Download PPT Melon Insects

Melon Insects
Frank G. Zalom, Department of Entomology, UC Davis
T. urticae
Spider Mites
Tetranychus spp.
• Adults about 0.75 mm long
• Eggs are spherical, laid on
underside of leaves,
sometimes in webbing
• Infestations may include a
mixture of spider mite
species
• Many generations per year
Carmine Mite
Spider Mites
Damage
• Leaves become pale, stippled,
and in later stages of infestation
dry up and die; resembles a virus
• Loss of color is pronounced on the under surface of
leaves before it becomes apparent on the upper side
• Light infestations can be
tolerated; heavier infestation
can result in lowered yield and
reduced quality of fruit
Spider mite larvae have 6 legs
Spider Mites
Control
• Good water management
increases plant tolerance to mites
• If mite populations are building,
either spot or completely treat the
field before webbing occurs or
before runners are 14 inches in length
• After runners are 14 inches long, mite feeding is less
critical except to maintain the plant canopy; natural
enemies often control pest mite populations at this time
Whiteflies
Bemisia spp.
Greenhouse whitefly
Bemisia
Greenhouse whiteflies hold their wings flat over body
Bemisia hold their wings at an angle, rooflike over body
4th instar nymphs Greenhouse whitefly nymphs have
long waxy filaments around the edge of
their bodies
Bemisia nymphs do not
Whiteflies colonize the
underside of leaves
Greenhouse whitefly
Eggs
Whiteflies
Damage
• Feeding by Bemisia causes
leaves to turn whitish or silver
• Desiccation of plants occurs with moderate to heavy
populations, and the production of honeydew gives
rise to develop sooty mold
• Plant may become weak and nonproductive, and
the fruit rendered unmarketable
• Bemisia transmits lettuce
infectious yellows virus and
squash leaf curl virus
Whiteflies
Control
• When possible, plant
melons at least 0.8 km
upwind from key whitefly
hosts such as tomatoes,
cole crops, and cotton
• Inspect transplants for
whitefly infestation
• Rotate with non-host crops
Reflective mulch
• Use reflective polyethylene mulches on planting
beds if virus transmission is a major concern
Whiteflies
Bemisia pupae (yellow
are parasitized)
Control
• Several wasps parasitize nymphs;
bigeyed bugs, lacewing larvae, and
lady beetles are general predators
• If populations are higher at field
margins than at field centers, treat
only the field margins; this reduces
treatment costs and preserves
beneficials
Eretmocerus wasp
• Preplant treatment with a soil
applied neonicotinoid insecticide is effective
Armyworms
Spodoptera spp.
Damage
• Armyworms are primarily foliage
feeders, but will also feed on fruit
surface, creating circular or irregular
holes
• Feeding is often superficial; however,
damage canbe unsightly and decay
organisms can enter wounds and rot
the fruit
• Larvae occasionally develop inside the fruit
Armyworms
Spodoptera spp.
Control
• Infestations originate from
moths or larvae that migrate
from adjacent fields or weeds that are infested;
cleaning up crop residue and weeds reduces density
• Monitor foliage for small larvae and treat before fruit
damage occurs; treat only if armyworm feeding is
observed on fruit
• Treat young larvae with Bt; larger larvae will require
a different insecticide
Aphids
• Populations tend to start on
lower leaves and move up the
plant
• Cluster on the underside of growing
leaves
• Aphids attacking melons have a wide
host range
• Aphids move into melon fields from
surrounding vegetation, carrying
viruses as they move and feed from
one plant to another
Aphid seasonal cycle
Multivoltine; alternating
generations
Sexual &
Oviparous
Alate
Eggs
Nymphs
Stem mother
Parthenogenetic
& Viviparous
Aphids
Damage
• Vector of several viruses
• Feeding causes leaves to
distort and curl
• Aphids produce honeydew,
creating substrate for sooty
mold
• Treatment may be needed
when nearby fields are
found to have a virus that
affects melons
watermelon mosaic virus
Papaya ringspot virus
Aphids
Management
• Prevent establishment of early colonies; spot treat
with insecticide or remove and destroy the few
heavily-infested plants as they appear in spring
• Control weeds in noncultivated areas from which
aphids migrate
• Delay planting until warm temperatures (26° to
29°C) occur and the spring flight of early season
aphids is over
• Avoid over-fertilizing with nitrogen
Aphids
Management
• Beneficials can have a
Melon aphids and parasitized mummy
significant impact
• Use non-disruptive insecticides to conserve natural
enemies
• Reflective mulches repel aphids
• Floating row covers exclude aphids
• Preserve habitat for beneficials; planting a habitat
for beneficial insects, such as sweet alyssum,
around the field may be helpful
Cucumber Beetle
Diabrotica spp.
• Adults typically have black spots or black and
yellow stripes
• Overwinter as adults; in spring, adults lay eggs at
the base of plants
• Larvae feed on plant roots and complete their
development in the soil; adults feed on vegetation
• About three generations a year
Cucumber Beetle
Diabrotica spp.
• Adults migrate into melons from alfalfa, corn, and
other crops and from uncultivated land
• Prefer smooth-skinned varieties such as honeydew,
crenshaw, and casaba
• Adults are attracted to moisture and dislike heat;
thus, melon fields are especially attractive in hot
weather during and after an irrigation
Damage on zucchini
Cucumber Beetle
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Damage
The beetles chew holes
in leaves and scar
runners and young
fruits, and can destroy flowers
Feeding on stems of young plants followed by
sustained winds result in severe stand reductions
After the skin hardens, melons are much less
subject to attack
Larvae may injure plants by feeding on roots
Beetles also spread squash mosaic virus
Cucumber Beetle
Control
• Treat adults if there is an average of 1 beetle a plant
during the seedling-to-10-cm-tall stage
• Infestations later in the season are usually not as
damaging as earlier infestations because population
densities tend to be lower
• Natural enemies usually do not reduce populations
below economically acceptable levels