l\ S. DEPARTMENT OF AGRICULTURE, 
 
 BUREAU 01 KNTOMoUk.Y — CIRCULAR No. 162. 
 
 I () HOW \KD. I nlofnologut .nd Chief of Burr.u 
 
 THE POTATO-TUBEB MOTH 
 
 A PRELIMINARY ACCOUNT. 
 
 MY 
 
 V. II. CHITTENDEN, s« . D.. 
 
 I top am/ Stored Pro 
 
 
BUREAU OF ENTOMOLOG V. 
 
 I.. 0. Howard, Entomologist and Chief of Bureau. 
 C. L. Marlatt, Entomologist and Acting Chief in Absence of Chief . 
 
 R. S. ('UPTON, Knculin Assistant. 
 
 \V. F. Tastet, Chief. Clerk. 
 
 F. H. Chittenden, in chargt of truck crop and store/ ■product ins,ct investigations. 
 
 A. I». Hopkins, in charge of forest insect investigations. 
 
 W. D. Hunter, in charge of southern field crop insect investigations. 
 
 V. M. Webster, in chargt of cereal and forage insert investigations. 
 
 A. L. Quaintance, in churn, of deciduous fruit insect investigations. 
 
 E. F. Phillips, in chargt of bet culture. 
 
 I). M. Rogers, in dung, ,,j prevt nting spread of moths, field work. 
 
 Rolla P. Currik. in charge of editorial work. 
 
 Mabel Colcord, in charge of library. 
 
 Truck ('nor and Stored Product [nsect [nvestioations. 
 
 F. II. Chittenden, in charge. 
 
 II. M. Russell, C. H. Popenoe, Wm. B. Parker, II. 0. Marsh, M. M. High, 
 Fred A. Johnston, D. E. Fink, John E. Graf, A B. Duckett, entomological 
 
 assistants. 
 I.J. Condit, collaborator in California. 
 W. X. (Inn, collaborator in Oregon. 
 THOS. II. JoNES, collaborator in Porto Rico. 
 
 Marion 'I'. Van Horn, Pauline M. Johnson, Anita M. Ballinger, preparalors. 
 ii 
 
 ADDITIONAL COPIES of this publication 
 -£*- may be procured from the Superintend- 
 ent or Documents, Government Printing 
 Office. Washington. D. Cat S cents per copy 
 
Circular No. 162. 
 
 
 United States Department of Agriculture, 
 
 BUREAU OP KNTOMOLOGY. 
 
 1 O HOWARD 1 ' ■ ■" ul Chief of Hureau. 
 
 I Ml. POTATO-T1 BER MOTH. 
 
 /■- . / i /.ill 
 
 I || Qhittbnden, Si D 
 
 I \ i i:< iin ( n >t:i . 
 
 For m;iii\ years the potato-tuber moth, known scientifically as 
 
 Phthorimxa opercuhlla Zell., has I n the worsj potato pesl in 
 
 California. Ii has now reached the State 
 ,.i' Washington and menaces adjacent 
 States. This insecl feeds also upon to- % 
 mato, eggplant, and tobacco, which 'I" 
 not. however.as a rule, suffer much injury. 
 When ii occurs on tobacco ii is known as 
 the splitworm. 
 
 The mature moth of this species, which 
 is quite small and grayish in color, is 
 shown in 6gure I, a; the Ian a is shown in 
 b and c; and the pupa in </. Si/..'- are in- 
 dicated by the size lines in the figure. 
 
 The eggs mas be laid upon the le&\ es oi i 
 
 ■ 
 
 ■ ■[.) 
 
 0$ 
 
 
 
 *3L i — ~*-~2* 
 
 It is believed thai there 
 
 on other part- of the plant-, and the mi 
 
 ante caterpillars or worms quickly bore 
 
 between the surfaces of the leave- or into 
 
 the potatoskin, which they mine in every 
 
 direction, finally devouring the exterior. 
 
 are two or more generations in the course of a summer, and certainly 
 
 another one can be produced in store. It tint- happen- that tlusmsecl 
 
 belongs to both truck-crop and stored-producl insecl pests. 
 
 An example of injury by this species to potatoes is shown in figure 
 _>. At a isasection showing the eggs at the top; at h, a badly mfesti d 
 
 I will 
 
 in' . 
 
THE l'OTVio I iki.i: MOTH. 
 
 potato in section; at the left is a section containing two pits, (Zand 
 /, in which the larva lias been at work, while at l> and c are shown 
 t he egg, highly magnified. 
 
 DISTRIBUTION. 
 
 This species is widespread in its distribution, but in this country, 
 mil il the present year (1912), we did not know of its rapid dissemina- 
 tion. Abroad it is well known in Hawaii, all portions of Australia, 
 New Zealand. Algeria, and many other countries, including southern 
 Europe. As an enemy to tobacco it has been known for several 
 years in Florida and in North Carolina, South Carolina, and Virginia. 1 
 
 The directions for applying remedies 
 which follow are for the benefit of per- 
 sons inquiring in regard to means of 
 control. Which of these should be 
 used can be best determined by trial in 
 the different localities under the differ- 
 ent conditions in which the insect ex- 
 ists. This applies especially to the 
 question as to the. best material for 
 iumigat ion. 
 
 EVIDENCE OF IMPORTANCE. 
 
 As evidence of the importance of the 
 
 pest a few ([notations or notes should he 
 made. 
 r <t Mr. J. E. Graf, working under the 
 
 Fig. 2.- Work of the potato-tuber moth: o, direction of the writer, wrote: 
 Section of tuber, showing eye and eggs 
 
 deposited about il; 6, egg in outline; e, In September. 1012. ail unusual outbreak of 
 egg, lateral view; ,/,/, mines of larva in this pest occurred at El Motile, (al., due entirely 
 
 to a combination of circumstances. Thousands 
 of acres of potatoes were planted in southern Cali- 
 fornia— many more than the market would stand. 
 This meant that the market was continually clogged and the prices were poor, so that 
 the crop was worked off very slowly. The tuber moth (Pkthorimeea operculella) is 
 always found here, but the crop is generally handled so quickly and carefully that small 
 loss results. This year, however, careless work and the leaving of potatoes in the 
 ground too long have given tile insect a tremendous start, and now its ravages are 
 greater than ever before. A combination of the moth and low prices has so discouraged 
 many of the growers that they are Leavingtheir potatoes to rot. ami as these are becoming 
 infested there will be a great number of moths wailing for the fall potatoes. * * 
 
 Later, September 17, 1912, Mr. Graf wrote in regard to this species 
 that two growers near El Monte, Cal., lost Slid. not) and 870,000, 
 respectively, on potatoes that year. Items of this kind show the 
 necessity of investigating the problem. 
 
 potato, a, Natural size; 6, c, greatly en- 
 larged; d, somewhat reduced. (Redrawn 
 from Riley and Howard.) 
 
 i it is somewhat doubtful if the splitworm on tobacco ami the potato-tuber moth are the same insect, 
 although they appear to !«• identical according t" the best authorities on the subject. This is a matter to 
 
 be settled later. 
 
I ill P0TAT0-T1 BED M"i H. 8 
 
 le from numerous similar complaints, including the usual nun, 
 ber from California for the pasl two years, this species has been pi 
 ceivetl from Eagle Lake and Hallettsville, Tex ; San Jo* Co ta Rica; 
 - attle Auburn, and Yakima, Wash. ; New"} ork City, where it hat not 
 become acclimatized so far as known; Fort Collins, Colo : and Lari- 
 morc, V Dak. These records include onlj occurrences on potato. 
 
 In the case of the lasl report the tuber moth was 9tated to have 
 been imported into southern California in potatoes from China. It is 
 doubtful if the species has been introduced into North Dakota, but 
 inquiries have been made in regard t<> the danger of it- being intro 
 duced there as well as into Minnesota and some other Stati 
 
 M I nil s 
 
 The potato-tuber moth is a difficull insect t" control. It i- nol 
 possible it) reach the tuber wofms in their mines in the potatoes or in 
 the stalks or tubers growing in the Geld, which make- it neccssan to 
 proceed against the pesl l>\ other methods. Of these, several must be 
 emplo) ril to insure buc< i 
 
 The first measure consists in the maintenance "I clean methods <>f 
 cultivation. This implies that all infested potato plants and solana- 
 ceous weeds, such as ground cherry, bull nettles, horse nettles, and 
 vol u nt err potato plant-, gro^ ing in the same vicinity as the potatoes, 
 must be destroyed. This can be done by prompt burning as soon 
 as insect infestation is manifest. The burning of the weed- will 
 eliminate places for the breeding of the insect or for its successful 
 hibernation. Domestic animals such as sheep and hogs are valuable 
 for the destruction of remnant- and may be utilized l>\ merely turn- 
 ing them into the field. 
 
 Crop rotation, as in mosl other cases of insect injury, is desirable 
 w here possible, and the cooperal ion of all potato growers of the neigh- 
 borhood i- practically a necessity. In certain cases, as, for example, 
 in a county where many potatoes are grown, it mighl l>e |><>--il>le l>\ 
 legislat ion to enforce the discontinuance of potato planting for a year, 
 requiring at the same time the destruction of the weed- which serve as 
 I'ood plant-. There are several alternate food crops which do not 
 suffer materially from this insect. About the best of these are 
 Leguminous crop-, like beans, peas, cowpeas, alfalfa, and clover. 
 These possess a dual value, as the) all ad as soil restorers. Sugar 
 beets, celery, and crucifers are also good as alternate food crops. 
 Grains may serve in the same way, as they are not attacked by the 
 tuber moth. Care in digging i- ad\ isable in order not to cut into t he 
 tuber or leave dug potatoes in the field over night where reinfestation 
 coidd occur. 
 
 II MM, \I1'"N 
 
 ^hile all of these remedies are of value, the best remedj i- the 
 fumigation of infested tubers u ith bisulphid of carbon or hj drocj anic- 
 
4 j II K I'll I A I ti- I I'KKl; MOTH. 
 
 acid gas. If bisulphid of carbon is used, it should be at the rate of 
 3 pounds to 1,000 cubic feel of air space, including the potatoes; 
 1 ounce to a barrel of 96 pounds' capacity would not be excessive. 
 With an exposure of not more than 2 l hours, no harm should be done 
 to the potatoes for planting. The bisulphid should be evaporated in 
 
 Fig. 3.— Fumigator used for stored products infested by insects. (Author's illustration. ) 
 
 tins, like pie plates, and a cover should be placed on the top of the 
 fumigating barrel or box so as to make it as nearly air-tight as possi- 
 ble. At the end of 24 hours the potatoes should be removed, placed 
 in a fresh barrel, and closed up. 
 
 Where it can be conveniently done hydrocyanic-acid gas should 
 be used in a specially constructed fumigator (see fig. 3), also Lras- 
 
I ill P01 HO ii in i: \l'»i ii. 
 
 tight. In ill'- case of bisulphid of carbon there i-^ great danger in 
 bringing the chemical into proximity i" fire, Buch as a lighted lantern 
 or cigar, for the gaa is 1 1 1 ■_•■ 1 1 1 v inflammable and even explosive. Thin, 
 too, the bisulphid-of-carbon method costs Blight!} more than tin- 
 bydroc} anic-acid-gas method. 
 
 Fumigation with hydrocyanic acid :_ r a>, properh performed, is 
 nol dangerous, but it improperl} performed is decidedly dangerous 
 to human and other animal life, a> the fumes are ven poisonous and 
 me deadh when inhaled in an\ amount. This gaa i-> more penc 
 trating than bisulphid of carbon and can !><• used l>\ an intelligent 
 person without trouble, it he first familiarizes himself thorough!} 
 with the procedure by careful!} studying the printed directions or 
 assisting some one who has bad experience in this work. The cubic 
 contents <>l* the receptacle t" be fumigated, on which is based the 
 amount of chemicals to l>e used, can be readil} computed. 
 
 i ii i i n\8TH \ i)l \ ii mil . 
 
 A building, box, or room (see fig. 3) of about 100 to 200 bushels' 
 capacity suitable for the fumigation of a quantity of potatoes would 
 contain about 500 cubic feet. A fumigator of 1 1 1 i— cubic capacity 
 
 might In' built 8 feet square b\ 8 feet in height. A _ r I, and perhaps 
 
 the best, means of preventing the escape of the gas would be to line 
 the fumigator with sheet tin, with soldered joints, and over sheathing. 
 Another method would be to sheath the room inside, cover the walls, 
 ceiling, and floor with tarred or heav} building paper, with joints 
 well lapped, and cover the inside with matched ceiling boards. The 
 fumigator should always be equipped with a tight door in which the 
 joints have been broken, similar to the door of a refrigerator or safe, 
 and should (lose with two refrigerator catches against a thick felt 
 w.athcr >tri|>, which should render it practical!} gas-tight. Thus 
 constructed it would furnish sufficient space for the fumigation if 
 about 200 bushels of material. There would also be sufficient spaoe 
 for the application and diffusion of the hydrocyanic-acid gas, 1 carbon 
 bisulphid, or other fumigant from the top with a charge more than 
 necessary for the quantity of potatoes treated. 
 
 Approved : 
 
 James Wilson, 
 
 ?< cretary <>f A<p u ultun . 
 
 Washington, D. C, September SO, 1912. 
 
 i a rh hydi 
 anyone who requests It, stating that il ed f- >r the potato-tuba n 
 
 o 
 
UNIVERSITY OF FLORIDA 
 
 3 1262 09216 6072