Compatibility of Insect Growth Regulators with Eretmocerus eremicus (Hymenoptera: Aphelinidae) for Whitefly (Homoptera: Alyerodidae) Control on Poinsettias: II. Trials in Commercial Poinsettia Crops

The efficacy and cost of reduced release rates of the parasitoid Eretmocerus eremicus Rose and Zolnerowich (Hymenoptera: Aphelinidae) when combined with application of the insect growth regulator buprofezin were compared to those of a higher parasitoid release rate used alone for whitefly control (Homoptera: Aleyrodidae) on poinsettia (Euphorbia pulcherrima Willd. ex Koltz.). The trial was conducted in seven greenhouses in Methuen, Massachusetts from August through December 1997 and employed commercial poinsettia production practices. Two whiteflies species, Trialeurodes vaporariorum (Westwood) and Bemisia argentifolii Bellows and Perring (= Bemisia tabaci [Gennadius] strain B), were present. Three treatments were examined: (1) E. eremicus used alone at a release rate of three females per plant per week (two greenhouses); (2) E. eremicus at an intermediate release rate of two females per plant per week, combined with mid-season use of buprofezin (two applications, spaced 1 week apart, applied in weeks 9 and 10) (two greenhouses); and (3) E. eremicus at a low release rate of one female per plant per week, combined with mid-season use of buprofezin, applied as in treatment 2 (two greenhouses). In addition, observations were made in one additional greenhouse at the site, in which the grower used pesticides for whitefly control. Prior to the start of the trial, cuttings used for all treatments experienced some pesticide use, first abamectinduring rooting and later buprofezin at potting to reduce whitefly numbers, which were initially very high. At harvest, densities of live whitefly nymphs were not statistically different among the biological control treatments, indicating that a low parasitoid release rate combined with buprofezin was as effective as a higher release rate of the parasitoid used alone. Nymphal densities in separate market samples (based on smaller sample sizes) showed differences among treatments, but all treatments, including the low parasitoid release rate + buprofezin maintained densities of live nymphs + pupae at or below approximately two per leaf, a level commercially acceptable in local markets. Control costs per single-stemmed poinsettia plant were $1.18 for the high parasitoid release treatment, $0.75 for the treatment of weekly releases of two female parasitoids per plant per week + buprofezin, $0.38 for the treatment of releases of one female parasitoid per plant per week + buprofezin, and $0.14 for the chemical control greenhouse.     

Interactions between Phaedrotoma scabriventris Nixon (Hymenoptera: Braconidae) and Diglyphus isaea Walker (Hymenoptera: Eulophidae), parasitoids of Liriomyza huidobrensis (Blanchard) (Diptera: Agromyzidae)

Liriomyza leafminer flies represent a serious threat to horticultural production in East Africa. Total field parasitism rates recorded in Kenya are below 5%, with the indigenous ectoparasitoid Diglyphus isaea Walker being one of the key parasitoid species. The International Centre of Insect Physiology and Ecology (icipe), in collaboration with the International Potato Centre (CIP), imported into Kenya the endoparasitoid Phaedrotoma scabriventris Nixon to improve natural control of leafminers. The objective of this study was to investigate the interactions between D. isaea and P. scabriventris when used together for the biological control of Liriomyza species. These interactions were studied under laboratory conditions, using treatments that involved single, simultaneous and sequential releases of the different parasitoid species onto plants infested by L. huidobrensis larvae. While used separately, parasitism rates of D. isaea and P. scabriventris were 30.4 ± 10.9% and 63.6 ± 7.7% respectively. However, when used simultaneously, the total parasitism rate increased to 77.0 ± 5.3%. Although P. scabriventris had no effect on D. isaea, the presence of D. isaea reduced the specific parasitism rate of P. scabriventris. In addition, both parasitoids induced leafminer mortality through larval-feeding and stinging. However, feeding and stinging mortality induced by D. isaea (41.9 ± 9.1%) was significantly higher compared to P. scabriventris (11.9 ± 8.7). Similarly, pupal mortality due to feeding and stinging activity was 49.1 ± 6.5% and 21.6 ± 1.9% when exposed to D. isaea and P. scabriventris respectively. The implication for simultaneous use of both parasitoids in East Africa is discussed.     

cis-Jasmone indirect action on egg parasitoids (Hymenoptera: Scelionidae) and its application in biological control of soybean stink bugs (Hemiptera: Pentatomidae)

In many plants, the secondary metabolite cis-jasmone activates the metabolic pathway that produces volatile organic compounds attractive to natural enemies and, sometimes, repellent to herbivores. Previous studies indicate that the feeding damage caused by the herbivore Euschistus heros or the exogenous application of cis-jasmone in soybean plants induces the release of herbivore-induced plant volatiles (HIPVs) with a similar chemical profile and these compounds can attract the stink bug egg parasitoid Telenomus podisi (Scelionidae). Herein we tested in field conditions the effect of exogenous application of cis-jasmone in soybean plants on the parasitoid and stink bug community and on stink bug egg parasitism. In two areas, one within a soybean and another within a Crotalaria matrix, we randomly distributed 2 m² plots, with soybean plants induced (treatment, n = 5) or not induced by cis-jasmone (control, n = 5) in the field. We sampled the parasitoid community weekly with yellow sticky traps (n = 3/plot) and monitored parasitism with sentinel eggs of E. heros (n = 150/plot). We also monitored the population of stink bugs weekly, by sampling each plot with shake-cloth technique. The abundance of Scelionidae was highest overall and also in treated plots during the first four weeks in the area with a soybean matrix, but decreased thereafter. The richness of parasitoid families was similar between treatment and control plots in the area with a soybean matrix, but higher in control plots in the area with a Crotalaria matrix. Evenness was higher in control plots in the area with soybean matrix, whereas the reverse occurred in the area with a Crotalaria matrix. Results suggest that treatment with cis-jasmone effectively attracted and enhanced the population of scelionid parasitoids, but had no effect on the occurrence and intensity of parasitism and in the number of stink bugs.     

Long-term effects and persistence of Steinernema scarabaei applied for suppression of Anomala orientalis (Coleoptera: Scarabaeidae)

The entomopathogenic nematode, Steinernema scarabaei, is adapted to scarab larvae as hosts and has already shown exceptional potential for inundative control of these pests. To determine the long-term effects of S. scarabaei application on scarab populations and the nematode’s persistence, S. scarabaei was applied in mid-September at rates from 0.06 to 2.5 × 10⁹ infective juveniles (IJs)/ha to turfgrass plots seeded with oriental beetle, Anomala orientalis, larvae. Scarab and nematode populations were monitored for 3–4 years thereafter. S. scarabaei provided excellent A. orientalis control (77–100%) within 1 month of application at rates of 0.25–2.5 × 10⁹ (IJs)/ha and particularly in the following spring at rates of 0.1–2.5 × 10⁹ (IJs)/ha (86–100%). S. scarabaei provided significant control in the next A. orientalis generation in two out of 10 treatments in fall (i.e., 13 months after application) and six out of 10 treatments in the following spring. Thereafter, significant control was only observed occasionally. S. scarabaei numbers were highly variable, and few significant differences among treatments were observed. S. scarabaei recovery from the treated plots was generally more consistent through the first spring after application and became more variable thereafter, but S. scarabaei was recovered for up to 4 years in the experimental plots. Endemic populations of Heterorhabditis bacteriophora and Steinernema carpocapsae, regularly recovered from the experimental plots and often in higher numbers than S. scarabaei, had no significant effect on A. orientalis densities but were able to coexist with S. scarabaei. Our observations suggest that, once current problems with its mass production can be overcome, S. scarabaei could be augmented periodically in areas with recurrent scarab infestations to provide long-term suppression.     

Foraging efficiency of Lysiphlebus fabarum Marshall (Hymenoptera: Aphidiidae) parasitizing the black bean aphid,Aphis fabae Scopoli (Hemiptera: Aphididae), under laboratory conditions

Foraging efficiency of Lysiphlebus fabarum Marshall, the most abundant and effective parasitoid of the black bean aphid, Aphis fabae Scopoli, in terms of functional and numerical responses and mutual interference, was studied on broad bean plants in a growth chamber at 21 °C, 70 ± 5% RH and a photoperiod of 16:8 (L:D) h. Using logistic regression, a type II functional response was determined for L. fabarum. Nonlinear least-square regression was used to estimate the searching efficiency (a') and handling time (T_h). Numerical response of L. fabarum to cumulative host densities was partially linearly increasing. Nicholson's model and linear regression were used to determine the per capita searching efficiency and interference coefficient, respectively. In general, the per capita parasitism and, consequently, the per capita searching efficiency decreased significantly as parasitoid density increased. Mutual interference and quest constants were ? 0.508 and ? 0.697, respectively. The results of this study suggest that both the host and parasitoid densities have no significant impact on the progeny sex ratio. The information provided here will be useful in assessing the efficiency of L. fabarum as a biological control agent of A. fabae, devising mass-rearing protocols and implementing release programs for this parasitoid.     

Characterization of Paecilomycescinnamomeus from the camellia whitefly, Aleurocanthus camelliae (Hemiptera: Aleyrodidae), infesting tea in Japan

The whitefly, Aleurocanthus camelliae Kanmiya and Kasai (Hemiptera: Aleyrodidae), is an invasive species in Japan that was first discovered in 2004 on tea in Kyoto. Soon after its arrival epizootics of an entomopathogenic fungus were observed in populations of the whitefly in many tea-growing regions. Here we identify this fungus as Paecilomyces cinnamomeus (Petch) Samson and W. Gams (Hypocreales: Clavicipitaceae) based on morphological characteristics and molecular analyses. This is the first record of P. cinnamomeus in Japan and also the first time it has been recorded from the genus Aleurocanthus. A isolate of P. cinnamomeus caused greater than 50% and 90% infection in whitefly nymphs at 1 × 10⁶ and 1 × 10⁷ conidia/ml respectively, while the commercial mycoinsecticides Preferd® (Isaria fumosorosea) and Mycotal® (Lecanicillium muscarium) caused <10% infection at their recommended field rates (5 × 10⁶ and 9 × 10⁶ conidia/ml, respectively), suggesting that P. cinnamomeus may be more useful as a control agent than the currently available mycoinsecticides. Optimum and upper limit temperatures for in vitro growth of P. cinnamomeus isolates were 22.5–25 °C and 32.5 °C, respectively. At field rates, the fungicide thiophanate-methyl caused some inhibition of in vitro growth of P. cinnamomeus isolates, and the bactericide copper oxychloride and the insecticides tolfenpyrad and methidathion were strongly inhibitory. The findings obtained in this study will be useful in the development of microbial control programs using P. cinnamomeus against A. camelliae.     

Proteomic interactions between the parasitoid Diachasmimorpha longicaudata and the oriental fruit fly,Bactrocera dorsalis during host parasitism

The oriental fruit fly, Bactrocera dorsalis, is an important agricultural pest and biological control is one of the most effective control methodologies. We conducted an investigation on the molecular response of the fruit fly to parasitism by the larval parasitoid, Diachasmimorpha longicaudata using two-dimensional gel electrophoresis and mass spectroscopy. We identified 285 differentially expressed protein spots (109 proteins) during parasitism. The molecular processes affected by parasitism varied at different time point during development. Transferrin and muscle specific protein 20 are the only two proteins differentially expressed that play a role in host immunity 24 h after parasitism. Developmental and metabolic proteins from parasitoids (transferrin and enolase) were up-regulated to ensure establishment and early development of parasitoids 48 h post parasitism. 72 h after parasitism, larval cuticle proteins, transferrin and CREG1 were overexpressed to support the survival of parasitoids while host metabolism proteins and parasitoid regulatory proteins were down-regulated. Host development slowed down while parasitoid development went up at 96 h after parasitism. All developmental, regulatory, structural, and metabolic proteins were expressed at their optimum at 120 h post parasitism. Host development was reduced, metabolism and regulatory proteins were strongly involved in the activities. The development deteriorated further at 144 h after parasitism. Enolase and CREG1 were indicators of parasitoid survival. Hexamerin and transferrin from the parasitoid was peaked at 168–216 h after parasitism, strongly indicating that parasitoid would survive. This study represents the first report that reveals the molecular players involved in the interaction between the host and parasitoid.     

An adjustable action threshold using larval parasitism of Helicoverpa armigera (Lepidoptera: Noctuidae) in IPM for processing tomatoes

An adjustable action threshold that uses estimates of larval parasitism of Helicoverpa armigera (Hübner) in individual fields was assessed over three consecutive years in processing tomatoes in Hawke’s Bay, New Zealand. Tomato fields were monitored weekly for levels of infestation by H. armigera larvae. When infestation levels became of concern, either approaching or exceeding the standard action threshold of one larva per plant, collections of 30+ representative larvae were made. These larvae were measured and reared individually at 30 °C, and after 4 days rates of parasitism were estimated visually. From these data, spray recommendations were made using a formula that adjusted the action threshold to allow for mortality from parasitism. At harvest, damage assessments were made to validate these recommendations. Results showed that estimates of parasitism after 4 days were accurate predictors of final assessments of parasitism. Overall parasitism during the three seasons was 71%, confirming that the original threshold, which relies on about 50% parasitism, needed revision. The dominant parasitoid was Cotesia kazak, reared from 91% of all parasitized larvae over the 3 years. Microplitis croceipes and the self introduced polyphagous parasitoid Meteorus pulchricornis were reared from 4% and 5% of the parasitized larvae respectively. In 16 of 17 fields examined, the adjustable threshold kept fruit damage at harvest below the tolerated level of 5%. The single crop with excessive damage had only 0.5% fruit damage above this level. This adjustable threshold, which varied in this study from 1–8.3 larvae per plant, has been incorporated into an updated IPM programme and contributed to a 95% reduction in insecticide use.     

Can Beauveria bassiana Bals. (Vuill) (Ascomycetes: Hypocreales) and Tamarixia triozae (Burks) (Hymenoptera: Eulophidae) be used together for improved biological control of Bactericera cockerelli (Hemiptera: Triozidae)?

Bactericera cockerelli (Sulc.) is an important pest of solanaceous crops and a vector of the pathogen Candidatus Liberibacter psyllaurous. Biocontrol of this pest has been attempted with either entomopathogenic fungi or the parasitoid Tamarixia triozae (Burks), but prior to this study, their potential impact in combination had not been studied. The aim of the present study was to evaluate T. triozae parasitism rates on B. cockerelli nymphs that were previously infected for different periods of time by three isolates of Beauveria bassiana (Bals.) Vuill. Two native isolates (BB40 and BB42) and one commercial isolate (GHA) were used. The virulence of these isolates was first estimated against B. cockerelli and T. triozae. LC₅₀ values for the native isolates BB40 and BB42 against B. cockerelli were 9.5 × 10⁵ and 2.42 × 10⁶ conidia mL⁻¹ respectively; they were significantly more virulent than isolate GHA with an LC₅₀ of 1.97 × 10⁷ conidia mL⁻¹. However, isolate GHA was significantly more virulent against T. triozae with an LC₅₀ of 1.11 × 10⁷ conidia mL⁻¹ compared with LC₅₀s of 1.49 × 10⁷ and 1.14 × 10⁸ conidia mL⁻¹ for the native isolates BB40 and BB42 respectively. Groups of nymphs were then inoculated with LC₂₀, LC₅₀ or LC₉₀ concentrations of each isolate and presented to T. triozae as hosts either on the day of inoculation or 1, 2, 3, 4, 5, 6 days after inoculation. Subsequent levels of parasitism were recorded. Overall, parasitism rates were similar in inoculated and control nymphs. No parasitism occurred in nymphs 6 days after fungal inoculation. Parasitoids used to parasitize uninoculated B. cockerelli nymphs survived significantly longer (7.8 days) than parasitoids that had been used to parasitize fungus-inoculated nymphs (7.3 days). This suggests an inability of the parasitoid to avoid infection when foraging on inoculated nymphs. In conclusion, although the parasitism rate in control and fungus-treated nymphs was similar, suggesting a combination of both biological control agents is possible, we believe there are also negative implications for the parasitoid because its survival was greatly reduced after attacking infected nymphs.     

Long-term monitoring of the introduced emerald ash borer (Coleoptera: Buprestidae) egg parasitoid,Oobius agrili (Hymenoptera: Encyrtidae), in Michigan,USA and evaluation of a newly developed monitoring technique

Emerald ash borer (EAB), Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), is a serious invasive pest of ash trees (Fraxinus spp.) in North America from China. The egg parasitoid Oobius agrili Zhang and Huang (Hymenoptera: Encyrtidae) was introduced from China as a biological control agent for this pest in Michigan and throughout the infested area of the United States. A critical component of any biological control program is post-release monitoring and evaluation; however, because of the small size and cryptic nature of O. agrili, evaluation of its impact is difficult. We compared two methods for measuring parasitism of emerald ash borer eggs: (1) timed visual searches of bark on standing ash trees and (2) bark collection, sifting, and sorting. Both methods were carried out in paired parasitoid-release and control plots, the visual search method over a six-year period (2008–2013) and the more recently developed bark-collection and sifting method for 2 years (2012–2013). The visual search method found parasitism in release plots remained low (0.7–4.2%) in samples taken from 2008 to 2012 and reached 10.6% in 2013. In comparison, the bark-sifting method found that rates of egg parasitism were considerably higher in release plots, 21.8% and 18.9% for samples taken in 2012 and 2013, respectively. These findings indicate that the population-level impact of O. agrili is increasing and may be an important source of mortality for EAB populations. We recommend the bark-collection and sifting method as the more effective method to recover parasitoids and estimate parasitism rates of O. agrili.     

Supplemental releases of specialist parasitic wasps improve whitefly and psyllid control by <Emphasis Type="Italic">Dicyphus hesperus</Emphasis> in tomato

Dicyphus hesperus Knight (Heteroptera: Miridae) can contribute to the suppression of populations of Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) and Bactericera cockerelli Sulcer (Hemiptera: Psyllidae) in tomato. Nevertheless, the remaining levels of these pests could still be too high for the crop to tolerate. We thus tested here whether the combination of D. hesperus with the specialist parasitoids Eretmocerus eremicus Rose & Zolnerowich (Hymenoptera: Aphelinidae) (whitefly) and Tamarixia triozae (psyllid) can result in better pest control compared with methods based exclusively on single-species releases in tomato. We conducted two simultaneous experiments in tomato (‘Whitefly’ and ‘Psyllid’ Experiment), where we compared the effectiveness against B. tabaci and B. cockerelli in cages receiving releases of the predator or the specialist parasitoid alone, or in combination. Although all natural enemies reduced pest levels when released separately, the combination of D. hesperus with E. eremicus and D. hesperus with T. triozae resulted in better whitefly and psyllid control, respectively, compared with the separate releases.     

Enhancing biological control by an omnivorous lacewing: Floral resources reduce aphid numbers at low aphid densities

The availability of plant resources to omnivorous arthropod predators may have a positive, negative or negligible effect on their population densities and predation rates, depending on the availability of prey. At high prey densities, flowering buckwheat has been shown to negatively impact populations of the brown lacewing, an omnivorous predator, due to the probable increase in parasitism rate of lacewing larvae by their primary parasitoid, Anacharis zealandica. However, little is known about the effect of buckwheat flowers on this insect community at low prey densities. We used field cages to assess the effects of nectar provision by flowering buckwheat on the population dynamics of the pea aphid, the brown lacewing and its parasitoid A. zealandica in an alfalfa field, under low aphid densities in the New Zealand summer. The insects were sampled every 2 weeks with a suction device, then counted and released on each sampling date from 15 January to 15 March 2007. Buckwheat significantly increased lacewing populations and significantly decreased aphid numbers by 70% and 39%, respectively. The buckwheat had its greatest effect at the end of summer (February/March) for both these species. It had no effect on A. zealandica abundance.     

Effects of combining releases of non-viable host eggs with insecticide application on Riptortus pedestris population and its egg parasitoids

Our previous study demonstrated that the release of refrigerated non-viable eggs of Riptortus pedestris (Fabricius) (Hemiptera: Alydidae) enhanced parasitism rates in soybean fields but did not result in the reduction of R. pedestris populations. This study was further conducted using an open-cage exclusion design in a soybean field in order to evaluate the compatibility of combining releases of non-viable host eggs with a single pre-harvest application of insecticide for the control of R. pedestris. Refrigerated eggs of R. pedestris were released twice in treatment plots, and fresh (< 1 day old) eggs of R. pedestris were deployed in all experimental arenas, every 6 days, for host resource and measurement of field parasitism. The releases of host eggs did not reduce the number of R. pedestris in any life stage except the adult stage on two sampling dates. However, parasitism by Gryon japonicum (Ashmead) (Hymenoptera: Scelionidae) was higher in treated plots (9–25%) than in the control plots (1–9%). Statistical significant reduction was not found in the pest population, but parasitism rates significantly increased. Pesticide application did not reduce the bug population but did affect the parasitoids population. Pest management tactics, using both artificially deployed host eggs and insecticide, are discussed.     

Host age preference of Microplitis mediator (Hymenoptera: Braconidae), an endoparasitoid of Mythimna separata (Lepidoptera: Noctuidae)

Microplitis mediator (Haliday) is a solitary endoparasitoid of larvae of the cotton bollworm, Helicoverpa armigera (Hübner) and the oriental armyworm, Mythimna = Leucania separata (Walker). The preference and suitability of different instars of M. separata for M. mediator were determined under laboratory conditions at a constant temperature of 26 ± 1 °C, 65 ± 5% RH and L14:D10 photoperiod. The selection coefficient revealed that M. mediator parasitized 1st to 4th instars, but preferred 2nd and 3rd instars. Seventy-one percent of parasitism was achieved within 24 h when the 2nd instars were used as hosts at a density of one parasitoid per 20 Larvae. Parasitoid egression and pupation were dependent on the host instar parasitized and occurred from the 1st through the 4th instar. The mean developmental time from egg to prepupae of M. mediator within 1st to 4th instars of the host was 8.27, 8.30, 8.30 and 9.20 days, respectively. Cocoon weights were lower when 1st and 2nd instars served as hosts rather than 3rd and 4th instars. The percentage of host larva that died before parasitoid egression declined as the age of the host increased, ranging from 26% to 2% for 1st–5th instars, respectively. The results of this study suggest that 2nd and 3rd instars of M. separata would be the best host stages for mass production of M. mediator in the laboratory and the best host instars to target for effective control in field releases.     

Performance of Microplitis tuberculifer (Hymenoptera: Braconidae) parasitizing Mythimna separata (Lepidoptera: Noctuidae) in different larval instars

The solitary parasitoid Microplitis tuberculifer (Wesmael) is an important biological control agent of various lepidopteran pests in Asia. We examined the preference of M. tuberculifer for different instars of its common host, Mythimna separata (Walker), host instar effects on parasitoid development, and the consequences of parasitism in different stages for growth and consumption of host larvae. The wasp successfully parasitized the first four larval instars of M. separata, but not the fifth, which appeared to be behaviorally resistant. First and second instars were parasitized at higher rates compared to thirds and fourths in no-choice situations, ostensibly due to longer handling times for the latter, but second instars were most preferred in a choice test that presented all stages simultaneously. Although later instar hosts yielded heavier cocoons, the fastest parasitoid development was obtained in second instars. Lower sex ratios were obtained from first instars as females appeared to lay a smaller proportion of fertilized eggs in small hosts. Both weight gain and food consumption of parasitized larvae were reduced significantly within 24 h of parasitism, regardless of the stage parasitized, and final body weights were less than 10% those of unparasitized larvae. Thus, M. tuberculifer has good potential as a biological control agent of M. separata, successfully parasitizing the first four larval instars and dramatically reducing plant consumption by the host in all cases.     

Compatibility of Insect Growth Regulators with Eretmocerus eremicus (Hymenoptera: Aphelinidae) for Whitefly (Homoptera: Aleyrodidae) Control on Poinsettias: I. Laboratory Assays

The compatibility of five insect growth regulators (IGRs), buprofezin, pyriproxyfen, fenoxycarb, pymetrozine, and kinoprene, were tested in the laboratory for compatibility with the whitefly parasitoid Eretmocerus eremicus Rose and Zolnerowich (Hymenoptera: Aphelinidae). The survivorship of adult parasitoids foraging on poinsettia leaves with residues 6, 24, and 96 h of age was determined. The toxicity of Bemisia argentifolii Bellows and Perring (Homoptera: Aleyrodidae) patches treated with IGRs presented to female parasitoids 24 and 96 h posttreatment was quantified. Survivorship of immature E. eremicus developing within B. argentifolii nymphs was determined by treating whitefly nymphs with IGRs 5 and 13 days postoviposition by female parasitoids. Finally, behavioral observations of female parasitoids foraging on IGR-treated and untreated B. argentifolii patches presented simultaneously were quantified to determine whether IGR residues had a repellant effect toward E. eremicus. Averaging ranks for IGRs based on their compatibility with E. eremicus and their ability to kill B. argentifolii nymphs produced the following parasitoid compatibility order: buprofezin > fenoxycarb > pymetrozine = pyriproxyfen > kinoprene. Further work in greenhouses assessing the efficacy of buprofezin with E. eremicus for B. argentifolii control on poinsettias is recommended.     

The effect of diet on longevity,fecundity, and the sex ratio of Clitostethus arcuatus (Rossi) (Coleoptera: Coccinellidae)

Clitostethus arcuatus is a major, cosmopolitan predator of some Aleyrodidae. Field collected adult beetles were reared in the laboratory on different diets: Siphoninus phillyreae eggs, Trialeurodes vaporariorum eggs, Sitotroga cerealella eggs, or an artificial diet consisting of honey, yeast, and pollen. All experiments were conducted at 25 ± 2 °C, 65 ± 5% RH and a photoperiod of 16:8 (L:D) h. Female and male C. arcuatus consumed a mean (± SE) of 61 ± 0.6 and 27 ± 0.9 T. vaporariorum eggs d^? 1, respectively, and a mean of 56 ± 2.2 and 29 ± 1.1 S. phillyreae eggs d^? 1, respectively. Significant differences were noted between sexes and between hosts consumed by female C. arcuatus. No feeding occurred on S. cerealella eggs. Although there was a significant difference between rates of oviposition due to diet, fertility rates on different diets did not show significant differences. The sex ratio of C. arcuatus (female:male) was 51.4:48.6, 55.2:44.8, and 54.6:45:4 when adults fed on T. vaporariorum, S. phillyreae, and artificial diet, respectively. These differences were not significantly different. Average longevity (± SE) was 66.4 ± 2.6, 54.9 ± 2.5; 77.3 ± 6.9, 67.5 ± 7.2; and 86.4 ± 4.5 70.3 ± 3.6 days for female and male C. arctuatus, respectively, on T. vaporariorum, S. phillyreae and artificial diet, respectively, with significant differences between sexes and diets. Although developmental duration on T. vaporariorum was longer than ash whitefly, this difference was not significant (mean 27.68 ± 0.31 and 25.09 ± 0.21 days for predators reared on T. vaporariorum and S. phillyreae, respectively). Given its longevity and fecundity on T. vaporariorum, C. arcuatus may be a good choice for mass release on glasshouse crops infected by greenhouse whitefly.     

Quality assessment of Riptortus pedestris (Hemiptera: Alydidae) eggs cold-stored at different temperature and relative humidity regime

Supplementation of host resource can be more economical method for the biological control of insect pest compared to direct release of adult parasitoids. Periodical release of non-viable cold-stored eggs of Riptortus pedestris (Fabricius) (Hemiptera: Alydidae) has been found to enhance parasitism of this pest in soybean fields. To find the optimum environmental conditions for cold storage of these host eggs, we evaluated nine different combinations of temperature (2, 6, and 10 °C) and relative humidity (high 90–95%, medium 70–75%, and low 30–35%). After 30 d of cold-storage, eggs were weighed and held at 26.6 °C and 75% relative humidity for 8 d before testing. To test the eggs’ suitability as hosts following cold storage, females of Ooencyrtus nezarae Ishii (Hymenoptera: Encyrtidae) were released individually onto batches of eggs, and parasitization rates and the development, emergence, sex ratio, adult longevity, and size of parasitoid progeny were examined. Eggs stored at high relative humidity showed less weight loss than those stored at low relative humidity. The number of eggs parasitized was highest (5.9/15) on eggs stored at 6 °C and high relative humidity. Developmental times and adult emergence were optimal on host eggs stored at 2 °C and high relative humidity. A significantly lower proportion of eggs produced male parasitoids when eggs were stored at 2 or 6 °C. Adult longevity was not affected by egg storage conditions, but adult size of progeny decreased in eggs stored at 10 °C. In conclusion, eggs of R. pedestris stored below 6 °C and with a high relative humidity maintained the best quality for parasitization by O. nezarae.     

How far a protected area contributes to conserve habitat species composition and population structure of endangered African tree species (Benin,West Africa)

The Pendjari Biosphere Reserve located in the Sudanian zone of Bénin, is a protected area well managed, but mainly aimed at wild animal conservation. This study assessed its effectiveness to conserve habitat species composition and population structure of three endangered African tree species: Afzelia africana Sm., Pterocarpus erinaceus Poir. and Khaya senegalensis (Desv.) A. Juss. We randomly sampled 120 plots in the protected and surrounding unprotected habitats by inventorying plant species. For the three target species, we estimated adult and juvenile densities and recorded size classes. According to floristic composition four habitats groups were recognized in relation to human disturbance, vegetation type, and moisture. These were protected savannas, unprotected savannas, old fallows and gallery forests. The estimated adult densities of A. africana were similar between protected (14 ± 1.2 tree/ha) and unprotected savannas (17 ± 0.9 tree/ha) while for P. erinaceus the adult density was significantly higher in protected (12 ± 3.7 tree/ha) than in unprotected savannas (5 ± 1.9 tree/ha). Estimated adult density of K. senegalensis was also significantly higher in protected gallery forest (40 ± 5.8 tree/ha) than in unprotected one (29 ± 4.8 tree/ha). Juvenile densities of A. africana, K. senegalensis and P. erinaceus were higher in protected habitats than in unprotected ones but the difference was not significant. Skewness coefficient indicated that populations of investigated trees were declining in their protected habitats. However, in the case of A. africana and K. senegalensis populations seemed to be mostly threatened in the protected area. We concluded that although the studied protected area is effective to conserve some habitats species compositions, protection is not sufficient to guarantee future conservation of some threatened tree species.     

Comparative assessments of Gonatocerus ashmeadi and the ‘new association’ parasitoid Gonatocerus tuberculifemur (Hymenoptera: Mymaridae) as biological control agents of Homalodisca vitripennis (Hemiptera: Cicadellidae)

Egg age preference, competitive ability, and behavior of Gonatocerus tuberculifemur (‘new association’ parasitoid) and Gonatocerus ashmeadi (‘old association’ parasitoid) were investigated in the laboratory to determine if one species exhibited competitive superiority. When searching concurrently for Homalodisca vitripennis egg masses, G. ashmeadi consistently outperformed G. tuberculifemur by parasitizing 25–53% more eggs under three different experimental systems in the laboratory with varying host densities, egg ages, and exposure times. G. ashmeadi parasitism in control vials containing one parasitoid ranged from 81–97% across all egg ages. G. tuberculifemur in control vials parasitized 60–66% of eggs 1 and 3 days old, and just 18% of eggs 5 days old. G. ashmeadi produced 5–16% more female offspring than G. tuberculifemur for all experimental conditions. In comparison to G. ashmeadi, G. tuberculifemur was observed off leaves with host eggs 20% more frequently and it oviposited 15% less frequently. G. ashmeadi and G. tuberculifemur when confined together allocated ∼1% of behaviors to antennating or aggressively chasing competitors off egg masses, and up to 2% of behaviors to antennating host egg masses and/or ovipositing into eggs from the opposite side of the leaf. These latter behaviors did not occur when parasitoids were confined alone with host eggs.