Pests on Soybeans
Two-spotted Spider Mite
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Order Acari
Family Tetranychidae
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Tetranychus urticae
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Distribution: Worldwide
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Description: Small: 0.3-0.4 mm
long, broadly joined cephalothorax and abdomen, greenish-yellow to orange in
color with two large black spots on both sides of the body.
Two-Spotted Spider Mite
Two-spotted Spider Mite Life History
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All stages are found on plant
structures
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Feed mainly on undersides
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Have one 6-legged larval stage
and two 8-legged larval stages
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In northern states they
overwinter as adults. In warmer places they remain partially active
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On heavily infested plants,
females climb up on leaves to be dispersed via wind
Two-spotted Spider Mite Life History
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There are multiple generations
per year
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Females produce up to 300
offspring in first month of egg laying
Two-spotted Spider Mite Damage
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Often recognized by evidence of
feeding and not actually by seeing the mites
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Feed mainly on leaf undersides
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Small yellow or white spots
appear on leaves (stipples)
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reduction in photosynthetic
activity
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Extensive feeding results in
yellow/brown leaves that eventually drop off
Two-spotted Spider Mite Damage
Two-spotted Spider Mite Management
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Two natural enemies: predaceous
phytosiid mites and a fungal pathogen (Neozygites floridana)
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In soybeans, control of spider
mite outbreaks is primarily through chemical application
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Initial monitoring for the mites
should begin along the field edges, where infestations should be first
evident
Bean Leaf Beetle
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Order Coleoptera
Family Chrysomelidae
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Cerotoma trifurcata
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Origin: Native, especially
abundant in the eastern U.S.
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Description: adults 5mm long.
Elytra yellow with black dots and marginal stripe. Black triangle behind the
prothorax. Larvae are white and cylindrical with a black head
Bean Leaf Beetle
Bean Leaf Beetle Life History
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Adults leave overwintering
habitats in April and move into alfalfa fields
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When soybeans emerge, they move
into the soybean fields
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Females lay eggs in soybean
fields (130-200 eggs/ female)
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Larvae feed on roots and nodules
Bean Leaf Beetle Life History
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Mature larvae build an earthen
cell and pupate
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1 to 2 generations/year in the
north and 3 generations/year in the south
Bean Leaf Beetle Damage
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Larvae feed on roots, root
hairs, and nodules
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Adults defoliate. This can be
recognized as small round holes between major leaflet veins
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Most defoliation is early season
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Adults may feed on pods, causing
seed vulnerability. Can be recognized by shrunken, discolored, and moldy
seeds
Bean Leaf Beetle Damage
Bean Leaf Beetle Management
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Plant soybeans as late as
possible within the recommended planting period of a certain variety
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Estimate population levels with
regular sampling and consultation of economic thresholds
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Application of pesticides if
necessary
Potato Leafhopper
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Order: Homoptera Family:
Cicadellidae
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Empoasca fabae
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Distribution: native. widely
distributed in eastern North America
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Description: Adults are small,
3.5m long. Wedge shaped, and pale green in color. Females have bladelike
structure = ovipositor
Potato Leafhopper
Potato Leafhopper Life History
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Overwinter near Gulf of Mexico
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Immigrating adults first appear
in alfalfa and other crops when migrating north until soybeans emerge
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Adults females insert eggs into
soybean plants (2-3 eggs/day)
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One or more generations can
occur on soybean during a single growing season
Potato Leafhopper Damage
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Use mouthparts to tap into the
plant’s phloem tissues
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Distorted leaf veins
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Leaves often yellow-brown in
color, a.k.a. “hopperburn”
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Plant growth often stunted by
leaf damage
Potato Leafhopper Damage
Potato Leafhopper Management
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Approx. economic threshold is 5
leafhoppers/plant in early season and 9/plant in late season
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Soybean varieties with dense
pubescence provide a mechanical barrier that makes it difficult for
leafhoppers to feed or have successful oviposition
Mexican Bean Beetle
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Order: Coleoptera
Family: Coccinellidae
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Epilachna varivestis
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Origin: Native to Mexico
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Distribution: Found in Central
America, Mexico, U.S., Quebec and Ontario
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Description: Adult is oval
shaped, orange-red color with 8 black spots per elytron. Larvae are
yellow-orange with six rows of branched spines
Mexican Bean Beetle
Mexican Bean Beetle Life History
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Adults overwinter in plant
debris or under rocks near soybean field
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Adults emerge in spring when
temperatures increase above 50F (10C)
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Females lay between 700 and 1000
eggs over approximately 40 days
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4th instars attach to internode
of leaf and pupate (5-10 days)
Mexican Bean Beetle Damage
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They damage several legume
species
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Adults and larvae defoliate the
plants
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Adults may also feed on stems
and pods
Mexican Bean Beetle Damage
Mexican Bean Beetle Management
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Greatest potential for economic
loss is during the reproductive stages of soybean
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Defoliation levels above 15% in
determinate and indeterminate cultivars can require management. Defoliation
must exceed 35% once full pods are present in order to be of economic
significance
Grasshoppers
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Redlegged and differential
grasshoppers are sporadic, yet serious pests of soybean
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Consecutive years of drought
often result in the build up of damaging population numbers
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Infestation generally starts
along the edges of a field
Grasshopper
Grasshopper Damage
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Feeding is primarily on leaves
before pods are available
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Leaf and pod feeding both occur
once pods are formed, consuming often the whole pod (including seeds)
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If seeds remain, the feeding may
make them more vulnerable to fungal infection
Grasshopper in Soybean Field
Grasshopper Management
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Biological control of high
grasshopper densities is often accomplished with particular fungal spores
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Often insecticides are used
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Economic Thresholds: 30-45
nymphs/sq. yard and 8-14 adults/sq. yard
Seedcorn Maggot
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Seedcorn maggot is a common
soybean pest
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Often problems in recently
disturbed fields with organic matter, such as manure
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Damage more likely when
conditions are cool and wet
Seedcorn Maggot Injury
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Larvae feed on both germinating
soybean seeds and cotyledons
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Plants have variable emergence,
or no emergence due to seed feeding
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Larval feeding can damage the
growing tip of the soybean plant, causing y-shaped tops
Seedcorn Maggot Damage
Seedcorn Maggot Management
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Chemical seed treatment is often
used in fields with lots of organic ground matter
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Delaying of seed planting