Feeding Preferences of Larval and Adult Microtheca ochroloma (Coleoptera: Cht-ysomelidae)

for Crucifer Foliage 1

Abdullah! O. Ameen and Hichard N. Story2

Department of Entomology Louisiana Agricultural Experiment Station

Louisiana 5t:lle University Agricultural Center l3aton Houge. ]..,(,uisiana 70803 USA

J. ,\j(Tic. Entmnul. H(·U: 363..':168 (Oclo!>"r. 19911 ABSTRACT Feeding pruference.~ of first and third instal's. and the adult yel10wmargined leuf bcetlu, MiI,ru/h"';(1 m;/irolol>ln Stll1. for the foliage of cabhage, Bmssi(;(, olaoccl1 I"ar mfJi/ala L.; collard, 11 Olclx,cca var acc/JIo,'/n L.; mustard, B. jutlcea Cosson: turnip, B. mpa L.: and rndish, lfaphullw; saliulis L., were evaluated with leaf disk choice tesls. Each of the lhreo developmental stages showed statislitally significant (I' < 0.05) feeding preference for some crucifer hosts O\'cr others. In general, turnip and mustard were Ihe more preferred plants. and cahbage, the least preferred. Although first instal'S strongly preferred turnip to all other plants. third instars showed equill preference for turnip and mustard. and adult ueetles con~ullled ahout the SHllle amount of turnip, lllo~l,lr[I. and radish. Beetles' choice of leaf disk Wfl~ not significflnlly innlll!llCed ( l' > 0.05) uy the host plant on which they were conditioned prior to feeding preference evaluation.

KEY WOIU>S Micm/hem ochrolomn. Coleoptera. Chl)'SOllWlid,le,Crucifer:.le. fC(.'(ling preference, leaf disk, cllnsumpt.ion

The yellowmaJ1,rined lenfbeetle, Micro/heca ochroio/llo Still. is a selious foliar pest of cruciferous crops in Louisiana (Oliver & Chapin 1983). This 1x.'Ctle, indigenous to South America, was accidentally introduced into the United Stales around 1945 {Chamberlin & Tippins H)-181. The beetle is presently restricted in disuibution to the Gulf Coast states lind has 1x.'Cn collected on cabl)llge, Bmssica oleracca val' capitola L.; collard, B. olemcea val' at"CpholtJ L.; mustard, IJ. jwu:ea Cosson; tumip, B. mpa L.; radish, Raphallll.~ satiVlI~' L.; lind watercress, Nasturtium offici//rde It Brown (Chamberlin & Tippins l!H8, Haeussler 1951, Woodrufl'1974, Balsbaugh 1978, Oliver & Chapin 1983). These plants belong to the family Cruciferae, whose principal allclochemical is Illustard oil glucosides (Hicks 197'1, Feeny l!J77). Both adult and larval M. ochroloma damage hosts by fceding on the foliage, The adults chew holes in

',\cecpted ror publio"t;on 6 ,\pril 1997. 'To whom reprint requests should be "en!.

363

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the lean:!s and sometimes feed upon lenf margins, whereas the larvae feed frequently in groups and when almndnnt. consume large portions of foliage of infested plants (Chamberlin & Tillpins 1948). Becuuse the foliage of these plants is harvested for sale in local fresh market.s as "grccns.~ their marketability is subject to an aesthetic damage threshold in which there is n ncar zero tolerance for insect feeding holes on the leaves.

The biology of this beetle hilS not been well studied, despite its wide distribution in the southeastern United States and its damaging impact to crucifers. Labol'ntory experiments were conducted 10 evaluate the prcfcnmccs of M. ochr%llla for the foliage of cnubngc. collanl, mustard, t'ndish, and turnip, partly to aid Our undcrstanding of its biology and also to enable an assessment of its potential for field crop damagc.

l\1ateriuls and Methods

Host plants and insects. The cuhi\'ars 'Early Round Dutch' cabbage, 'Georgia' colinI'd, 'lo'iorida Broadlellr mustard, 'Scnrlet Globe' radish. nnd 'Purple Top White Globe' turnip were used. These plants were raised in the greenhouse to ensure that a source of insecticide and disease-free foliage was a\'ailable to feed the beetles. Plants were raised on a Jiffy-mi,.@medium (Jiffy Products of America, Inc., B:ltavi3, Illinois), and fertilized 011 alternate days by using MiJ·acle·Gro® (Stern's i\'lirncle-GJ'O Products, Inc., Port Washington. New York), n 20:20:20 water soluble NPI< fertilizel' mixture. New plantings were made evcry 10 d to l~nsurc that young: foliage (3 tu {) wk) was continuously available.

A laboratory colony of the yellowmarg-ined leaf beetle wns started in the fall of 1992 from hC!etles collected on mustard (cv 'Florida Bl'oadleal") at the St. Gnbriel Rescarch Stlltion. Louisiana Slate University Ab'Ticuhural Experiment Station, lberville Pnrish, Louisial1n, A total of 291 Sl)(!cimens was collected at five weekly intcn'uls between 23 Septcmber and 30 October 1992. In the spring of 1993, a total of 87 beetles was colletted from a second mustard plot at the same location on 13 November 1992, and 18 January and 25 January 1993. These beetles werc maintaincd continuously for> II generations. initially on mustard foliagc obtaincd from the field until plants raised in the greenhouse became available. Beetles were held in filler-paper-lined Petri dishes (100 mm X 15 mm) in growth chambers maintained at 20~C and a photoperiod of 14:10 (L:D) h with 50'); RH.

Fecding prefcr'eoee studies. To hegin the study, about 500 eggs were collected from the lwetle colony (described abovc), when it cllntained abllut 400 Ocelles (with approximutely GOt;} fcmlllc!!). These eggs were randomly di\'ided into five groups lind each group was nllldomly assigned to ench of the five host plants. Feeding preference evaluation was carried out nncr beetles had been conditioned on the assigned host plant for two generations, The experimcilt was set up as a randomizcd complete block design and replicated at fi\'e weekly illternrls. For each developmental Singe, twenty I·d·old lest insects were exposed to five randomly generated arrnngements of host plant leaf disks. Leaf disks (15 cm2) werc excised from "'oung foliage of host plant (2 to 3 wk old) obtained from the grl.-cnhousc and were circularly arranged in filter-paper-lined

1\.\tEEN &. STORY: F~~ding Prd"~r~IK6""M. nc/'m/"I!I" 3()5

Petr'i dishes (140 mm X 50 rnm). The dishes were placed on trays and the trays were arrn.nged on benches in 11 growth room maintained at 20 ~ t

366 ,I. Agric. Entolllol. Vol. 1'1, No. 'I (1997)

Table l. Feeding IlI'eferellces of first- lind third-instar M. ochro!ol/lCl as determined by the number of larvae associated with leaf disk of cabbage, colhwd, mustard, mdish, and turnip after 24 h.

Meana (:! SE) number of insects ussociuted with leaf disk of host plant

Host plant First instal" Third instal'

Cabbage 1.12 ~ 0.26c 1.88 ~ 0.31c

Colbrd 1.52 ~ 0.34c 2.32 :! 0,4,1c

Mustard 5.90 ~ 1.07b 4.80 :!: 0,49b

Radish 2.32 :! 0,42c 3.36 :!: 0.58bc

Turnip 9.16:!: 1.05a 7.04:! 0.85a

;,\Ienn~ within mh"nns followed hy ~""1C letler(51 arC nol ~i~n;f,c"ntl)" different (I' > 0.05. "l"ukc)' '

367 A~tEE:-: So: STOR Y: Feelling I'rderenn:\ of .\/. ",lim/oil/II

Table 2. Feeding prefcl'cDCCS of third inshH'S and adult. M, ochroloma fOl' cabbage, collard, mustard, rfidish, and turnip determined by leaf consumption (in milligrams) aftel' 24 h,

t\'lean" (~ SE) leaf consulll ptiOll

Host plant Third in,;\[ll' Adult

CabbHge

Collard

Mustard

Badish

Turnip

16.16:!: 2.21c

19.8,1 :!: 2.65c

45.55 ~ 2.9.'ia

32.6 J :!: 2.77b

55.51 ~ 3.Gb

24.1G:!: 3.52c

36,19 :!: 5,36bc

50.0 11~ 2.63n

43.89:!: 4.05ab

49.68 :!: 3.21a

/lleans within columns r"lIowed loy "nm" lettcTi'~1 arc not .il(l1ifienntl.v different (I' >0.05. 'filley Ie;;! ISAS 111"tiul1e 19!101l. For each C

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References Cited

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beetle (MicrotJlCca oc/lro!oma). United Stalell Depllrtrnent of I\griculture Cooperative Economic Insect Report I: 12,1.

Hiekll, K. L (197-1). Mustard uil glucosidcs: Feeding stimulants for adl111 eahbage nell beetles. Phyllolrcta cruci{croc (Coleoptera: Chr)',somelidac). Ann. Entomol. Soc. Am. 67: 261-264.

Ihelll,tWam. E. U. 1981. The relationship bell',cen weighl of insect, age, hardiness and nitrogen content of cribbage lellvCil 1I11d fecundity of the cllbbagc whiten}" Meyrodcs bruuirne Wlk. (Homoptera: Ale)·rodidoel. Z. Ang. EnL 91: 349-35