■' 
 
 Circular No 43. Sicono Edition. 1 
 
 
 United States Departmenl of Agriculture. 
 
 BUREAU OK ENTOMOLOGY, 
 
 HOWARD ' I Chief ol Bureau. 
 
 THE PEA APHIS. 
 
 ! 1/." rosiphum pisi Kalt . ) 
 
 \ **^ 
 
 V 
 
 B] I'. II. ('ill I 11 MM ' 
 
 ■/,i;-,/,' ,./' ; /> «K«/ Spec iai 
 
 One ol fhe most destructive and troublesome insects 
 
 n plant-louse which, from its injury to peas, is known as the 
 
 Pea BPbli 
 natui 
 
 Bblynunl 
 
 Knee it first attracted attention by its ravages in May .if 
 teadily ii in injuriousness, and has been the 
 
 > Reprint, with slight i f Cirealai Th e 
 
 ophora <i- 
 Several art. I d published on I ct, notably by Messrs. John- 
 
 son gj g . the writer. The former gave it the scientific 
 
 it the latter gives reasons to show that this 
 . reality the E tropean the present change ol title. 
 
 \ 19 
 
of great loss in the principal pea-growing regions of this country, espec- 
 ially where peas are grown for canning. It was, in fact, one of the 
 most important of all insects that ravaged crops in the United States 
 during the seasons of 1899 and 1900, and there appears to be little 
 prospect, unless the unforeseen happens, of any decrease in its devasta- 
 tions. On the contrary, it is to be expected that it will widen its range, 
 as it has apparently already done to some extent. 
 
 DESCRIPTIVE. 
 
 The pea aphis is one of unusual size among those found infesting 
 gardens, and the largest of the green species which attack the pea and 
 related plants. The length of the body of winged, viviparous females 
 is about -16 inch (4.5 mm .), and the total wing expanse about tV inch 
 (9 to 11 mm .). The general color of both the winged and apterous or 
 wingless forms is uniform pea-green, the same color as the insect's 
 favorite food plant. The eyes are prominent and reddish brown in 
 color. The antennae are lighter than the body and the tubercles promi- 
 nent; the joints are darker than the rest of the segments, the seventh 
 joint filiform and fuscous. The legs are long and conspicuous; tarsi, 
 distal ends of tibiae, and femora fuscous. The nectaries are fuscous at 
 the tips, otherwise of the same color as the body. 
 
 A typical female of this insect is shown in figure 1 with wings 
 expanded, showing venation at 0, and a lateral view of the same with 
 wings folded in their natural position when the insect is at rest or feed- 
 ing is presented at b. At c an apterous or wingless form of the insect 
 is shown, and d illustrates the nymph in its last stage. The structure 
 of the third antennal joint of the winged form may be seen at e, highly 
 magnified. 
 
 DISTRIBUTION. 
 
 There are good reasons for believing that this aphis was introduced 
 from abroad, probably from Europe, one being that injury of the 
 severity noted by a species of insect hitherto unrecognized as distinct 
 from others of its kind is almost without a parallel in the history of 
 economic entomologj 7 . It seems probable, therefore, that we have in 
 the pea aphis a case analogous to that of the European gipsy moth, 
 which was present in this country for about twenty-five years before it 
 became a pest. 
 
 The first notice of severe attack to pea that can with positiveness be 
 attributed to the pea aphis was reported to this office, in a letter dated 
 May 16, 1899, by Mr. Thomas Bridges, Bridges, Va. This was followed 
 within the next few days by reports from Virginia and Maryland, and 
 soon afterward injury was recognized in other States and in Canada. 
 During the previous season (1898), however, this pest was present in 
 
 AC 4'J 
 
some numbers in certain fields in Maryland and was noticed on late 
 
 in New J 
 
 This insect, as has been Btated, was generally injurious daring the 
 1899 and 1900, although Bomewhat locally in Borne States, bom 
 8 itia south to North Carolina and westward to Wisconsin. The 
 t's occurrence in destructive abundance was noted by L900 in 
 Scotia, New Brunswick, and Ontario, Canada; Maine, Vermont, 
 ichuaetts, Connecticut, New York, New Jersey, Pennsylvania, Del- 
 aware, Maryland, District of Columbia, Virginia, North Carolina, Mich- 
 igan, Ohio, Illinois, and Wisconsin. 1 Sanderson has recorded the 
 lining also in Minnesota and Nebraska. Injury in Wis- 
 consin was not notice. 1 prior to 1900. 
 
 At intervals since 1901 this Bpecies has been injurious locally but 
 there have been no widespread outbreaks. During the past three years 
 is been rather unusually troublesome, judging by com- 
 plaints. In 1906 injuries were reported in localities in New York, Vir- 
 ginia. Illinois, and Texas. In 1907 the range of destructiveness em- 
 braced portions of eastern, central, and western New York and parts of 
 
 Maryland, Virginia, and the District of Columbia. The insect also 
 made its initial appearance as a pest in Louisiana. In 1908 Complaints 
 
 made of ravages on Long Island and in Maryland, Virginia, Penn- 
 sylvania, New Jersey, and California. In New Hampshire early peas 
 
 destroyed and in tidewater Virginia late peas were injured. It is 
 evident from recent reports, e. g., those of injuries in Texas, Louisiana, 
 and California, that the Bpeciesis likely to he a pest any year practically 
 throughout the United States and Canada where peas are grown. 
 
 EXTENT OF IN.lfKY AND METHOD OP WORK. 
 
 This pea aphis during the first season of it.- abundance overran and 
 laid waste fields of pea- from Nova Scotia and Maine to Virginia and 
 Maryland, in the last and in some neighboring States destroying about 
 50 per cent of the annual output and doing similar injury the following 
 year, in spite of vigorous efforts that were made to control it. 
 
 An estimate of the total loss for the year 1899 in the Atlantic Coast 
 States reached the Bum of $3,000,000. During 1900 the loss over 
 the Same area was placed, as early as -June 1"). at $4,000,000. Several 
 - of Bever* i ported in Maryland, in which SO per cent 
 
 or more of the peas on farms of 5"0 or 600 acres were completely 
 destroyed. In short, the pea growers of the Atlantic region and west- 
 ward as far as Wisconsin Buffered vn; losses, which gave rise to 
 the expression that this country had been visited by a veritable scourge. 
 
 •There is evidence that tl trved od crimson clover in Dela- 
 
 ware U early as 1890, and has perhaps b< nt along the Potomac > 
 
 since, or priori - Bnl. No.26,n.e , Div. Ent., U. S. Dept. Agric.,pp. 5G 
 
The reasons why the species has hecome so conspicuous a pest are 
 threefold: First, because of its ravages to a crop hitherto little troubled 
 by insect attack, if we except the pea weevil, which has always been 
 present in gardens and fields for upwards of a century and has come to 
 be looked upon as a necessary evil ; second, because it is a species never 
 before noticed, so far as records go, as having been destructive to peas 
 in this country ; third, because of the great difficulty that has been 
 experienced in its treatment, pea growers during the first year of its 
 ravages having met with almost complete failure in the remedial meas- 
 ures applied. 
 
 Although garden and field peas are the crops most injured by this 
 aphis, sweet peas, red and crimson clover, as well as vetches and tares 1 
 are affected, and in some cases have been damaged. Attack begins on 
 the young pea vines; the "lice" gather in clusters at first under and 
 within the terminals, and as the leaves become covered they attack also 
 the stems, and by their numbers and voracity sap the life of the plant. 
 Whole areas of vines are frequently seen covered with the aphides, 
 which in a very few weeks are able to destroy a crop. Attack is seldom 
 noticed until May 2 in the more southern States in which the insect is 
 found, and a little later in its more northern range. 
 
 The complete life history of this species is not known, but like other 
 aphides it produces many generations each year. 
 
 According to present knowledge, the pea aphis hibernates chiefly on 
 clover, particularly crimson clover, from Delaware southward. In the 
 District of Columbia it winters also on vetch. From these plants the 
 "lice" spread by flight in April and May to peas, which they attack 
 while the vines are young. 
 
 As with other aphides, the females at certain periods produce living 
 young. Thej r attain maturity in from ten to fifteen days, and possibly 
 in less time in the hottest weather. Young that were born March 4 
 reached maturity (winged form) March 16, or twelve days from the 
 time of birth, and reproduced young three days later. 
 
 As an instance of the rapid reproductive powers of this insect, 
 Professor Johnson's estimate is interesting. He found that females 
 produce from 110 to 120 young and that in one case where aphides 
 were observed on the first of May the fields were abandoned on account 
 of ravages three weeks later. Calculating from the average number of 
 
 • A considerable number of alternate food plants has been observed for 
 Macros iphum pisi in Europe. 
 
 2 In 1901 Mr. Samuel R. Haynes, Portsmouth, Va., reported the presence of 
 this species in that locality about April 7. During the second week of May the 
 writer found it numerous on crimson clover and vetches at Washington, D. C, 
 and May 14 it was reported at work upon peas in the District of Columbia, near 
 the Maryland State line. 
 
Km. 2.— Spotted Iti'lyl'. "■ larva : 
 
 h. empty papal ^kin . e, beetle, with ■ i nteim a 
 
 Ul enlarged. (Author's illustration.) 
 
 insects produced each day, which is six, one Individoal would become 
 tlif paogenitor of 123,912 of these aphides in one Beason. 
 
 N \n B M. INKMII 99. 
 
 The efficiency of natural agents in the destruction "f aphides is bo 
 well known that it has been hoped that some one or more of the many 
 species observed to attack the pea aphis would increase in Buch num- 
 
 to have the effect 
 of limiting its multipli- 
 cation. In Bpite, however, 
 of the closeel observation 
 by ;i number of persons, 
 tlic natural enemies have 
 been found to produce 
 only transient relief, and 
 this only in limited areas, 
 as a rule late in the Beason 
 after damage has been ac- 
 complished. 
 
 The pns. nt list of m- 
 
 - known to attack this 
 
 aphis includes Beven Bpecies of ladybirds, or "ladybugs" as they are 
 
 familiarly termed, 1 three species of Byrphus flies, 8 a lace-wing fly, 8 a 
 
 Boldier beetle,* and a few minute four-winged hymenopterous parasites. 5 
 
 The ladybirds are destructive both as beetles and larva-, thesyrphus 
 flies only in the larval condition, which is true also of the lace-wing fly. 
 The efficiency of the Byrphus flies is greatly impaired by the presence 
 of a braconid parasite,' which is Bometimes very prevalent, almost com- 
 pletely exterminating its hosts in many fields. Nearly all the species 
 observed are well-known enemies of other aphides, and in fact greatly 
 prefer as hosts the cabbage aphis and Bpecies found on weeds to the 
 pea aphis. The Bpotted ladybird {Megilla maculata I ><■<;.) and a lace- 
 wing By [Ghrysopa oculata Say) are shown in their different stages 
 in figures 2 and lively. 
 
 In addition to the natural enemies that have already been enumer- 
 ated, several other insects attack the pea aphis, among them a small 
 red mite, Ehffncholophus parvus Banks. 
 
 \la novemmrtata Hbst., Hippodamia ■ - Goer., Megilla 
 
 ilata DeG., Hippodamia gku ilit Fab., Adalia bipunetata I... Hippoda- 
 ,„,,,; i I.., and Coccinella sanguinea L. t Allograptaobliqua Bay, 
 
 Si/rjiluis amerieamma Wied., tnd Sphorophoria cylindrica Bay. 'Chtytoji 
 
 lata Bay. i Fodabru» rugosulue Lee. i Aphidiua tcashingtot Lshm. 
 
 US.? . .1. fleteheri (Ashm. MS.?), Pro taphia Fitch. J i ml- 
 
 garis Walk. ' Bastus Uetatoriua Fab. 
 
 In the above list the Bpecies ol each class are named in approximate order of 
 abundance in Maryland, Virginia, and the District of Columbia, and consequent 
 efficiency as dt of the aphis in that region. 
 
 A6 19 
 
Considering the inefficiency of natural agencies, if we except atmos- 
 pheric conditions, in the control of this pest, it is hoped that a com- 
 mon fungous disease of aphides, known as Empusa aphidis, may become 
 an important factor. As the development of this fungus is dependent 
 upon rather warm, humid weather and is retarded by drought, it is 
 fairly certain that atmospheric conditions, after all, are most important 
 in the limitation of this insect. It is within the bounds of possibility 
 that the fungus might be cultivated artificially and be used during 
 weather conditions favorable in the control of this pest. 
 
 Fir. 3.— A lace-wing fly {Chrysopa oeulata): a, Eggs; 6. full-grown larva ; c, foot of same ; d, same 
 devouring pear-tree psylla ; <•, cocoon ; /, adult insect ; g. head of same ; ft, adult. All enlarged 
 except ft, which is natural size. (From Marlatt.) 
 
 METHODS OF CONTROL. 
 
 In some instances natural enemies of the pea aphis have rendered effi- 
 cient service. Seldom, however, do they destroy the insects early enough 
 in the season to save a crop. In the course of time — many years in all 
 likelihood — these enemies may become more effective; hence, in view 
 of the fact that the extermination of the species even in a limited area 
 is a practical impossibility, anything that can be done to destroy the 
 aphis without harming its insect enemies is advisable. If this can be 
 accomplished it will afford in itself a reason for the rejection of insecti- 
 cides, none of which is in all respects satisfactory. 1 
 
 !For the benefit of some persons who are not wholly familiar with the feeding 
 habits of this species it should be stated that it obtains nourishment by suction, 
 and can not therefore be reached by means of internal or stomach poisons such 
 as Paris green and other arsenicals. 
 
 A6 49 
 
Kerosem emulsion. — Kerosene-soap emulsion, a standard remedy for 
 aphides, carefully prepared and diluted with about twelve parts of water, 
 sprayed upon the infested plants upon the first appearanoe of the 
 aphides, and bo applied thai the leaves are wet on both the under and 
 upi" r Buri • es, lias thus far been found to he the mosl effective <>f the 
 Insectioides tried. A Btronger solution than thai specified is apt to bum 
 or Bcald the plant, particularly while the vines are young and tender. 
 Sprays of whale-oil and other Boape have been found less useful. The 
 oosl oi the kerosene emulsion remedy, however, and the difficulty of 
 underspraying, ita rapid evaporation, and the necessity for Erequenl 
 
 application.-, are BUCh SS hardly to warrant its use on a large BCale. 
 
 
 uiiaK.i',1 ioap, showing method <>f preparation and 
 
 application. 
 
 The method of preparing tobacco-whale-oil soap, a Bpecial preparation 
 
 of nm|i of particular value for aphides, anil the implements used in its 
 application are illustrated by figtu 
 
 Tin brush-and-euUivator method. — The hest remedial measure that 
 has yet been devised is the growing of peas in rows with sufficient dis- 
 tance between them to admit a onediorse cultivator. The "lice" are 
 hrushed from the plants with DOUghs ofpine with their leaves on. and a 
 cultivator then follows down the rows as soon afterward ble. For 
 
 the perfect BUCCeSB of this method it should he practiced in the h< I 
 the day, when the ground is dry and hot, ami the repetition of the 
 hrushing is necessary every three to seven days until the crop is ready 
 
 A6 49 
 
8 
 
 for picking. Such lice as are not buried in the ground by the cultivator 
 will be killed by the dust which closes their breathing pores, while a 
 considerable proportion is destroyed also by the force of the brusbing. 
 This method has the advantage of not being so destructive to the natural 
 enemies as other means that might be employed, the aphis being more 
 fragile and delicate than any of its insect enemies. Moreover, peas 
 planted in rows to permit of frequent cultivation suffer much less injury 
 than when sown broadcast. As soon as the last picking has been made 
 infested plants should be promptly destroyed by plowing under. 1 
 
 Fig. 5.— Field of peas saved by brush-and-oultivator method, showing implements used. 
 
 The brush-and-pan method.— A method which consists in jarring the 
 aphides from the vines into specially prepared, long, shallow pans in 
 which a little kerosene is floating, dragged between the rows, has given 
 good results, the insects as they come into contact with the kerosene 
 being all killed. A bushel of " lice " was caught to each row, 125 rods 
 long, in one instance where this remedy was used. It is practicable 
 onlj' for small areas. 
 
 •We have abundant testimony to the value of this method, but perhaps none 
 more striking than that on the farm of Mr. C. H. Pearson, a Maryland pea- 
 grower. During the season of 1900, a 600-acre pea plantation was practically 
 saved by this method. After other means had failed, the fields were brushed 
 and cultivated every third day for a period of two weeks. The previous season 
 peas over the same area were sown broadcast ; so that it was impossible to combat 
 the pest in this manner, and as a consequence 480 acres were entirelv ruined. 
 (Bui. 20, n. s., p. 94; Bui. 26, p. 57, Div. Ent., U. S. Dept. Agr.) 
 
 A6 49 
 
9 
 
 A field of peas Baved by the use of the brush-and-cultivator method 
 is illtutrated in figun 
 
 In figure 8 the manner oi applying the brush-and-pan method i- 
 ahown. Figures l 7, illustrating the practical methods ol combating 
 tin- pea aphis, were first osed by the late \V. G. Johnson in an article 
 published in Bulletin No. 26 of this Bureau. 
 
 Cultural methods.— Ol cultural methods, there is testimony to the 
 value of early planting, the earliest p lorn being infested, or ;it 
 
 least only slightly injured. Very large plantings of peas to be used 
 for canning have also escaped ravages in some instances, hut it may l>e 
 
 !fi 
 
 
 1 
 
 JL^E 
 
 'K- 
 
 ■to, 8.— Field of peu mvi \ by the bru method, showing the tppu 
 
 that atmospheric conditions have had something to do with exemption 
 in the cases which have come under notice. 
 
 Rotation of crops is advisable, and it is unwise to plant peas on the 
 same portion of a farm or garden, in successive years, or in the vicinity 
 of fields of red or crimson clover, or other leguminous plants, such as 
 vetch, which are likely to harbor thi~ 
 
 A.S has been said, this insect passes the winter on the plants I 
 tioned, because peas are not available, and it might be possible to 
 - small plants of some one of them as trap crops. Crimson clover 
 would probably be best because of its conspicuousness and the early 
 start that it gets in the spring. On the trap plants the aphides could 
 be killed by hand methods, such as brushing from the plants into | 
 
 A6 19 
 
10 
 
 and thus large numbers of the insects could be killed early in the sea- 
 son before they had opportunity to spread to peas. 
 
 In Delaware it has been shown that the practice of keeping the land 
 well fertilized and frequently cultivated enables the peas, in spite of 
 aphis attack, to produce better crops than would otherwise be made. 
 
 Alternate host plants.— The subject of alternate host plants is an 
 important one, since the pea, being an annual, is not available as food 
 for this aphis during winter. It is desirable to ascertain all of the host 
 plants of the pea aphis, and more especially the weeds, as some one or 
 
 Fig. 7.- 
 
 ■Section of a 600-acre pea field, rows one mile long, showing spraying outfit ready for 
 work. Peas finally saved by brush-and-cultivator method. 
 
 more of these may be factors of importance in the life economy of the 
 species. It might be necessary in the future, should the depredations 
 of this insect increase, to limit the growing of clover and other legumes, 
 as well as other alternate host plants, if such be found, in the vicinity 
 of pea fields. If all of the principal alternate plants could be discov- 
 ered this might furnish a solution of the problem of how to deal with 
 the insect. 
 
 Approved : 
 
 James Wilson, 
 
 Secretary/ of Agriculture. 
 
 Washington, D. C, January 21, 1009. A6 — 19 
 
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UNIVERSITY OF FLORIDA 
 
 3 1262 09216 4960