Pests, Diseases and Disorders of Sweet Corn

A FIELD IDENTIFICATION GUIDE Millimetres 0 10 20 30

First published June 2015 © Horticulture Innovation Australia Limited.

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National Library of Australia Cataloguing-in-Publication entry 50 60 70 Author: Jenny Ekman (AHR). Title: Pests, diseases and disorders of sweet corn: a field identification guide ISBN: 978-0-9925251-3-2 (paperback) Subjects: Sweet corn—Diseases and Pests—Australia. Dewey number: 635.672

This project has been funded by Horticulture Innovation Australia using the vegetable industry levy and funds from the Australian Government. 80 90 Guide produced by Applied Horticultural Research Designed by Noel Wendtman Design

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disclaims all warranties (to the extent permitted by law) about the accuracy, completeness, or 100 currency of information in this book. Reliance on any information provided by HIA Ltd is entirely at your own risk. HIA Ltd is not responsible for, and will not be liable for, any loss, damage, claim, expense, cost (including 110 legal costs) or other liability arising in any way (including from HIA Ltd or any other person’s negligence or otherwise) from your use or non-use of information in this book, or from reliance on information contained in the material or that HIA Ltd provides to you by any other means. 120 130 Pests, Diseases and Disorders of Sweet Corn

A FIELD IDENTIFICATION GUIDE

Jenny Ekman Contents Acknowledgements INSECTS African black beetle 3 Lacewing 25 This project was made possible by funding from Horticulture Aphid — corn 4 Ladybird 26 Innovation Australia using the national vegetable levy Aphid — green peach 5 Maize leafhopper 28 and matched funds from the Australian Government. Armyworm 6 Maize thrips 29 Production of the guide would not have been possible without Assassin bug 8 Mite — predatory 30 the generous assistance of fellow researchers, agronomists, Big eyed bug 9 Mite — two-spotted 31 extension officers and interested amateur photographers. Black headed mirid 10 Parasitoid wasps 32 Special thanks are due to; Brown marmorated stink bug 11 Pirate bug 34 Jerry Lovatt and John Duff – QDAF Cluster caterpillar 12 Plague soldier beetle 35 Andy Ryland – IPMC Cricket — black field 13 Planthopper 36 Cricket — mole 14 Red and blue beetle 37 Stuart Learmonth – DAFWA Cutworm 15 Red-shouldered leaf beetle 38 Len Tesoriero – NSW DPI Damsel bug 16 Rutherglen bug 39 Dried fruit beetle 17 Sorghum head caterpillar 40 Earwig — black field 18 Symphyla 41 Photographs Earwig — brown 19 Tachinid flies 42 Pictures other than those taken by the author are attributed to Glossy shield bug 20 White fringed weevil 43 the photographer and/or their organisation. Every effort has been Green vegetable bug 21 Wireworms 44 made to contact photographers and obtain their permission Heliothis 22 Yellow peach moth 46 to reproduce material. The publisher apologises for any errors Hoverfly 24 or omissions in attribution and would be grateful if notified of DISEASES corrections that can be incorporated into future editions. Boil smut 48 Northern/Turcicum leaf blight 54 Brown spot 49 Rust — common 55 Abbreviations Damping off 50 Rust — tropical / Polysora 56 Fusarium cob rot 51 Virus — Johnsongrass mosaic 57 CIMMYT International Maize and Wheat Improvement Centre Head smut 52 Virus — maize stripe 58 CSU Colorado State University Java downy mildew 53 DAFWA Department of Agriculture and Food WA DISORDERS IPNI International Plant Nutrition Institute Blanking 60 Phosphorus deficiency 69 MAF Ministry of Agriculture and Food Boron deficiency 61 Potassium deficiency 70 NSW DPI NSW Department of Primary Industries Calcium deficiency 62 Salinity 71 OMAFRA Ontario Ministry of Agriculture, Food and Rural Affairs Copper deficiency 63 Sulphur deficiency 72 Iron deficiency 64 Uneven germination/growth 73 PaDIL Pest and Disease Image Library Magnesium deficiency 65 Zinc deficiency 74 QDAF Qld Department of Agriculture and Fisheries Manganese deficiency 66 Nutrient deficiency symptoms 75 USDA ARS United States Department of Agriculture Nitrogen deficiency 67 Agricultural Research Service Overmaturity 68 Problem solver 76 WSU Washington State University iv INSECTS

Insects 1 INSECTS 2 INSECTS African black beetle larvae or African blackbeetle larvae ‘curl grub’ andadult beetle(PaDIL) spring. in occasionally and March–April occur by adults flights flier.dispersal Mass Strong digging. for adapted 10–15 around beetle bodied Adult: tinge. agrey has sometimes end rear The 6legs. and head brown light with to up 30 grub Larvae: Heteronychus arator African black beetle DESCRIPTION mm long. Legs are are Legs long. mm Shiny black, stout stout Shiny black, Whitish C-shaped Whitish mm long long mm

dry spring and summer. and spring dry by awarm, followed rainfall WA.of Favoured by winter regions south-western and Qld to south-east Victoria from areas coastal in mainly summer, early and Spring seedlings. ringbarking and plants of bases the by chewing damage major cause can Adults plants. small killing potentially and growth reducing roots, plant on feed Larvae MOST COMMON DAMAGE 3 INSECTS 4 INSECTS Rhopalosiphum maidis Aphid —corn projections) and dark head. (tube-like cornicles rear the of bases at the spots purple dark with green Adult: smaller. though Nymph: to adult Similar Corn and acolony aphids inclose-up, intheemerging tassel DESCRIPTION Light to olive to olive Light districts throughoutdistricts the year. growing most in found be can but to autumn, Spring streaks. brownish-red and yellow vigour. Leaves develop plant reducing sap, Sucks MOST COMMON DAMAGE large range of host plants. of host range large a on months warmer During contaminatecan cob. and feeding through distortion leaf Causes bodies. patterned and eyes red dark with heads have black females Winged 2 around and to green yellow pale are Adult: Nymph: persicae Myzus Aphid —green peach MOST COMMON DAMAGE DESCRIPTION Wingless adults adults Wingless Yellowish to green. mm long. long. mm

form (SBauerUSDA ARS) nymphs onsowthistle andwinged Green peachaphidmature adultsand 5 INSECTS 6 INSECTS (D Ironside QDAF)(D Ironside QDAF) WesselsMature andAfrican armyworms common armyworm (J held flat along body. along flat held 20 around Adult: immediately behind the head. starting stripes to yellow white obvious three and body to brown green headOrange-brown with prolegs. central four with 30–40 caterpillar Caterpillar: material. cottony with topped masses egg shaped lay large, irregularly armyworms African material. plant dry on often crevices, or cracks in eggs lay of clumps Egg: Mythimna convecta, Spodoptera exempta, Persectania ewingii Persectania exempta, Spodoptera convecta, Mythimna — Armyworm DESCRIPTION Common armyworms Plain, brownish moth moth Plain, brownish mm long, wings wings long, mm Hairless Hairless mm long long mm common, African, southern when moths are active. active. are moths when summer, to early Spring whorl during the day. leaf central the in to hide tend and nocturnal mainly are Caterpillars damaged. severely others killed, be may leaf. plants Small each of edges outer the along starting damage, chewing ragged characteristic causes Feeding MOST COMMON DAMAGE

Armyworm insidecorn leafwhorl, showing ragged feeding damage(UniDelaware) B Richardson andDHobern) Adult moths ofcommon, armyworms African (DHobern, andsouthern 7 INSECTS 8 INSECTS Pristhesancus plagipennis Assassin bug (J Wessels QDAF) WesselsCommon andnymph assassinbug adult(PChew) (J may consume nymph A single caterpillars. bodied soft particularly insects, other on predators aggressive are nymphs and Adults prey. grasping for legs front distinct patterning. Strong and brown, sometimes with to red orange from varies Colour mouthpart. sucking curved, powerful, eyes and 10–30 Adult: wingless. but adult Nymph: DESCRIPTION BENEFIT mm long with large large with long mm Shield-shaped bug bug Shield-shaped Similar to Any time of year. of Any time 3months. than less in 150–200 caterpillars heliothis MOST COMMON insect Beneficial ✓ Geocoris spp. Geocoris eyedBig bug flat over its back. back. its flat over folded wings clear with Fast eyes. dark moving, 5 Adult: in later instars. appearing buds Wing eyes. prominent with pear-shaped brown, Nymph: Adult bug(Alain CFlickr) big-eyed DESCRIPTION mm long with prominent prominent with long mm Black bug around around bug Black Patterned Any time of year. of Any time caterpillars. small and eggs heliothis mites, aphids, on prey nymphs and Adults MOST COMMON BENEFIT insect Beneficial

✓ 9 INSECTS 10 INSECTS Any time of year. of Any time eggs. heliothis eat nymphs and Adults back. its along flat held wings semitransparent with Fast antennae. moving, long 3 around Adult: antennae. eyes banded and reddish dark with bug shaped Nymph: pear- Pale green, Tytthus chinensis mirid headed Black (American Natural History Museum (top), Museum QDAF) Adult NaturalHistory (American mirids MOST COMMON BENEFIT DESCRIPTION Slender black bug bug black Slender mm long with with long mm insect Beneficial ✓ Halyomorpha halys marmoratedBrown stink bug Brown marmorated stink stink marmorated Brown inside buildings. overwinter Adults damage. severe sweet corn kernels, causes including leaves, and fruit on stages by life all sucking Sap antennae. on bands white 17 approximately bug shaped Adult: markings. rust-red with brown to patterned progressing orange, and Nymph: (TP Kuhar VirginiaKuhar Tech) damage to (TP kernels Brown marmorated stinkbugoncorn (BLittleUni Georgia), anadult, and feeding DAMAGE DESCRIPTION mm long. Two long. mm distinctive Brown and white shield shield white and Brown Initially black black Initially active during summer. Most containers. shipping inside detected been has Australia in yet Not pest. major horticultural a now are and rapidly USAthe 1998, in spread in found first were bugs MOST COMMON pest Exotic , but , but

✗ 11 INSECTS 12 INSECTS Caterpillars skeletonise leaves. tent body. over the a in held wings with moth grey and cream Adult: disturbed. if into aball curl to tend Larvae triangles. and spots dark conspicuous and stripes yellow thin with distinctively patterned are They skinned. smooth 30–40 are grow. caterpillars Mature as they separate but group, a in feeds and green grey- Initially Caterpillar: material. brown light fluffy with covered usually Egg: Spodoptera litura Spodoptera caterpillar Cluster Cluster caterpillar and adultmoth DAMAGE DESCRIPTION Laid in a large mass, mass, alarge in Laid Patterned brown, brown, Patterned mm long and and long mm

in Queensland. to autumn Spring MOST COMMON Teleogryllus commodus Cricket field black — chirruping call at dusk. call chirruping make distinctive Males ovipositor. have long Females legs. rear powerful and wings short head, large with cricket black Stout, Adult: with less developed wings. but Nymph: to adult, Similar Black field cricket DESCRIPTION

come out at night to feed. to at feed. night out come day the and during crevices or cracks in hide usually Crickets months. warmer during Active tape. drip on chewing by irrigation damage also Can roots. prop on chewing by damage cause can but problem, amajor usually Not MOST COMMON DAMAGE 13 INSECTS 14 INSECTS Females are capable flyers. capable are Females crickets. to other compared small are legs Hind covers. thickened with reinforced are thorax and head the and digging for adapted are Forelegs appearance. muscular with long 3–4 cricket cylindrical Adult: with less developed wings. Nymph: Family Gryllotalpidae Cricket mole — DESCRIPTION Mole cricket (Wikicommons) cricket Mole Brown, roughly roughly Brown, Similar to adult, but but to adult, Similar cm cm vibrating call at dusk. call vibrating loud, adistinctive produce and burrows resonating special dig males when months, warmer during active Most grasslands. well-watered and areas Urban burrows. of a network using accesses it which ground, below and above both roots, plant Eats MOST COMMON DAMAGE Agrotis spp. Agrotis Cutworm the night. Plants may be may be Plants night. the during usually level, soil at seedlings off cut Larvae back. tent over its a in held wings with moth grey and cream Adult: creamand markings. yellow red, inconspicuous with to grey black dark and to up 40 hairless, are Maturelarvae age. initially, as they darkening Caterpillar: cluster. acompact in laid but eggs to heliothis Similar Egg: corn (QDAF) andadult moth Active Cutworm cutworm; damageto DAMAGE DESCRIPTION Ribbed creamy domes. creamy domes. Ribbed Patterned brown, brown, Patterned Grey-green Grey-green mm long long mm

converted to cropping. newly areas damp in especially spring, during likely is most Damage day. the during on feed dragged underground to MOST COMMON 15 INSECTS 16 INSECTS for grasping prey. grasping for stronger two front with legs, Long mouthpart. long, prominent sucking 8–12bug Adult: wingless. and smaller except Nymph: Nabisi spp. Nabisi bug Damsel Damsel bug DESCRIPTION Slender, light tan Slender, tan light Similar to adults to adults Similar mm long with with long mm Any time of year. of Any time caterpillars. small and eggs moth leafhoppers, aphids, including insects many other on predators aggressive are adults and Nymphs MOST COMMON BENEFIT insect Beneficial ✓ Carpophilus spp. Carpophilus Dried fruit beetle contamination issue. a are and kernels the on chew They disease. or (eg heliothis) insects other by to damage due loosened have which been husks corn inside get Beetles corn. infest can species different Several beetles. to brownish black long), oval-shaped Adult: grub. coloured Larvae: Beetles incorn showingBeetles feeding damage DAMAGE DESCRIPTION Small (2–3 Small Tiny cream- Tiny mm mm

adequately controlled. is not heliothis if summer, especially During MOST COMMON 17 INSECTS 18 INSECTS than other earwig species. earwig other than smaller and Darker females. in straighter and males in curved are which body the of end at the pincers of pair Obvious antennae. beaded to up 15body with slender flattened Adult: developed wings and pincers. less with and colour in lighter Nymph: Nala lividipes field black — Earwig ; Blackfield earwig (DHobern) Adult male blackfieldearwig DESCRIPTION Dark brown to black to black brown Dark Similar to adult but but to adult Similar mm long and and long mm to emerge during spring. conditions. Nymphs tend moist and soils heavy,In black roots. corn of parts upper and plants young and seeds germinating eat also can material. However, they plant decaying on feeds that pest aminor Usually MOST COMMON DAMAGE Labidura truncata Labidura brown — Earwig Any time of year. of Any time asheliothis. such pupae, moth and caterpillars Attacks in females. straighter and males in curved are which tail, the on pincers Large eyes. dark and patches brown to 35 up body segmented and Adult: coloured. lighter and smaller Nymph: (J Adult (J brownWessels earwigs QDAF, A HendersonMinibeast Wildlife) MOST COMMON BENEFIT DESCRIPTION mm long with dark dark with long mm Light brown, flattened flattened brown, Light Similar to adult but but to adult Similar insect Beneficial

✓ 19 INSECTS 20 INSECTS and sucking mouthpart. mouthpart. sucking and piercing Obvious markings. yellow light small and patterning to black brown toup 12 bug Shield-shaped Adult: markings. black and develop bright red, orange instars Later legs. and head black with bodies red bright Nymph: stem. or aleaf on 50 eggs to up of raft aneat in laid spines white short with Egg: Cermatulus nasalis bug shield Glossy Glossy shield bugnymph andadult(C bug (PChew) Harding MAF) DESCRIPTION Cylindrical, black eggs eggs Cylindrical, black mm long with with long mm Early instars have instars Early Spring to summer. caterpillars. as heliothis such insects bodied soft attack adults and Nymphs MOST COMMON BENEFIT insect Beneficial ✓ Nezara viridula Green vegetable bug bug around 15 around bug shield-shaped Green, Adult: groups. in to stay white patterning. Tend and green red, bright red, then darkening with Nymph: mature. asthey golden on leaf undersides, turning creamy laid eggs shaped, Egg: Green vegetable bugeggs, andadult nymph (A Ryland) DESCRIPTION Neat rafts of barrel- of rafts Neat Initially orange- Initially mm long. mm

spring and summer. and spring during common most pest, occasional An diseased. become can sites developing kernels. Feeding from directly and shoots young from sap Sucks MOST COMMON DAMAGE 21 INSECTS 22 INSECTS Caterpillars thetasselsandcob (A attacking Ryland) Caterpillar: hatching. before to brown Darken groups. small in or 1 Egg: Helicoverpa armigera Heliothis to 30–40 Up reddish. or greenish to brown from ranges Colour stripes. distinctive develop and darken they 15 around reach they When heads. dark with brown light long, DESCRIPTION mm diameter laid singly singly laid diameter mm Ribbed white Ribbed domes mm long. mm Initially 1.5 Initially mm long long mm mm mm damage to silks, large ragged ragged large to silks, damage in results feeding Larvae towards margin the section a dark with pale are wings body. Hind the across flat brownpatterned wings held Adult: stimulates emergence. Rain surface. soil the under just found usually and Pupae: DAMAGE Stout moth with lightly lightly with Stout moth Golden brown brown Golden . moths often hide in the leaf whorl during theday during hidein the leafwhorl moths often by thebiopesticide Heliothiscaterpillar killed left: Vivus (avirus);right: Heliothis frass intheleafwhorl Heliothis egglaidsinglyonacorn silk(QDAF) feeding andtypical damageand in to autumn late spring Warm weather, asfrom such corn. sweet of pest serious most is the Heliothis removed. are caterpillars issue, even if acontamination Frass be can and destruction of the cobs. husks in holes leaves, in holes MOST COMMON

can assist control. assist can (marketed as ViVUS) viruses polyhedrosis Nuclear many insecticides. to is resistant Heliothis late summer.during peak usually Populations states. southern more in summer and Queensland 23 INSECTS 24 INSECTS numbers of aphids. of numbers eat large Larvae pollen. and nectar on hovers near flowers, feeding Often harmless. actually but abdomen, flattened rather its across bands yellow and black with wasp Adult: to up 10 hooks, mouth dark and surface upper on stripe with maggot Larvae: Syrphidae spp. Hoverfly (P Scanlon DAFWA) aphids(PScanlon attacking larvae Hoverfly andadult BENEFIT DESCRIPTION Resembles a bee or or abee Resembles Cream to brownish to Cream brownish mm long. mm especially summer. especially Warm weather, MOST COMMON insect Beneficial ✓ Micromus tasmaniae Micromus Lacewing the remains of their prey. their of remains the camouflage themselveswith 8 to up bodied, thicker are nymphs lacewing Green tail. along jaws and large but head asmallish with to up 10and slender, are brown nymphs Nymph: Brown and green adult lacewings; Green lacewing nymph (SBroughton DAFWA) from above:Clockwise Brown lacewing nymph aphids(C Freebairn attacking QDAF); DESCRIPTION mm long and usually usually and long mm Brown lacewing lacewing Brown mm long long mm — brown and green and brown Year round. mites. and thrips caterpillars, small aphids, of predators voracious are nymphs and Adults body. the along upright delicately-veined wings held antennae. have Both large, long eyes and red round large to up 15are lacewings Green eyes. green toup 8 Adult: MOST COMMON BENEFIT Brown lacewings are lacewings Brown mm long with large large with long mm mm long with with long mm insect Beneficial

✓ 25 INSECTS 26 INSECTS thrips, moth eggs and mites. and eggs moth thrips, aphids, of predators active are larvae and adults Both Transverse ladybird (C.transversa) adult hairy and 1–2 and hairy is black, Stethorus contrast, In covers. wing outer their on stripes and spots distinctive 3–5 beetles dome-shaped coloured, Adult: to up 6 appearance, ‘crocodile like’ and markings Nymph: Coccinella transversa, Hippodamia variegate, Harmonia conformis Ladybird BENEFIT DESCRIPTION Most are brightly brightly are Most Black with coloured coloured with Black mm long with with long mm mm long. mm mm long. mm Late spring to autumn. spring Late MOST COMMON White collared ladybird (H.variegate) adultandnymph (opposite) with two spotted mites (QDAF) Common spotted ladybird (H.conformis) andmite eating ladybird (Stethorus) insect Beneficial

✓ 27 INSECTS 28 INSECTS Cicadulina bimaculata (Wallaby leafhopper Maize ear) Symptoms of ‘wallaby ear’ dueto leafhopperdamage (HLockyer NSW DPI); Maize leafhoppers onaleaf(QDAF) andinclose-up as‘wallaby known syndrome a toxin causes This feeding. during toxin into leaf the a inject leafhoppers Maize disturbed. if any direction away jump in quickly They like atiny (3 ‘nose’. the of side either Looks spots black eyes and dark wings, clear with insect yellow Adult: wingless. and smaller, paler Nymph: DESCRIPTION DAMAGE Wedge-shaped golden Similar to adult but but to adult Similar mm long) cicada. cicada. long) mm leafhoppers areleafhoppers controlled. if symptoms ear wallaby from recover can Plants others. than to damage susceptible more are varieties Some areas. coastal in summer,Late particularly habit. upright shortened, a developing in-roll, and Leaves to crinkle veins. tend leaf the of swelling and growth stunted severely ear’. Symptoms include MOST COMMON (J DuffQDAF) (J close-up Feeding damageonsweet corn leaves. isjust visibleinthe A singlethrips Frankliniella williamsi thrips Maize to significantly affect plant affect to significantly appear not this does While yellow developing. streaks with cupped, and distorted leaves to the become cause can whorl leaf the in Feeding backs. their along held are hairs long with fringed wings transparent Narrow long. 1–2 and torpedo-shaped Adult: generally <1 wingless, yellowish, Nymph: DESCRIPTION DAMAGE Light to dark brown, brown, to dark Light Cream to to Cream

mm long. mm mm

Warm to hot, dry weather. dry Warm to hot, asFusarium. such diseases for point entry an creates cob the on feeding growth, MOST COMMON 29 INSECTS 30 INSECTS Phytoseiulus persimilis predatory — Mite and larger than pest mites. than pest larger and Faster moving shaped. pear Adult: shaped. pear Nymph: Pale orange, crops. unsprayed in found be also can mites predatory commercially. Various other P. persimilis Predatory mite Phytoseiulis atwo spotted mite persimilis attacking (QDAF) DESCRIPTION Orange to reddish, to reddish, Orange can be purchased purchased be can temperatures >26° C. temperatures at rapidly Multiplies mite. spotted two- on Predatory MOST COMMON BENEFIT insect Beneficial ✓ Two-spotted spidermites (FPeairs CSUBugwood.org) andleafdamage withclose-up Tetranychus urticae Mite —two-spotted As populations increase increase populations As areas. stippled yellow light develop initially which leaves, damages Feeding legs. white and body red adark has form Overwintering body. its of side either spot olive adark with long 0.5 around green, Adult: in overwintering form. tochanging orange bright Nymph: DESCRIPTION DAMAGE Whitish to yellow to yellow Whitish Translucent white, mm mm (25–30° Hot covered in fine webbing. Leaf undersides become mayand reddish. turn spreads area yellowed the MOST COMMON

C) dry weather. dry C) 31 INSECTS 32 INSECTS Trichogramma spp Parasitoid wasps parasitise heliothis eggs eggs heliothis parasitise Trichogramma Telenomus and heliothis eggs Telenomus spp. QDAF) (B Scholz andTrichogramma spp. (NSWDPI) laying into larger, 3to 20 are parasitoids Larval long. <0.5 wasps brown basalis Telenomus Trissolcus and asTrichogramma, such Adult: aphids. and caterpillars of control for commercially sold are anumber which of wasp, parasitoid of types many are different There DESCRIPTION BENEFIT are tiny black or or tiny are black Egg parasitoids parasitoids Egg mm long. long. mm . Cotesia Telenomus spp. spp. Microplitis spp. mm mm Any time of year. of Any time host. dead the of outside the on pupae white fluffy forming 30 mature larvae to up with caterpillars, head sorghum and armyworm heliothis, parasitise spp. asCotesia such wasps Braconid caterpillars. spp. Spodoptera and into heliothis egg lays asingle Microplitis eggs. bug vegetable green basalis T. while MOST COMMON attacks attacks

Cotesia DuffQDAF) wasp pupae(J Parasitoid wasp DuffQDAF); newlyemerged from itsmummifiedaphid host(J Microplitis spp. Lindsey) (JK insect Beneficial

✓ 33 INSECTS 34 INSECTS sucking mouthpart. sucking and piercing Prominent back. its across flat folded wings clear with long 2–3 bug Oval Adult: eyes appearance. plump and red dark with nymph wingless orange-red, Nymph: Bright Orius Pirate bug and pirate bug hunting oncorn silks, showing itssmallsize Pirate bugnymph (A SissonIowa State UniBugwood.org) DAFWA), adult(PScanlon DESCRIPTION spp. mm mm In summer. heliothis. including eggs moth of a variety and mites thrips, on Feeds MOST COMMON BENEFIT insect Beneficial ✓ Chauliognathus lugubris beetle soldier Plague Up to 15 wings. green metallic and bright orange abdomen Adult: caterpillars. young and eggs pupae, insect eats that carnivore A strict Larvae: and contaminateand cobs. damage crop may cause numbers large However pests. other and eggs caterpillar aphids, on Predatory Plague soldier beetlesinglyand swarming on corn tassels(A Ryland) DESCRIPTION BENEFIT / DAMAGE / BENEFIT Slender with beetle

Soil dwelling grub. grub. dwelling Soil mm long. mm 35 INSECTS 36 INSECTS Family Delphacidae Planthopper species undetermined Maize planthopper (Peregrinus maidis ) (USDA ARS);Planthopper adult, where whorl, leaf the inside numbers large in gather can nymphs and Adults 4 around being withlong-winged, the latter or short- may be Adults tiny cicadas. Resemble head. the of top the on patch lighter Adult: stubs. wing short with nymph oval coloured, Nymph: DESCRIPTION DAMAGE Mottled brown with with brown Mottled Creamy Creamy mm long. long. mm Warm, humid weather.Warm, humid virus. stripe maize particularly viruses, transmit can photosynthesis. Planthoppers reduces honeydew on mould sooty of Growth killed. may be withering. Young seedlings and wilting yellowing, leaf in vigour, plant resulting reduces honeydew.excrete This and sap plant suck they MOST COMMON distinctive antennae ‘clubs’ distinctive Female red andbluebeetle hunting aphids (top) andmale beetleshowing pollen. eat sometimes also Adults caterpillars. small and eggs heliothis on Feeds end. at the tip orange an centre and the across band distinctive broad orange covers have wing a blue metallic The thorax. orange 5 Adult: grub. dwelling Larvae: Dicranolaius bellulus Red and blue beetle BENEFIT DESCRIPTION mm long with blue head and and head blue with long mm Glossy beetle around around beetle Glossy Creamy, soil- and at sunset. and morning early the in summer. mainly In Active MOST COMMON insect Beneficial

✓ 37 INSECTS 38 INSECTS Monolepta australis Red-shouldered leaf beetle present in large numbers. in large present if damage severe cause can but apest occasionally Only corn. in aproblem generally not are but roots plant on feed Larvae leaves. eat Adults cover. wing each on spot red adark and shoulders the across band red dark 6 around Adult: to up 10 tail, and head at the plates brown Larvae: Adult; Red-shouldered beetle (PChew) leafbeetlefeeding ontheleaf(QDAF) DAMAGE DESCRIPTION Golden yellow beetle beetle yellow Golden White grub with with grub White mm long with with long mm mm long. mm NSW and Queensland. northern of areas coastal in to autumn, particularly spring from appear Swarms MOST COMMON and theresulting outtassels (A dried Ryland) Rutherglen bug adultonacob, sap from inlarge thetassel, numbers sucking are unavailable. hosts other moves when intoUsually corn species. weed in summer early and spring during Multiplies cobs. packed contaminate Can husks. leaves and damage as aswell silks and tassels out dry can sucking Sap eyes. black large and wings transparent with 5mm long Adult: weeds. on feed mainly Nymphs wingless. and brown Nymph: Nysius vinitor bug Rutherglen MOST COMMON DAMAGE DESCRIPTION Slender, dark grey bugs bugs grey Slender, dark

Pear-shaped, reddish 39 INSECTS 40 INSECTS Cryptoblabes adoceta Cryptoblabes caterpillar head Sorghum close up(QDAF) Young sorghum headcaterpillar with damage, andthe caterpillar andmoth leaves cobs. of wrapper and silks on feed Caterpillars body. the along folded toup 8 moth reddish-brown and Adult: stripes behind the head. white three distinguishing the (up to 13 smaller are but armyworm Resemble darker stripes. with grey or to brown age with darken but beige are Caterpillar: DESCRIPTION DAMAGE Slender grey mottled mm long. Wings are are Wings long. mm mm long) and lack lack and long) mm Young larvae Mainly attacks sorghum. attacks Mainly NT. the and Queensland NSW, in pest occasional An issue. acontamination be can frass their and larvae Both MOST COMMON (M Hinderager) andwitha damagedseedshowing sizeSymphyla incloseup(SMartinez) seedlings. and seeds germinating of losses major cause can infestations Heavy hairs. root and roots seeds, germinating attack also will they vegetation, decaying eat normally symphyla While light. the to escape soil the in gaps and pores move rapidly through symphilids disturbed, If pairs. twelve of maximum a reaching moults, animal the time each increases legs of pairs of number The centipedes. soft-bodied tiny (3–7 like look adults and Juveniles spp. Scutigerella Symphyla DAMAGE DESCRIPTION mm long),mm white,

seeds in dry conditions. dry in seeds to attack likely less are so levels, to moisture response in profile soil the down or move Symphyla up mild. are temperatures if particularly soils, moist Well structured, MOST COMMON 41 INSECTS 42 INSECTS Tachinid flies with a stout appearance. appearance. astout with strongly bristled and often tobut ahousefly,similar brown, or grey are Most range. size large a very Adult: host. the inside lives that maggot shaped Larvae: caterpillar. ahost of skin the onto directly stuck usually group, asmall in or singly Egg: Tachinid a heliothiscaterpillar(QDAF) and attacking fly(PChew) DESCRIPTION Creamy oval egg, laid laid Creamy egg, oval Tachinidhave flies White, carrot- White, Any time of year. of Any time pupation. during dies immediately, it host the kill not do they Although asheliothis. such caterpillars inside feed Larvae MOST COMMON BENEFIT insect Beneficial ✓ White fringed weevil larvae (S Andreoli BGA AgriServices) and adult (SAndreoliWhite BGA AgriServices) weevil fringed larvae They roots. plant eat they where soil the in live Larvae distances. long walk can but fly cannot Adults Upto 12snout. long. mm side band and broad short white with weevil striped Adult: toup 15 long. mm jaws, black and head creamy with grub legless Larvae: leucolomaNaupactus White fringed weevil DESCRIPTION DAMAGE Pale grey-brown grey-brown Pale Whitish C-shaped Whitish

emerge during summer. adults to spring, autumn from active are Larvae crop. susceptible amore after is grown it if especially corn attack will but lucerne, and aspeas such legumes of apest Mainly damage. major cause rarely Adults surface. soil the below stem the through chewing by seedlings young kill can MOST COMMON 43 INSECTS 44 INSECTS Gonocephalum spp. False — true Wireworms and with a serrated edge. aserrated with forked is usually tail the and wireworms false than bodied softer are They tail. and a darker, head reddish with creamy to brown light True wireworm are larvae mouthparts. dark and head around with long to up 30 and to brown golden smooth, are larvae Larvae: False (Virginia Tech wireworm larvae andtrue(GRDC) Extension) DESCRIPTION False wireworm , Family Elateridae , Family mm mm if placed upside down. upside placed if aclick with themselves right can they because called so ‘click beetles’, torpedo-shaped True wireworms become dish). (likepie a edges flanged with have athorax beetles oval-shaped dark, These beetles. into ‘darkling’ mature Adult: False wireworms

with pasture or mulches. or pasture with planted formerly a field in is planted corn when aproblem to be likely Most bases. stem and roots plant young seeds, germinating on feed they where soil the in live Larvae wireworm) beetle(adult falsewireworm) andclickbeetle (adulttrue (USchmidt) Darkling MOST COMMON DAMAGE 45 INSECTS DISEASES 47 Diseases mm 20 Up to Bright orange

MOST COMMON MOST DAMAGE DESCRIPTION

Young yellow peach moth caterpillar, caterpillar with feeding damage in corn damage in corn with feeding caterpillar peach moth caterpillar, yellow Young (J and adult moth (QDAF) Tann) Yellow peach moth Yellow punctiferalis Conogethes December May. to developing cobs. developing Caterpillars feed on held out from body. black markings. Wings yellow moth with spotted Adult: with dark spots maturity. at yellow bright to pink body long with a dark head. Creamy Caterpillar:

INSECTS 46 48 DISEASES Ustilago maydis Ustilago smut Boil wind and in irrigation water, irrigation in and wind the on carried are Spores nitrogen. soil as by high well as damaged, is physically corn if is increased Infection spores. dark of masses releasing burst, eventually These cobs. the on diameter to up 150reaching enlarge, and form galls to grey green Pale leaves. and tassels stems, also but plant, commonly the cobs, the of part growing rapidly any infects fungus The SYMPTOMS FAVOURED BY FAVOURED mm mm soil for more than 15 than more for soil years. the in survive potentially to known are residues crop on spores resting while (Z Bliska) andleaf Bugwood.org), cob (CIMMYT) smutonatassel(B Boil Watt UniMaine Atherton Tablelands. the on common Most rain. heavy after likely more water, free is so requires weather.humid Infection Warm (23–30° collapsing. result in plants can infection Severe blade. leaf the on spotting rust-like lighter, with ribs mid the along appear spots Dark whorls. and axils leaf the in initially lesions develop, usually brown chocolate oval Small, Brown spot lesionsonpetiole(QDAF) Iowa andleaf (D Mueller State UniBugwood.org) Physoderma maydis Brown spot FAVOURED BY FAVOURED SYMPTOMS

C) and and C) 49 DISEASES 50 DISEASES and plants may collapse. may collapse. plants and junction soil the near stem emerging the on appear soaked, brown lesions Water- growth. stunted have and colour lose wilt, emerge do that Seedlings is poor. emergence Crop Pythium spp. Pythium off Damping and round, brownish sclerotes (resting structures) Brown Bugwood.org) rolfsii; Sclerotinia funguson soil, showing white mycelium Damping offof seedling,corn showing brown (WM lesion nearthesoiljunction SYMPTOMS , Fusarium spp , Fusarium ., Sclerotium rolfsii, Rhizoctonia solani Rhizoctonia rolfsii, Sclerotium ., spores or in crop residues. crop in or spores asresting either periods, extended for soil the in can survive off damping for responsible fungi different The conditions. Wet soil FAVOURED BY FAVOURED toxins in the infected cob. infected toxins the in produces mould The disease. the of characteristic are (‘starburst’) kernels individual tips of the from radiating streaks cob. White whole over the extend or kernels individual affect can growth fungal pink to pale White fungal threads (OMAFRA) Fusarium cob rot (QDAF) showing andinclose-up, typical ‘starburst’ pattern of Fusarium F. vertilliodes, Fusarium rot cob SYMPTOMS spp.

central to southern NSW. to southern central Commonly found in irrigation. to uneven due split kernels cobs or damage insects if likely is more Infection stress. moisture and temperatures High FAVOURED BY FAVOURED 51 DISEASES 52 DISEASES stringy appearance. stringy adistinctive, bundle spore the giving intact, relatively remains system vascular the this mass, cob. Within entire the replace usually spores black with bursting galls smut large Inside, silks. lack and teardrop shape into cobs grow a infected of husks The spores. black of masses develop and Tassels distorted become silk. and the cob affects only smut head smut, Unlike boil Sphacelotheca reiliana Head smut Head smut (RLCroissant Bugwood.org) SYMPTOMS (20–30° warm under likely most infection with soils dry cool, 5–7 in at least years survive can Spores cob formation. and flowering until expressed not are symptoms although seedlings, are plants when occurs usually Infection FAVOURED BY FAVOURED C), dry conditions. C), dry or cobs. deformed multiple forming distorted, and are stunted plants Mature surface. leaf the of side either on appear may growth Downy grows. plant asthe increasing area affected the with borders, have clear These veins. leaf striping develops along the to yellowish green Pale Leaf dueto striping downy Uni Georgia mildew (BKemerait Bugwood.org) maydis Peronosclerospora mildew downy Java SYMPTOMS

north Queensland.north of areas drier in found is mainly disease why the is which ahost, is also Sorghum age. with resistant more becoming plants with seedlings, in occurs Infection most commonly FAVOURED BY FAVOURED 53 DISEASES 54 DISEASES produced inside the lesions. are spores dark of masses weather moist In leaves. lower the in is often infection Initial surface. leaf cover the of much eventually streaks greyish and expand, These halo. ayellow with often develop, Elongated grey-brown lesions Exserohilum turcicum Turcicum / Northern blight leaf Initial Initial SYMPTOMS andmore advanced Khampanich) leafblight (OMAFRA) symptoms ofnorthern (W wind and irrigation water. irrigation and wind by spread are and residues crop in survive Spores or overhead irrigation. dew heavy with occur can as conditions, Warm, wet FAVOURED BY FAVOURED can become fragile. become can Leaves and yellow black. brownish turn they mature these As surfaces. leaf lower and upper the over both scattered appear pustules Elongated, reddish-brown Common rust symptoms and close-up ofpustules Common rustsymptoms andclose-up Puccinia sorghi common — Rust SYMPTOMS resistant to common rust. to common resistant are varieties corn sweet Some distances. long disperse can and by wind spread easily are Spores dews. heavy or humidity high with combined Warm (16–24° FAVOURED BY FAVOURED

C) weather weather C) 55 DISEASES 56 DISEASES can become fragile. become can Leaves and yellow black. brownish turn they mature these As husks. and stems the on develop also can Spots surfaces. leaf upper over the scattered appear to up 2 pustules Oval, orange-brown Puccinia polysora Puccinia Rust —tropical /Polysora Symptoms andstem (UniNebraska) oftropical ruston thecorn plant upper leafsurface SYMPTOMS mm long long mm and presence on stems. on presence and surfaces leaf lower from colour,lighter absence by its rust common from distinguished be can Polysora Queensland.northern in as occurs humidity, high with combined Warm conditions to hot FAVOURED BY FAVOURED

in NSW and Queensland. and NSW in is widespread which virus, the for as reservoirs act sorghum wild and grass injury. Johnson mechanical Transmission or is by aphids is reduced. yield and stunted Plants are appearance. amarbled with yellowed Leavesveins. become the with parallel running lines asbroken appearing particularly leaves, the on develop green dark and light of patches Stippled Virus symptoms on the plant and close-up ofleaf(QDAF)Virus symptoms onthe plant andclose-up Johnsongrass mosaic — Virus FAVOURED BY FAVOURED SYMPTOMS 57 DISEASES Virus — maize stripe DISORDERS SYMPTOMS FAVOURED BY Initially appears as small Although commonly yellow flecks in the young found in coastal areas, it leaves. These broaden and is usually a minor issue. DISEASES expand with plant growth, The virus is transmitted by forming wide, pale yellow the maize planthopper. stripes parallel with the veins. Affected plants are stunted and deformed.

Disorders

Maize stripe disease (CIMMYT) 58 59 Blanking Boron deficiency DISORDERS SYMPTOMS SYMPTOMS CAUSED BY Blank areas or unevenly sized effect, but may not be a Younger leaves are inrolled, Alkaline or strongly acid kernels occur on the cob. This problem if corn is processed. erect and brittle, developing sandy soils, particularly can be a particular problem pale yellow streaks and in cold weather or very on the tip of the cob, which mottled appearance. Plants dry conditions. DISORDERS fails to develop kernels. are shortened with stout, oval stems. Boron affects silk CAUSED BY development and pollination, Usually due to wet conditions so cobs are curved, small or hot, dry and windy and/or have blank areas. weather during pollination. Stress caused by too much or too little water, nutrient deficiencies or high night temperatures (over 22° C) during pollination and tip filling can also cause blanking. Tip blanking can be a varietal

Severe blanking, caused by heat stress during pollination (P Deuter QDAF); Partial (top) and tip blanking Boron deficiency symptoms in leaves (JE Espinosa IPNI) and cobs (QDAF) 60 61 Calcium deficiency Copper deficiency DISORDERS SYMPTOMS CAUSED BY SYMPTOMS New leaves develop pale, Most likely in acid (pH<5.0), Younger leaves are yellowed the veins gives leaves a whitish lesions that tear sandy soils or soils high as they emerge. Leaves striped appearance. easily. In severe cases the in sodium, magnesium develop a distorted, CAUSED BY youngest leaves tend to or potassium. twisted habit and may DISORDERS inroll with leaf tips remaining brown and crack along the Most likely on acid joined to together, causing edges. Yellowing between (pH>7.5), organic soils. a ladder-like appearance.

Calcium deficiency symptoms (MK Sharma & P Kumar IPNI) Distorted leaves due to copper deficiency (T Yamada IPNI) 62 63 Iron deficiency Magnesium deficiency DISORDERS SYMPTOMS SYMPTOMS Iron is immobile in the plant matter, or those with a high Bright yellowing of the older of calcium and potassium in but is needed for chlorophyll pH (>7). Iron deficiencies leaves, initially between the the soil can make magnesium formation. Distinct and are more likely in cool, veins. Yellowing starts from unavailable to the plant. severe yellowing between damp springs. Symptoms the leaf tip and margins and DISORDERS the veins therefore develops are worst on seedlings. spreads inward towards the in the youngest leaves. Plants central rib. This develops into develop a striped appearance. a characteristic reddening Symptoms are similar to or browning, with only the manganese deficiency, but central rib area remaining chlorotic areas have a more green and the leaf edges distinct boundary, with becoming dry and papery. veins remaining green. CAUSED BY CAUSED BY Deficiency is most likely in Insufficient iron available acid, sandy soils. High levels to the plant. Worst in sandy soils with low organic

Initial yellowing between the veins due to iron deficiency gives a striped Magnesium-deficient plant and close-up of leaf showing reddish colour between appearance to the younger leaves (MK Sharma and P Kumar IPNI) the centre vein and leaf edge (MK Sharma and P Kumar IPNI) 64 65 Manganese deficiency Nitrogen deficiency DISORDERS SYMPTOMS SYMPTOMS Manganese is immobile As nitrogen is mobile in the nitrogen from soils, especially in the plant but is needed plant, yellowing is initially from light, sandy soils. for chlorophyll formation. observed in the older Yellowing between the leaves. Symptoms can then DISORDERS veins therefore occurs in the spread to the whole plant, youngest leaves. Plants can which becomes pale and develop a striped appearance. spindly. Older leaves may Pale, streaky lesions may die prematurely. Yellowing occur in severe cases. Cobs tends to appear in a V-shape, are malformed, with poor or starting at the leaf tip and uneven kernel development. progressing down the midrib to the leaf base. CAUSED BY Deficiency is associated CAUSED BY with pH>8, particularly Insufficient nitrogen is most in chalky soils. likely in cold, waterlogged soils lacking organic matter. Heavy rain and high carbon Nitrogen deficient leaves compared crop residues can remove to healthy leaf at right

Interveinal yellowing on young leaves due to manganese deficiency (MK Sharma Symptoms of nitrogen deficiency on a leaf (GR Pugliese IPNI) and whole plants & P Kumar IPNI) (MK Sharma & P Kumar IPNI) 66 67 Overmaturity Phosphorus deficiency DISORDERS SYMPTOMS SYMPTOMS Kernels develop dimples and/ can occur in supersweet Older leaves develop reddish Note: seedlings of some or individual kernels brown varieties, especially under purple leaf tips and margins. varieties develop purple and soften, developing warm, humid conditions. Occurs most frequently in colours even when a fermented flavour. Harvest should occur at young seedlings, which tend phosphorus is adequate. DISORDERS Cobs lack sweetness. the milk stage (squeezed to be small with reduced kernels release milky liquid), vigour. Older plants have CAUSED BY before cobs start to dry, and a shallow root system, silk Incorrect assessment of convert sugars to starch. emergence is delayed and maturity, resulting in late cobs have missing kernels. harvest. Fermentation CAUSED BY Soils low in organic matter or high in iron, which ties up phosphorus in a less available form. Symptoms are most likely in cold soils that are excessively wet or dry.

Phosphorus deficient seedlings and symptoms on a mature leaf (MK Sharma & Dimpled kernels due to overmaturity (QDAF) P Kumar IPNI) 68 69 Potassium deficiency Salinity DISORDERS SYMPTOMS CAUSED BY SYMPTOMS CAUSED BY Yellowing and then browning Heavy rain leaching Seed germination may be High levels of salts, especially of the older leaves starting at potassium from the soil, slow and patchy. The tips sodium chloride, in the soil the leaf tip and outer margin. especially if early root growth and margins of the older and/or irrigation water. Symptoms usually don’t has been limited by dry leaves become yellowed and While salt tolerance differs DISORDERS appear until at least a month or compacted soil. Excess necrotic. Leaves are short, widely between varieties, after planting. As the plant calcium and magnesium erect and may tend to inroll water with an EC reading grows the lower leaves yellow reduce potassium availability. along the margins. Severe >1.5 dS/m may affect growth. and die back from the tip. salinity can kill plants.

Potassium deficient leaf and resulting death of the older leaves in a crop (MK Sharma & P Kumar IPNI) Effect of high levels of dissolved salts on plant leaves 70 71 Sulphur deficiency Uneven germination or growth DISORDERS SYMPTOMS SYMPTOMS Younger leaves are pale Crop fails to grow uniformly. (increasing seed rots), planting to yellowed. Yellowing while soil temperatures are CAUSED BY may be interveinal, or still below 13° C and uneven quite diffuse across the Possible causes include watering resulting in dry DISORDERS leaf. Plants are stunted changes in soil type, uneven or waterlogged areas. Soil with delayed maturity. planting depth, poor seed borne fungi and nematodes quality or old seed, planting can also cause this effect. CAUSED BY too deep early in the season Most likely in sandy, acid soils with low organic matter, especially if conditions are cold and dry after planting.

Yellowing of the younger leaves may be interveinal (R Taylor Uni Delaware) or diffuse (MK Sharma & P Kumar IPNI) Uneven crop of sweet corn 72 73 Zinc deficiency Nutrient deficiency symptoms DISORDERS SYMPTOMS The following is a diagrammatic representation only. A broad creamy white to sandy or low in organic matter Note that symptoms can vary significantly between cultivars, translucent band appears due to removal of the topsoil. environments and soil types. either side of the midrib, High levels of soil phosphorus starting at the bases of reduce uptake of zinc. DISORDERS younger leaves. Bleaching does not normally extend as far as Healthy leaf the leaf tip; the leaf margins and midrib usually remain green. Plants are stunted Nitrogen due to shortened lengths deficiency between the leaf nodes. CAUSED BY Usually occurs in soils with Potassium pH>7, especially where soil is deficiency

Phosphorus deficiency

Zinc deficiency

Magnesium deficiency

Zinc deficient plants and leaf showing white band either side of the midrib (MK Sharma & P Kumar IPNI) 74 75 Problem solver for sweet corn pests, diseases and disorders Pages Black mould Aphids 4–5 Planthopper 36 Bleached or Green veg bug 21 dry areas Planthopper 36 Rutherglen bug 39 Cobs deformed Blanking 60 Boron deficiency 61 Overmaturity 68 Cobs diseased Boil smut, head smut 48, 52 Fusarium cob rot 51 Cob/kernel eaten Dried fruit beetle 17 Heliothis 22–23 Sorghum head caterpillar 40 Yellow peach moth 46 Leaves with holes Armyworm 6–7 or chewing Cluster caterpillar 12 Heliothis 22–23 Red shouldered leaf beetle 38 Leaves Java downy mildew 53 discoloured/ Northern/Turcicum blight 54 striped Viruses 57–58 Nutrient deficiencies 62, 64–67, 69–70, 72, 74 Leaves distorted Aphids 4–5 Maize leafhopper 28 Maize thrips 29 Boron or copper deficiency 61, 63 Leaves speckled Mite–two spotted 31 Maize thrips 29 Leaves with spots Brown spot 49 Rusts 55–56 Salinity 71 Seedlings die Cutworm 15 Symphyla 41 White fringed weevil 43 Damping off 50–51 Root damage African black beetle 3 Crickets 13–14 White fringed weevil 43 Wireworms 44–45 76