The effort to manage the Mexican bromeliad weevil began over a decade ago, as the effects of the weevil on Florida's bromeliads began to be evaluated. Knowledge of the weevil's biology and habits was minimal, and the development of a biological control project against the weevil has required several preliminary studies, some of which are ongoing.

1.) Tracking of the spread of the weevil throughout south Florida:

Surveys were conducted for weevil presence and damage beginning in 1991, when 23 larvae, 32 pupae and 22 adults were collected and damage was observed in several Broward County parks (Tree Tops Park, Secret Woods Nature Center, Easterlin Park, Parks HQ, Tradewinds Park, Fern Forest Nature Center). On various trips in 1991-1993, several places known to have large populations of native Tillandsia spp. bromeliads were visited in Palm Beach, Broward, Miami-Dade, and Monroe counties. Early sightings from Lee County were also investigated. Since then, several trips have been taken each year to both southeast and southwest Florida to monitor the spread of the weevil.

2.) Documentation of the Mexican origin of the weevil:

Bromeliad importers and growers were interviewed, and lists of intercepted plant pests published by USDA-APHIS were examined to evaluate the possibility that the weevil escaped detection by plant inspectors. In July of 1992, a survey was carried out in Veracruz, Mexico, the place of the first record of the weevil. The weevil was found to be uncommon in natural areas. Largest numbers were collected from the shadehouses of a Veracruz bromeliad grower. Given the lack of weevil presence in other parts of what had been considered its natural range, it is very likely that the weevil entered Florida on an infested plant(s) imported from Veracruz, Mexico.

3.) Documentation of the native Florida bromeliads that have already been attacked:

As a result of reporting the weevil damage to Tillandsia utriculata, Tillandsia fasciculata, Tillandsia paucifolia, Tillandsia flexuosa, and Tillandsia balbisiana, the first 2 species were listed by the state as endangered plant species, offering them certain protection under Florida state law.

4.) Study of the hostplant range of the weevil by documenting the genera of bromeliads that the weevil is capable of attacking:

Commercially grown exotic bromeliads were exposed to weevils in a greenhouse and examined for weevil damage. The weevil was found to attack cultivated bromeliads of 13 genera in Florida: Aechmea, Ananas, Canistrum, Cryptanthus, Dyckia, Guzmania, Hohenbergia, Neoregelia, Nidularium, Orthophytum, Quesnelia, Tillandsia, and Vriesia.

5.) Study of the weevil's biology, and development of laboratory rearing methods:

During 1998, Jorge Salas, a post-doctoral researcher from FONAIAP, in Venezuela, studied the weevil's biology and development in Florida. Field-collected weevils were first reared on Tillandsia utriculata plants. Two kinds of commercial artificial insect diet were tested, a diet for rearing black vine weevil (Otiorhynchus sulcatus) and one for rearing boll weevil (Anthonomus grandis). When reared on artificial diet, the larvae must be placed individually in small plastic containers, because they will attack each other when coming into contact. (In large plants in the field, many larvae can develop in the same plant without contacting each other, and up to 25 individuals (eggs, larvae and pupae) have been found in a single plant). The black vine weevil diet was found to be more effective than the boll weevil diet, and the addition of an extract of blended Tillandsia utriculata leaves to the diet did not increase weevil survival.

About one-quarter of Mexican bromeliad weevil larvae reared on the black vine weevil diet do not survive. The greatest limiting factor for the diet, however, is that very small larvae do not survive on it. An artificial oviposition substrate has not yet been found, so plants must still be provided for weevils to lay eggs on and for small larvae to eat before being transferred to the artificial diet. The most cost-effective rearing method has been found to be the establishment of a colony in two greenhouses filled with pineapple tops planted in soil. The weevils are currently being reared in that way.

All life stages of the weevil (egg, larva, pupa and adult) may be found on the same plant. Females lay eggs in slits they make at the base of leaves, close to where they feed. After hatching from the egg, the young larvae eat through the leaf tissue, making their way down to the stem. As they grow, larvae tunnel into the base of the plant, forming large holes. When fully developed, the larva constructs a cocoon from shredded stem material, within which it passes the pupal stage.

The weevil's development time was measured under laboratory conditions to estimate how fast it may complete its life cycle in the field. When reared on pineapple in the laboratory, it was found to develop from egg to adult in about 8 weeks. In south Florida, the weevil apparently continues to mate and reproduce throughout the year. Each generation is estimated to take 13-17 weeks to complete, so there are probably 3-4 generations each year in south Florida. Development times of the Mexican bromeliad weevil are detailed in a recent paper, "Development of Metamasius callizona on Pineapple Stems" (available in PDF format), published in Florida Entomologist.

6.) Explorations in Mexico, Honduras, Panama and Guatemala for the weevil and its natural enemies:

Mexico, July 1992: Howard Frank and Mike Thomas found 54 weevils in a grower shadehouse on Mexican bromeliads. Other than on cultivated bromeliads, the weevil was found only in Tillandsia spp. (mainly Tillandsia utriculata) in shade trees in coffee plantations near Coatepec. In general, it was seen to be very uncommon in natural areas. No potential biological control agents were found.

Mexico, April - Sept. 1995: The weevil was very uncommon. Cactophagus validirostris and Metamasius flavopictus were found to attack bromeliads. No potential biological control agent was found.

Panama, June 1994: Howard Frank and Al Muzell found no weevils in the province of Chiriquí, from which an early record of the weevil exists. Also, no specimens of the weevil are housed at the Smithsonian Tropical Research Institute in Panama City, despite many specimens of other Metamasius species. Therefore, the early record from Panama is considered questionable, being more likely that the weevil's natural range extends only from southern Mexico to Guatemala

Guatemala, June-August 2000: Barbra Larson searched natural bromeliad populations in the departments (states) of Alta Verapaz and Baja Verapaz, since an early record of the weevil reports it from Alta Verapaz. No Mexican bromeliad weevils were found, although very low populations of Metamasius quadrilineatus were found, as well as 1 adult each of Metamasius rugipectus and Metamasius dimidiatipennis. No potential biological control agent was encountered, except for 1 Metamasius quadrilineatus larva parasitized by the same Lixophaga sp. fly found in Honduras (the current candidate biological control agent).

7.) Study of the potential biological control agent found in Honduras:

8.) Importation of the potential biological control agent to quarantine in Gainesville:

Two attempts to establish a colony of Lixophaga (in early 2000 and 2001) in Florida have failed. Rearing difficulties during the first year were exacerbated by failure of temperature control equipment in the quarantine facility. During the second year, after some modification of rearing methods, many more weevils were parasitized. However, most fly pupae failed to emerge as adults, probably because of imadequate humidity conditions. All of the adult flies that emerged were males.

Developing rearing methods for insects with limited knowledge of their biology requires additional time and resources. With what has been learned during the first two importation attempts, rearing success is more likely the next time the flies are imported. One important finding during attempts to establish a colony is that under laboratory conditions the fly does attack the Mexican bromeliad weevil in Tillandsia utriculata plants.

9.) Development of colonies of related weevil species for non-target testing:

Before a release permit is issued to allow a biological control agent to be removed from the quarantine facility and released in nature, results of non-target testing must demonstrate that its release will have no detrimental effects on any native species. There are only two other species of Metamasius weevils in Florida, and non-target testing will begin with them. If the biological control agent attacks neither Metamasius hemipterus (silky cane weevil), an immigrant pest that attacks sugarcane and bananas in south Florida, nor the native Metamasius mosieri (Florida bromeliad weevil), further host range testing will not be necessary.

Colonies of both of these species were developed and are being maintained for use in non-target testing of the fly. In addition, a colony of Mexican bromeliad weevil is maintained for research and future fly rearing.

See Steps to Manage the Mexican Bromeliad Weevil Through Classical Biological Control for the additional activities that need to be completed.