Dw'~gjcate CIRCULAR 65 (Reprinted 1937) MAY MY13 1934 Time of Turning Legumes and Planting Corn To Avoid Injury from the Southern Corn Root jWorm By F. S. ARANT AGRICULTURAL EXPERIMENT STATION OF THE ALABAMA POLYTECHNIC INSTITUTE M. J. FUNCHESS, AUBURN Director Contents LIFE HISTORY DESCRIPTION OF STAGES INSECTS MISTAKEN FOR THE SOUTHERN CORN ROOT WORM--CONTROL STUDIES SUMMARY ---------------------------------------------------- 3------------- 4------------4 6------------10 Time of Turning Legumes and Planting Corn to Avoid Injury from the Southern Corn Root Worm By F. S. ARANT Assistant Entomologist (Diabrotica duodecempunctata root THE southernmajorlegumeswormAlabama. grown on bottomonlands Fabr.) is a corn pest of seedling corn the Detailed data in or following winter life history and preliminary data on three years of control work for this insect were published in 1929*. The results of six years of experimental work to determine the best time to turn winter legumes and plant corn in order to avoid serious injury from the southern corn root worm are reported in this circular. A brief account of the life history is also included. LIFE HISTORY The adults of the southern corn root worm (Figure 1), known as spotted cucumber beetles, overwinter in the southern states in rubbish, on winter legumes, or other green plants. During very cold weather they become inactive and hide under leaves or in other protected places, but when the temperature rises well above freezing they become active once more and begin feeding. Many of the beetles congregate and feed on winter legumes in the winter and early spring. The females deposit their eggs in the soil nearby. Egg laying begins in January or February and continues throughout most of the summer; it is most abundant during March and the first part of April. After an incubation period of about eight to twelve days the larvae emerge from the eggs and feed on the roots of winter legumes, grasses, or other plants. When corn is planted following the turning of winter legumes, the larvae often attack the seedling corn, boring into the stalks and thereby causing the buds to wilt and die; the stand of corn may be greatly reduced (Figure 4). After feeding for about two weeks the larvae form inactive pupae which in turn develop into adults in about a FIGURE 1.-The Adult of the Southern C o r n week. oot worm. larged about 41/2 The time required for develop- En- times.) 1929. *Arant, F. S. Expt. Sta. Bul. 230. Biology and Control of the Southern Corn Root Worm, Ala. Agr. froml t-, to aduhlt v arles coiiittei'ahx re: it is ahout four to fix wxitli the teflplert xeeks duing v\1wx ar11, xxeat ei. ment i 'Ihriee cointllel e genieratiolls cor riooiit xx liii nmax hl Iitl all> e c little damage 1 With the ennIP the f irst :-neeatinh. II of -tilner wxeather the adults milgrat ,fi1 liecufii serious nnottxx atid xxherc llex lwst of euiiltit- andit other plats in the celldstate-. SBulme uietlis nmay tri weil nilx cturn Iw efoind in A Lohama tin ugthmoit the summer t he spin" DESCRIPTION OF STAGES iif the sothern occur I hutall ill Alato (lili is prodiluced by ( Fi -ul ahilti itI ) is isi an t r t ciiiit-ma ee t h js ltaeIk I anhut atites. I (I th r the intel boiix - lit". 1lhe head and1( a vaijah le \ ellois VIeetr Color' xx th each xxitm mtairked hi- six colspiicuous black spouts. iii elloxx . ixal shaped ifft~iut to see: it ilesthan 1 :12 iuch lbug. object wxhichlis Thte iln a ni" *l"iluu~ill is > ellowx~ish xxhite in coulol ; it is~ ai (t r ich Ii ml- yv-hell matunit ( Fiure 2). The hiead~ is liather ci nspticuouts anl ts (ira~iii hiin\\n int couliti: the lidi> is lIealIX cvxlical ilt s~hape. is sutiviexhat clirved. anid tapiers slightlt toxward thle aliteiort end: txo di(istiltct l'~iiuxt shkilds are tpresenit oul the uppier surface. Olte ((I the fir1st setttielit ifthle t horax and the oither (in the le last se ,rnent uft h abditt ni. The pupila. whLi is rairev see n, is light YIellotx abotwl tlhe same lenigt h ar tihe adult. INSECTS MISTAKEN in cudor amd is FOR THE SOUTHERN CORN ROOT WORM z;;exeral specieso C(Il insects produt~ce injull lite -. illiitar ers andt uothei atlicitur til xx ((kcrs arei ctant ltl' cmlul isili 1 le-u ins~ect- xxithI the sii'thleiin coli rouut xx irl. it seetns adisahle ti> (litili Ihetxveeii the x alnhn> species as diIit(Itel as po ssilei. On o tle itnsects Calisingi luiuer .0-called lesser coin stalk (i/t.-,o 1 ,)piI~s u. "Iiudxxnm" illjttlv is the /I,toscII's Zellei i The larv of t141his slender,1 insiect is a reeiiish-color- ((I I So uthern or R o vv 01111 with indistinct transv>\erse hand1(s (of a Wor liuhtui color1 on the anterior' marigin of the se42gmentsl ( Figure ",). It is usuIally a little less than11 on11 inch1 101ng wheni maitureI. The2 larva eiats holes ill the unfo4ling leaves> or bor4es tu nnels in t he stailk. The most 14oo4l., uland11. s a1 n1 d y IxC Cr Stal H('r I soils. wally The hest canl ushe distinguished tulle-shad(ed xxci which the 1lrv sh>~'ins at the surfac 4 o14 he s11 oil1. Ill lesser 0 (; corn1 g r ,talk co4\\ borer( 44a>, 14eeds on1 sor4g11um, .Johna1 s s, Oral Su1thet)411n (lrgr 2 (044n Stalk Bort nt I )I' . h Southetn or (' om 44ote c1ro14. The adult is a1 velloxx ishl)10\ 11 to llack ishl 41 4 ed~4( moth w ih a wing11 th1an1 on1e inch. mouther inisect pr14ducIinfg inijury is the soth~le1 414411 stalk 14o41er (Di), Thlis ins~ect is oftenil (1i1r2y-white caterpila I iigur ac and( xxhen full growxx isI mariked ) xxithl lnumerous distinct blak or1 (larkhrw sp)4x41 each1 of xxhich ots, hears a1 short1 hristle: it is about~t (tie inch lon111. Thle lar1a play Oat le 1(14 th1le unfold1(ing 1lxa (4 itut typ~ically IH)res in~to tile ase of/ tile s14alk, causin>11 the lan14t to xx lt or xxealkening the4 stailk sot drillinig in stalks o41 corn1 o 444)a , (t,44idi . Gr404/ ote) cakledl the largier cor stal1 borer14441: it i- a tat. by that it is easHYi I ro)ken (Ionv xx1yl the xxind1. The adult11 o f this ins>ect i5 a light, smoky -yelloxv mo1th vviti a1 xvi lp expans11e of1 a1144t1 1 i. iniches. ~A third specie -41 o1 insect xxich produ f 144(11ce s-calledl "iudwoli" in~jury is the c'1 in (e11xx 01 (11lb ti4 .s 4)1444/4tol 1814.) . Thy lama )t Ihis 1insect vari1es ini color4 1fon li,,ght gn-eel to4 lbrown and11( 41 1s m~arkedI xxt atl 1terna4tingy light and( dar4k stripes 1r11111111 lengthwi se1 th 114 y :44l is' it '(twox) in11hes( l(4ng whe1n11 full g)wnxxi. Tile a1o4 caterp~illar eats hole> i11 thle unfllhldinr leavxes earlyx ill the season1 atod feedIs in the tassei the Season4/I. The adllt isi a moVth wi\it h a w\iln, exhansof a11out 1 1 inches: the I i 1- h t -a -i--h in a rk e dI \ it Ih eirr uInc li ne: the hindl x\inns are \\ hue wVith /18 LA) lncIKi n A fouth spie4~~(s of intI sert p)1oducing in niy ta himi. darkerII u~llall- l iso 101012l' t t1() c111 mistake4ll f is the This nynial calne is a1 :e 2144l c.r I A44 1ater. d '_ %e k Lec.). ihnsect l)eetle aIbout 1 inch IW -J 5IlI1W to a4 C1(I1111 I lle The coin nn/I thispo 44l 4uthc/ 1 C,)rn hug,"Ijury"* to corn1 is 1)oduced b(/ the adult y ealt ing4 into t he stalk ust K blowh' rio 14*(.yc (4 14y /Ihe 4,4 l m4/. the Surfate oft the ,round,/i oni- 1h(ehl) atnd \\-e 41k 'lin l' the stai k 1)11d often11 t sinhumit tO wVilt. e\ 4-14 -I l \\ccsO 1lre\\ 5((4IliuI4 colln I/ut it doesA- n44t tioni of thle various l-ecies (bl/ted 1hea11 IeetI4. 1)iu(4/,, il \ Ihite gruhs l>) 1414. ld to- alte4nl 4 a ( this circulari. seelll attack descip- 44414144/4Lec.) tv Im4/t~ a~ttlacks -4((Iliu12 4011 i'his lll"\ a is lm~no4 Sotlelo1 Cuorn roolto" idIenticl l'll. in strinctuore with the harva of tin- CONTROL STUDIES t114 loot ;ildle" corn) illsAct \\ol 41811 llinA 114' inl co 1//holi n the sou(thern colle sea-ion-, it is (Iesiral to so time the of1 c//In that >/Al1441V illnr 1118 may1 44a\oided4 eachl yenar. 1lay Ihe 41' grelt \a1111/ certainl dur~ingy 21(t't fo]/tllowin amounit it damagi1ie in A \\ ilutc 1( l4O mS lIFigures I14 and laham (4c1011s I 4ll5 ai series Of' ex- J44rili/llts 211>s conducltedt/ at Auhur1/n ove al s1 ix-Vear period4 to4 dellillle iihe let tinle 14to turn legunt> and( pln 41111 .411 to avXoid injuryI . p -, n t'Iym these tf ie series > andt check itlots (%\ihoutlegrumes) wvere Beginning, the day fiillxx lu itch (4 - ci was mad l l ~' the leg e an ld the check series each xxeek unili fixve plantings N\tie m1ade. (0)5Nvcem made at serv athis interx als of tw toi ii ixe dlays to dhetlerline the sout1herni cy corni loot xxirm itrned on tis Miltrch 2L1; corn pit tlt- etl 2 wxeeks latet. little by ltfttXuIt o The c c plot XXast jttjtticd c the t. souithernt The gireatest amnltit of occtuired inux' in corn p~lanted n0 the seiles of blots turiiedi INIt ih 15 antd1( the least itmound (( t oil the selries tuined Apil 15 (TAhl I ) . Tin sitx year maxiage inlfestatiolt in cornt p~lanted on the series (it' 1)p1lottne !latich 15 xvatied 1100m 12.8 to 51.5 per cent til the le m plo tst 1111d f1r1m 6A to 12.2 lier cent oin the cheecks: on the series itf plo ts turnelld Apl 1 1 it variedi frowtl.12 to -49.2 ter cet on the legumtt ;lts andl friim 2.)) to S8G per cent till the check-: tin the seies t plots turned April I5 the ( infestattion xaied tfromll0. to 21. pier ccett til the legttme itlitis atnd froml I )t to 2.9 on the checks. The data in 'Tatiie 1 indicate thait noi serioits injur oiyiccturred to citln ptlanted at Aub~urn Aptiil :1) oI thteeafter tiilloiixiig the turing otf legumes 10n 01 bettire Apiiil 15. The figuties in this the iet cenit it infestedl plats ltable, liivcx ci. reprlesent tly wxhich occurried bjefore the pIa The appar~tent tiotal injuttl Its caime up. ltable 2 as tilt pier is expilessed ill upi. Siiie cornt til tile control pilots xxas not usually- daimagited to any\ gleat extent atnd~ since xxveathlet cintditins atffectedl germlillatlit f chl(iecks alike til botth series iif lots. the diIifee nces ini faxoi uth (Taitle 2) reliresenlt tfirl acct alt-e the I tial sidu thern citrn riiii xxormn inijury toi (011n lantedi after xxwinler legtumels. It xxill bte nlitedl tihat coid~erablle in~jurx uccurred to aill citrn iplanted itil the leptihil iplots prev ious to April d)) little iir no injur 01 iccturredl tto cornl ptlanted April :1) tir thereafter ( Tabtle 2 atind Figtre 6y) TABLE 1.-Six-Year Average Per Cent of Corn Plants Infested with the Southern Corn Root Worm, 1927-1933. Average per cent of corn infested Date of turning land* March March March March March April April April April April April April April April April 15 15 15 15 15 1 1 1 1 1 15 15 15 15 15 Date of planting corn" March 16 March 23 March following Legunmes 45.7 55.5 39.2 30.0 12.3 49.2 29.6 28.6 * 9.6 3.2 24.7 8.6 2.1 0.6 0.1 No legumes 8.7 7.9 12.2 7.5 6.6 8.3 8.6 4.35 April 6 April 13 April 2 April 9 April 16 April April 30 23 30 30 4.9 2.0 2.9 2.3 April 16 April 23 April May 7 May 14 2.0 0.8 0.0 *Approximate date. *'Five-year average; 1933 not included due to mouse injury. TABLE 2.-Six-Year Average Per Cent Total Failure in the Stand of Corn, 1927-1933. Date of turning land* Date of planting corn* Average per cent total failure in the stand of corn* Difference No attributed to Following root worm legumes legumes injury 68.1 74.1 79.2 63.3 46.5 67.8 77.1 58.9 57.2 37.9 61.2 48.1 30.9 26.7 I 22.7 l 37.7 38.7 45.0 37.9 32.1 38.5 44.8 36.2 45.3 37.7 30.8 32.0 33.3 26.3 22.1 30.4 35.4 34.2 25.4 14.4 29.3 32.3 22.7 11.9 0.2 March March March March March April April April April April April April April April April 15 15 15 15 15 1 1 1 1 1 15 15 15 15 15 March March March April April 16 23 30 6 13 April 2 April 9 April 16 April 23 April 30 7 April 16 April 23 April May i 30 May 14 I r 30.4 16.1 -2.4 0.4 0.6 *Approximate date. **Per cent of total failure in the stand of corn= No. seed not coming up + No. plants infested x 10 0 No. seed planted ,rje itiontiti 8 ii ek atr I ir cu no injury tromt he sothr nrv at A iiiuiii was the samte regard~less of wvhet her the dhiage "as exipressedl in terms of plants knii )V1 to have b een inflestedl 'lahle 1 ) or total failuire ini the stand ofi eoen (fahle 2). All aual.ahlle diata idicate that the saflesit proiedurle ini tlalling eorni folloin g xxintel legumes is to till and clickl the le unhil: onl or lietore Apl 15 and Plant the enil eaily in Mlay. Own1 may lx lanited tone to two xek h~efottiav 1 ipt\ ideil tihe we atheri has La eln waim and reastonlahly dlry, and1( provided ftiher the legumes efotre Airil 1. Nv ere tunelbi ii legumhies andt ptlanit toin ttt avid\t sttutheii torn rott wor tin ijury inl dlifferent uct iots iii tli ;tate. It is ho,-,al to suipptose, llogvever,. that the diate of turingli and pllanting should lie a tew days earlier inl South Alabama antd a fetv- days later inl Notith Alaltima than ill the v icinity tot Auburn. It is lsot logidcil ttt suptttse than the date of turninug and ptiing ill any lttcal ity shldt he later (Itrin g an extremely eoo] seasonI than (11111ng_ a nitre nlealy ntormal spring. 10 SUMMARY (1) Adults of the southern corn root worm congregate on winter legumes in the early spring and deposit their eggs in the soil nearby. (2) The larvae emerge from the eggs and feed on the roots of the legumes, grasses, or other plants. (3) When corn is grown following the turning of winter legumes, the larvae often attack the seedling plants, boring into the stalks and thereby causing the buds to wilt and die. (4) Several species of insects produce injury similar to that of the southern corn root worm and are often mistaken for it. Insects commonly mistaken for the southern corn root worm are the lesser corn stalk borer, the southern (larger) corn stalk borer, the corn earworm, the sugar cane beetle, wireworms, and white grubs. (5) Experimental work has been conducted at Auburn over a period of six years to determine the best time to turn winter legumes and plant corn in order to avoid serious injury from the southern corn root worm. (6) The most serious injury occurred in corn planted following the turning of legumes March 15 and the least injury following the turning April 15. (7) No serious injury occurred to any corn planted at Auburn April 30 or thereafter following the turning and disking of winter legumes on or before April 15.