Bryan J. Ulmer

TOXICITY OF PESTICIDES USED IN CITRUS TO APROSTOCETUS VAQUITARUM (HYMENOPTERA: EULOPHIDAE), AN EGG PARASITOID OF DIAPREPES ABBREVIATUS (COLEOPTERA: CURCULIONIDAE)

Abstract Twelve pesticides used in citrus were tested for their contact toxicity to Aprostocetus vaquitarum Wolcott (Hymenoptera: Eulophidae) a parasitoid of Diaprepes abbreviatus (L.) (Coleoptera: Curculionidae). Sevin® 80 WSP, Malathion 5 EC, and Imidan® 70 WSB resulted in the most rapid death of A. vaquitarum adults. Admire® 2F, Danitol® 2.4EC, and Surround® WP were also very detrimental. Kocide® 101 WP, Citrus Soluble Oil, Micromite® 80 WGS, Acramite® 50 WS, Micromite® 80 WGS + Citrus Soluble Oil, Aliette WDG, and Agrimek® 0.15 EC + Citrus Soluble Oil were slightly to non-toxic to A. vaquitarum. The relative toxicity of the pesticides was consistent up to four weeks after application. Significantly fewer adult A. vaquitarum emerged from D. abbreviatus eggs laid on foliage treated in the field with Sevin® XLR and Imidan® 70 WSB than emerged from the water treated control. Field residues of Sevin® XLR remained toxic for seven days while the effects of Imidan® 70 WSB were no longer significant after one week. The number of A. vaquitarum adults emerging from host eggs laid on treated foliage was not significantly different among Micromite® 80 WGS, Acramite® 50 WS, and the control, but significantly fewer adults emerged from foliage treated with either Micromite® 80 WGS + Citrus Soluble Oil or Citrus Soluble Oil alone. There were no significant differences between oviposition or new generation adults when A. vaquitarum was exposed to Micromite® 80 WGS or a water control.

Thermal requirements of Fidiobia dominica (Hymenoptera: Platygastridae) and Haeckeliania sperata (Hymenoptera: Trichogrammatidae), two exotic egg parasitoids of Diaprepes abbreviatus (Coleoptera: Curculionidae)

Diaprepes abbreviatus is an exotic root weevil occurring in southern US. It is a highly polyphagous species which can complete its entire life cycle on citrus and several woody ornamental plants. The lack of native egg parasitoids for this weevil in citrus orchards has triggered efforts to evaluate candidate egg parasitoids from the Caribbean Region into Florida. The egg parasitoids Fidiobia dominica and Haeckeliania sperata are two exotic natural enemies of D. abbreviatus recently introduced in the US in a classical biological control program. The thermal requirements of both parasitoids were studied in the laboratory. The upper development threshold (UDT) of F. dominica was 30.0°C, its maximal development rate (MDR) occurred at 27.6°C, its lower development threshold (LDT) was 9.6°C and its thermal constant (K) for development from egg to adult was 293.1 DD. For H. sperata, UDT was 35.0°C, MDR occurred at 31.0°C, LDT was around 15°C and K was 188.1 DD. Based on these results, both species would be able to complete 17 to 18 generations annually in southern Florida. However, host availability during critical periods could severely impair the ability of these egg parasitoids to establish and successfully control D. abbreviatus in areas where winter temperatures fluctuate around 12°C, the LDT for this pest.

Life history and larval morphology of Eurhinus magnificus Gyllenhal (Coleoptera: Curculionidae), a new weevil to the United States

Eurhinus magnificus Gyllenhal has been collected in south Florida, presumably introduced through trade with countries in its native range. Very little information has been published on the biology or taxonomy of this insect. We conducted studies to investigate various aspects of its life history and host plant associations. The pre-imaginal life stages of E. magnificus are described for the first time. Dimensions of the adult, egg, larval, and pupal stages are also provided; head capsule measurement revealed five larval instars. All life stages of E. magnificus were collected at several sites in Broward and Miami-Dade counties from the host plant Cissus verticillata (L.) Nicolson & Jarvis (Vitaceae). Eggs were laid singly within the succulent, young subterminal portion of the host plant stem, one or two occurring between two nodes. Gall formation was apparent by the first to third instar and continued to increase in size until pupation which occurred within the gall. Predators and pathogens appeared to be responsible for considerable mortality in the field; there was no evidence of parasitism of any of the life stages. Greenhouse studies were undertaken to determine E. magnificus development time and host specificity. Adult weevils attacked grape cultivars (Vitis spp.) and feeding opened the stems to fungal agents but no physical evidence of larval development was apparent on grapes.

THE OCCURRENCE OF PARASITOIDS ATTACKING CITRUS WEEVIL EGGS ON SAINT LUCIA

Three species of hymenopteran egg parasitoid were found attacking citrus weevil (Diaprepes abbreviatus, Litostylus pudens, D. boxi and Oxyderces cretaceous) eggs in the island of St. Lucia, Florida, USA: Haeckeliania sperata, Baryscapus fennahi and Quadrastichus haitiensis. Overall, 12% of the citrus weevil egg masses found in the island were parasitized. Numerous egg masses were also consumed by an unidentified predator. Citrus weevils and their egg parasitoids were more abundant within pure stands of citrus than when citrus was grown as part of a polyculture with other crops, such as banana. In the laboratory, B. fennahi accepted D. abbreviatus eggs on citrus and Conocarpus erectus. The late instar feeding habit and pupation of B. fennahi resembled that of an ectoparasitoid. H. sperata also accepted D. abbreviatus eggs on citrus and C. erectus.

Reproductive Biology of Fidiobia dominica (Hymenoptera: Platygastridae), an Egg Parasitoid of Diaprepes abbreviatus (Coleoptera: Curculionidae)

Abstract The reproductive biology of Fidiobia dominica Evans (Hymenoptera: Platygastridae) was studied in the laboratory (25.6 ± 1°C) using host eggs of Diaprepes abbreviatus L. (Coleoptera: Curculionidae). F. dominica readily parasitized D. abbreviatus eggs on both host plant and wax paper substrates. The number of egg masses parasitized and the number of offspring produced were higher when females were offered more than one host egg mass but did not differ when either two or three egg masses were offered. Female parasitoids that were provided with host eggs and a honey food source lived significantly longer than those that were not provided a food source; however, they did not parasitize more D. abbreviatus eggs. Oviposition occurred in host eggs from 0 to 7 d old, and host mortality was relatively consistent for eggs 0–5 d old and lower for eggs 6–7 d old. Successful parasitoid emergence seldom occurred after host eggs were 4 d old, and by 7 d, no adults successfully emerged. Developmental time from egg to adult was 19.3 ± 0.2 d for males, significantly more rapid than the females (20.4 ± 0.1 d). The mean longevity of adult females was 8.0 ± 0.4 d, with a mean oviposition period of 2.7 ± 0.3 d; males survived 8.1 ± 0.4 d. The demographic parameters including intrinsic rate of increase (rm), generation time (T), and net reproduction (Ro) were 0.142/d, 22 d, and 22.4 female eggs/d, respectively.

Biological Control with Egg Parasitoids other than Trichogramma – the Citrus and Grape Cases

Egg parasitoids of economic significance are found in the families Trichogrammatidae, Mymaridae, Scelionidae and Platygastridae. Research on egg parasitoids other than Trichogramma has increased at a slower level during the last 15 years. For instance, the last International Organization of Biological Control review on egg parasitoids summarizing references from 1997 to 2003 listed 77 references on Trichogrammatidae, 50 on Mymaridae, 72 on Scelionidae and none on Platygastridae (Table 13.1). Within the Trichogrammatidae, 94% of these references are on the genus Trichogramma, 1% on the genus Brachyufens and 5% on the genus Uscana and none on Haeckeliania (Herz et al. 2003). Moreover, from the late 60s through mid 2004, Agricola (2003) cites a total of 219 publications on the Trichogrammatidae; of these, 86% are references on the genus Trichogramma, 0.4% on Brachyufens, 0.4% on Chaetogramma Doutt, 8% on Oligosita , 3.6% on Megaphragma , 0.8% on Ufens , 0.8% on Zagella and none on Haeckeliania (Table 13.2). The major objective of this chapter is to discuss biological control of root weevils affecting primarily citrus and biological control of cicadellids affecting grape with egg parasitoids other than Trichogramma.

Egg Parasitoids of Citrus Weevils in Guadeloupe

To determine parasitism and mortality factors affecting citrus weevils in Guadeloupe an explor atory trip to the island was taken in the summer of 2006. Guadeloupe was surveyed for egg parasi toids and other natural enemies with the intent of augmenting the parasitoid species that have al ready been imported and released to control the citrus root weevil, Diaprepes abbreviatus (L.) (Co le?ptera: Curculionidae), in Florida. Diaprepes abbreviatus has been a serious economic pest of citrus and ornamentals in Florida since it was dis covered in the mid 1960s (Woodruff 1964); in re cent years it has also established in Texas (Skaria & French 2001) and has been found in California (Grafton-Cardwell et al. 2004; Anonymous 2005). Efforts to establish biological control agents of the weevil are ongoing and to date include releases of 5 egg parasitoids attacking D. abbreviatus throughout the Caribbean. Quadrastichus hai tiensis Gahan (Hymenoptera: Eulophidae) was imported from Puerto Rico, Aprostocetus vaquita rum Wolcott (Hymenoptera: Eulophidae) from the Dominican Republic, Ceratogramma etiennei Del vare (Hymenoptera: Trichogrammatidae) from Guadeloupe (Hall et al. 2001; Pe?a et al. 2004), Fidiobia dominica Evans and Pe?a (Hy menoptera: Platygastridae), and Haeckeliania sperata Pinto (Hymenoptera: Trichogramma tidae) from Dominica (Jacas et al. 2008). Although Q. haitiensis and A. vaquitarum have established in extreme southeastern Florida (Miami-Dade and Broward counties) following multiple re leases since 2000 (Pe?a et al. 2004), these species have not expanded their range into central Flor ida (Castillo et al. 2005; Ulmer et al. 2006a). Cer atogramma etiennei thrived in the first year after multiple releases near Homestead, FL in 1998 but subsequently failed to establish in the state (Hall et al. 2002; Pe?a et al. 2004). The lack of establish ment of introduced egg parasitoids outside of the extreme southeast region of the state has been linked to climactic conditions as well as pesticide use and seasonal host availability (Hall et al. 2002; Castillo et al. 2005; Ulmer et al. 2006a, 2006b). Fidiobia dominica and H. sperata were recently released in southern Florida and the re sults of these releases have yet to be determined. Most of the citrus growing regions in Guade loupe are in Basse Terre, the western half of the country. In this area citrus is grown at higher el evations (382 m) that experience slightly lower temperatures. It is possible that parasitoids found attacking D. abbreviatus in this area would be more likely to survive and expand into the cooler regions of Florida. On this trip we surveyed the islands citrus growing regions to evaluate the mortality factors and parasitoid species associ ated with citrus weevils. Eight locations were surveyed on 19-22 Jun 2006. Depending on the size of the grove, 2 people spent 0.5 to 5 h collecting egg masses at each site, and some fields were surveyed more than once. Egg masses were saved in plastic vials in the field, then trimmed and transferred to glass vials each evening as per Ulmer et al. (2006c). Egg masses were hand carried in an insulated box to the quarantine facility at the Tropical Research and Education Center (USDA-APHIS PPQ form 526, permit no. 68313), Homestead, FL. Citrus weevil eggs were collected from 5 of 8 sites surveyed on the island and parasitism was observed at 4 of those 5 sites (Table 1). All sites at which weevil eggs were found were stands of pure citrus rather than mixed plantings with other fruit crops. In total 236 egg masses were collected; 20 egg masses were not included in the data (Ta ble 1) because they were overcome by fungal pathogens. Only egg masses for which every host egg could be accounted for are included in Table 2, thus some egg masses, which are included in Ta ble 1 are not included in Table 2. The majority of the egg masses collected were from a single low elevation site; however, several egg masses were also collected from the higher elevation sites (Ta ble 1). A total of 3060 parasitoids emerged from the egg masses collected and 82% of the egg masses collected on Guadeloupe were parasitized by at least 1 species. This is substantially higher than the 12.0% found by Ulmer et al. (2006c) on St. Lucia, but comparable to the 87% found para sitized in Belize by Hall et al. (2002). Adults of 3 weevil species were collected dur ing the trip: Diaprepes abbreviatus, Famelicus sp., and Litostylus sp. Adults of D. abbreviatus were found at all the sites where parasitism oc curred but mixed weevil populations were evident at most sites. Though the adults collected were predominantly D. abbreviatus, it is likely that some of the egg masses collected were deposited by other weevil species associated with citrus. Etienne & Delvare (1991) reported Aprostoce tus sp., Aprostocetus gala (= A. vaquitarum), Aprostocetus haitiensis (= Quadrastichus haitien sis), and Ceratogramma etiennei in Guadeloupe.