Trichogramma pretiosum parasitism of Pseudoplusia includens and Anticarsia gemmatalis eggs at different temperatures

Egg parasitism of Trichogramma pretiosum strain RV when presented with eggs of Anticarsia gemmatalis and Pseudoplusia includens was investigated at 18, 20, 22, 25, 28, 30 and 32 °C. The number of eggs parasitized per day decreased for both hosts as a function of the age of parasitoids, reaching 80% of lifetime parasitism more rapidly as temperature increased; on the 4th day at 32 °C and on the 12th day at 18 °C. The lifetime number of parasitized P. includens eggs achieved by the parasitoid maintained at 20 °C (44.95 ± 3.94) differed from the results recorded at 32 °C (28.5 ± 1.33). Differently, the lifetime number of A. gemmatalis parasitized eggs did not differ among the temperatures. When T. pretiosum reached 100% of lifetime parasitism, each adult female had parasitized from 28.5 ± 1.33 to 44.95 ± 3.94 and from 29.58 ± 2.80 to 45.36 ± 4.50 P. includens and A. gemmatalis eggs, respectively. Also, the longevity of these adult T. pretiosum females, for which P. includens or A. gemmatalis eggs were offered, was inversely correlated with temperature. Not only were the survival curves of those adult T. pretiosum females of type I when they were presented with eggs of A. gemmatalis but also with eggs of P. includens, i.e., there was an increase in the mortality rate with time as the temperature increased. In conclusion, T. pretiosum strain RV parasitism was impacted by temperature when on both host eggs; however, the parasitoid still exhibited high survival and, more importantly, high number of parasitized A. gemmatalis and P. includens eggs even at the extremes tested temperatures of 18 and 32 °C. Those results indicate that T. pretiosum strain RV might be well adapted to this studied temperature range and, thus, be potentially suitable for use in biological control programs of P. includens and A. gemmatalis in different geographical areas that fits in this range. It is important to emphasize the results here presented are from laboratory studies and, therefore, field trials still need to be carried out in the future with this strain in order to support the full development of the technology intend to use this egg parasitoid in soybean fields worldwide.     

Inactivation of the ecdysteroid UDP-glucosyltransferase (egt) gene of Anticarsia gemmatalis nucleopolyhedrovirus (AgMNPV) improves its virulence towards its insect host

Some baculovirus have been genetically modified for the inactivation of their ecdysteroid glucosyltransferase (egt) gene, and these viruses were shown to kill infected larvae more rapidly when compared to wild-type virus infections. We have previously identified, cloned, and sequenced the egt gene of Anticarsia gemmatalis nucleopolyhedrovirus (AgMNPV). Here we present data regarding the construction of an egt minus (egt−) AgMNPV and its virulence towards its insect host. We have inserted an hsp70-lacZ (3.7 kb) gene cassette into the egt gene open reading frame (ORF) and purified a recombinant AgMNPV (vAgEGTΔ-lacZ). Bioassays with third-instar A. gemmatalis larvae showed that viral occlusion body (OB) production were consistently lower from infections with vAgEGTΔ-lacZ compared to the wild-type virus. A mean of 20.4×10⁸ OBs/g/larva and 40.7×10⁸ OBs/g/larva was produced from vAgEGTΔ-lacZ and AgMNPV infections, respectively. The mean lethal concentration which killed 50% of insects in a treatment group (LC₅₀) for the 10th day after virus treatment (DAT) was 3.9-fold higher for the wild-type virus compared to vAgEGTΔ-lacZ. The recombinant virus killed A. gemmatalis larvae significantly faster (ca. 1–2.8 days), than the wild-type AgMNPV. Therefore, the vAgEGTΔ-lacZ was more efficacious for the control of A. gemmatalis larvae (in bioassays) compared to wild-type AgMNPV.     

Biological characteristics and thermal requirements of a Brazilian strain of the parasitoid Trichogramma pretiosum reared on eggs of Pseudoplusia includens and Anticarsia gemmatalis

A new strain of the parasitoid Trichogramma pretiosum, was collected in Rio Verde County, State of Goiás, Central Brazil, and designated as T. pretiosum RV. This strain was then found to be the most effective one among several different strains of T. pretiosum tested in a parasitoid selection assay. Therefore, its biological characteristics and thermal requirements were studied, aiming at allowing its multiplication under controlled environmental conditions in the laboratory. The parasitoid was reared on eggs of Pseudoplusia includens and Anticarsia gemmatalis at different constant temperatures within an 18–32 °C temperature range. The number of annual generations of the parasitoid was also estimated at those temperatures. Results have shown that T. pretiosum RV developmental time, from egg to adult, was influenced by all temperatures tested within the range, varying from 6.8 to 20.3 days and 6.0 to 17.0 days on eggs of P. includens and A. gemmatalis, respectively. The emergence of T. pretiosum RV from eggs of A. gemmatalis was higher than 94% at all temperatures tested. When this variable was evaluated on eggs of P. includens, however, the figures were higher than that within the 18–30 °C range (more than 98%), and were also statistically higher than the emergence observed at 32 °C (90.2%). The sex ratio of the parasitoids emerged from eggs of A. gemmatalis decreased from 0.55 to 0.29 at 18–32 °C, respectively. However, for those emerged from eggs of P. includens, the sex ratio was similar (0.73, 0.72 and 0.71) at 20, 28 and 32 °C, respectively. The lower temperature threshold (Tb) and thermal constant (K) were 10.65 °C and 151.25 degree-days when the parasitoid was reared on eggs of P. includens; and 11.64 °C and 127.60 degree-days when reared on eggs of A. gemmatalis. The number of generations per month increased from 1.45 to 4.23 and from 1.49 to 4.79 when the parasitoid was reared on eggs of P. includens and A. gemmatalis, respectively, following the increases in the temperature.     

Fluorescent Brighteners Improve Anticarsia gemmatalis (Lepidoptera: Noctuidae) Nucleopolyhedrovirus (AgMNPV) Activity on AgMNPV-Susceptible and Resistant Strains of the Insect

Fluorescent (optical) brighteners are known for their characteristics of protecting baculoviruses against deactivation by ultraviolet (UV) light and enhancing the activity of these agents as microbial insecticides on hosts and semipermissive hosts. These substances were evaluated in combination with the velvetbean caterpillar, Anticarsia gemmatalis Hübner, multiple-embedded nucleopolyhedrovirus (AgMNPV). The first trial involved 4 fluorescent brighteners (Blankophor BBH, Blankophor HRS, Blankophor RKH, and Tinopal LPW) obtained from the United States. The second trial was conducted with 11 fluorescent brighteners (Tinopal UNPA-GX, Tinopal DMS, Tinopal CBS, Leukophor DUB, Leukophor BSBB, Hostalux KS-N, Hostalux ETBN, BRY 10 D2 100, BRY 10 D2 150, Uvitex BHT, and Uvitex NFW) available in Brazil in combination with the AgMNPV to determine the degree of enhancement of viral activity. These brighteners were also evaluated with regard to AgMNPV protection against deactivation by UV light. Combinations of the virus with selected fluorescent brighteners were tested against both AgMNPV-susceptible and resistant strains of A. gemmatalis. In the first trial, brighteners obtained from the United States promoted increases in AgMNPV activity from 5.2-fold (Blankophor HRS) to 76.6-fold (Blankophor RKH) and reduced the mean time to death by 2.8 to 3.5 days. In the second trial, the most effective brightener (Tinopal UNPA-GX) reduced the LC₅₀ in A. gemmatalis larvae from 7083 occlusion bodies (OBs)/ml (virus alone) to 77.8 OBs/ml (≈90-fold). When 4 selected brighteners were tested in combination with the AgMNPV in resistant insects, the LC₅₀ was reduced by ca. 10,000-fold (Leukophor DUB) to ca. 62,000-fold (Tinopal UNPA-GX), in comparison to the LC₅₀ of 3.7 × 10⁷ OBs/ml observed for the virus alone. Therefore, mortality of highly resistant A. gemmatalis larvae to the AgMNPV increased dramatically when the virus was combined with some fluorescent brighteners. UV protection measured by original activity remaining (OAR) varied from <30% OAR (Uvitex NFW) to >90% OAR (Tinopal UNPA-GX and BRY 10 D2 100). All efficacious brighteners were stilbene disulfonic acid derivatives and, when used alone, none showed negative effects against A. gemmatalis larvae.     

Screening of Brazilian Bacillus thuringiensis isolates active against Spodoptera frugiperda,Plutella xylostella and Anticarsia gemmatalis

The toxicity of a collection of 1400 isolates of Bacillus thuringiensis was assessed against the Lepidoptera Spodoptera frugiperda, Anticarsia gemmantalis and Plutella xylostella. Twenty seven isolates showed toxicity to the larvae of these insects with three isolates demonstrating significantly greater potency than the standard strain against Lepidoptera, B. thuringiensis serovar kurstaki HD1. These isolates were all found to produce bipyramidal crystals and major spore-associated protein bands of approximately 130 and 65 kDa, consistent with the detection of at least one cry1 and one cry2 family gene in each. The high level of insecticidal activity of these isolates makes them excellent candidates for further development for use in the field.     

Susceptibility of larvae of Trichoplusia ni and Anticarsia gemmatalis to intrahemocoelic injections of conidia and blastospores of Nomuraea rileyi

The LD₅₀ for larvae of Trichoplusia ni injected with blastospores of Nomuraea rileyi was 4.30 ± 1.16 hyphal bodies/larva; the LD₅₀ for injected conidia was ca. 25,000 conidia/larva. The dose-mortality regression line for blastospores was Y = 4.6504 + 0.5487 X. Larval mortalities of Anticarsia gemmatalis and T. ni at 100 blastospores/larva were 0.4 ± 0.5% and 96.7 ± 1.9%, respectively. At a dosage of 25,000 conidia/larva, larval mortalities for A. gemmatalis and T. ni were 0.4 ± 0.5% and 43.1 ± 8.7%, respectively. Thus, larvae of A. gemmatalis were > 100 times and >200 times more resistant to injected conidia and blastospores, respectively, than were larvae of T. ni. Resistance of A. gemmatalis to N. rileyi may not be solely at the integumental barrier, as is often believed, but may also be a function of an internal physiological response.     

Comparative susceptibility of two different hosts to genotypic variants of the Anticarsia gemmatalis nuclear polyhedrosis virus

The susceptibility of third instar larvae of Anticarsia gemmatalis (Lepidoptera: Noctuidae) and Diatraea saccharalis (Lepidoptera: Pyralidae) to ten distinct plaque purified genotypic variants of a selected isolate of the Anticarsia gemmatalis multiple-embedded nuclear polyhedrosis virus (AgMNPV), was compared. Despite the fact that this isolate, AgMNPV-Ds20, represents a wild strain of the AgMNPV selected for higher virulence to D. saccharalis, an alternate host, most of the variants are much more virulent to the original host Anticarsia than to Diatraea. Bioassays have shown an over one hundred-fold variation in LD₅₀ values ranging from 1700 polyhedron inclusion bodies (PIBs) to more than 200 000 PIBs/larva. The PIB production in infected larvae increased with the pathogenicity of the variant to the host, showing an average ten-fold reduction in Diatraea when compared to Anticarsia for the same variant. The virus particle yield ranged from 6×10⁷ to more than 10⁹ PIBs/g of infected larvae in Diatraea and from 8×10⁸ to more than 10¹⁰ PIBs/g of infected Anticarsia larvae. The data show a clear difference of the pathogenicity of the genotypic variants of AgMNPV in vivo both between the original and alternate host and between the individual variants for the same host. These differences found in vivo indicate that monitoring of shifts in variant frequency of wild and laboratory-propagated viral isolates in these highly heterogeneous populations would help ensure the efficacy of biological control programs.     

Effect of leaf toughness and temperature on development in the lilac pyralid,Palpita nigropunctalis (Bremer) (Lepidoptera: Crambidae)

This study focuses on three factors that affect the survival of the lilac pyralid, Palpita nigropunctalis (Lepidoptera:Crambidae): (1) the effect of leaf toughness on survival rate to clarify the availability of leaves as food, (2) the effect of temperature on immature development to determine the lower thermal threshold, and (3) the effect of temperature on head capsule width to clarify whether head capsule width can be used to discriminate among field-collected larval instars. Larvae could develop on Osmanthus fragrans var. aurantiacus leaves collected in April, but not on leaves collected in June or September which were too tough to eat. More than 80% of the larvae on the leaves of Ligustrum lucidum, Ligustrum japonicum, Ligustrum obtusifolium and Syringa vulgaris completed development, regardless of the collection time. P. nigropunctalis completed development on L. lucidum at temperatures from 15 to 27.5 °C with a photoperiod of either 15 L:9D or 16 L:8D, but not at 30 °C, at which temperature no eggs hatched. The lower thermal threshold and thermal constant for total development from egg to adult were estimated at about 7 °C and 450–460 degree-days. Most of the larvae were 5-instar type larvae (passed through 5 instars) regardless of the temperature, but a few 6-instar type larvae (4 of 355) were noted at temperatures of 22.5 °C and higher. No overlap of the ranges of head capsule widths was detected for the 5-instar type larvae, indicating that head capsule width can be used to discriminate among field-collected larval instars.     

Influence of host plant nitrogen fertilization on hemolymph protein profiles of herbivore Spodoptera exigua and development of its endoparasitoid Cotesia marginiventris

Nitrogen has complex effects on plant–herbivore–parasitoid tritrophic interactions. The negative effects of low nitrogen fertilization in host plants on insect herbivores can be amplified to the higher trophic levels. In the present study, we examined the impact of varying nitrogen fertilization (42, 112, 196, and 280 ppm) of cotton plants (Gossypium hirsutum L.) on the interactions between the beet armyworm, Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae), and the hymenopteran endoparasitoid Cotesia marginiventris (Cresson) (Hymenoptera: Braconidae). We predicted that the development and fitness of C. marginiventris would be adversely affected by low host plant nitrogen fertilization through the herbivore S. exigua. The percentage of C. marginiventris offspring developing to emerge and spin a cocoon, and total mortality of parasitized S. exigua larvae were unaffected by nitrogen level. The developmental time of C. marginiventris larvae in S. exigua larvae feeding on low (42 ppm) nitrogen cotton plants was approximately 30% longer than that of those feeding on higher (112, 196, and 280 ppm) nitrogen plants. Parasitoid size (length of right metathoracic tibia), a proxy for fitness, of C. marginiventris males was positively affected by nitrogen level. Total amounts of S. exigua hemolymph proteins were not affected by nitrogen level, but were reduced by parasitism by C. marginiventris. Two proteins with molecular weights of ca. 84 and 170 kDa dominated the S. exigua larval hemolymph proteins. Concentrations of the 170 kDa hemolymph protein were unaffected by nitrogen treatment, but parasitism reduced concentrations of the 170 kDa protein. Concentrations of the 84 kDa protein, on the other hand, were interactively affected by parasitism and nitrogen treatment: higher nitrogen fertilization (112, 196, and 280 ppm) increased protein concentrations relative to the 42 ppm treatment for unparasitized S. exigua larvae, whereas nitrogen treatment had no effects on parasitized larvae. For S. exigua larvae feeding on 42 ppm nitrogen plants, parasitism increased concentration of the 84 kDa protein, while for those feeding on 112, 196, and 280 ppm nitrogen plants, parasitism decreased concentrations of the protein. Possible mechanisms and ecological consequences for the extended development of C. marginiventris on S. exigua hosts grown on low-nitrogen plants are discussed.     

Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) eggs as alternative food for rearing of lady beetles Eriopis connexa (Germar) (Coleoptera: Coccinellidae)

Eriopis connexa (Germar) (Coleoptera: Coccinellidae) is an important predator with potential for biological control of insect pests. This research evaluated the development of E. connexa larvae fed on fresh eggs of Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) without (T1) or with (T2) scales or one-day (T3) or six-month (T4) frozen, or newly-hatched larvae of S. frugiperda (T5). The percentage of E. connexa adults was higher when larvae feeding on fresh S. frugiperda eggs with or without scales, or one-day frozen eggs of this prey and lower with eggs of this Lepidoptera after frozen for six months or with newly-hatched larvae of S. frugiperda. Duration of the larval period of E. connexa was 15.7, 15.8, 16.0, 17.6, and 17.3 days, respectively, with these diets. The high survival of E. connexa fed with eggs of S. frugiperda shows the potential use of this prey in the laboratory to maintain this natural enemy.     

Nutritional characterization of Mucuna pruriens: 4. Does replacing soybean meal with Mucuna pruriens in lamb diets affect ruminal,blood and tissue l-dopa concentrations?

The harmful effects of the 3,4-dihydroxy-l-phenylalanine (l-dopa) in Mucuna pruriens (Velvet bean) seeds have limited its use as a protein supplement for monogastrics and humans. Little is known about the extent of metabolism of Mucuna l-dopa in ruminants or its accumulation in ruminant tissues consumed as food by humans. This study aimed to determine if replacing soybean meal (SB) with Mucuna increases concentrations of l-dopa in rumen fluid, blood and muscle tissue of lambs. Twenty-seven RM lambs (RM; initial body weight, BW = 33.8 ± 5.44 kg) and 12 Florida Native (FN; initial BW = 24.9 ± 8.63 kg) lambs were assigned to four treatments and fed a basal diet of coastal bermudagrass hay, corn grain, and liquid molasses for 42 (FN) or 49 days (RM) and then slaughtered. Dietary supplements were formulated by substituting 0 (SB), 330 (Lo), 670 (Med) or at least 1000 (Hi) g/kg of SB with rolled Mucuna seeds (l-dopa, 24 g/kg dry matter, DM). Body weight was measured weekly and carcass characteristics and concentrations of l-dopa in rumen fluid, blood and the sterno-mandibularis muscle were measured at slaughter when concentrations of blood urea N, glucose, haptoglobin and cerruloplasmin were also measured. Lambs fed SB had higher (P<0.05) average daily gain than those fed Mucuna (0.20 versus 0.15 kg/day for RM; 0.21 versus 0.14 kg/day for FN). However, concentrate protein source did not affect dressing and concentrations of blood urea N, or blood glucose. Feeding the Hi diet versus the SB diet did not increase concentrations of blood cerruloplasmin, or l-dopa or concentrations of l-dopa metabolites in blood. No l-dopa was found in the ruminal fluid of the lambs and l-dopa concentrations in the sterno-mandibularis muscle were low (i.e., <5 ng l-dopa/g), and unaffected (P>0.05) by diet. Ingested Mucuna l-dopa was extensively metabolized in lambs, and did not accumulate to toxic levels in muscle tissues.     

Biology and thermal requirements of Chrysoperla genanigra (Neuroptera: Chrysopidae) reared on Sitotroga cerealella (Lepidoptera: Gelechiidae) eggs

Chrysoperla genanigra Freitas is a common green lacewing associated with melon pests in the Northeastern Brazil. All life stages of this recently described species were studied under a range of constant temperature conditions (17, 21, 25, 29, 33, 35 and 37 °C), a photoperiod of 12 h:12 h (L:D) and 70 ± 10% relative humidity. Adults of C. genanigra were fed on a diet consisting of a 1:1 (v/v) mixture of brewer’s yeast and honey, while larvae were provided with eggs of Sitotroga cerealella (Olivier) ad libitum. The duration of preimaginal development of the species was inversely proportional to temperature and ranged from approximately 63 days at 17 °C to 15 days at 35 °C. The percentage of adult emergence varied from 6.7% at 17 °C to 76.7% at 25 °C, although no larvae were able to complete development at 37 °C. The lower thermal threshold for total preimaginal development was approximately 10.8 °C and the thermal requirement was 336.7 degree-days. Egg production, along with the longevity of both males and females, were significantly affected by temperature. It is concluded that the best temperature for rearing C. genanigra is 25 °C, with the lowest preimaginal mortality and the highest egg production (992.7 eggs/female).     

Cannibalism and Virus Production in Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) Larvae Fed with Two Leaf Substrates Inoculated with Baculovirus spodoptera

Cannibalism in the fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) (FAW), is a limiting factor in a baculovirus production system. To detect the impact of cannibalism, a two-step bioassay was conducted with different larval ages of FAW fed on two food sources (corn and castor bean leaves) contaminated with the S. frugiperda multiple-embedded nucleopolyhedrovirus. In a first bioassay, the food source affected the cannibalism, being higher for all larval ages tested (5-, 6- and 7-day-old larvae) in larvae fed on corn than on those fed on castor bean leaves. Larval mortality, weight equivalent and larval equivalents (LEs) per hectare decreased as the larval age increased. Larval weight, occlusion bodies (OBs)/larva and total OBs increased when the larval age increased. In a second bioassay, in which only 6- and 7-day-old larvae were used because of the performance in the first bioassay, the cannibalism rates were affected by the interaction between food sources and time of feeding (48 and 72 h), reaching the highest values for 6- and 7-day-old larvae fed on corn leaves for 72 h. Mortality of the FAW was affected by the interaction between food sources, larval age and time of feeding. The lowest mortalities were on 7-day-old larvae when they were fed on castor bean leaves for 48 and 72 h. Larval weight, OBs/larva, total OBs and LEs were affected by the interaction between food sources and larval age. A significant correlation was observed between larval weight and OBs/larva that fed on both food sources, suggesting that larval weight can be used to achieve a concentration to be sprayed in 1 ha.     

Effects of Fetal Bovine Serum deprivation in cell cultures on the production of <Emphasis Type="Italic">Anticarsia gemmatalis</Emphasis> Multinucleopolyhedrovirus

Background  

Anticarsia gemmatalis is a pest in South America's soybean crops, which could be controlled by the Multinucleopolyhedrovirus of A. gemmatalis (AgMNPV). Currently, its commercial production is based on infected larvae. However, the possibility of using modified baculoviruses in Integrated Pest Management programs has stimulated an interest to develop alternative multiplication processes. This study evaluated the AgMNPV production in UFL-Ag-286 cells previously deprived Fetal Bovine Serum.     

Reproductive responses of ram lambs under short-term exposure to endophyte-infected tall fescue seed

Our objective was to determine the influence of short-term exposure to endophyte-infected tall fescue on reproductive function of ram lambs. Rams (214 days of age) were fed a diet free of endophyte-infected fescue seed (EF; n = 8) or endophyte-infected fescue seed (EI; n = 9; 34% of diet; 4.8 μg g⁻¹ ergovaline) for 6 weeks. Feed offered to EF rams, individually fed, was reduced to the average intake of EI lambs from previous day so that intake was similar between treatments and averaged 2.4% BW (DM basis), leading to daily intake of 33.7 μg ergovaline kg⁻¹ BW for the EI fed lambs. Daily high ambient temperature for the trial ranged between 16 and 26 °C. Respiration rate and rectal temperature were measured at 14:00 daily. Blood was collected for serum concentrations of prolactin (weekly) and testosterone (twice weekly). Body weight and body condition scores (BCS; 1 = thin; 5 = fat) were determined every 14 days. Scrotal circumference, scrotal skin temperature, and semen characteristics were determined weekly. Rams were slaughtered after 6 weeks of feeding. Signs of fescue toxicosis in EI fed rams included increased rectal temperature (P < 0.001, R² = 0.11) and respiration rate (day, P < 0.001, R² = 0.25) when high ambient temperature exceeded 22 °C and reduced serum concentrations of prolactin (diet × day, P < 0.001). Body weight of EI fed rams tended to decrease after 36 days of feeding compared with EF fed rams (−3.0 kg versus 0.51 kg; P < 0.07) and BCS was similar between treatment throughout the trial. Serum concentrations of testosterone were greater in EI compared with EF fed rams (diet × day, P < 0.005, R² = 0.08). Scrotal skin temperature, scrotal circumference, semen volume, percent sperm motility, and percent abnormal sperm were similar between treatments. Spermatozoa concentration tended to be greater in EF compared with EI fed rams after 43 days of feeding (P < 0.10; R² = 0.15). Rate of forward movement of spermatozoa tended to increase at a greater rate between Days 8 and 29 in EF compared with EI fed rams (diet × day, P < 0.08). Feeding endophyte-infected fescue seed to ram lambs was associated with potential decreased fertility and increased serum concentrations of testosterone. Short term exposure of endophyte toxins to male ruminants may negatively impact reproductive responses. Feeding for longer periods may further reduce fertility and merits further research.     

Temperature-dependent physiological and biochemical responses of the marine medaka Oryzias melastigma with consideration of both low and high thermal extremes

This study aimed to investigate temperature effect on physiological and biochemical responses of the marine medaka Oryzias melastigma larvae. The fish were subjected to a stepwise temperature change at a rate of 1 °C/h increasing or decreasing from 25 °C (the control) to six target temperatures (12, 13, 15, 20, 28 and 32 °C) respectively, followed by a 7-day thermal acclimation at each target temperature. The fish were fed ad libitum during the experiment. The results showed that cumulative mortalities were significantly increased at low temperatures (12 and 13 °C) and at the highest temperature (32 °C). For the survivors, their growth profile closely followed the left-skewed ‘thermal performance curve’. Routine oxygen consumption rates of fish larvae were significantly elevated at 32 °C but suppressed at 13 and 15 °C (due to a high mortality, larvae from 12 °C were not examined). Levels of heat shock proteins and activities of malate dehydrogenase and lactate dehydrogenase were also measured in fish larvae exposed at 15, 25 and 32 °C. The activities of both enzymes were significantly increased at both 15 and 32 °C, where the fish larvae probably suffered from thermal discomfort and increased anaerobic components so as to compensate the mismatch of energy demand and supply at these thermal extremes. Coincidently, heat shock proteins were also up-regulated at both 15 and 32 °C, enabling cellular protection. Moreover, the critical thermal maxima and minima of fish larvae increased significantly with increasing acclimation temperature, implying that the fish could develop some degrees of thermal tolerance through temperature acclimation.     

Dietary supplementation of green synthesized manganese-oxide nanoparticles and its effect on growth performance,muscle composition and digestive enzyme activities of the giant freshwater prawn Macrobrachium rosenbergii

The green synthesized Mn₃O₄ nanoparticles (manganese-oxide nanoparticles) using Ananas comosus (L.) peel extract was characterized by various techniques. HR-SEM photograph showed that manganese-oxide nanoparticles (Mn-oxide NPs) were spherical in shape, with an average size of 40–50 nm. The Zeta potential revealed the surface charge of Mn-oxide NPs to be negative. Further, the Mn-oxide NPs were dietary supplemented for freshwater prawn Macrobrachium rosenbergii. The experimental basal diets were supplemented with Mn-oxide NPs at the rates of 0 (control), 3.0, 6.0, 9.0, 12, 15 and 18 mg/kg dry feed weight. The as-supplemented Mn-oxide NPs were fed in M. rosenbergii for a period of 90 days. The experimental study demonstrated that prawns fed with diet supplemented with 3–18 mg Mn-oxide NPs/kg shows enhanced (P < 0.05) growth performance, including final weight and weight gain (WG). Significant differences (P < 0.05) in feed conversion ratio (FCR) were observed in prawn fed with different diets. Additionally, prawns fed with 3.0–18 mg/kg Mn-oxide NPs supplemented diets achieved significant (P < 0.05) improvement in growth performance, digestive enzyme activities and muscle biochemical compositions, while, the prawns fed with 16 mg/kg of Mn-oxide NPs showed enhanced performance. Prawns fed on diet supplemented with 16 mg/kg Mn-oxide NPs showed significantly (P < 0.05) higher total protein level. The antioxidants enzymatic activity (SOD and CAT) metabolic enzymes status in muscle and hepatopancreas showed no significant (P > 0.05) alterations in prawns fed with 3.0–18 mg/kg of Mn-oxide NPs supplemented diets. Consequently, the present work proposed that 16 mg/kg of Mn-oxide NPs could be supplemented for flexible enhanced survival, growth and production of M. rosenbergii. Therefore, the data of the present study recommend the addition of 16 mg/kg of Mn-oxide NPs diet to developed prawn growth and antioxidant defense system.     

Clinical profile of sheep fed non-conventional feeds containing phenols and condensed tannins

A study was carried out to investigate the effects of feeding low quality non-conventional feeds (NCF) containing phenols and condensed tannins on the clinical profiles of sheep. Thirty-two Omani sheep were fed one of four diets with two base roughages, urea-treated palm frond (UTPF) and Rhodesgrass hay (RGH) and two concentrates, commercial concentrate (CC) and a by-products concentrate (BC) for 120 days. Haematological, serum biochemical and urine analyses were used to assess sheep health. Non-conventional feeds (urea-treated palm frond and by-products concentrate) contained higher levels of polyphenols and condensed tannins than conventional feeds (Rhodesgrass hay and commercial cubes). Feeds based on urea-treated palm frond had lower dry matter, crude protein, acid detergent fibre, neutral detergent fibre, gross energy (P < 0.001) and ash (P < 0.05) digestibility coefficients than those based on Rhodesgrass hay. Animals fed NCF had lower feed intake (P < 0.001) and lower body gain (P < 0.001) than those fed conventional ones. They also produced larger volumes of faeces (P < 0.01) which contained higher levels of nitrogen (P < 0.001) and had lower viscosity values of intestinal content (P < 0.001). Rumen liquor of NCF-fed animals had higher pH and lower ammonia–nitrogen levels (P < 0.01). Animals fed urea-treated palm frond plus by-products concentrate had lower lymphocyte (P < 0.01), monocyte (P < 0.05) and eosinophil (P < 0.05) counts by the end of the trial than those fed Rhodesgrass hay based diets. The urea-treated palm frond and by-products concentrate fed animals had lower blood urea nitrogen (BUN) levels (P < 0.05), higher (P < 0.01) alanine aminotransferase (ALT) and lower serum iron (P < 0.001) than those fed Rhodesgrass hay based diets. There was a trend of increasing blood, leukocytes and specific gravity in the urine of NCF-fed animals. This experiment implies that feeding low quality non-conventional feeds containing antinutritional factors for relatively long periods might produce subtle negative effects on the physiology and chemistry of the digestive system and blood parameters which might negatively affect sheep health and make them more susceptible to diseases.     

Integrating insecticides and Trichogramma ostriniae to control European corn borer in sweet corn: Economic analysis

We compared the economics of controlling European corn borer (Ostrinia nubilalis) in sweet corn by using the egg parasitoid, Trichogramma ostriniae, alone and integrated with insecticidal sprays. An initial experiment in 2003 compared T. ostriniae alone against insecticide alone and a second set of experiments conducted over 3 years (2006–2008) compared (1) insecticide alone [Insecticide]; (2) no insecticide, no T. ostriniae [Untreated Check]; (3) T. ostriniae alone [T. ostriniae 1X]; and (4) T. ostriniae + insecticide [Integrated]. In 2007 and 2008, a fifth treatment was added consisting of three approximately weekly releases of T. ostriniae [T. ostriniae 3X]. Parasitism of O. nubilalis eggs was higher in plots receiving T. ostriniae; O. nubilalis eclosion was lower with T. ostriniae; there was no interaction of T. ostriniae and insecticide on parasitism, O. nubilalis eclosion, or total O. nubilalis larvae at harvest time. Partial crop budgets were conducted for each treatment. In three of the 4 years, Untreated Checks had the highest sweet corn ear damage. Ear damage after a single release of T. ostriniae was statistically no different than using insecticides. In two of the three years, the Integrated treatment (T. ostriniae 1X + insecticide) generated the largest increase in profitability. The insecticide only treatment generated the second best increase in profitability. When comparing a single release of T. ostriniae to the insecticide only, the latter provided a better combination of efficacy and profitability. The breakeven costs of the T. ostriniae justified their use relative to the Untreated Check treatment, but not when compared to the Insecticide treatment. The breakeven costs for T. ostriniae in the Integrated treatment exceeded the actual cost in two out of three years, suggesting again that conventional growers could benefit from integrating T. ostriniae with insecticidal treatments. Projected profitability based on ear packout obtained by combining data among years suggests that in general, for low prices and yields, the increase in profit is quite modest. In the lowest price-yield combination, the change in profit is T. ostriniae 3X > Integrated > Insecticide > T. ostriniae 1X ? Untreated Check. At high prices and high yields, the differences between the management options when compared to Untreated Check are considerable. In the highest price-yield combination, the change in profit is T. ostriniae 3X > Integrated ? Insecticide > T. ostriniae 1X ? Untreated Check.