TWO- STR I P E D GRASSHOPPER 1 .5 i n .
RED- LEGGED GRASSHOPPER
These five species of grasshop·
pers are t h e most damaging to field and forage crops i n the Un ited States. The ear of corn above has only a few scattered kernel s because g rasshoppers ate off s i l ks before pol l i nation.
Bare range land was scoured by fora g i n g grasshopper horde. Grass still grows heavy under screened plot.
Oth�rs a re exposed to the weather o r to pred ators . Poisoned baits (sweetened bran contai n i n g a rsenic, chlordane, or similar poisons) are used effectively to kill ad u lts, a n d large areas i n western states are sprayed with contact in secticides from airplanes.
F I ElD AND FORAGE CROPS 99
APHIDS d a m a g e plants by sucking the sap from the ste m s, leaves, or roots. They stunt the p l a n t 's g rowth, or i n heavy i nfestations cause it to d i e . Aphids h ave complex life cycles ( p . 66).
GREENBUGS a r e aphid pests of grains. In warm climates they are active throughout the year.
I n cool c l i mates males and fe
m a les are produced in late sum·
m er. They mate, a n d the females deposit eggs i n the folds of leaves. Greenbugs are parasit
ized by a s m a l l wasp that Jays its eggs in the aphid's body.
The wasp's larvae feed on the aphid's internal organs. I n o cool spring, the a p h i d s build up a Iorge population before the wasps becom e active. Plow un
der vol unteer crops. Plant resis
tant varieties. Use contact insec
ticides to check infestations of Green bugs.
C O R N ROOT APHIDS i n fest the roots of corn . The corn g rows wel l until about a foot tal l a n d then becomes stunted a n d yel lowed.
The aphids winter i n the egg stage, stored in the nests of the Cornfield A n t. As soon as they hatch in spring, the youn g are pastured fi rst on the roots of weeds or grasses, then on corn p l a n ts . T h e a p h i d s p ro d u ce winged generations that fly to other plants, where they are cap
lured by ants an d put to work.
The ants eat the honeydew ex
pel led by the aphids. Ant nests should be destroyed by plowi ng or by treati n g the soil with a contact insecticide.
SPITTLEBUGS d a m a g e p l a nts as nym p h s, sucking the j uices from ste m s or leaves. The nym phs surround them
selves with a mass of froth, or spittle, as they feed . The squat, broad a d u lts are sometimes called frogh o p pers . The Meadow Spittlebug, a pest of alfalfa a n d other legumes and also of m a ny ornamentals, p roduces only one generation i n a season. The nym p h s hatch from eggs laid in stubble. Spray plants with contact i n sec
ticides before fa l l h a rvest to kill egg-laying a d u lts or i n early spri n g to ki l l you n g nym p h s .
PLANT BUGS, a lso c a l l e d leaf b u g s , are a fa m i ly of true bugs conta i n i n g m a ny species that d a m a g e a n d d eform pla nts b y s u c k i n g o u t juices. S o m e feed o n o n ly one group of pla nts, such as g rasses; others, such as the Tarnished Plant Bug ( p . 7 1 ), are g e n eral feed ers .
LEGUME BUGS ore pests of le
g u m e s and other plants. Nymphs ore most damaging, but adults a l so feed o n plants. Both i n tro
d u ce a toxi n causing deformities.
Adults overwi nter, and females loy their eggs i n plant tissues in spring, with four or five genera
tions produced in a season. Use a contact i n secticide i n spring when nymphs begin to feed. Do not spray plants i n fl ower, t h u s k i l l i n g b e e s that pol l i nate crop.
F I ELD AND FORAGE CROPS 1 0 1
C H INCH BUGS a re major pests of corn but also d a m age o t h e r grains a n d g rasses . Adu lts overwinter in d e b r i s , a n d i n the s p r i n g the fe ma les l a y eggs at the base of pla nts, on which the nymphs feed by sucking out juices. Young plants are com monly killed; older pla nts s u rvive but may not produce. As food plants are exha usted in one place, the nymphs m i g rate i n d roves to fi n d new food plants. Chinch Bugs can be killed with contact i n secticides sprayed or dusted o n i nfested pla nts, or the insecticides may be used as a c h e m ical barrier to preve nt entry of crawling nym phs. Some crop varieties a re resistant to Chinch Bugs. C rop rotation prevents population buildup.
CEREAL L E A F BEETLES, from Europe, were fi rst fou n d i n the U . S . i n 1 962 a n d a r e now a potential major pest of grain c rops i n the Midwest. Adults survive cold wi nters by h i b ernati n g u n d e r debris. Th e larvae hatch from eggs laid i n early spring and feed on the leaves of you n g pla nts. They pu pate in J u ne, and a d ults appear i n J u ly, fee d i n g until winter.
ROOTWORMS a re gru bs, or beetle la rvae, that in jure pla nts by fee d i n g on or i n their roots . Often th e ad ults d a mage e n tirely d iffere nt plants.
N O R T H E R N C O R N R O O T WORMS, w h i c h feed o n l y o n corn, o r e pests f r o m New Yor k westward t o the Rocky Mou n ta ins, especial l y i n the northern Mississippi Valley. I nfested plants grow slowly a n d are wea kened so that they topple i n wind or heavy ra i n . The larvae also tra ns
m it wi lt, a bacterial d i sease. I n m id s u m m e r t h e larvae l eave t h e roots a n d p upate i n the s o i l . The adu lts, which f e e d on a variety of plants, d i e after lay
i n g eggs aro u n d roots of corn
sta l k s i n the fall. Eggs hatch the fol lowi ng spri ng. Rotating crops i s effective. C h e m i cal controls include soi l treat m e n t with con
tact i nsecticide before plowi ng, or sprays or d usts on a d u l ts.
S O U T H E R N C O R N R O O T WORM d a m a g e i s s i m ilar to i n j u ry by the Northern Corn Rootworm, but worm s a l so bore i nto stalks at soil l i ne. Ad u l ts are equally d a m a g i n g .
GRAPE COLASPIS grubs (Clover Rootworms) feed o n the ste m s a n d foliage of g rapes a n d other plants. Ad ult beetles e m erge in m id s u m m e r and lay their eggs arou n d roots of cover crops such as clover. The grubs feed o n the roots u n t i l cold weather, then h i bernate until spring, when they conti n u e feed i n g . I f a field i s p l owed i n s p r i n g a n d t h e n planted i n corn, the half-grown grubs feed o n roots. Fall p low
ing exposes grubs to freez i n g .
0.7 i n .
WHEAT WIREWORM
FLEA BEETLES, especially abun
dant i n cool, wet seasons, attac k many fl e l d a n d g a rden crops. In a d d ition to eating leaves a n d gen
erally wea ken i ng a p l a n t, they tran s m it the bacteria for Stewart's disease, a wilt. Heavy infestations sometimes cause a com plete loss of crops. Keep flelds free of weeds u n d er which the beetles hi bernate in winter. For oth er controls see p. 6 2 .
WHITE GRUBS o f a n u m ber of species eat the roots of l awn grasses, corn, wheat, and forage crops. I nfested corn plants may die after growi ng to a height of a bout two feet. In a d d ition to the g rubs of May and J u n e beetles, larvae of the Oriental Beetle are serious pests. Control by soil fumi
g ation a n d by other m ethods de
scribed on p . 65.
WIREWORMS of severa l species injure corn, wheat, lawn g rasses, and root crops. The Plains False Wireworm, particularly d a maging to wheat, is a darkling beetle larva rather than a click beetle as a re true wireworms. Controls a re g iven o n p . 6 3 .
WEEVILS, the largest fa m i ly of beetles, a re easily rec
tact insecti cide. Consult agricul
tural agent for best time to
grub become relatively inactive until fal l , then m ate a n d the females adult stage. Larvae complete their development by late spring,
LESSER CLOVER LEAF WEE
VILS are m ost damaging to red clover but m ay a l so attack a l falfa and sweetclovers. The d a m a g e , greatest in dry seasons, i s done largely by the g r u b s , w h i c h f e e d on the ste ms, leaves, and buds. A n i n fested plant wilts and dies. No goad control meth
ods hove been d iscovered.
BOLL WEEV I LS are one of the more than 1 00 i n sect pests of cotto n . As m a ny as seven g e n erations of Bol l Weevi ls o r e pro
d u ced in a seaso n , damaging the plont at a l l stages of its g rowth. Each generation com pletes i t s development i n about three wee ks i n good weather.
Adu lts that e m erge from h i ber
nation i n debris near cotton fields beg i n feed i n g on the buds of you n g cotton pla nts. The fe
males l oy one egg i n a deep p u n cture i n each developing fl ower bud, o r squore. I f not enough sq uares are ava i lable, more than o n e egg may be laid i n a squore. T h e larvae feed in the square, causing it to turn yellow and drop. In heovy i nfes
tations t h e bloom of a n entire crop is destroyed. When bolls do form , the weevi l s feed in
side. You n g b o l l s drop from the pio n!; older ones are stai ned or decoy. Controls consist of de
stroying cotton sta l k s or debris i n which adults h i .bernole, plant
i n g eorly maturing varieties of cotto n , and using contact i n sec
ticides to kill t h e feed i n g larvae and adults. Ti m i n g i s critical i n t h e success o f these contro l s a n d varies with local conditions. Con
sult reg ional agricu ltural agent.
1 08
C ATERPILLARS of moths ·and butterfl ies a re common pests of fi el d a n d forage crops. Methods of com bating them are much the same as those used i n controlling caterpillars that d a m age vegetable crops (p. 80). Al l have strong chewing mouth parts .
COnON LEAFWORMS crawl by looping their body, l i ke m easuring worms. U n l i ke almost a l l other moths, the adults may be pests, using their spiny mouthparts to make slits in g rapes, peaches, or other fru it to gel the ·sweet ju ices. The lar
vae hatch from eggs laid on the u nd e r s i d e of colto n l e aves.
Later they pupate in folded l eaves. A l i fe cycle i s com p l eted i n about a month, with as many as three or four generations a season . No stage survives win
ter i n the U.S., the pest i nvad
ing each year from Centra l Ameri ca. Both stomach-poison and contact insecticides a re
ef-LEAFWORM
PINK BOLLWORMS feed on cotton b l o s s o m s , or s q u a res, causing them to wilt a n d drop.
Later they feed in the bolls. P i n k Bollworms winter i n cocoons i n t h e soil, i nside bol l s, or i n t h e seed. Larvae may r e m a i n i n this resting stage for more than two years, which accou n ts for the world-wide spread of this pest.
Each generation req u i res about a month, with a s many as six generations a season. Wor m s i n the seed a r e kil led by h e a l ( 1 45 degrees F . ) or by f u m iga
tion. Early crops give h a rvests before the pests are n u m erous.
Plow under crop resid ues or use contact i n secticides. Consult lo
cal agricultural agent for t i m i n g .
CORN EARWORMS, known as Bol lworms and Tom ato Fruit
worms, are t h e m a jor pests of sweet corn i n the U.S. From 500 to more than 2,000 eggs are l a i d by e a c h female. The larvae feed on the unfol d i n g leaves, same
l i m e s stu n t i n g the plants. Great
est damage occurs when the corn i s in the tassel, or s i l k , stage, as the larvae that hatch on the silks feed there and a l so on the developing kernels. In addition to destroyi ng the kern els, the larvae open aven ues for molds a n d for other insect pests. The wor m s feed a l so on t h e fl owers of tomatoes and eat the green fruit. They feed o n the buds of
tobacco p l a n ts and i n the seed pods. In calion -growing a reas they feed o n the lips of the plants, on t h e blossom , a n d in the bolls. U p to seven g e nera
tions ore produced each year in warm c l i mates; th ree or four in the Corn Bell, only o n e i n nort h e r n states. C o r n Earworms over
winter in the soil in a pupa case, hence plowing in late fall de
stroys many o r exposes t h e m to freezing te m peratures. Feed i n g worms can be k i l led with confa cf
i n secficide d usts. Some hybrid corn varieties are resistant to Corn Earworms. Early maturing varieties can b e harvested before th e pest population b u i l d s u p .
F I ELD AND FORAGE CROPS 1 09
ARMYWORM
A R MYWORMS h i b e r n a t e a s hal f-g rawn caterpi llars that be
gin feed i n g in spring and are f u l l g rawn by early s u m m er.
They burrow into the soi l, pu
pate, and e m erge as n i g h t-flyi ng moths tho! are identified by the white d ot on each front wing.
Female moths, offer a period of feed ing on nectar or decay
ing fruit, lay their eggs on grass or other plants. larvae hatch in about a week and beg i n feeding ravenously on the pla nts around them. I f conditions have been favora ble, many thousands of caterpi l lars are produced. When the plants are consu m ed i n one area, the h u ng ry hordes move in "arm ies" to find a new sup�
full-grown larva 1 .5 in.
ply. Caterpi l lars of this second, or s u m m er, generation become full grown i n late s u m m er. They pupate, and the a d u lts e merge i n the fall, each female laying as many as 2,000 eggs, i n c l usters of 25 to 1 00. These hatch i n to the larvae that overw i n ter.
The s u m m e r generation does the greatest damage, and i n t h e years of severe outbreaks m a n y crops a r e attacked and com pletely destroyed. Th e caterp i l l a r s hide d u r i n g t h e day a n d f e e d at night; h ence a c rop m ay be destroyed com pletely before the caterp i l lars are n o t i c e d . Armyworms a r e parasitized b y a fly that lays its eggs on t h e cat
erpillar's bac k; the fly's larvae F A LL ARMYWORM
egg cl uster o n corn leaf
1 1 0 F I ELD AND FORAGE CROPS
then feed on caterpi l l a r a n d k i l l i t . A tiny w a s p t h a t lays i t s e g g s i n s i d e t h e Armywo r m ' s e g g s is an e v e n m o re effective n atural control of this pest.
Adva n c i n g "armies" of these caterp i l l a rs c a n be tra pped in deep f urrows conta i n i n g kero
sene or a contact i nsecti cide.
Poison-bran baits such as those used for grasshop pers (p. 98) can be spread i n the path of the m igrating caterpil lars, or fields can be sprayed with con
tact i n s e c t i c i d e s . When t h e worm s d isappear, i n d icating that they have b urrowed i nto the g ro u n d to p u p ate, s h a llow plow
ing will expose the pupae to predators and to weather.
southern species closely related to the Armyworm s . Someti m es the moths fly into northern slates, appearing there i n the fal l . T h ey do not survive northern wi nters, however. In the South a s m a ny as six generations are prod uced i n one season. The caterp i l lars feed fi rst on grass, then move to corn or other field a n d vegeta ble crops. I n the South the caterpil
lars go by t h e n a m e of Grass Worms. Fall Armyworms do not h ide during the day as do Army
worm s . I n addition to the con
trols effective against the Army
worm, it i s i m porta nt to keep fields free o f g rass o n w h i c h the larvae f e e d fi rst.
F I ELD AND FORAGE CROPS 1 1 1
EUROPEAN CORN BORERS are
Originally the European Corn Borer produced only one genera
tion each season, but i n the East
Europea n Corn Borers overwinter as caterpi llars in the stem s of
Where there are two generation s p e r year, the fi rst is com p l eted
corn should be planted. Some caterpil lars. Contact i nsecticides can be applied Ia infested plants
boscis fits. Swift-flying adults are called sphinx or hawkmoths.
CAROLINA SPHINX 4-5 in.
LESSER CORNSTALK BORER
WEB!WORMS are general feed
ers, though some species are es
pecially damaging to lawns or to particular field crops. Blue
grass Webworms and related species are lawn pests. They feed only at n i g h t, cutti ng off blades of grass and d ragg i n g them i nto their s i l k- l ined tun
nels formed along the surface of the ground. The adult moths, which have a pro m i nent snout, are commonly seen flying over g rassy areas at dusk. The Corn Root Webworm (illustrated) at
tacks corn, tobacco, and other crops as wel l as g rasses i n which they h i bernate. Plowing is a n effective control f o r pests o f field crops. Lawns can be treated with a contact i nsecticide.
ALFALFA CATERPI LLARS feed on alfalfa and other legumes.
Winter is passed i n the pupa stage, from which butterfl ies e m erge i n early spring. Females lay eggs on the leaves of plants, on which the larvae feed. There may be seven generations a year. Plants can be sprayed with a contact i nsecticide if the crop is not used for hay.
C L O V E R HEAD CATERPIUARS feed in the clover h ead, pre
venting flowers from ope n i n g , or on g reen developing seeds. First
g e n er a t i o n m o t h s a p p e a r i n early s u m m e r a n d lay eggs on clover plants, where the larvae feed and pu pate. Th ree gen era
tions m ay be produced each season . Early cutting of crop de
stroys many larvae. The larvae are a l so parasitized by a wasp.
CLOVER HEAD CATERPILLAR 0.3 in.
FLY MAGGOTS of only a few species are serious pests attacked. Wheat Stem Maggots overwi nter as l a rvae i n side the and destruction of straw i n which the l a rvae are feed i n g are ef
fective controls.
HESSIAN FLIES are the most wheat is ready for harvest. Adult fl ies e m erge i n late s u m m e r and larvae to complete development before cold weather. A local agricultural agent can specify the proper t i m e for planting. Vol u n
SAWFLIES AND CHALCIDS are among the few i n sect pests of pla nts that belong to the large order contain
ing bees, wasps, a n d a nts.
WHEAT S T E M SAWFLIES are destructive to wheat and other s m a l l gra i n s. The larvae feed i n s i d e the ste m s , working from the top of the plant, where the eggs are laid, toward t h e bot
tom. Near the g round level the larvae eat out the i n side of the stem com p letely, caus i n g it to brea k off. The l a rvae plug the open base with drop p i n g s a n d then pass the w i n t e r i n this cham ber. Pupae are formed i n the spring , a n d a d u l t sawflies emerge i n early s u m m er. The best control i s p lowi ng under stubble. Planting corn, legumes, or other crops not attac ked by the Wheat Stem Sawfly prevents buildup of pests. Resista nt va
rieties of wheat are avai lable.
WHEAT JOINTWORM damage is s i m i lar to the i n j u ry done by the Hessian Fly, caus i n g the wheat plants to brea k over. The brea k occurs at a g a l l - l i k e swe l l ing on the inside of which are the feed i n g m aggots. Adult fe
males have a stiff ovi positor, with which they dri l l a hole i nto the stem of a wheat plant j ust above a joint. I n s ide the stem they lay from one to two dozen eggs. The feedi n g of the larvae on the tissues causes the stem to swell and twi st. The f u l l grown larvae remain in the stem , wintering either as larvae or as pupae. Adults emerge i n spri ng.
Wheat stubble should be plowed under or burned.
WHEAT STRAW-WORMS have twa generations a year. Yau n g plants a r e attacked in t h e spring a n d stunted by l a rvae that eat into the stem a n d deve loping heads. larvae of the first gen
eration, f u l l g rown by May, form pu pae i n the plant stem a n d e m erge as w i n g e d a d ults b y early J u n e . The females deposit their eggs i n wheat stems, usual
ly only one egg per ste m , a n d the larvae f e e d inside t h ro u g h the s u m m er. They p u pate in t h e fall a n d e m erge f r o m the straw or stu bble as wingless a d u l ts in early spring. T h ey look m u c h l i ke ants. The females lay eggs on you ng wheat, t h u s renewing the cycle. Crop rotation is effective.
Stu bble and volu nteer wheat should be plowed un der.
CLOVER S E E D CHALCIDS de
stroy the seeds of alfalfa and c lovers. The larvae winter inside the seeds on t h e g ro u n d , form
ing pupae i n early spring and e m e r g i n g a s a d u l t s in l a t e spring. The t i n y a d u lts l a y t h e i r egg s i n the formed but sti l l soft seeds, which then become food for the larvae. Adu lts are pro
d u ced from t h i s gen eration by m i d su m m er, a n d another gen
eration i s started. In warm cli
mates there are as many as th ree generations. There is no good control for t h i s pest.
THIEF ANTS are not only house
hold pests (p. 24) but may also be field pests. They prefer pro
tein foods, but w i l l eat corn a n d other seeds. Best control is c u l tivation of field to brea k u p ant nests.
P E S T S O F F R U I T S A N D F R U I T T R E E S
Entire fruit c rops are sometimes lost because of i nsect pests. Some species attac k through the roots, trunk, branches, or leaves. Other insects attack only the fruit.
Some do d a m age i n o n ly one stage of their life h istory,
CANKERWORMS eat leaves of