Insect pests of legume and grass crops in Western Canada.

40 Pages·1991·2.8 MB·English

by  Soroka, Juliana J

^
Agriculture *«
Canada
Publication 1435/E
legume
Insect pests of
and
grass crops in
western Canada
Canada
Digitized by the Internet Archive
2013
in
http://archive.org/details/insectpestsofleg1435soro
legume
Insect pests of
and grass crops in
western Canada
Juliana J. Soroka
Research Station
Saskatoon, Saskatchewan
Recommendations for pesticide use in this publication are intended as
guidelines only. Any application ofa pesticide must be in accordance with
directionsprintedontheproductlabelofthatpesticideasprescribedunder
thePestControlProductsAct.Alwaysreadthelabel.Apesticideshould
alsoberecommendedbyprovincialauthorities. Becauserecommendations
for use may vary from province to province, consult your provincial
agricultural representative for specific advice.
Cover illustration
An adultlygus bug,Lygus borealis (Kelton)
Agriculture CanadaPublication 1435/E
available from
Communications Branch, Agriculture Canada
Ottawa, Ont. K1A0C7
©Minister ofSupplyand Services Canada 1991
Cat. No. A43-1435/1991E ISBN0-662-19129-3
Printed 1971 Revised 1973 Reprinted 1989 Revised 1991 5M-12:91
ProducedbyResearch Program Service
Egalementdisponible en francais sous le titre
Ravageurs des legumineuses etdesgraminees de I'ouestdu Canada
Contents
Acknowledgments 5
Summary ofmain insect pests 6
Integrated management oflegume and grass pests 9
General insect pests 10
Grasshoppers 10
Cutworms 11
Insect pests of alfalfa 15
Plant bugs 15
Lygus bugs 15
Alfalfa plant bug 17
Pea aphid 18
Other legume aphids 19
Alfalfa weevil 20
Alfalfa seed chalcid 21
Alfalfa curculio 22
Webworms 23
Insect pests of sweetclover 24
Sweetclover weevil 24
Insect pests ofred clover 26
Lesser clover leafweevil 26
Clover thrips 27
Insect pests ofwhite and alsike clovers 28
Clover seed weevil 28
Clover leafweevil 28
Insect pests of grasses 30
Bromegrass seed midge 30
Grass plant bugs 31
Cereal aphids 32
Russian wheat aphid 32
Spittlebugs 33
European skipper 34
Grass thrips 35
Other pests oflegume and grass crops 36
Beneficial insects 36
Precautions on the use ofinsecticides 38
Acknowledgments
C. Harvey Craig wrote an earlier edition ofthis publication. The critical
comments of the many people who reviewed this bulletin are greatly
appreciated. Photo credits include M. Okuda for Plates 5a,b and 66; J.L.
Harris for Plates 2a,b and 5f; K.A. Pivnick for Plate 2c and/; Agriculture
Canada LethbridgeforPlates 5eand 6a; andWashington State University
for Plate 6e toy. R.E. Underwood, Agriculture Canada, Saskatoon, took
many ofthe photographs and compiled the plates.
1
coc bcce E CO
e e Ih «« +J ft
c*o-1 co"<Oc 9, d;theifinso 'o? fCOt S.S C0CJ3O CO
S u
CO 'erseedforeJunede O^j CC 03 3^_-1 o-os c
03 be O.^ 03 bCJo3^l5
O59 fBtf&t «f8COt*<<^v3 Dnootfieldsoenfdinsecticiused O co 3ccurC•oOjj PE-1 cIo.5
R
ft
be 03 03
+00aX^5> XX+O1©5J" fCOiCOl£l^ CfOto .t0M*S5>o-f-&SStic£ccC£occC ^+bcc*copcc<ocjcv T•c0§H2C3•CC0Cc8OO3Oo !cscnS*|+b^O^letCogbo-e«gfgt *xS-IJ~:3
+oo^ +£o^ ^^+£ +> CO f"1 £" O) p o ft >,* 52o5
CJ <H CO o>
<0
a
a
03
ft CC CO 03 co
o
>>0-Q
o ^c1p 7C3O > O CO ,cc
CO 3 ft-O
O rS CO 03 OX5 ft
s
be
TXcgC3ccof£3JCOCot S^c£M*co^^3c££c£ IC7x*+Cc3jO*^cI—Xboc0o5o3>e M"^*£c£0,T|CSO3OOg"i«c5C .CibCCCOSOc.C"bc0pSC3Cc.c_"O0O7i_33l0c3o C—^0I00OJ°33^XI0Oc->5,3c XSc^0ccc3oj3cI-C0aO3 S<bc£ooe0$3 fX_-Xi0cs0!3ca3c!3o3c•-•.-OcccC^*§CcO. f.poff£_att0_0fC3c3t
CC 03-cc
| 53
CO
ic-1 CO
c£3e*hs sCCOO<5>£3»§£fl ^e3g -g^ csos £c5 0ic3n
I*)CXC f53t < co be < sJ3
cO .5 bo
>> I 1
©cGO ao<3C+-O 2 c So-^c3p ^gbc
co ti<->— CaO 9
cp aC.l-T9 cp
oc CO =3
Onlyseriousdryland £Oh5CO |Wo §05 |> &a?|SrS
boP 05 GO.fSl
CD
X)
co
co.5"<33
p §5 <o
bebp3jo?be £ b O<cjnvo +bC«eOexcc>c,"C1c~ol
co
£*£CiO?S EgHwco oo gf8*e &
O
CCpO i0>n3
O
f o
^H
CP CO C<Op"c>u
£ cp
CO £
£^
be
C£O £Oh CO X3 6"fX3 ^c5 XC3P
XX£CaC£o)>OO £1C|£O°c£OotxX^ocC5c^>3O53 P'r~XCgQSC*3O^tciiCHopnO hjC=C>Jo3PCtSXOC23O -£f*Ct&C£COp PxdCcCC3hTOOPO^^CC>JO S1HC*ooC^3O;O-J 9«c"o,CccCp^„OpoC3 O^_XfccCes3rooc.te•E-ecCc2CcgeoPpOu.llSecapv .•—fc-S£oitcdSCcc^pp +^B«CC^OO I'fe—?ijIxt+Xm-H)1T+50OH3R5
^1 cp -'F! 05
^-^ CO
ft
o8 I05ISU'00cS55o.fJ£S-,t'
CO
.2 § .5 cu
S> Sis>wcu CO CO 0Ct5OS'CrtO eCEOxCJU CO CO
-m co cu sis £ s
Ch cu
s S ftv ibaotSen5o Pbfiet"oi-32 5c£CoU <a>u? CU Pbeco
O CO +f
CO CO CO E-1 cc.5 E-1 oc.5 E-1 co
cu cu
T3 TD
ocu _+c2u f+O3
cu cu
o o cu cu
CCO C&O
ft^S
bX)GC^
CO O«hXCU
*3
CO
cu ^ O CO
CO .2 > it
cu S £ £
CU CO I!
h3 . 1 cu CU to li PQ co
cc
ft
be E CO
C£O o *cfot > «o-t= "cSu3 —
-sCGCco6dOOo 0cCcC>3DccC 5-2Coc3oUu" 1bco -CofCaOOt -.ccccC,auxouuO cCoXCCi Sc.fc,t3CcCcOuOu-"*c^>o>o^ rCcCcc3OcUoc-—cc£cgouoc 5£coe3o 5pE3 1cu
S tcou fCOt QSCO 5 o zO cCuU—D E O
CO ft
ft
o8
Integrated management of legume
and grass pests
Integrated pestmanagementis thetimelyuseofvarious controlstrategies
to decrease pest populations to below levels of economic injury while
minimizing harmful effects on the environment. These control strategies
are biological, cultural, and chemical in nature.
Beneficial insects playan importantbiological role in controllingpest
species. Between them, beneficial insects, disease organisms, and
inclement weather can destroy 50-90% ofa pest population. Some ofthe
most common and effective insects found in forage fields are listed under
"Beneficial insects."
Itis important forgrowers to knowwhetherthe insects in theircrops
are harmful or beneficial. Although insect identification may seem
dauntingat first, with practice growers soon learn to recognize the main
pest and beneficial insect species in their fields. The easiest way to
determinewhetherthepopulationsaregrowingordecliningisbysampling
with asweep net 38-cm in diameter. Such anetcanbe eitherpurchased or
madefromahoop ofheavygaugewire 38 cm in diameter, a0.6-m dowel or
broom handle, and a cotton bag about 50 cm deep, with an opening to fit
over the hoop. Even sweepingthe canopywith acap is enough to indicate
some ofthe insects present in a crop.
Take samples when conditions are calm, warm, and dry. Begin
sampling when the crop nears a susceptible growth stage, such as at bud
formation for alfalfa infested with lygus bugs. Plan to continue sampling
weekly throughout the summer or until the susceptible stage ofthe crop
has passed. Ideally, try to collect three or more samples throughout the
field; there should be at least one sample per2-4 ha. The samplingunit is
five sweeps of180° withabouthalfofthenetinthe canopy(see Plate 6b).
,
Aftereach sweep moveforward one ortwo steps untilthefive sweepshave
been taken. Identifyand count the insects orplace them in plasticbags to
be identified later by someone such as the local provincial agricultural
representative. Some publications have stated economic thresholds of
insects in numbers per 90° sweep ofa net. Doubling those numbers will
approximate thresholds per 180° sweep.
Thefollowingculturalpracticeshelptocontrolinsectpestpopulations:
• weed control
• early springand postharvest harrowing
• field burning
• cleanup and burning oftrash and screenings in seed crops.
Avoid seedinghay fields next to seed fields and new stands near old ones.
Insecticides can control many pest insect populations; however,
because theydestroybeneficial species and pollinators, considertheiruse
asacontrolmethodoflastresort. Useinsecticidesonlywhenfieldsampling
indicates that economic damage to the crop by a pest insect is imminent.
Often, environmental conditions leading either to the rapid buildup of
diseases or parasites ofthe pest, or to the rapid growth ofthe crop, may
decrease potentially damaging numbers ofa pest to below the economic
threshold. Chemicals may be the control measure of choice when pest
numbers explode rapidlyand unexpectedly.Alternative strategies, suchas
crop rotation or the use of less susceptible crops, are more appropriate
when a pest insect presents a chronic problem in an area.
General insect pests
Grasshoppers
Description The four major species ofgrasshoppers in western Canada
are the clearwinged (Camnula pellucida (Scudder)), twostriped
(Melanoplus bivittatus (Say)), migratory (M. sanguinipes (Fabricius))
(Plate le), and Packard (M.packardii Scudder) grasshoppers. The species
have different host preferences; clearwinged grasshoppers are more
frequently associated with grasses than with forage legumes. Usually
several grasshopper species can be found in most legume and grass seed
crops, forage fields, and rangelands. The species vary in size, coloration,
andhabitsbutallcausethesametypeofcropdamage.Younggrasshoppers
or nymphs resemble adults, except that they are smaller and do not have
wings.
Lifecycle Mostspecies ofgrasshoppers inwestern Canada overwinteras
eggs laidbelowthe soil surface in protectivepods containing 10-100 eggs.
The eggs start hatching in late spring or early summer. Newly emerged
mm
nymphs are 3-4 long. As theygrowthey molt five times; the stages of
development between molts are called instars, so grasshoppers develop
through five instars. They become adults in July. Mating and egg laying
continue until the end ofthe season. Hot, dry weather increases not only
the rate at which grasshoppers develop but also crop susceptibility to
feeding injury. Twostriped, migratory, and Packard grasshoppers lay eggs
throughout fields and along ditch banks and fence lines, dispersing their
eggs to varying degrees. Clearwinged grasshoppers lay eggs in beds in
sparsely vegetated pastures, fence lines, headlands, and along roadsides.
Grasshoppers deposit eggpods in late summer and fall and have only one
generation peryear. Some rangeland grasshoppers overwinteras nymphs
or adults. When these become active in the spring, false reports may
circulate that the main hatch has begun.
Damage Alfalfaandgrass inhayfields, pastures, andonrangeland canbe
damaged extensivelybygrasshoppersfeedingonleaves,buds, flowers,and
seed pods (Plate lf,g). Severe crop damage may occurwhen the foliage is
short and sparse. Grasshoppers that emerge from egg beds outside the
fields injure the plants from the field margins inward; those that emerge
from eggs laid within the fields feed throughout the crop. Grasshoppers
emergingfromrangelandeggbedsoccasionallymigrateintoadjacentcrops
andcauseconsiderabledamage. Grasshoppersdonotusuallyinvadealush,
10