Ambrosia Beetles

Scientific Name: Platypus spp. (Insecta: Coleoptera: Platypodidae)

Introduction:

The family Platypodidae includes approximately 1,000 species, most of which are found in the tropics (Schedl 1972). Seven species of platypodids, all in the genus Platypus, are found in the United States, four of which occur in Florida. All species found in Florida are borers of trunks and large branches of recently killed trees and may cause economic damage to unmilled logs or standing dead timber. The most recent key to species was published 60 years ago (Chamberlin 1939), does not include all species known from the United States (Wood 1979), and has long been out of print.

Identification:

The Platypodidae are closely related to the Scolytidae, but can be distinguished by the elongate body form, short abdomen (shorter than metathorax in lateral view), and elongate first tarsal segment which is longer than the remaining segments combined. Males of all species have more developed armature [spineous or chitinous processes] of the elytral declivity [sloping area] than females.Females of species occurring in Florida lack terminal spines on the elytra except for Platypus flavicornis (Fabricius) which has blunt projections. Females of all species have larger maxillary palpi and a larger gular region than males. [See figures displaying ventral view of heads.]

Key to Species of Platypus of Florida :

1. Male declivity with large acuminate process arising from interstria 9 on posterolateral margins of elytra; interstria 3 continuing posteriorly as a spinose process, interstria 1 not elevated; female declivity with blunt projection at apex of interstria 3 or at apex of interstria 9, apical margin of declivity straight, not explanate (spread out and flattened) . . . . . 21' Male declivity with large blunt process arising from interstria 9 on posterolateral margins of elytra ending in three terminal spines; interstria 1 continuing posteriorly as a spinose process, interstria 3 not elevated or conspicuously less so than 1; female declivity blunt, without projecting apical tubercles or processes, apical margin of declivity shallowly divaricate (forked) at suture, slightly explanate.

2. Male declivity with prominent spines on venter of third visible abdominal segment, posterolateral processes of declivity laterally compressed; female declivity without apical projection of posterolatreal area of elytra; female pronotum with pair of large conspicuous pores in middle. Southeastern U.S. In oaks quadridentatus (Olivier) 2' Male declivity without spines on venter of abdomen; posterolateral processes of declivity acute, not compressed; female declivity with blunt posterolateral projections on elytra, less acute than those of male; female pronotum without conspicuous pores. Southeastern U.S. In pines flavicornis (Fabricius).

3. Pronotum of both sexes with a pair of tiny pores in middle; male elytral stride shallowly impressed, interstriae 3 times as wide as striae at base of declivity. Southeastern U.S. Neotropics compositus (Say). 3' Pronotum without conspicuous pores in either sex; male elytral striae deeply impressed, subequal in width to interstriae at base of declivity. Southern Florida. Circumtropical parallellus (Fabricius).

Biology And Behavior:

All species are ambrosia beetles and generally breed in large diameter host material. Galleries are initiated by males; each male is joined by a single female. Apparently pheromones are produced and large numbers of simultaneous attacks are frequently observed. Mated pairs tunnel into the heartwood and introduce ectosymbiotic fungi into their tunnels upon which they and their brood feed. For the most part the wood is not actually consumed. Larvae move freely inside the parental tunnels and excavate individual pupal cells off the main tunnels. Adults emerge through the original entry hole. Platypodids can only breed in undegraded, recently killed host material, with a high moisture content. Decaying wood or wood which has dried out is unsuitable. Normally, only a single generation can be produced in a given host. Platypus flavicornis and P. quadridentatus are respectively restricted to pines and oaks. Platypus compositus and P. parallelus are extremely polyphagous and will breed in most trees within their ranges. These latter two species are commonly attracted to light.

Damage:

Female beetles bore into the trunks and branches (1.0-2.5 inches in diameter) of young trees and excavate galleries in the heartwood. In addition to boring damage, female beetles inoculate trees with ambrosia fungus which can block xylem vessels and interfere with vascular transport. In addition they can introduce or create entry points for pathogenic fungi such as Fusarium spp. Infested plants often die from boring damage, ambrosia fungus, or infection by a secondary pathogen.
Although tree health likely plays a role in susceptibility to these beetles, little is known about how trees are selected by female granulate ambrosia beetles. They attack seemingly healthy trees as well as stressed or unhealthy trees. Visible symptoms include wilted foliage and strands of boring dust protruding from small holes. Serious attacks that result in tree death usually occur during leafing-out stage.
Infested nursery stock typically dies or is unmarketable and should be burned or chipped to prevent new adults from emerging. Landscape trees may survive attacks but should be monitored for dieback and removed if necessary.

Control:

Preventative applications of pyrethroid insecticides can protect trees by preventing Granulate Ambrosia Beetles from excavating galleries. However, once beetles are inside trees they cannot be killed with insecticides and fungicides are ineffective against the ambrosia fungus. Thus, the timing of preventative insecticide applications is crucial to protect trees from damage by this pest. Apply sprays after beetles are first detected in monitoring traps.
Heavily infested plants or plant parts should be removed and destroyed. It may be best for large growers to wait 3-4 weeks after trees are attacked before removal so as to concentrate and destroy the greatest number of beetles, possibly sparing some healthy trees.