BROWN CITRUS APHID (BCA): Toxoptera citricida (Kirkaldy) Order - Hemiptera: Family - Aphididae

DISTRIBUTION : Southeast Asia, Africa south of the Sahara, Australia, New Zealand, the Pacific, South America, the Caribbean and most recently Florida.

DESCRIPTION: There are no eggs because ♀s give birth to live young. Nymphs (Fig 3) are dark reddish-brown. All aphids have a pair of upward and backwardly pointing tubes on the bottom of the abdomen called cornicles (sphunculi). BCAs are slightly larger (3.2 mm) than other aphids found on citrus. Winged adults (alatae – Figs 1 and 2) are black with yellow and black striped legs. They have conspicuous black antennal segments I, II, and III. All BCAs in the US are ♀ and parthenogenetic (they may develop an embryo without fertilization by a ♂). Adult (capable of reproducing) wingless forms (apterae) are very shiny black (Figs 3 and 4).

HOSTS: Citrus and other closely related Rutaceae are preferred. It is possible that they reproduce only on these plants; however, BCA has been associated (possibly feeding) on 26 other families of plants.

DAMAGE: BCA can feed on young citrus foliage, depleting sap. They also produce honeydew that allows sooty mold to grow. More damaging, the BCA is an efficient vector of the citrus tisteza virus (CTV). BCA is 6 to 25 times as efficient as melon aphid in spreading CTV. Disastrous epidemics of CTV have occurred in Argentina, Brazil, Colombia and Peru following introduction of BCA.

INSPECTION TIPS: Look for large aphid populations on new growths of citrus feeding on leaf midribs and green stems. Field identification can be difficult because other regularly collected species of aphids can be dark in color and colonize new growth (Fig 5). Additionally, mixed colonies of two or more aphid species are common. Collect colonies for microscopic examination. Winged forms are more easily identified but they have a tendency to leave the colony soon after they emerge.

LIFE CYCLE: BCA are all ♀ (adult form winged and wingless)producing live young (nymphs) that develop into adults. The mean generation time in Florida ranges from 8-51 days depending upon environmental factors and host plant. BCA prefers to feed on newly developed terminals including unexpanded and young leaves (Fig 5) and flower buds of citrus. As a result, the maturity and dispersal of colonies in citrus coincides with the hardening of shoots. Large developing populations are generally associated with citrus flushes (summer, fall, spring), which may only last a week or two. Once the tissue becomes unfavorable for feeding, the colonies produce alate (winged) adults for dispersal. The remaining nymphs either die or leave searching for other branches or trees. Nymphs may move from one tree to another by crawling to a distance of up to 8-12 m. BCA is not a strong flyer. Wind currents aid long distance dispersal

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