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The red spider on cotton (Tetranychus bimaculatus Harvey)

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Title:
The red spider on cotton (Tetranychus bimaculatus Harvey)
Creator:
McGregor, E. A
Place of Publication:
Washington, D.C.
Publisher:
U.S. G.P.O.
Publication Date:
Language:
English

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Source Institution:
University of Florida
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This item is a work of the U.S. federal government and not subject to copyright pursuant to 17 U.S.C. §105.
Resource Identifier:
30219300 ( ALEPH )
28102128 ( OCLC )

Full Text
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U. S. DEPARTMENT OF AGRICULTUREIVk
BUREAU OF ENTOMOI''.Y CIRCULAR No. V'.
L. 0. HOW I'. '. EL orn logit and Chief of Bureru.


I Ili RED SPIER ON ( )TTON.



BtY

E. A. -McGI]OKl ,

P


312120-'-cr C'ii 1-)-12















BUREAU OF ENTOMOLOGY.


L. 0. HOWARD, Entontologixt alnd Chief of Bureaa.
C. I, MARLATTv, Entomologist and Acting Chief in Absence of Chirf.
R. S. CLIFTON, Executive Assistant.
W. F. TASTET, ( LI, f ('1, 1,.

F. I. ('1HITTENDEN. i chargere of truck crop and storedd product inM'eTt i c.vetigatioiils.
A. D. HOPKINS, in charge of forest insect inrltc iatigations.
W. D. HUNTER, in charge of southern field crop insect investigations.
F. M. A\i ii ..i it. in charge of cereal and forage insect investigations.
A. 1. QUAINTANCE, in charge of deeiduoux fruit isc(t investigatiions.
E. F. PItILLIPS, in charge of bele culture.
D. M. ROGERS, in charge of ,,' "i ,lhi spread of moths, field work.
ROLLA P. CUBRIE, in chafgre" of editorial work.
MABEL COLCORD. in 'l, hIP of library.

SOUTiILERN FILID) CROP INSECT INVESTIGATIONS.

W. 1). HUNTEKR, ill chatie.

F. C. BisiioPP, A. II. JENNINUS, H. I'. WOOD, W. V. KING;, enga(iged in tick lif .
history ,*,,i i iuail1;,,,,.
WV. D. PIERCE, (. 1). SMITH, J. I). AITCIIELL., IIARRY PINKUS. B. R. COAD, R. W.
MORELAND, engaged in cotton-boll treeci! investigations.
A. C. MORGAN, G. A. tRUNNER, S. E. CRUMB, I). C. PARMAN, f'aicig c in- tobacco
in5'ct investigation.
T. E. IIOLLOWAY, E. RI. BARBER, engaged in .*ict,'.tat( insect investigations.
E. A. McG(mGoR, W. A. THIIOMAS, engaged in red spider and other cotton insect
it ret igations.
J. L. VEBB,m engaged in rice insect investigations.
R. A. (C'OOLEY, I). L. VAN DINE, A. F. CONRADI, C. C. KRUMBIIAAR, collaborators.







CIRCULAR No. 150.
I',silcd Ai 1,rI I 12l
United States Department of Agriculture,
BUREAU OF ENTOMOLOGY,
L 0. HOWARD. Entomoloist ind Chie f ot Bureau.
THE 111,41) SPIDE'll ON
( 7Tctitaji h us bimat-nuhtui1 1tit larvey.)
By I'L A. Mc(;IIm :,
Sri(c i/hit"i 1s i I .
INTRODU'CTo1i1.
The minuiite, reddish H-iiiit,.n mite commloitnlv known as.thie red
s)ider is rapidly assuming i position of importan'e. amonw cottIon
pes.ts. At Ilatesburn, S. C., ill 1 l1 it I I
first became noticeable on cotton alxmt '
June 1, ealisin,.z little m1ore than lpssin, '' /
notice iat, that tiite ;,ii',I._. the farmers. ;
but by the 1st of July it had increased so *//,
enormously that tlie e4fec-t upon c(otton t \ | ;
in certain pllaces was most alarm inp. ,' .."'J"'', .... ".""/
Seasons of excessive dro flightt -I .itly fa- \ '/ /
vor thle tulltiplilaItion of the mIites until1
the 11.,,nil i,,injuries are often S;) seveiv "-- ....^"'""
as to cause the death of imany plantst. -.
Red-siide, 1infestAation is frequently /\ \
miscalled rust by faillners, since in-
fe'sted leaves soonll turn ,deep red ()on their / \
uplper surface. Suhlevs, however. If -{*( v p
examined tiderleatllei, reveal the plres- '\
ence of the red spiders anid the inlcon- : / \
spicuous webs belhind which they are ,c '
fev ',lin." and la\ i t,. their *,Ll .I'\

HIiSTORY AND) D)ISTIItlITION.
I'K; 1 T'l r,- pd siil< Irt.
u / h u h i 1 1 0 1 1'u : A\ d u l t
W ith the exception of an mnt.Ireal, in /, '". .;r .- ', ,
Louisiana. reported bYv P'rof. 11. A. Mor- Ir, .,I :uIk.
..ii illn 1-'". severe occurrein'e (Af lih cotton re(l spider hiad not
been reported until P'.,1. at which lile complaints ot f -o ,1,.Ie calime
'[hits eircr lar Is hasod prininrily iv iptt work donei n :I t I]:ili-slr;;, S! t'., i> 1911.
bytder the dirction of Mr \V. A., Ilu0t1I tut al, itFlnhd.'s tu rngs ulls Ol opsrrva iemS
by MI'ssr.. I; .\. Itutnt'i tnd II. 1V. \Vilsnti t]irltR .I th o t\x pr ti ending 'lS sonsn,





THE RED SPIDER ON COTTON.


from South Carolina and Georgia. In 1904 'Mr. E. S. G. Titus,'
then of this bureau, found severe infestation in fields about Bates-
'irg. S. C.. and the following year he reported severe injury in
North Carolina, South Carolina, Georgia, and Alabama. Since
then the additional records of Dr. F. H. Chittenden 2 and Me-,-rs.
G. P. Weldoin, D. T. Fullaway, and others establish the presence
of the common red spider in Maine. M:i~-achusetts, New York, New
Jersey, District of Columbia. Virginia, North Carolina, South Caro-
lina, (G,,'ri;i, Florid,i, Alabama, M1i--i--ippi. Louisiana. Texas, Ohio,
western Colorado, Wyolig, Idaho, Washingtmn. California, and
the IHlawaiian Islands.
The red spider was described by Harvey in 1';13 as T, f.iix ,".,.
:-mac,(latiUs. Harvey considered it quite distinct from the European
species 7. tIlabils L. His types were from Orono, Me,. In '.I 17 Prof.
H. A. Morgan published observations on the cotton mite. and ap-
parently accepted the determination of the species as T. telarius.
In 1900 Mr:'. Nathan Banks described the cotton mite under a dis-
tinct name-7''e(av/yeIfs glocri-but from the study of additional
specimens, has now concluded that the name is synonymous with
Harvey's 7. b1);'a South Carolina have upon two recent occasions been determined by
Prof. A. Berlese as the continental species-TIctrany hui.s ftlarius.
As there seems to )e considerable doubt on this point, we shall follow
Mr. Banks in considering the form with which we are (l,1ling as
T /,,i,' 'i, ,, ins tac I latits.

DESC('RIII I'TION.

The typical female (fig. 1) is 0.46 mm. long by 0.24 mm. wide,
broad-oval, widest in front, and the legs are shorter than the body.
Its color is usually brick-red. The typical male is 0.27 mm. long by
0.15 nmn. wide, oval-wedg. lpc. narrowed behind, the legs about
equaling the length of the body, and its color is usually reddish
amber. Individuals of both sexes usually possess on either side of
the body a dark spot. caused by the food contents. This spot may
vary greatly in color, size, and outline. Similarly, depeiding upon
thie host plant and upon locality, the general color of the red spider
is subject to great variation.
Thlie ,.-g are very minute, )but in proportion to the mites they are
large. They are perfectly nrimd. and when first laid are as clear as
water. Each female lays (in the months of Juine. July, and August)
aI)out .50 to 60 eggs, depositing about 6 per day for a period of about
nine days. Less than 3 eggs or more than 9 are rarely deposited each
Cir. 65, Bur. Int. U. S. Dept. Agr., 1905.
:'fir. 104. Blur. Ent., IT. S. Dept. Agr., 1905.
"Ann. i. [ri Maine Agr. Exp. Sta. for 1892, Pt. IV, pp. 1:13-140.






TIHE RED SPIDER ON COI ITON.


d(lay in summer weather. Durin., tile warmer months tile vg_.- hatch
in about four days after I', iiL_, laid.
The newly hatched red spider, called tlie larva, is almost round,
has six lh.- and is nearly colorless. It ,.gii- fe(,iii_- at once, and
(in summer time) after two days* activity it becomes quiet, darkens
in color, casts its skin for the first time. and iInIn,, as the primary
nymph with an added pair of 1,.- n.liV eight.
The prilnary nymp)h becomes larger in size and darker in color,
but gi v, no indication (of sex. Feeding continues actively and at the
termination of another two-day period (in suinmmier months) a second
Inlillg occurs which gives rise to the third -I.ie-thlie secondary
nymph.
With this last nymnipiial -l:i, the fint indi(cationll of sex appears.
As with the preceding stages, two days usually siflice in sumniner
for the completion of this period, at tlie end of which time tlie
skin in shed for the third time and at last the perfectly developed(
adult mites appear. At thlie occurrence of each miolt the skini splits il
two, crosswise, and tlie c're:ature cr:iwls out of thle two halves. The
old cast skins are usually to be seen in abundance among tlie fibrils
of thle web.
',li1; ADi I.lT MALES AND) FEMALES (OM 'AREI)D.

Cnri'iiiL,-" the relative abliundance of females and males it may be
said that there seems to be a piredominiance of femtiales througlghout
the summer, buit toward thle appI)roach of (old weather thle occurrence
of thie sexes IWecoimeis more nearly equal. Thlie period of life of tlie
adult fenimale varies from 17 days in midsuinmmnier to several months
in winter. The male is shorter lived. As IMv'fore stated, thle female
is decidedly larger than thie in.il., more rounded behind, and of a
mncelh deeper color. She does not move about much, and whliel she
does hert motion i.s rather sl n te other. l0.ii, l when not mating1.
the male is frequently seen i\ii]_''\ rapidly about. The bol v aind
h are well beset witli bristles, which are smievlwhat more con-
spicuous in thle males than inl thle females. Thle *.v -. colsi-sting eacli
of two 1)'1)-, oie close lehlinl thle other, are situnated l near the front
ei_'l' of the body directly )ver tile second pair of l. o -.

MA. TI N .

Almost imiedliatelyv u1poin lec',,i, adult, tlihe rced splilers late
and ,,iti ,,,_ h iiiL. 'lThe males sc' ee I to i.... *' ji/zc uiinh'e t ili/cle
females within ease. The first a .-- arre free(|litlv depositecl o(n tlhe
same day lpon which tlile tranlsformiat lion occurs from the last
nymiphal to the adult stage.






4 THE RED SPIDER ON COTTON.

PARTIIENOGENESIS.

Experiments conducted with unminated female red spiders clearly
proved that they are normally capable of laying eg.-. which in turn
hatch anid develop into mature individuals. No t-t-, however, have
been successfully conducted to determine the sexual fertility of the
latter.
GENERATIONS.

The season of 1911 at Batesburg, S. C., was one of unusual drought
and heat and there were about 17 generations between March 11 and
November 5. The time required for a single generation varied from
35 days in March and early April to 10 days thr'iii,'iit most of
June, July, and August, and to 25 days in the greater portion of
October and early November. The following table presents the
duration of each stage of each of the 17 generations:

TABLE I.-Dcvelopment of generations of the cotton red spider.

Grr Incuba- Larval N "[.[,h Nymph Ovipo-
aGener- P'eriod covered by generation. tion period. ( (2) sition to
aln.period. period, period, adult.

Days. Days. Days. Days. Days.
1 -. M ar. 11 to Apr. 14 ... .... .. ............... 9 6 7 35
2... .. Apr. 15 to Apr. 29 .......................... 6 3 3 3 15
3.... Apr. 30 to May 13 ..................... 6 3 3 2 14
4..... May 14 to May 25 .......................... 5 3 2 2 12
5 .. ... M ay 26 to June .......................... 5 3 2 2 12
S.... June 7 to June 17.................... ..... 4.5 2.5 2 2 11
7..... June 18 to June 27......................... 4 2 2 2 10
8 ..... June28toJuly 7...................... 4 2 2 2 10
9.. ... Jul 8 Jul yto uly 18 .......... ........... 4 2.5 2.5 2 11
10. .... July 19 to July 28....,......... .......... 4 2 2 2 10
11- ... July 29 to Aug. 7........................... 4 2 2 2 10
12... Aug. 8 toAug. 17.......... ... .... 4 2 2 2 10
13 .... Au lS to Aug. 29 ........ ... ..... 5 2.5 2 2.5 12
14 ..... Aug. 30 to Sept. 9 ................... . 5 2 2 2 11
15 .. .. Sept. 10 to Sept. 24................ .. .... 5 3.5 3 3.5 15
16 ... .. Sept. 25 to Oct. 10... ...................... 6 3 3 4 16
17 .... Oct. 11 to Nov. 4 ... .. ..... ........ 9 (1 5 5 25
Average............ 5.5 1 2.7 2 14

RELATION OF W'EATIIER TO BREEDING ACTIVITIES.

The influence of the weather on 1,r.i,1iii activity is very notice-
able. Hot, dry conditions greatly favor and hasten development.
while cool, wet weather correspondingly retards it. A female layigr
normally about 6 or 7 eggs per day will often upon the occurrence
of a very hot day, suddenly increase the number to 15 or even more
(_.- per day, or upon a (chilly (lay may drop as suddenly to 1 or 2
e(rgs.r It is easy then to lmderstand the remarkable rate at which
tiis pest increases durinii! times of unusual drought.
OBS1:I1VATIO()NS ON IIABITS.

In establishing lierself upon cotton the female selects a concave
areal between the uimider veins of the leaf and !,gii-,l at once to deposit
S'- These1 1 may be attached to the fibrils of the web slightly above
the surface, or, as seemnis most often the case, they are placed directly






THE iED SPID)ER ll (N COTTON. 5

upon the leaf. The r.-- are u-uall cluhtered rather clos-ey alnd
rarelyv occpy ;iy a'rea -,l-iter in siZ-e thanl that (of ai die. leediIr
c(.ontiles inlterrulptedly h ,.. -1Ijout twhe period of :,'! lax i ,' and tie
affected area of the leaf ecolmies thickly \l dotted with the bhlackish-
green puncture mIarks. Meallwxile a winlle-red l pot, lias al)pp)ea.red ol
the upper s-urfaie of the leaf directly over tlie y',ili,- col *y, which
spreads as the cololly il As the '- hatchl thle larva'i remain close to the place of their birth.
The ilites seem of a decidedly scial dis iti. a ecila .C "II'112 coltnv
there is usutially v little web forlmeld, buit where ie l spiders are very
abundant the web) lmay become (quite conspicuious. It doubtless
affords some protection from adverse weather coliditions, anlid upon
several occasions hostile insects- have been obervedl ensnared and d(lead
a .ii,,' the tibers. New females, after latlinl,. eil her select an att rac-
tive spot on the leaf, or iiii-rate upward
to a more tenim)tin, leaf. or in soioe
cases mlay even travel to another plat. :i .

THE VIOLET \S lST.

When cotton (die', or becomes muitet- i..'' lip -.' *'.;
i ,-, in the late fall an exodus of red ::-:^^::'^'
spiders from the (cotton fields occurs in l.:. .. ...
the effort to find more suitable food 1 a a a
plants. At this time cotton mites may 0 "
be easily found on a number of native ._______
and cultivated plants, prominent :ii,11111,1 1',. 2.-I)iiram showing how vio
which are cowpeas. tomato. Jamnestown lets growing in dooryard giv
rise to red spider infestation in
weed, ironweed, and cultivated violets, adjoining fleld. The infestation
r a i i 1is Mlost severe near the vard.
111-1 of these plants die after the frosts, Thi. dianr:mn is typical of mIaly
but the violet remains -omewhat green e.s, found during I1911 i(rig-
throii'lll lit the winter, and it is upon a
this plant, probably, that the vast majority of miles overwinter. (Out
of many case- of cotton infesatition in\, -1i.;ated the vast, majority v
have indicated most clearly tlihat tlie original source of lthe pest w as
doulbtle'ss this iin oceit pet of the housewife, tlie Englisl violet.
(See fig. 2.)
OTHER MISTS.

In all. thle red slider hail been fotiund in 1911 upoll)l over 0 V) -".'
of plants, ilnclIdinlg l\ weeds-. oriallelital plants, and _. irdeli a1dil field
crops. Ipon mtOI t of o hese lie Ie-st was oloV oc1 asiolallv s(een, but
it was fonllild colilloll( thlii"idouit tie :itive seas Oli upl)on the fol-
lol\ ii .1 plants: BICall.'. (owpeas. (alia. irollweed. 4l.ersalelnil-oak
wee, ,Jamestowi w, ,,,. okra, tomato, wild blacklerry; alid wild
.eranliulii.






THE RED SPIDER ON COTTON.


HIBERNATION VERSUS WINTERING.

Some observers have thought that the red spider commonly hiber-
nates in trash or in the soil in cotton fields, but the past season's
inv-,-tig:Aion,. have produced absolutely no evidence to support this
idea. During the early spring, before the active season for the red
spider commenced, trash was several times taken from fields in which
the infestation had previously been severe and examined with great
care. A few minute dormant acarids and other forms were thus
obtained, but no red spiders could be found in such material. Simi-
larly, during December, 1911, ample quantities of trash, etc., from
recently infested fields were carefully examined, but always without
finding any trace of the red spider. That this pest remains more or
less active throughout the winter there can be no doubt. Mr. G. A.
Runner found active adults at Batesburg, S. C., on December 21,
1909. Mr. II. F. Wilson observed red spiders f,-.ding in early Feb-
ruary at the same locality. The writer found all -thaz,- on violets on
March 11, and adults as late as December 19, on the same host at
Batesburg. The finding of the active red spiders diringL the coldest
weather is certainly an additional indication that hibernation does
not take place in South Carolina.

DISPERSION.

How do red spiders become established upon cotton? They have
no wings and their legs are very minute. Close observations reveal
that on the ground they normally travel at the rate of 1 inch per
15 seconds, which, if maintained, would total 480 feet in 24 hours.
Red spiders are doubtless occasionally transferred by dog.. chickens.
other domestic animals, insects, and birds. Strong winds may serve
occasionally to transfer them from plant to plant. It is the writer's
firm belief, however, that the chief means of dispersion is the red
spider's own efforts. When once established in a field they may be
further distributed by farm hands and by stock while cultivation is
being carried on. They also spread from plant to plant along the
interlacing branches, but traps specially prepared with "t:inglc-foot"
and placed in the field have proven that individuals commonly crawl
from plant to plant by way of the stalk and the groiundl.
Since the red spider apparently uses no instinct or intelligIi.e in
fiplinL- cotton plants, it follows that the pest must hit upon the cotton
stalks entirely by chance. Tlie result of this haphazard manner of
migration must necessarily result often in the penetration of the
spiders far into the center of fields, thus -i\ iii, rise to the mistaken
impression that they had h il)ernated at these points.
Firthlermnore, as the likelihood of the discovery of cotton by the
spider is doubtless in proportion to the thickiine.s of the "stand," it






TiHl HE1> SPIDEH ON ('OIT')N.


should follow that the thiick r'oatdcnstin; of ;ai niarow order strip
:ai-,iu thn l 1. '_e of : tiehl adjoining ;i sour'e of in'statIioni would serve
as d trap Top tlo inttrcept the majority of mlLi'.iing -piders. This
strip should he plowed in Is -011 as there se'vms to be (ii] i- '' of a
"'u, ii' 11 movement to (lie main Hield. (For a practical test of this
idea. see under Prevention. Ip. 10.)

NA nTE (IF DAM1.ME.


seed ii2.:- inches hiigh were fo1dml ilnfeted on 1ay I. Iut
.Auie I did thle work of ithe pest leiome notieeableh. The


vv'|. ;W, Cn^, ym bn Wf n<>rii);il v'otton i'.I t lf:
1W r^ Oriarim in


b, ,1- m rin" I
T rid han -wn 1


presenct'e of the pest on cotton is lirit rev'ealed v tlhe alqpeiarnei otil
thlie upper -l' 1-face of the] leaf of ai blood-red -spot. \As leave- becoe
badlv infested they redden over-the entire a surfaeM. Ieo,. distorted.
and drop. The homer leaves are first alttaked, bht infestato sp- 1lAread-
upw ird intil ofteli otly thle blare stalk and onte or tIwo teriniiill
leaves rl't' aiinl. Sul'i plants almost invariall v die 1. AVo in it
the leaf :"I thlie disiodor:ition whiSh follow X thlie ofeeiiv of (hie ,ils
are easily vihder -tood la- referrin- to figure :l which rlepesnt, Wi/)
the apeai'ranee of healthy eottoi leaf-tislues :aind (/) tlie (nilition
of the ii--lRe :nite r teedi .L'. I) ite )It'tes. As previii ly ilntima:te t le. i,
worst s])ots of infe-tation are W-1uallY to be fould in Wlose proximitY


(Cotton
not until






THE RED SPIDER ON COTTON.


to yards with borders of violets. Large fields are probably never
completely d`-ii.ig-,l. but small fields frequently becoine wholly
affected. The crop of one 5-acre field near Leesville, S. C., was
)probably reduced at least 50 per cent by this pest. Local spots with
from 25.) to 100 per cent damage are frequently to be seen.

NATI RAL CONTROLLING; AGENCIES.

lled spider occurrence was most severe throughout July and was
still at its height on August 1. Within three weeks of the latter
d(late, however, the pest had become so greatly diminished that it was
hardly noticeable and was doing practically no damage. This
phenomenon indeed happened suddenly, and the agencies which
worked to produce it are unquestionably of great economic value.
The toughening of the leaves at that time may have caused many
mnites to desert cotton for other plants, but another factor of much
more importance was the appearance in abundance of several species
of insect enemies.
CLIMATIC INFLUENCES.

As before mentioned, climatic conditions exert a marked influence
upon the welfare of the pest. During times of little rainfall and
high temperature reproduction goes on by leaps and bounds; on
the other hand, long, heavy rains work havoc to the red spider
population. In spite of the fact that the red spiders inhabit the
underside of the leaves, many are washed off by rains and many more
are destroyed by the upward bombardment of sand particles, which
may always be seen coating the lower leaves after storms. From
observations made both early in the season and at the ,beginniing of
winter it is doubtless true that the young stages are killed by freez-
ing weather. This naturally prevents any cionsi(lerable winter in-
crease, and in addition many adults probably perish.

INSECT ENETMIES.

Hot weather, although fa',,iiiLg red-sp)ider development, also en-
courages the increase of insect enemies, of which several have been
observed(. Were it not for these Iii -iipi 1ii,0- friends of tlie farmer
thle depredation to his crops by the red spider would unquestionably
be far more severe. The following are a few of the more important
beneficial species observed this season at Batesburg, S. C.
Ji'Jtph/cps ;vh4dLoo.s Say (fiu,. 4), a small anthrocorid lni^y, was
s(eein from (lithe begiing of August, and both in the nymphal and
ad(lult stages was probably thle most effective eienmy of the slider.
Coinl iig iponm a red spider like a flash. the a(ldult thrusts its sharp
l)roboscis through the pest's back and proceeds (quietly to siphon out






TIE IlEU S'PIDERI ON COTTON.


the bodv contents. The firlt viclinI o) rved was- "(drained" iII
about five minutes, but ea(ch iicceedinl nlg':1t was of shorter (t*li011
as tile appet ite became .-.
-, tilei,., TI. T e a ci'a t I...

of the iyvilph (f i. 5
ar1e i, i t i,. but the ill-
dividuals obse-rved were
,-cen on ly to de-troy 71 V.(==
,.*..*, of the spider. In ll "
this ojp'ritiou t he pro-
t)scis was not inserted
far into tile OVIln. and'
two ilinites Iufliced for
,I,':,i, ii",, all "-e'
A !.Pecies of Chry-
soa 1Or lace-winiged fly
Wa;IS !el abllnda tly v
thl'0 ii l iitlllt m ost of thile Ft. 4.--Tril)phll p inxrdlioi ..... al i imirtnt en imy of ti,
s illIler, thlie larlva of rod p11idr Much nI -iinal. t
which is doubtless very active inll reducing tlle pest.
Two species of thrips. Etf/iJlt /fuus, II inds and E. o(,cdentaHi
Prgaindl.. have been determined this senso()nl from il co(tton. They aire
('commonlv found thr, iiill1,t,
< the seansot, about red spider
colonliev-, and may be very in-
Sstrllmentl i l in spider destrnc-
tion. ,,olo:-It/p)s s(vimiaca/ota
1) .P I de 1(h Ias ITeenI recorded as
lan eneiny of tile red spider by
I ) I'.i de :ii,,d by 1)DIIffv.
i dv-hbeetle liarvva an adults
^*- \ ofsvrlsiei- were COM-
11Iol, v seen on infested leaves.
W0,10 11,11 v w r- usuall either
,, 'Ir i '(l bia l)- f ftiti II b1 t. or
/lltip odai m i <'o'i ( o.G ( 16ir.,
"m lint :I small lflaek S]ec-ies,
Jr4! !`c l.tiots) S cf/ho{r' tn p ii
l-',;. 5>.*** *riplih IIM, inxiilti i : Nymi>. LCC.,(ff'L e N\a1 () (Orcatly enlarged. (O)riinag 'he 1 ll' -re Ig etles wI ere )ro, )-
Ily 1 ltore intent uon ootton aphids, but theti llt-melnlionil tlw e.i,
althou --h late in ;ippe(ariirg and not vrv mlit]n,)r,,-. seems to hei, more
restricted to the cotton milte than are other species.






THE RED SPIDER ON COTTON,


REMEDIAL MEASURES.
PREVENTION.
(Control on violets.-First along preventive measures against the
red spider is that of its control on violets. In most cases, as before
stated, infested cotton fields upon examination are found to have
near them infested violet borders. In early June of the past season,
in one particular instance, violets adlj(iniilg fields of past severe
annual infestation were thoroughly sprayed. It is of great interest
to record that subsequent infestation in these fields was practically
negligible. These and similar observations certainly emphasize the
important part that the violet plays in the seasonal history of the red
spider.
Clean culture.-Borders of weeds and underbrush about fields
should be burned or grubbed out. Margining a field close to a spot
which was heavily infested the previous season there was found to
occur a thick border of wild geranium, dock, and other weeds which
at that time contained many red spiders. Tlives weeds were de-
stroyed by burning over them a heavy application of straw. No
spiders appeared in the adjoining cotton throughout the season.
Broadcasted cotton.-An opportunity was accidentally provided of
teItil-r the value of thickly brn'ad1:-tAilnrg cotton at the boundary of
a field as a trap crop for red spiders. This cotton, intended as a
cover crop, intervened between the cotton field proper and a l:irge.
heavily infested border of violets-a former abundant source of
migration. The broadcasted cotton became infested and was later
plowed in. The adjoining field remained free from mites. The suc-
cess of this experiment would strongly indicate that the cotton trap
crop is one of the most practical cultural expedients to be used in
controlling this pest.
p!.,, ',ii,.-Experimients at Ba tili ri, S. C.. have shown that the
red spider commonly travels between plants upon the ground. This
shows the futility of spacing as a remedial measure.
Time of planting.-The advantages of early or of late planting
are not sufficiently clear to justify serious consideration. It would
seemni reasonable, however, to suppose that early planting._ would en-
able the plants to attain greater size and vigir by the time of the
appearance of the spiders and that this would perhaps assist the
plants in witli-tu'iiidg the w,:ik.iiiini, effects of the pest.
Rotato-n.-In an effort to test the rotational value of other crops,
cowpeas. corn. beets, and peanuts were planted in or near infested
area,. In addition, grains, beans, peas. onions, tomatoes, squash,
watermelon, okra, turnip, lettuce, and other vcLe,.t hh.s in infested
locations have been observed frequently. Exceptini.- the grin o and
peanuts, the red spider has been seen commonly upon all of these.






THIE RED) SPID)EIt ON COTT'O)N.


()On the othlier hand, should an immune crop be found and employed,.
it is extremlely probable that tihe pest would reinvade the fields upOll
the return to cotton culture with as L.._.it ease and quickness as it
has done duirigi any previous season, prov idi0 i tihe sulIrces of inife-,la-
tion were yet at hand. iRotati,.t, then. does not promise to contribute
toward tlie solution of the problem.
Eff!'et of fert 'ii'.:-s.\ ratlheir labo)arate series of tests ith fer-
tilizers was instituted in an attemlipt to 0terminim, wihetiei (li tie \ariou-
applications assisted cotton to itlhst-:lnd thle in jti-ious ill'cti of
iii tI',-it.1iOn. Since almost no infestaii,i ap4 ipjearedl il thee ic- les lales
it, was impos.i)hle to deduce positive conewlu ,)ion-. I( wa- very xx tioe-
abl,., however, that plants receivixi hewavv applliati(oIns withsalltood ihe
Vrv severe diii,,1,,l conditions whlichli prvadei, in M",mluth Carolina in
1911 conspicuously I'v better tlian did plaInts which wi er( ot so() trealcdl.
It seems reasonable to iipp-se. therefore. tat. plants whiiih have
xe'en fortified lv a li e'ral '.i ititv of' fertilizer will le as-is--t .d, upon
occurrence of Csevere inieslati<,ii. in resisting it, ell'ect.-s.
1I,'| R NI'(.SI)N.

We have just disclussed cultural m\l-urns wvlli il1i mav liel) to pre-
vent infestation. We will niow (consider xwhat may lbe dole to combat
thle pest when it hlas already gained entranm'ice to a field.
Pllli;nr bimftc(d pln if..-.-Thw experiment wxas made in o)ni( fielo d of
pllluir._ up and destro(yil_ tile first few plulants which lshowevd iinfe'sta-
tion. In this particular e-ase thle operation xvwas repcatedi tIlmee times.
Care was taken to find every plant showL l- i the characteristic r(,d
-po(,-. and these were carried front thie field and burnedl. Tihe result
was most, satisfactory, and thle pest was completely eradicated.
If infestation hla-as spread until ;a conMiderahle patch has lheroine
involved it migliht le advisable, in the case of a large ieldl. to )low\
up the affected portion in order to save t (i balan ice of the field 1. Su ich
a drastiic measure, however, should only he resorted to in 'I extrnme
'.'-,. and the planter concerned must be the judge of its desira)iliI v.
I M(t c(.;h c.-In all. :2(I spray combinations were tiol '.'2lxlv te-ted
tinder conditions entirely natural. The field used fo(r thiis P)iM-p'o
waIs about 1 acre in extent, and infestation lihad become loth vexr imen-
eral and very severe. A strip tlhrni,.i=li tie middle of the field. <-ios-ini
each sprayed plat. wvas left unisprayed to -serve a- a check. Since no
substance was discovered which could safel y Ibe used t) dc,-strv all
vg-, in one application, it was found nece--:ssary to spray tw N ice with
an interval of six or seven days. so as to (dest() (lie hatching larxva'.
Thei killi,.'" ability of all these sprays \\a- ('comlputed. amid tlhe per-
i.lmtige-, r.ii 1 f-romn 100 to 0. Each of tlie followii,' six comnx ina-
tions (see Table II) was found to le ve-ry satisfact(ory. These are
presented to ind(licate the manner of preparation, ,11 .''.ther with the






THIE RED SPIDER ON COTTON.


cost of 100 gallons of each. If one of these were to be used in
preference to all others it should undoubtedly be potassium sulphid.
This insecticide commends itself from every standpoint-cheapness,
simplicity of preparation, continued readiness for use, ability to kill
quickly, and safety of foliage. Altogether it seems to be an ideal
red-spider spray. It was found that 100 gallons, when applied as a
misty spray, about sufficed to treat an acre of average-sized cotton.

'I'ABL II.-Somi(' satisfactory swtrtils for the red spider.

Spray Formula and itemPs. Total Per cent
No. cost. killed.

I Potassium sulphid, 3 pounds, at 25 cents ..... .. ...................... $0.75 100
Water, 100 gallons.
II Flowers of sulphur, 15 pounds, at 4 cents .................... $0.
Fresh lime, 20 pounds, at 4 cents....... boiled ...................... -SO
Water, 100 gallons.. .................. J 1.40 100
III Miscible oil, 5 gallons, at $1 ........... ...................................... 5.00 100
Water to make 100 gallons (1 to 20).
IV Potassiun: p' r m ", ,ra t,. 1i pounds, at 50 cents.......................... 8.25 100
W ater to l, i.e I-,,' ll,._- k, per cent solution).
V Miscible oil, 21 gallons, at $1. .. ....... ......... .................. $2.50
Black-leaf tobacco extract, 40%., 1 gallon, at $1.25 per pound ......... 2.00
4.50 99
VI Flowers of sulphur, 28 pounds, at 4 cents........................... $1.12
il .. ['. 14 ounces, at 40 cents per pound ............... ..... .35
\\ i. r i.. make 100 gallons. 1.50 98

SU-MIMARY.
The female red spider, tippearing to the naked eye like a dot of
reddish ink from the point of a fine peni, liyv about 50 or 60 round,
colorless ( which hatch in summertime in about four days.
The colorless, newborn spider has six legs, feeds at once, and molts
in two days to the primary nymph.
This first nymphal stage (and all later stages) possesses eight
leg--, and has become larger in size and darker in color. In two more
days (in summer) it. in turn, molts to the secondary nymnph.
The second ny)mphal stage lasts two days, at the end of which
time, after 1114lti,.2 the fully formed adult .ii,",-. M:ltiig occurs
at once and c4.r laying commences immediately afterwards.
Thus, one generation requires in summer weather in South Caro-
linta about 10 or 11 days. There are probably about 15 generations
in an average y ear in that locality.
The red-spider colonies live on the underside of the cotton leaves,
and their constant feeding causes blood-red spots to appear on the
tops of the leaves. The effect upon the cotton plant is that the
leaves drop), one by one, until usually the plant dies.
The )est increases and spreads most rapidly in hot, dry weather
Until (toward the end of July) several acres of a field may become
badly damagLed.




TIlE 1i) SPIDER ON COTTON.


Sev eral insects have been di-,covered Iwh ich destroy mIany mi tes.
and are thus of -reat benefit to thlie planter.
At the end of lthe colt. iiTowi1tI,' 11easol ioo>t f lie reId spiders
inii'lgri afoot in search of greener planlis lie naijority of those
whieh survive >ectli,,.. ultimately upon |lie cultivat.1 d violet.

101 tiCO MENOI lONs.

(1) (',a cultr .-Bllurni or -rub out all weeds and underbrush
about cotton fields and practice fall plowing s faIr 1'as possible.
(2) (Cont o/f ,n '<',ist.- Sprav or destlro\ suspected violet, plants
in order to remove the sources of red spider infesiat ion.
(3) lroHldfSffId 1iw/p 1,or/'fi ,,.-Tliickl sow\ cotton i,' I,,mar-
-ill- of fields at points where infe-station lias appeared on former
occasions., and plow these ill about June 1. so as to intercept and
destroy the inva lliiL mites.
(4}) IPO '1*' .f., t '. ,fst/ul stdIks.-Maittaii a careful watch of
fields so that thlie lirs- attacked plants may be detected. removed, and
burned, thus ,pi \.iil iii further spread.
(t5) S/,.' ,,' ".-Ap)ply one of the insecticides recoImmiended above
to the infested portion of a field before occurrence lbeoolties too gen-
eral to prohibit its use. Two applications should be made; the first
to destroy the livin: mites, and thlie second, a week later, to kill the
recently hatched individuals which were *,'- at thlie time of tlie first
spraying,, .
Finally, the opinion will be ventured that the red spider is not a
,lifhi.ilt pest to combat. Unlike many other pests, it has no wings
and spreads ntainly by means of its tiny legs. Mii.i,,i does not
extend far from its winter quartersr. This maltkes every mla's prob-
lent virtually his own. In other words, if his infestation lias always
come from a certain spot upon his premises, pirolpecr attention to this
spot will yield him results inll spite of tlie lii ,dli,'ence of his neighbors.
Approved :
JAMNIES WI.sON,

s,',fiu/ ).w .C k ./1'c ,i f.',, .
WASniix+;'r+o, 1). ('., Fl"n !. iri 1.'f !0]2.




UNIVERSITY OF FLORIDA
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