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We report here that it is possible to rear D. areolatus on irradiated A. suspensa larvae without adversely affecting sex ratio and overall parasitoid emergence and with no adult A. suspense emergence. There was no difference in emergence of D. areolatus adults from irradiated versus non-irradiated hosts (72.4 ± 1.9% vs. 73.0 ± 1.9%), and no difference in sex ratio of parasitoids obtained from irradiated and non-irradiated hosts (50.0 ± 1.6 and 47.0 ± 1.4% female, respectively). The successful use of A. suspensa larval hosts can greatly ease the process of rearing, transporting, and releasing fruit fly parasitoids while eliminating the need to separate flies from parasitoids. Further improvements in the laboratory rearing process of D. areolatus, including irradiating late A. suspensa larvae at a lower dosage and irradiating A. suspensa as egg or early instars, are discussed.
Field and laboratory experiments were conducted to determine resistance of cotton Gossypium hirsutum L. cultivars differing in leaf morphology (shape and pubescence) to the B biotype of sweetpotato whitefly Bemisia tabaci (Gennadius) and impacts on its parasitoids. Five cotton cultivars were evaluated in a field-plot experiment at Hastings, Florida. The pubescent cultivars, DP DES 119 and Stoneville 453, were significantly hairier than moderately hairy okra-leaf cultivar, Gumbo 500, and smooth-leaved cultivars NU COTN 33B and DP 51. There were significant differences among cultivars in eggs laid on the second and fifth node leaves. DP DES 119 and Stoneville 453 had greater numbers of whitefly eggs than did the glabrous cultivars. The okra-leaf cultivar, Gumbo 500, had greater numbers of eggs than the 2 glabrous varieties. There were significant differences among cultivars in numbers of first and second instars (young instars), third instars, unparasitized fourth instars and red-eyed nymphs on fifth node leaves, with higher populations occurring on pubescent cultivars and lower populations on glabrous cultivars. The abundant parasitoids were Encarsia pergandiella Howard, Encarsia nigricephala Dozier and Eretmocerus spp., however parasitism did not differ among the cultivars. The responses of Eretmocerus rui Zolnerowich & Rose and Encarsia formosa Gahan (Nile Delta strain) (Hymenoptera: Aphelinidae) as a function of density of the host were investigated in laboratory experiments on 3 cotton cultivars differing in leaf pubescence and shape (DP 51, DP DES 119, and Gumbo 500). Eretmocerus rui showed a type II functional response to second instars of the host with the mean number of parasitized hosts increasing as host density increased on all 3 cultivars. Encarsia formosa showed a type II functional response to fourth instars, where the number of hosts parasitized increased up to a density of 16 but remained constant for 32 and 64 hosts. Significantly more whiteflies were parasitized by both E. formosa and E. rui on DP 51, the smooth-leaved cotton cultivar, than on the hairy cotton cultivars. We conclude that glabrous cotton cultivars are likely to support lower whitefly populations than pubescent cultivars because of reduced whitefly oviposition and increased parasitoid foraging efficiency.
We analyzed the volatiles emitted by Mexican populations of the female coffee leafminer moth Leucoptera coffeella that were collected in coffee plantations located in the Soconusco region of Chiapas. Our results confirmed previous results that L. coffeella females emitted 5,9-dimethylpentadecane as the major and 5,9-dimethylhexadecane as the minor component. Field response of the coffee leafminer moth to stereoisomers of the major component showed that delta traps baited with (5S,9R)-dimethylpentadecane caught a significantly greater number of coffee leafminer males when compared to those captured by traps baited with (5R,9R)-dimethylpentadecane, (5R,9S)-dimethylpentadecane and the control. The number of coffee leafminer captured by traps baited with (5S,9S)-dimethylpentadecane was not significantly different from the number captured by traps baited with (5R,9R)-dimethylpentadecane. The results are discussed in view of the possibility of using stereoisomers as bait for monitoring the leafminer moth.
The predatory mite Phytoseiulus macropilis Banks (Acari: Phytoseiidae) is native to Florida. Some biology and ecology of this phytoseiid have been documented, but its potential as a biological control agent of phytophagous mites (Acari: Tetranychidae) has received less attention. The response of P. macropilis to 12 acaricides, 3 tetranychid mite species and 5 potential alternate foods was evaluated in laboratory bioassays. Pesticide residual effects on P. macropilis were evaluated by a double-disk leaf residue method. The synthetic pyrethroids Tame (fenpropathrin), Cymbush (Cypermethrin) and Mavrik (fluvalinate) were highly toxic. Tolerance was observed to the acaricides, Omite (propargite), and Avid (abamectin), while Vendex (hexakis), Pentac (dienochlor), and Kelthane (dicofol) were highly toxic. The insecticides Orthene (acephate) and Diazinon and the fungicides, Domain (thiophanatemethyl) and Cleary (thiophanate) were not toxic to P. macropilis. Field efficacy tests of fenpropathrin and dicofol indicated that these chemicals lose toxicity to P. macropilis 21 and 7 d after application, respectively. In olfactometer bioassays, female predators were attracted to kairomones produced by their rearing host Tetranychus urticae Koch on bean leaves but not to kairomones of the tetranychids Oligonychus ununguis (Jacobi) and T. evansi Baker and Pitchard on their respective host plants. Predators did not respond significantly to selected alternate foods: pollen from the hybrid daylily Hemerocallis spp., Phylloxera spp. larvae, eggs of false oleander scale Pseudaulacaspis cockerelli (Cooley), a sugar-water solution and water. This study identified several pesticides that could be integrated with use of P. macropilis as a biological control. Results also indicate that the predator may have a narrow prey range and require specific species of mite prey for survival and oviposition.
Associations between ants and Hemiptera are common in the families Membracidae, Coccoidea and Aphidoidea, but there are only a few cases of ants using honeydew of Cicadellidae species. We surveyed plants of Roupala montana Aubl. (Proteaceae) in the cerrado area (savanna like vegetation) in the Federal District (Brazil) during the rainy season of 2006 and 2007. In this period the plants produce new leaves, which are consumed by the nymphs of a probable new species of Rotundicerus (Cicadellidae: Idiocerinae). The nymph groups are of variable size, with a mean of 20 individuals. We found 83% of them being tended by ants. A total of 21 ant species was documented, with predominance of Camponotus spp. and Cephalotes spp. There is a clear species turnover of ants on the nymph groups and attendance is not continuous in most of the cases, suggesting an opportunistic association between ants and Rotundicerus sp.
The impact of temperature was evaluated on Rhopalosiphum padi (L.) (Hemiptera: Aphididae). Nymphs, 12-h-old, were placed individually in cylindrical plastic dishes (2.5 × 2.5 cm), with a layer of 1% agar in which leaf disks of signal grass had been placed. The nymphs were reared at 12, 16, 20, 24, 28, and 32°C ± 1°C, RH of 70 ± 10% and 12-h photophase. We evaluated number of instars, duration of each instar and the nymphal period, survival of instars, duration of the reproductive period, daily and total production of nymphs, and longevity of the nymphal and adult phases. To construct the life expectancy table and fecundity, daily observations were made of 70 nymphs at each temperature, from birth to death. Development of R. padi was faster with increased temperature, but they did not complete the last nymphal instar at 32°C. The same pattern occurred for the pre-reproductive, reproductive, and post-reproductive periods. The highest fecundity rates were between 16°C and 24°C. The highest fertility (4 nymphs/female/day) was recorded at 12°C and 20°C. The highest net reproduction rates were at 24°C and 28°C, and the time interval between each generation (T) and the population doubling time (DT) diminished as temperature increased. The finite rate of increase (λ = 1.9 nymphs/female/day) and the intrinsic rate of increase (rm = 0.64) were greatest at 24°C and 28°C, respectively. There was a negative impact on the biology and life table of R. padi at 32°C, but the range of 12°C to 28°C, despite some fluctuations, was favorable for survival and reproduction.
Egg duration period, immature development time, and pre-oviposition period of the cycad aulacaspis scale, Aulacaspis yasumatsui Takagi, were measured at 9 constant temperatures in the laboratory. Egg duration period ranged from 15 d at 20°C to 7 d at 30°C. First instar development time was 30 d at 18°C but only 4 d at 35°C. No first instars completed development below 18°C or above 35°C. Development time of second instar females ranged from 19 d at 18 and 20°C to 9 d at 30°C. Development time of male second instar pupa ranged from 15 d at 20°C to 9–10 d at 25–32°C. Pre-oviposition period averaged 14 d at 20°C to 8 d at 25– 32°C; no females laid eggs at 18 and 35°C. The lowest temperature threshold for all stages ranged from 8 to 12°C and 538 degree-days were required for female immature development in a linear model. Development rates of the scale are compared to those of 3 of its natural enemies, Cybocephalus nipponicus Endrödy-Younga, Rhyzobius lophanthae (Blaisdell), and Coccobius fulvus (Compere and Annecke).
Human-mediated disturbances have altered every ecosystem on the planet and these changes may have important consequences for biodiversity and community structure. We tested how the degree of urbanization impacts a tri-trophic interaction among the Florida scrub endemic plant Palafoxia feayi, a gallmaking midge, and the associated parasitoid wasps. A combination of field surveys and laboratory rearings were used to determine whether habitat disturbance associated with housing development (e.g., land clearing, fire suppression) was correlated with changes in plant architecture, gallmaker abundance, or parasitoid diversity. We found significant differences in the number of side branches of plants at urban sites, and that the number of galls per plant increased with both the number of side branches and plant height. More parasitoids were found in galls collected from urban sites, but parasitoid diversity was unchanged by urbanization. We conclude that although urbanization influenced plant architecture, there was only a minor impact on gallmaker abundance and parasitoid diversity.
Field surveys of the emerald ash borer (EAB), Agrilus planipennis Fairmaire, and associated parasitoids were conducted in Cranberry Township, PA from 11 Mar to 23 Oct 2008. Several species of parasitic Hymenoptera were collected from EAB-infested green ash trees or reared from late-instar EAB larvae, prepupae, and/or pupae. These included Balcha indica (Mani & Kaul), Eupelmus pini Taylor (Eupelmidae), Dolichomitus vitticrus Townes (Ichneumonidae), and 2 additional unidentified ichneumonids, Orthizema sp. Townes and Cubocephalus sp. Townes. Together, these parasitoids caused about 3.6% parasitism of EAB in the field. The most abundant species was B. indica accounting for 82% of all parasitoids recovered during our survey. Subsequent laboratory assays confirmed that B. indica and E. pini are solitary ectoparasitoids of EAB larvae, prepupae, and/or pupae. In addition, both B. indica and E. pini reproduce through thelytokous parthenogenesis; i.e., virgin females produce daughters. These parasitoids may be complementary to current classical biological control programs against EAB in North America, which have been focusing primarily on the introduction of exotic larval and egg parasitoids from China.
Lophodiplosis trifida Gagné, an Australian gall midge on paperbark, Melaleuca quinquenervia (Myrtaceae), is a recent release in southern Florida for the biological control of that host. The larval stage is described for the first time and compared to that of other Lophodiplosis species. Photos of galls and illustrations of larvae are provided. Second and third instars of L. trifida are unusual among Cecidomyiidae for the lack of setae on most papillae.
The parasitoid fly Ormia ochracea uses the calling song of its host Gryllus spp. to locate an area inhabited by potential hosts. Once a calling male has been located, O. ochracea deposits live larvae on the host, and on substrates surrounding the host to enable the larvae to attach to and enter individuals in the vicinity of the calling male. In Texas, where O. ochracea parasitizes the Texas field cricket Gryllus texensis, we observed juvenile crickets in the mating aggregations that form around calling males. Juvenile G. texensis crickets are, therefore, potentially susceptible to parasitism by O. ochracea. Here we investigated whether laboratory reared juvenile field crickets could successfully host O. ochracea larvae. We found that juvenile crickets were appropriate hosts for O. ochracea.
The blueberry bud mite (BBM), Acalitus vaccinii (Keifer), is gaining importance as a pest of southern highbush blueberries. During a BBM population development study in a north-central Florida location, an epizootic was observed, and the mesothermic acarine mycopathogen, Hirsutella thompsonii (Fisher), was identified as the causal organism. In order to better understand the progression of an epizootic resulting from H. thompsonii ,the area was extensively sampled from Mar 2007 until Apr 2008. Terminal buds of the following developmental stages were collected, as follows: (1) tightly closed buds, (2) symptomatically swollen and reddened buds, and (3) separating or opened buds. A red food coloring staining technique commonly used to stain phyto-parasitic nematodes in or on roots was used to improve the visibility of the microscopic mite. Within 1 year, the population declined from 50% of the flower buds infected (up to 2,000 BBM per bud) to less than 5% of the flower buds infected (about 20 BBM per bud). During the summer, fall, and winter months, the preferred flower buds are scarce, causing low numbers of BBM to colonize less favorable leaf buds. At this time, infection by H. thompsonii remained above 50%. In months with average temperatures below 25°C (Dec through Mar), the frequency of the disease was reduced to 50% and less, allowing the BBM population to recover slightly.
The infectivity and horizontal transfer of Isaria fumosorosea Wize among Diaphorina citri Kuwayama was measured using a detached leaf bioassay in which blastospores were sprayed on citrus leaf sections or yellow plastic tags (artificial attractant surface). Four leaf sections or three leaf sections and one yellow tag were placed together in a Petri dish chamber. One to four of the leaf sections or the yellow tag was sprayed with I. fumosorosea (1.2–1.7×103 blastospores/mm2). After treatments dried, a single adult psyllid was released into each chamber. Mortality due to I. fumosorosea for the adult psyllid was observed 4.9 ± 0.21–6.1 ± 0.37 d following exposure to the pathogen. The rate of colonization by I. fumosorosea on adults in chambers with untreated leaf sections and one treated yellow tag was as effective in inducing mortality as in chambers with one treated leaf section at 8 days post application. Under high humidity, I. fumosorosea blastospores readily produced hyphae on the surface of leaves, which was useful for determining if adults were responsible for transmission of the fungus. In chambers with a single treated leaf section, adults came into contact with blastospores and moved these around to the non-treated leaves. The same phenomenon, of psyllid infection and subsequent spreading of the fungus to non-treated leaves, was observed when psyllids were placed into chambers with a treated yellow tag. The use of I. fumosorosea inoculated yellow tags has potential as a psyllid dissemination technique for managing pest populations.
Mosquitoes from different species endemic to North Florida were collected over a 12-month period, and blood meal analyses were conducted on engorged females to determine the range of vertebrate hosts each species fed on. Thirty-one mosquito blood meals from 6 mosquito species were identified, and blood meal hosts identified included horse, cow, armadillo, deer, raccoon, rabbit, and owl. Several mosquitoes captured in the study should be considered potential bridge vectors for encephalitis viruses considering their ubiquity, their preference for mammalian blood meals, and their competence as viral vectors.
Beauveria bassiana is a widespread entomopathogen which is infectious to a great variety of insects. A commercial preparation of this fungus was used to study its potential as a biocontrol agent of the citrus root weevil, Diaprepes abbreviatus. Laboratory reared adult weevils were placed in clean plastic bags with 0.05 g of powdered inoculum per bag, shaken for thirty seconds, and placed in holding cages. In order to determine the spore concentration, germination, and position of ingress, inoculated weevils were dipped in a collodion solution after 30 min, 6 h, 12 h, 18 h, and 30 h. Collodion peels from various areas of the exoskeleton were removed, stained with lactophenol cotton blue, and observed microscopically. At 12 h post-inoculation, spores began to swell, and at 18 h close to 25% germinated on all body parts except on the elytra. After 30 h, between 45% and 75% of the spores germinated, depending on the body part. Most active spore germination occurred around the eyes (75%), followed by the ventral abdomen (65%), the dorsal pronotum (60%), scales (45%), and dorsal surface of the elytra (7%). Spores were washed from the surface of inoculated weevils with distilled water and plating onto potato dextrose agar. Spore density on the weevils' surface was determined to be 15,815 ± 479 spores initially after inoculation, and was reduced to 5,782 ± 136 spores after 3 h.
Wireworms (larval Elateridae) are perennial pests of newly planted sugarcane causing stand loss directly by damaging growing points and indirectly by introducing disease. Two organophosphate insecticides, phorate and ethoprop, are currently labeled for controlling wireworms in sugar cane. In the first experiment, 4 rates of phorate (100, 87.5, 75, and 62.5% of the current maximum field rate) were used in 2 different types of soil: Dania Muck and Immokalee Fine Sand. In the second experiment, 4 rates of phorate and ethoprop (100, 75, 50, and 25% of current maximum field rates) were used in a Lauderhill Muck soil. A no-treatment and a wireworm-free treatment were used as controls in both experiments. The effect of the insecticide was evaluated in simulated field experiments conducted in 18.9-L (5-gallon) buckets filled with soil and artificially infested with 10 wireworms (Melanotus communis (Gyllenhall), Coleoptera: Elateridae) per bucket. After 60 d, the contents of the buckets were emptied to evaluate damage to the plant and count the surviving wireworms. Insecticides resulted in fewer live wireworms and reduced damage to sugarcane shoots, roots, and seed pieces compared to the no-treatment control. In the first experiment, phorate proved to be very effective at controlling wireworms even at the 62.5% rate. Phorate was more effective in the Immokalee Fine Sand than in the Dania Muck. In the second experiment, phorate was found to be more effective at reducing stand loss and wireworm numbers than ethoprop.
In this study we used 2 reciprocal transference experiments to estimate the mode and magnitude of selection on life history traits of the aphid Brevicoryne brassicae L. on 2 sympatric host plants, Brassica campestris L. and Brassica oleraceae L. In the first experiment, we recorded success in establishment, age at first reproduction, duration of reproduction, number of nymphs laid, reproductive rate, and rate of increase (ri) on each host. In the second experiment, the offspring of females collected on Br. campestris or Br. oleraceae were reared on hosts through 3 generations. Age at first reproduction, duration of reproduction, fecundity, and rate of increase (ri) were measured during the third generation in order to determine presence of maternal effects. Within each recipient host, we estimated selection gradients by performing a multiple linear regression of relative number of nymphs in relation to age at first reproduction and duration of reproduction. Results of the first experiment indicate that successful establishment was higher on the source host on which the mother was collected. A significant effect associated with the recipient host was detected for most life history traits. Positive directional selection on duration of reproduction was detected on both hosts whereas selection on the age at first reproduction was detected only in Br. oleraeae. In the second experiment we did not find evidence of maternal effects since the recipient host exerted a significant effect on fecundity. Again, the selection on duration of reproduction was detected on both hosts. Despite these results suggesting incipient ecological specialization in B. brassicae, we recognize factors that may prevent the evolution of host plant specialization.
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