatned in a discussionby Mr. Rosenfeld and Dr. Cross appearing in the. Louisiana Planter in recent years).

Mr. Clarke from Fiji stated that weevil borer practically wiped out some se­edling canes. Mr. Holloway questioned Mr. Rosenfeld-i-Is the reduction-an borerin the PO] canes due to the fact that they ratoon longer and that, therefore, thereis less plant cane? Mr. Rosenfeld states that he did not believe,tha'tthe~ehad yetbeen time enough for this to be a factor. ",

Mr. Howe of Australia stated that the weevil borer was, lessabund.ant "nowI . .

than in previous years, but. the reasons for this are not known.Dr. Jeswiet mentioned the different habit of the noble, varieties of cane as

against the Java varieties as a possible explanation of the difference in .resistanceto borer. The Java cane with a stronger root system and stooling habit' have theleaves. pressed together at the spindle so that the larvae, hatching from. the eggs laidon the leaves, are not able to get down into the stalk, perhaps.

Dr. Hinds:

Apparently the borer has different habits in different countries. In Louisianathe variety .PO] 234 has been very heavily attacked by-borer but on the strengthof Mr. Rosenfeld's experience it is being extended. There would seem to be someinconsistency in the reports from various countries. In Louisiana there 'appears tobe a tendency of the adult moth to seek out the densest, greenest canes for shelterwhile Dr. ]eswiet tells us that the drier parched areas are more heavily infested.

Mr. Barreto of Cuba remarked that the abundance of .borer in different partsof Cuba is variable. He had found an infestation of less than 15' % of the stalks ingeneral but that it is sometimes higher in localities where there are large areas ofnew plantings. He' advises deep planting as the remedy.

Seasonal and Geographical Abundance

The abundance and injury by the borer appears to vary widely under' differentclimatic conditions and in different seasons in the same locality.

Mr. Holloway said that in Louisiana he had previously considered that theamount of rainfall had no relationship to borer abundance, but that Mr. McDonaldof the U. S.Weather Service had correlated the amount of rainfall during" thewinter months with infestation the following Summer. After heavy winter rainsthere are fewer borers the following Sumer. (The Planter and Sugar Manufacturer,May 29-July 17, 1926).

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Mr. Matz of Porto Rico called attention to a definite relation between droughtsand very heavy infestation. Mr. Wolcott has found in Porto Rico that the borerinfestation is inversely, proportional to the amount of rain.

Dr. Hinds states that in Louisiana during January, February and March, 1926,there were 30' inches of rain' which has been followed by an unusually light infest­ation during the summer of 1926. He also considered that in the summer of 1924the length of'Hfeof the adults was affected by prolonged hot dry weather.

Dr: jeswiet stated that in Java there is much less injury from borer in thewestern part where there is a more even distribution of the rainfall,

Mr. Osborn of Mexico reported that in the southern tropical section of Mexicothe borer Diatraea saccharalis, does not appear to be avery serious problem. Inmost of these districts heavy rains occur, during the summer months. In the stateof Sinaloa on the west coast cane is grown only under irrigation, the rainfall beinguncertain. There is a distinct· winter season during which thecan~ makes slowgrowth. The injury from borer appears to be much more severe here than in thetropical sections, but there has been a very wide variation in abundance of infestationin different fields. In this locality a small borer, Chiloloftini, has for several yearsbeen of at least equal importance with the 'larger borer which here is _Diatraea linea­tella.

Host Plants other than Cane.

Mr. Holloway mentioned corn, sorghum, broom corn, Johnson grass and others,Mr. Plank presented a paper on this subject as found in Cuba.Dr: Hinds mentioned rice as a host plant.

Control Measures.-'-Plantation Practices.

Corn as a trap crop was discussed in a paper by Dr. Hinds.'Mr. Earle suggested that we' feed black strap molasses and cutout the corn, to

which Dr. Hinds replied to grow soy beans.

Mr. Holloway called attention to cases in Louisiana of the benefit of non-bum"ing of the cane trash as an aid to the parasites and hence as a help)9-i#t~ .cont~·~f

of borer. "dl,;'['"

Mr.Taggart explained that he had found it.,J?T,!st,icable to completely rot trashbefore spring if it was turned under ancldN},lypartially covered with dirt. He didnot believe that this. would b~ pI.'\\<P~icable in the tropics, however.

Mr. Holloway requested that two of the visiting Louisiana sugar plantation men,Mr. Kemper and.riMr. :Munson, be asked for their opinion as to the practicabilityoftj;l,e j control" measures, advocated by the Department of Agriculture and theLouisiana Experiment Station, for the sugar cane borer in Louisiana.

Mr. Kemper stated that they were very anxious to make use of the recorn­mendations, but that the system used on large plantations was largely forced uponthem by conditions, that the turning under of trash might be done on .a small-area,but, since every available source of labor is needed for other work at the time whentrash should be turned' under, it is next to impossible to do the work Also the,Louisiana planters urgently desire a substitute crop for corn but until a satisfactorysubstitute is found, they are under the necessity of growing corn for feed.

Mr. Earle said that there is no necessity for growing corn for mules as molas­ses is an excellent substitute.