Potential of extracts of the tropical plant Balanites aegyptiaca (L) Del. (Balanitaceae) to control the mealy bug, Maconellicoccus hirsutus (Homoptera: Pseudococcidae)

The effects of extracts of different parts of the perennial tropical plant Balanites aegyptiaca (L) Del., including various solvent extracts of roots, methanol extracts from leaves, fruits, flowers and roots, partially purified saponins obtained from its roots and a standard saponin were studied on the life cycle (adult longevity, number of eggs, crawlers, adults, weight of adults and % wax content) of a laboratory-reared parthenogenic line of the mealy bug, Maconellicoccus hirsutus (Homoptera: Pseudococcidae). Extracts derived from various parts of B. aegyptiaca (leaves, fruits, flowers, and roots in methanol) affected the life cycle of M. hirsutus with a methanol root extract being the most effective at a concentration of 500 μg ml⁻¹. Partially purified saponin of B. aegyptiaca and the commercial bark saponin extract (Sigma) from Quillaja saponaria at a concentration of 500 μg ml⁻¹ were effective in reducing the longevity of M. hirsutus. Significant reductions in oviposition by M. hirsutus were found for all the extracts at a concentration of 500 μg ml⁻¹. Extracts also affected the number of emerging crawlers, number of adults as well as the weight and wax content of emerging adults. These studies suggest that B. aegyptiaca plant extracts and saponins can be useful botanical insecticides for the protection of crops from mealy bugs.     

Evaluation of corn plant as potential banker plant for supporting predatory gall midge, Feltiella acarisuga (Diptera: Cecidomyiidae) against Tetranychus urticae (Acari: Tetranychidae) in greenhouse vegetable production

The twospotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), is one of the most important and highly polyphagous pests of vegetables and other crops worldwide. Experiments were conducted in the laboratory and greenhouse to evaluate corn (Zea mays L.) as a banker plant for the predatory gall midge, Feltiella acarisuga (Vallot) (Diptera: Cecidomyiidae) to potentially control T. urticae. Choice and no-choice experiments were carried out to determine the host plant preference of an alternative prey, Oligonychus pratensis (Banks)(Acari: Tetranychidae) to corn and green bean (Phaseolus vulgaris L.). Results showed that O. pratensis adults strongly preferred corn as a host plant and posed no risk to green bean. F. acarisuga was found to fly at least 7.0 m to search for new preys on green bean plants, and over 176 F. acarisuga larvae per leaf were recorded at 14 d after dispersal. F. acarisuga proved to be an excellent predator of both T. urticae and O. pratensis. The predation by F. acarisuga to T. urticae and O. pratensis ranged from 43.7 to 67.9% and 59.2 to 90.3%, respectively, under laboratory conditions. In a non-cage study, 81.2% of T. urticae population was suppressed by F. acarisuga in reference to the control (cage treatment). The results showed that this banker plant system has potential for controlling T. urticae in greenhouse vegetable production.     

Effects of host plant on the development, survivorship and reproduction of Dysmicoccus neobrevipes Beardsley (Hemiptera: Pseudoccocidae)

The effects of four host plants (Agave sisalana, Ag. americana var. marginata, Ananas comosus Baili and An. comosus Smooth Cayenne) on the biology of the mealybug Dysmicoccus neobrevipes Beardsley were studied in the laboratory at 26 ± 1 °C, 75-90% RH and 14:10 (L:D) photoperiod. The development, survivorship, longevity, reproduction and life table parameters of D. neobrevipes differed among the host plants. The shortest developmental period (from the first instar nymph to adult) was recorded on An. comosus Smooth Cayenne (22.4 days for females and 21.3 days for males), whereas the longest was recorded on An. comosus Baili (25.6 days for females and 24.7 days for males). The highest survivorship was found on An. comosus Baili (98% for both females and males) and the lowest was on Ag. americana var. marginata (39.6% for females and 50% for males). Meanwhile the sex ratio and fecundity were highest and the pre-lay period was shortest on Ag. sisalana. The longest longevity of females was 62.5 days on An. comosus Baili, whereas the other host plants did not differ significantly with grand mean longevities of 51.0 days for females, while the longest and shortest longevities of males were 4.6 days and 2.3 days on Ag. americana var. marginata and Ag. sisalana, respectively. Values for net reproductive rate, intrinsic rate of increase and finite rate of increase were highest on Ag. sisalana, whereas the mean generation time was shortest on An. comosus Smooth Cayenne. The results indicated that Ag. sisalana is the most suitable host for D. neobrevipes among the four tested plants. When reared on Ag. sisalana, D. neobrevipes had a short developmental period (females 22.7 days and males 23.8 days), high reproduction (418 nymphs/female) and a high intrinsic rate of increase (0.106). Results of this study indicated that host plant can largely influence the population dynamics of D. neobrevipes, and our findings are useful in understanding the roles of host plants in integrated management of this pest, including exploitation of these host plants in push-pull control.     

Field trials of Metarhizium anisopliae var. acridum (Ascomycota: Hypocreales) against oriental migratory locusts, Locusta migratoria manilensis (Meyen) in Northern China

During 2002–2006, nymph bands of Locusta migratoria manilensis (Meyen) were treated by ground and aerial applications in 6000 ha of grasslands and the nearby beach of Yellow river using a soybean oil miscible suspension ULV formulation of Metarhizium anisopliae var. acridum isolate CQMa102. The formulation was also applied in Tianjin, Henan, Hebei, Shandong and Shanxi provinces of Northern China by ground and aerial applications. During field studies, cage tests were carried out in corresponding field plots in order to estimate the mortality accurately. Doses of 3.3×10¹² and 5.0×10¹² conidia ha⁻¹ were equally effective and caused 90% mortality 9–13 days after treatment. In the ground spray trial, 3.3×10¹² conidia ha⁻¹ killed >90% of L. migratoria manilensis 11–15 days after treatment in a wide variety of vegetation and weather conditions. The decline of locust populations was slower where vegetation was taller and denser. In the aerial spray treatment, the final percent survival of locusts was lowered to 10% at 11 and 14 days in the field cage and open field locusts, respectively. Furthermore, the M. anisopliae oil miscible suspension formulation did not appear to harm natural enemies of locusts in the field.     

Emergence of cuphea seeds treated with different fungicides

Cuphea (Cuphea viscosissima Jacq. × C. lanceolata f. silenoides W.T. Aiton, Lythraceae) is an oilseed crop, with medium-chain fatty acids, being developed for the North Central United States for industrial applications in the manufacture of soaps and detergents. Seed germination and seedling emergence of cuphea is often low when compared to the commercial crops. Identification of seed treatments to optimize seedling emergence and stand establishment for cuphea are important for commercial production. The objective of this study was to determine the effect of several fungicide treatments on pure live seed emergence (PLSE) of cuphea. Pure live seed emergence is defined as total seedling emergence adjusted by the germination of the seed planted. Field experiments were conducted at Prosper, ND and Glyndon, MN, in 2005 and 2006. Previous crop rotations were soybean [Glycine max (L.) Merr.]/hard red spring wheat (Triticum aestivum L.), and soybean/hard red spring wheat/sugarbeet (Beta vulgaris var. saccharifera L.) at Prosper and Glyndon, respectively, for both years. The experimental design was a randomized complete block with six treatments and four replicates. Treatments were: no fungicide applied (check treatment), captan, mefenoxam, fludioxonil + mefenoxam, azoxystrobin, and azoxystrobin + mefenoxam. Plant stand was counted and PLSE was calculated 10 to 15 d after seeding at all locations by counting emerged seedlings in the center two-plot-rows and adjusting PLSE for germination. Greenhouse experiments were conducted with soil treatments (pasteurized and non-pasteurized) and the same fungicide seed treatments as the field experiment. Pure live seed emergence, vigor index, and percent of diseased seedlings were recorded. Plant stand and PLSE were significantly greater for the seed treatments that had mefenoxam at the Glyndon, MN, environments, in which the previous crop was sugarbeet. Soil treatment (pasteurization) increased PLSE and vigor index. All fungicide seed treatments improved PLSE and vigor index and reduced damping-off compared to the untreated check. Results suggest that seed treatments including mefenoxam would be beneficial for commercial cuphea production.     

Time-mortality relationships of larvae and adults of grain beetles exposed to extreme cold

Mortality effects of low temperature exposure to −16 °C were investigated on larvae and adults of the grain beetles Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae), Oryzaephilus surinamensis (L.) (Coleoptera: Silvanidae) and Trogoderma granarium (Everts) (Coleoptera: Dermestidae), in the laboratory. The main effects and interactions of exposure time (0.2, 0.5, 1, 2, 4, 8, 12, 24 and 48 h), developmental stage (larva and adult) and individual’s age (young and old) were examined. After 4 h of exposure 100% mortality has been achieved in most of the treatments. The only exceptions were that of old larvae of T. granarium and O. surinamensis, and adults of T. granarium which needed 48, 8, and 24 h, respectively. T. granarium was the most cold-hardy species irrespective of developmental stage, and age, followed in decreasing order by O. surinamensis and T. confusum. Younger adults were generally more susceptible to cold in the cases of O. surinamensis and T. confusum. On the contrary, older adults of T. granarium suffered higher mortality than younger ones. Larvae of T. granarium were generally more cold-tolerant than adults but the opposite pattern was observed in O. surinamensis and T. confusum. Main effects of exposure time, developmental stage and individual’s age on mortality proved to be significant for all species, with the exception of T. granarium where the effect of developmental stage proved to be insignificant. Lethal time values were estimated via probit analysis. Values of LT₅₀ ranged between 0.7 and 1.0 h for T. confusum, 0.7-1.9 h for O. surinamensis and 1.2-3.4 h for T. granarium. Our results are discussed with findings from relevant studies and the possibility of including extreme cooling to IPM programs against stored product pests is investigated.     

Biomass yield and energy balance of three perennial crops for energy use in the semi-arid Mediterranean environment

Three different lignocellulosic energy crops (a local clone of Arundo donax L., Miscanthus x giganteus Greef et Deu. and Cynara cardunculus L. var. altilis D.C. cv. “Cardo gigante inerme”) were compared over 5 years (2002–2007) for crop yield, net energy yield and energy ratio. In a hilly interior area of Sicily (Italy), two different irrigation treatments (75 and 25% of ETm restoration) and two nitrogen fertilization levels (100 and 50 kg ha⁻¹) were evaluated in a split-plot experiment. In the fourth and fifth years of the field experiment (2005–2007) no fertilizer or irrigation was used.From crop establishment to the third year, above ground dry matter yield increased over all studied factors, in A. donax from 6.1 to 38.8 t ha⁻¹ and in M. x giganteus from 2.5 to 26.9 t ha⁻¹. Fifteen months after sowing, C. cardunculus yielded 24.7 t ha⁻¹ of d.m. decreasing to 8.0 t ha⁻¹ in the third year. In the fourth and fifth years, above ground dry matter yields of all crops decreased, but A. donax and M. x giganteus still maintained high productivity levels in both years. By contrast the yield of C. cardunculus yield fell to less than 1 t ha⁻¹ of d.m. by the fourth year.Energy inputs of A. donax and M. x giganteus were higher in the year of establishment than that of C. cardunculus (34 GJ ha⁻¹ for A. donax and M. x giganteus and 12 GJ ha⁻¹ for C. cardunculus), mainly due to irrigation.Net energy yield showed low or negative values in the establishment year in A. donax and M. x giganteus. In the second and third year, net energy yield of A. donax was exceptionally high (487.2 and 611.5 GJ ha⁻¹, respectively), whilst M x giganteus had lower values (232.2 and 425.9 GJ ha⁻¹, respectively). M x giganteus attained its highest net energy yield in the fourth year (447.2 GJ ha⁻¹). Net energy yield of C. cardunculus reflected energy output of the crop, being high in the first compared to subsequent years (364.7, 277.0 and 119.2 GJ ha⁻¹, respectively for the first, second and third years).A significant effect of the different irrigation treatments was noted on all the studied parameters in all species. Conversely, only A. donax was affected by nitrogen fertilization.     

Effect of processing method on the quality of cowpea (Vigna unguiculata) flour for akara preparation

An indigenous food mixture containing rice flour, milk coprecipitate, sprouted green gram paste and tomato pulp (2: 1: 1: 1 w/w) was developed and called a RCGT food mixture. It was autoclaved (1.5 kg/cm², 15min, 121 °C), cooled and fermented with 2% liquid culture (containing 10⁶ cells/ml broth). Two types of fermentations were carried out i.e. one step single culture fermentation [L. casei or L. plantarum (37 °C, 24 hr.)] and sequential culture fermentation [S. boulardii (25 °C, 24 hr.) +L. casei (37 °C, 24 hr.)]; [S. boulardii (25 °C, 24 hr.) + L. plantarum (37 °C, 24 hr.)]. All fermentations drastically reduced the contents of phytic acid, polyphenols and trypsin inhibitor activity while significantly improving the in vitro digestibilities of starch and protein. Sequential culture fermentations brought about further changes compared to one step single culture fermentation.     

Potential use of Asteraceae extracts to control Spodoptera frugiperda (Lepidoptera: Noctuidae) and selectivity to their parasitoids Trichogramma pretiosum (Hymenoptera: Trichogrammatidae) and Telenomus remus (Hymenoptera: Scelionidae)

Extracts of 12 Asteraceae were tested on Spodoptera frugiperda (Lepidoptera: Noctuidae) and on their parasitoids Telenomus remus (Hymenoptera: Scelionidae) and Trichogramma pretiosum (Hymenoptera: Trichogrammatidae). The plants Lychnophora ericoides and Trichogonia villosa were toxic for 97.7 ± 0.15% of one-day-old eggs of S. frugiperda and Lepidaploa lilacina for 72.0 ± 2.50% for two-day-old eggs of this insect. Extracts of Vernonia holosenicea, Lychnophora ramosissima and Chromolaena chaseae had higher impact on S. frugiperda, while those of Eremanthus elaeagnus and L. ericoides were more selective to T. pretiosum and T. remus. Asteraceae extracts present potential for integrated pest management programs of S. frugiperda.     

Effects of different brassicaceous host plants on the fitness of Pieris brassicae (L.)

Pieris brassicae (L.) is a destructive cosmopolitan pest of cruciferous crops. It is present wherever its host plants occur and it is considered to be one of the most widely distributed of all the Lepidoptera. We investigated the affect of various host plants on the fitness of P. brassicae to survive, develop and reproduce. We quantified development time, survival and mortality on cabbage (Brassica oleracea capitata), cauliflower (Brassica oleracea botrytis), radish (Raphanus sativus), broccoli (Brassica oleracea italica), and mustard (Brassica campestris) under laboratory conditions. The developmental time from eggs to adult eclosion was the shortest (30.3 days) on cabbage and the longest (38.0 days) on radish. However, adult longevity was significantly (P < 0.001) greatest on cabbage compared with the other host plants tested. Similarly, the developmental rate of P. brassicae was found to be faster on cabbage than other cole crops. Moreover, the lowest immature mortality was evident on cabbage and highest on mustard and radish. Differences in reproductive parameters of the P. brassicae among host plants were analyzed using pseudo-values, which were produced by jackknife re-sampling. The data showed that the higher intrinsic rate of natural increase (0.116 females/female/day) was found on cabbage. Cabbage was recognized as the most suitable host for P. brassicae because of shorter developmental period, higher percentage survival, lower doubling time (6.00), and higher number of adult emergence (29.7%).     

Efficacy of a hydroxytyrosol-rich preparation from olive mill wastewater for control of olive psyllid, Euphyllura olivina, infestations

Olive mill wastewater (OMW) is a problematic by-product in Mediterranean countries. Despite this, it is a raw material that is an unfailing source of bioactive molecules. A hydroxytyrosol-rich preparation (HRP) (49.6% weight:dry weight) was extracted from fresh OMW using a hydrolysis and post-hydrolysis purification process. The field efficacy of HRP as a spray treatment (2500 l ha⁻¹) against olive psyllid, Euphyllura olivina (Hemiptera: Psyllidae), was evaluated in 2008 and 2009 in a drip-irrigated olive orchard.The HRP showed strong insecticidal activity against E. olivina at a concentration of 2 g l⁻¹ hydroxytyrosol. Application of HRP resulted in 41.1 and 72.1% control of nymphs and adults, respectively. However, HRP application did not reduce egg hatch. Neither phytotoxicity nor toxicity to auxiliary-fauna was recorded with concentrations of 1.25 g l⁻¹ or 2 g l⁻¹ HRP. But, the 2.5 g l⁻¹ concentration was slightly phytotoxic, especially at the E and F floral phenological stages of the grapes. HRP offers a natural and effective extract for control of olive psyllid and opens a new opportunity for the reuse of OMW.     

Biological factors influencing the transmission of potato leafroll virus by different aphid species

Summary Macrosiphum euphorbiae, collected in the field from potato plants infected with potato leafroll virus (PLRV), transmitted the virus to fewer potato plants in a field trial than did laboratory-rearedMyzus persicae. In the laboratory,M. persicae was the only efficient vector of PLRV fromPhysalis floridana seedlings, potato sprouts or excised leaves toP. floridana. Two clones ofM. euphorbiae and one clone ofAulacorthum solani transmitted PLRV from infected potato plants toNicotiana clevelandii as effeciently asM. persicae but a clone ofAphis gossypii was an inefficient PLRV vector. An isolate of PLRV, whichM. persicae transmitted inefficiently from potato toN. clevelandii, was also transmitted inefficiently byM. euphorbiae andA. solani.     

Effect of different host plants on the fitness of diamond-back moth, Plutella xylostella (Lepidoptera: Plutellidae)

The diamond-back moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae) is a destructive cosmopolitan pest of cruciferous crops. The pest is present wherever its host plants exist and is considered to be one of the most widely distributed of all the Lepidoptera. We investigated the effect of various host plants on the fitness of P. xylostella and tested the hypothesis by studying development time, growth, fecundity and survival on cabbage (Brassica oleracea capitata), cauliflower (Brassica oleracea botrytis), radish (Raphanus sativus), turnip (Brassica rapa), mustard (Brassica compestris) and canola (Brassica napus var. canola). The developmental time from eggs to adult eclosion was the shortest (10 days) on canola and the longest (13 days) on turnip. Fecundity was greatest on canola (350) followed by cauliflower (268 eggs) by females eclosed from the pupae reared on canola and cauliflower, respectively, while the minimum numbers of eggs (184) were observed on cabbage. The number of eggs hatched was the highest (80%) when larvae fed on cauliflower. Survival to the adult stage was the highest (94%) on mustard followed by cauliflower and lowest (64%) on turnip. The net replacement rate was lowest for populations reared on cabbage (32.3), which was also reflected by the lowest intrinsic rate of population increase (0.20). The correlation between the intrinsic rate of population increase (r_m) and the mean relative growth rate was significant (t = 20.02 d.f. = 4, P < 0.05). Canola and mustard proved to be the most suitable hosts for P. xylostella because of shorter developmental period, higher percentage of survival and higher number of eggs. The data point to the role of host plants in increasing local P. xylostella populations.     

Persistence and efficacy of spinosad on wheat,maize and barley grains against four major stored product pests

The insecticidal and residual effect of spinosad on wheat, maize and barley grain was evaluated in the laboratory against adults of Sitophilus oryzae (F.) (Coleoptera: Curculionidae), Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae), Tribolium confusum (DuVal) (Coleoptera: Tenebrionidae), Cryptolestes ferrugineus (Stephens) (Coleoptera: Laemophloeidae) as well as against larvae of T. confusum. Spinosad was applied as a solution to 2 kg lots of each commodity at three concentrations, 0.1, 0.5 and 1 ppm, and the treated grain quantities were kept at 25 °C and 65% RH. Samples were taken from each concentration-commodity combination at the day of storage and every 30 d for 6 consecutive months (6 bioassays). The test species were exposed for 14 d to the samples and mortality and reproduction were assessed over this exposure interval. With the exception of T. confusum, 1 ppm of spinosad was highly effective against the remainder of the tested species and provided protection for a period of storage at least 4 months. Although in general, spinosad performance was not very much affected by the grain type, efficacy on maize was less stable over the 6-month period of storage and declined sooner compared to the other commodities. Spinosad almost suppressed progeny production of R. dominica during the storage period, but did not suppress progeny of the other species, since progeny were recorded even 30 d post application especially with the lowest of the tested concentrations. The results of this study indicated that spinosad may provide suitable protection for 6 months against S. oryzae or R. dominica, but is not suitable for long-term protection against T. confusum or C. ferrugineus.     

Antioxidant Activities of Four Edible Seaweeds from the Southern Coast of Thailand

The aqueous extracts of four marine algae, Caulerpa racemosa var. macrophysa, Gracilaria tenuistipitata var. tenuistipitata, Sargassum sp., and Ulva lactuca, from the coastal areas in Southern Thailand, were prepared by boiling dried seaweed powder in water for 3 h, and by autoclaving each sample at 120 °C for 3 h. They were then freeze-dried and evaluated for their antioxidant activities using DPPH (1, 1-diphenyl-2-picrylhydrazyl), hydroxyl radical (OH^•) and superoxide anion (O₂^•−) scavenging assays. Boiling extracts of the seaweeds, except C. racemosa, were found to have higher total phenolic contents (TPC) than those obtained from the autoclave method. The antioxidant results also showed that O₂^•− scavenging activity existed only in the boiling extracts of C. racemosa, G. tenuistipitata, and U. lactuca. In DPPH and OH^• assays, however, almost all the boiling extracts were less active than the autoclave ones. Among the four alga species, Sargassum sp. was the most active. Both extracts of this seaweed had the highest TPC and also displayed the strongest DPPH^• and OH^• inhibitory activities. A strong positive-correlation between the antioxidant potency and TPC of the autoclave extracts was found, while for the boiling extracts such relation was very weak. This result thus reflected that in addition to the phenolic compounds, there might be some other active components present in these extracts involved in the antioxidant activity.     

Prior weakening of Macrophomina phaseolina and Fusarium propagules for enhancing efficiency of Brassica amendments

In a two year field study, the effect of varying intensities of sub-lethal heating on the efficiency of Brassica amendments in controlling viable populations of Macrophomina phaseolina and Fusarium oxysporum f sp. cumini was determined in an arid region of India. After 30 d of dry summer exposure of pathogen infested soil, incorporation of mustard residues and oil cake (0.18% and 0.04% w/w) and then applying one irrigation caused significant reduction by 75.3–81.3% in viable counts of M. phaseolina that causes dry root rot of legumes and by 93.9% in counts of F.o. f. sp. cumini causing wilt of cumin (Cuminum cyminum L.) at 0–15 and 16–30 cm depths. Increasing duration of summer exposure to 60 d improved the reductions in viable propagules of M. phaseolina by 83.6–90.4% and in F.o. f. sp. cumini by 78.2–94.8% at same soil depths. At certain heat levels, reduction in viable population of Fusarium due to amendments and irrigation was greater than that recorded in Macrophomina. Significantly low levels of reduction in pathogenic propagules of Macrophomina (63.9–71.4%) and Fusarium (48.0–57.2%) under shade compared to unshaded conditions indicated that mild heating did not cause discernible weakening effect. In second season also, 89.2–91.5% and 78.5–95.8% reduction in counts of Macrophomina and Fusarium, respectively was achieved by the application of amendments after 60 d of summer exposure at 0–30 cm soil depth. These results suggested a new approach to improve the control of soil-borne plant pathogens in hot arid regions by combining prolonged sub-lethal heating, effective naturally available on-farm wastes as soil amendments and one summer irrigation.     

Efficacy of entomopathogenic nematodes (Nematoda: Rhabditida) and insecticide mixtures to control Spodoptera frugiperda (Smith, 1797) (Lepidoptera: Noctuidae) in corn crops

The main insect pest in Brazilian corn is fall armyworm, Spodoptera frugiperda (Smith, 1797) (Lepidoptera: Noctuidae). Entomopathogenic nematodes (EPNs) can be used to control this pest, and can be applied together with various insecticides. Thus, the objective of this work was to evaluate the efficacy of mixtures of EPNs and insecticides to control S. frugiperda in corn crops. In laboratory bioassays three species of EPNs were tested (Heterorhabditis indica, Steinernema carpocapsae and Steinernema glaseri) together with 18 registered insecticides to control S. frugiperda in corn. Efficacy of association between insecticides and EPNs on S. frugiperda larvae was evaluated against the insect's third instar, 2 and 4 days after applications in laboratory. Experiments in the field were performed in two consecutive years, with located application of H. indica and S. carpocapsae (250 IJs/cm²) mixed with chlorpyrifos (0.3 L/ha) and lufenuron (0.15 L/ha) on the corn husk. In laboratory, after two days exposure the interaction between chlorpyrifos and H. indica was synergistic, while interaction with cypermethrin, spinosad, methoxyfenozide and deltamethrin + triazofos was additive, as was interaction between lufenuron, chlorpyrifos and cypermethrin with S. carpocapsae. In contrast, the interaction between chlorpyrifos (Vexter™ and Lorsban™) and lufenuron with S. glaseri was synergistic. In the field, the best treatment was the mixture of H. indica with lufenuron (0.15 L/ha), with 62.5% and 57.5% larval mortality in the two evaluation years in the field, respectively.     

Alternate crop and weed host plant oviposition preferences by the Mexican rice borer (Lepidoptera: Crambidae)

The Mexican rice borer, Eoreuma loftini (Dyar), is the key pest of sugarcane, Saccharum hybrids, in south Texas, having largely displaced the sugarcane borer, Diatraea saccharalis (F.), and it is moving into rice- and sugarcane-growing areas of east Texas and Louisiana. While a number of alternative weed and crop hosts have been reported, the extent to which they might support Mexican rice borer populations is unknown. This study involved choice assays that compared oviposition preference for and larval infestations of five mature graminaceous weed species. Levels of infestation between sugarcane and corn, Zea mays L., crop hosts and between corn and sorghum, Sorghum bicolor (L.) Moench, were also assessed. We determined that the average number of larval entry holes in sudangrass stems was ≥2.5-fold more than for any of the other four weed host plants, that corn had ≥5.9-fold more larval entry holes than sorghum and ≥8.2-fold more than sugarcane. Greater oviposition and infestation of one non-crop host over another was not related to numbers of stems per plant, but was associated with the greater stem diameter and abundance of dry leaf tissue found in Sudangrass, Sorghum bicolor (L.) Moench ssp. drummondi (Nees ex Steud.) de Wet & Harlan, johnsongrass, S. halepense (L.) and barnyardgrass, Echinochloa crus-galli (L.) P. Beauv.; relative to the other weed species in this study. In terms of the crop plants, stalk diameter and quantity of dry leaf tissue were not associated with numbers of eggs or larval entry holes in the choice assays between corn and sorghum, and between sugarcane and corn. While corn has been known as a host of the Mexican rice borer for at least 84 yr, its role in area-wide population dynamics and control efforts has likely been greatly underestimated.     

Screening of essential oils from wild-growing plants in Tunisia for their yield and toxicity to the poultry red mite, Dermanyssus gallinae

A laboratory experiment was conducted with the poultry red mite Dermanysuss gallinae (De Geer) to assess the toxicity of a range of essential oils obtained from wild-growing plants in Tunisia to this pest. Details of the percentage essential oil yield from these plants were also recorded. For comparison, commercially sourced essential oil from Thymus vulgaris (L.) was also tested against D. gallinae after work elsewhere found this product to be acaricidal. Recently fed adult female D. gallinae were exposed to the essential oils at 0.1 mg oil/cm² in Petri-dishes at 22 °C over a period of 24 h.Results showed that the yield of essential oil varied considerably depending upon the source plant. Whilst maximum yields of 0.5% were achieved, three of the seven wild plants selected provided yields of less than 0.1%. Similar variability was recorded with respect to the toxicity of the essential oils to D. gallinae. Three of the essential oils tested did not cause significant D. gallinae mortality (in comparison to the control). However, all other selected oils provided mortality levels statistically similar to the 90% mortality achieved with commercial T. vulgaris essential oil, with the oil from Pelargonium graveolens (L’Hér.) killing 100% of D. gallinae exposed to it. Essential oil from P. graveolens in particular may be suitable for further development as a D. gallinae acaricide alongside or in place of commercial thyme essential oil.     

Host selection behavior of Bagrada hilaris (Hemiptera: Pentatomidae) on commercial cruciferous host plants

A series of host-choice tests were conducted under greenhouse conditions to evaluate the host selection behavior of the Bagrada bug, Bagrada hilaris on commercial cruciferous seedlings. In addition, a separate choice test was conducted to investigate the selection behavior of B. hilaris adults for broccoli plants of various growth stages: cotyledon, 1-leaf, 2-leaf, and 4-leaf plant stages. In comparing host selection among the commercial seedlings, observations on host attractiveness, host acceptance and host susceptibility of the cruciferous cultivars to B. hilaris adults were measured by recording numbers of adults per plant, the time at which feeding damage was first observed, and the time plant mortality occurred for each cultivar, respectively. Results showed that significantly more adult B. hilaris were attracted to a commercial radish cultivar than all other hosts, followed by red and green cabbage. Measurements of host acceptance varied among the cruciferous cultivars, however in terms of feeding damage, alyssum, arugula and broccoli appeared to be relatively less acceptable hosts for B. hilaris. Similarly, all host plants were susceptible to B. hilaris feeding damage and plant mortality varied among cultivars. In the broccoli growth-stage trials, experiments were designed in a similar fashion except that the experiment was conducted in plastic cages. A greater number of B. hilaris adults were attracted to 4-leaf-stage broccoli than other growth stages, but feeding damage was observed more quickly on cotyledon-stage plants. The implications of these findings for developing alternative pest management approaches for B. hilaris in commercial cruciferous crops are discussed.