This tool is part of the Citrus Resource

Citrus Pests

 

Scales, psyllids, and relatives

 

Scientific name

 

Order Hemiptera, suborders Sternorrhyncha and Auchenorrhyncha

Other common names

 

This group includes aphids, mealybugs, psyllids, soft scales, cottony scales, whiteflies, and sharpshooters.

Similar species

 

True bugs can be mistaken for cockroaches or beetles. Each group is distinguished by antennae type, mouthparts, and wing position at rest.

Beetles Cockroaches True bugs
Antennae Segmented antennae Long, filamentous Bristle-like, thread-like, or stubbed
Mouthparts Chewing Chewing Piercing-sucking
Wing position at rest Elytra close to create a straight line down the middle of the back Wings directly overlap on the back Wings gently overlap on the back or may appear roof-like

Adult aphids, mealybugs, psyllids, scales, whiteflies, and sharpshooters are often confused for one another. Several characteristics can be used to differentiate each group.

Aphids Mealybugs Psyllids Scales Whiteflies Sharpshooters
Body Shape Pear-shaped with two dark tubes protruding from the rear of the abdomen Oval or round with lateral appendages Elongate, oval Round and plump Elongate upside-down heart shape with a rounded tip Pointed projectile shape
Body Covering Dusty, dried honeydew Dusty, dried honeydew Dusty, dried honeydew Varies - waxy or covered with cotton-like filaments Dusty, dried honeydew Dried whitewash cover
Antennae Thread-like (filiform) Short, multi-segmented Short, bristle-like Short, segmented or reduced to stubs Thread-like (filiform) Short, bristle-like
Wings Translucent and membranous Membranous and clear Membranous and either clear or mottled Membranous and clear Dusty, membranous, and matches the body color Membranous and mostly clear, but partially spotted

Diagnostic characteristics

 
Adults
  • Smallest - 0.09 mm (0.04 in.).
  • Largest - 14 mm (0.55 in.).
  • Body color varies. Either monochrome from pink to black or multi-colored with a mottled appearance.
  • Piercing-sucking mouthparts present. Scales, whiteflies, and aphids have mouthparts arising from between the front legs. Sharpshooters have mouthparts arising from the posterior margin of the head.
  • Multi-segmented antennae are either uniform in color, shaded dark at the tips or base, or have alternating dark bands throughout the length. Mealybug and scale antennae are difficult to see without a microscope.
  • If winged (alate), psyllids, aphids, and whiteflies have one pair of forewings and hindwings that are held tent-like above the body when at rest.
  • When legs are present, scales, whiteflies, psyllids, and aphids have 1- or 2-segmented feet (tarsi). Sharpshooters have 3-segmented tarsi.
  • Psyllids have stouter hind legs than front legs. Mealybug and scale legs are difficult to see without a microscope.
Pupae

Hemipterans do not undergo true metamorphosis as characterized by a true pupal phase in between a larval and adult phase. The majority of hemipterans have juveniles termed nymphs that look similar to adults with the only change being external wing development as they mature. However, whiteflies and the males of certain mealybug and scale species do go through a radical developmental change to emerge as winged adults. This inactive developmental stage is termed a pupa.

  • Smallest - 0.7 mm
  • Largest - 1.5 mm
  • Flat, oval, round, or scale-like in shape.
  • Mostly uniform in color from black to orange-yellow.
  • Pupal edges may be translucent, smooth, or fringed in appearance.
Immatures
  • Smallest - 0.028 mm (0.001 in.).
  • Largest - 9 mm (0.35 in.).
  • Typically 3 - 5 nymphal instars.
  • Body shape varies between oval and flattened (dorso-ventrally compressed) or round and plump (rotund).
  • Mostly uniform in color from translucent to dark brown.
Eggs
  • Smallest - 0.3 mm (less than 0.1 in.).
  • Largest - 0.32 mm (less than 0.1 in.).
  • Opaque, yellow-white.
  • Several species of scales and mealybugs do not lay eggs but bear live young called crawlers.
  • Scale eggs may be underneath females or in a cotton-like egg sac called an ovisac.
  • Smooth, flattened, cigar-shaped (elliptical) or oval.

Hosts

 
Citrus hosts

Several species of hemipterans can feed on all citrus species and their hybrids, including the cottony cushion scale, Seychelles scale, coffee mealybug, pink hibiscus mealybug, and glassy-winged sharpshooter. See individual fact sheets for more detailed information.

Non-citrus hosts

Hemipterans have a broad host range that includes weeds as well as vegetables and field and flower crops. See individual fact sheets for more detailed information.

Host damage

 
Flowers
  • Adults and nymphs reduce the number of flowers present by feeding on flowers.
Fruit
  • Heavy infestation can lead to fruit pitting or fruit drop.
  • Honeydew excreted by hemipterans can coat the fruit skin thereby promoting sooty mold fungus growth. Fruit may appear black, moldy, and unattractive.
  • Reduced fruiting and production can also occur when pest densities are high.
Leaves
  • Honeydew excreted by hemipterans can coat leaves and inhibits photosynthesis, which weakens the host plant.
  • Newly infested leaves turn yellow from feeding and may drop.
  • Some hemipterans inject toxins during feeding which leaves a yellow spot around feeding areas.
Roots
  • Adults and nymphs can infest roots and extract essential nutrients away from the host plant.
Twigs
  • During heavy infestation, twigs and limbs can die back.

Biology

 

Females either lay eggs or bear live young called crawlers. During the first two instars, crawlers and newly hatched nymphs are mobile and feed on leaves, fruits, and stems by using their piercing-sucking mouthparts. After the third instar, several species of hemipterans become stationary and affix themselves to the leaves and fruit. Aphid, psyllid, and sharpshooter nymphs mature directly into adults. Whiteflies and certain species of scales and mealybugs undergo pupation. Adults emerge, resume feeding, and exude a highly concentrated sugary substance called honeydew. Ants utilize honeydew as a food resource. Therefore, populations of these insects are often protected by ants from natural enemies.

Comments

 

The adult female life stage is typically used for accurate scale and aphid identification.

The pupal life stage is most important for whitefly identification.

References

 

Davies, F. and L. Jackson. 2009. Pest disease and weed management for the bearing grove, pp. 204-221. In Citrus growing in Florida. 5th ed. University of Florida Press. Gainesville, Florida.

Smith, D., G.A. Beattie, M. Malipatil, D. James, D. Papacek. J. Altmann, A. Green, B. Woods, G. Furness, C. Freebairn, M. Stevens, G. Buchanan, D. Madge, C. Feutrill, J. Kennedy, B. Gallagher, P. Jones, R. Broadley, M. Edwards, G. Baker, S. Dix, P. Burne, B. Frost, J. Watson, M. Pywell. 1997. Citrus pests and their natural enemies: Integrated pest management in Australia. Desert Oak Publishing Services. Brisbane, Australia.

Triplehorn, C. and N. Johnson. 2004. Hemiptera pp. 268- 273. In Borror and DeLong's Introduction to the study of insects. 7th ed. Brooks/Cole Cengage Learning. Belmonte, California.

Authors

 

Guerrero, S., J.A. Weeks, and A.C. Hodges

 

Citrus Pests
Content last updated June, 2012
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