Embed Size (px)
Citation preview
Sorghum Insect Management
Jeff Whitworth, Holly Davis KSU Entomology
cropwatch.unl.edu/photos/cwphoto/sorghum.jpg
It’s been an interesEng season… Drought Tolerant Sorghum Plots
Wireworms • Belowground pest
• Attack sorghum seeds and seedling sorghum before emergence
• Controlled with seed treatments
Sorghum Poten8al above ground pests
l Aphids l Chinch bugs / False chinch bugs l Sugarcane rootstock weevil l Flea beetles l Grasshoppers l Spider mites l Cutworms l “Headworms” – Sorghum webworm, corn earworm,
etc. l Sorghum midge
Corn Leaf Aphids
• Short antennae
• Black legs
• Feed on upper leaf surface or in whorl
• Control rarely needed
• Should only be considered if infestations persist after heads have emerged
Greenbugs
• Light green aphids, with a dark green strip on back.
• Light green cornicals.
• Antennae as long as body.
• Normally feed on underside of leaves.
Texas A & M
Flea Beetles
• Occasional Pest that attacks early spring / seedling sorghum
• One or two generations / year. Overwinters in Kansas
• Can destroy sorghum seedlings by stripping protective upper leaf surfaces
Sugarcane Rootstock Weevil
• Native to Kansas • Can attack sorghum, field and sweet corn • May cause lodging especially under dry conditions
Chinch Bug
• Chinch bugs usually increase in dry periods and decline during weIer years
• Outbreaks tend to occur in roughly 7-‐ to 10-‐year cycles
Chinch Bug Life Cycle
• Adults primarily overwinter in bunch grasses
• Move into wheat in early spring where they lay eggs
• Move out of wheat as primarily a walking migration of nymphs as the wheat matures
Chinch Bug
Attack a wide range of plant species including forage, lawn, wild grasses and crop plants.
Most injury is caused by the nymphal stage
Chinch bugs cause damage by sucking juices from leaves, stalks, and leaf sheaths. Infested plants exhibit wilted, white lower leaves
Feeding prevents normal growth and results in dwarfing, lodging, and yield reduction
Dickinson Co. KS -‐ 2012
Chinch Bug Control
• Avoid planting sorghum next to wheat • Plant trap crop (sorghum between the two)
• Resistance • Carefully select hybrids that respond to
treatments better • Cultural Control
• Avoid poor stands and drought stress • Plant sorghum within 3 weeks of grain maturity
• Insecticides
False Chinch Bugs
• Nymphs are grayish – brown with yellow Enge, Adults are gray to brown
• Fields planted no-‐Ell into wheat stubble with delayed weed control are most at risk
• Adult swarms are spoIy and rarely jusEfy field-‐wide treatment
Nymph
Adults
Grasshoppers • Scout borders in early summer
to prevent migration into sorghum
• 15-20 nymphs / sq yd in borders or 5-8 nymphs / sq yd in field may justify treatment
Foliar Damage
Spider Mites • Prefer hot, dry weather • Most common in SW KS • Difficult to control once
they have spread throughout the canopy
www.agricomseeds.net/plagas.php
European Corn Borer (ECB)
www.ca.uky.edu/.../enVacts/images/ecblarv2.jpg
ECB Biology • 2 GeneraEons a year in corn • 1st gen. in May – June feeds
in whorls to give “shot-‐hole” appearance
• 2nd gen. from July – August causes more economic damage
• Treatment thresholds?
Cutworms
• Damage is likely in the two weeks a^er planEng
• Rescue treatments may be jusEfied if most larvae are under ½ inch long (these worms can each destroy 4-‐6 more plants)
• Older larvae are harder to kill
www.dpi.qld.gov.au/.../Cutworm-‐Larvae-‐500.jpg
Addi8onal examples of cutworm damage
CaRail Caterpillar Larva • Distinctively colored with mottled black body and black midline
• Orange crossrows
• Hairy
• Inverted “V”-shaped marking on head
Top Lateral
CaRail Caterpillar Leaf Feeding
CaRail Caterpillar Adult
• Dusky – white • Medium sized • Nondescript moth
2008 CaIail Caterpillar Dickinson Co., KS.
Treatment/Product Name Total number of cattail caterpillars 3 days after treatment/10plants/plot
Untreated 11.75 ± 1.03 a
Cobalt @ 16 fl. oz./acre 1.25 ± 0.95 b
Warrior II @ 2.0 fl. oz./acre 2.00 ± 0.91 b
Mustang Max @ 4.0 fl. oz./acre 0.75 ± 0.48 b
Mustang Max + Chlorpyrifos @ 4.0 fl. oz. + 4.0 fl. oz /acre
1.25 ± 0.63 b
Baythroid XL @ 2.0 fl. oz./acre 1.25 ± 0.63 b
Evaluation Date: July 28, 2008
Jeff Whitworth & Holly Davis
Sorghum Headworm (CEW) Biology • AIacks mulEple crops
including sorghum heads (late in the season)
• Overwinter in KS in the soil • Plants are most vulnerable
to injury during the bloom to milk stages, and larvae can heavily damage seed heads
Sorghum Headworm (CEW) • Check sorghum when it
begins to head. • 1-‐2 worms per head can
jusEfy control. • Generally consider 5%
loss per worm per head.
Photo by Brian McCornack
KSDA.gov
Fall Armyworm (FAW)
• Mature fall armyworm larva
• Four dark spots in a square-shaped pattern at rear of larva
FAW Biology • Migrates from the
Southern states • Adults arrive in KS in July
and lay eggs on leaves • Larva feed on leaves in
the whorl, but leaf damage has little effect on yield
• If 75% of plants show fresh damage with 1-2 live larvae/plant treatment may be considered
Photos by Holly Davis
“Ragged” Foliar Feeding on Young Sorghum
Typical of:
• Fall armyworm
• Corn earworm
• Cattail caterpillar
• Etc.
Treatment / Product Name FAW / Plant Asana 0.66 @ 0.015 GA/acre 0.92 ± 0.15a
Lannate 2.4 @ 0.045 GA/acre 1.25 ± 0.22a
Lorsban 4E @ 0.5 GA/acre 0.92 ± 0.19a
Baythroid 2E @ 0.03 GA/acre 0.75 ± 0.22a
Warrior 1E @ 0.02 GA/acre 0.92 ± 0.19a
Mustang 0.8 @ 0.017 GA/acre 0.83 ± 0.24a
Tracer @ 0.047 GA/acre 1.00 ± 0.17a
Untreated 1.58 ± 0.24a
2005 Fall Armyworm Control in Sorghum with Foliar Treatments
Gerald Wilde, Lindsborg, KS
Sorghum Webworm
• Feed in developing seeds – may be more severe in late planted sorghum
• Larvae acEve Aug – Oct • 5 or more worms per head during early post-‐bloom period may jusEfy treatment
insects.tamu.edu
Sorghum Midge • Overwinters as larvae within the florets or
spikelets (usually in the bottom third) of its host plants
– Silken cocoons provide protection from cold temperatures and drought. Larvae may remain in hibernation for three years
• Adults emerge in the spring (68-80 ºF), johnsongrass blooming
• Adult is small (< 1/8 inch long), orange with dark wings
– Adults rarely live more than two days – After a female has mated, she lays the eggs (30 to
100) within the flowering spikelets or seed husks • Larvae hatch within two to three days, feed 9-11
days before reaching maturity
Adult
• Occasional pest in Kansas – Normally confined to
SE and South Central parts of the state
– Numbers usually too low to detect or to justify insecticide treatment in Kansas
• Usually noticed after fly emergence because of remaining pupal cases
Sorghum Midge
Sorghum Midge Damage
• Detection usually occurs after damage which causes “blasted” heads (small malformed kernels)
• Late planted sorghum most at risk in KS
• Will not cause economic damage after flowering (pollination)
For IdenEficaEon any arthropod… Please contact the Insect DiagnosEc Lab at
Kansas State University
Free ID and informa8on!! Phone: 785-‐532-‐4739
E-‐mail: [email protected]
For more informaEon visit: www.entomology.ksu.edu
Click on Extension and then DiagnosEcian
Available Now: This book includes photos,
descripEons, basic biology, type of damage, and notes on management pracEces based on years of experience and research at Kansas State University. Crop Insects of Kansas is a valuable reference for everyone involved with Kansas agriculture.
Order via e-mail from [email protected] ; fax 785-532-7938; or phone 785-532-5830.
Thanks for Coming!
QuesEons?
