Mass rearing the weevil Hylobius transversovittatus (Coleoptera: Curculionidae), biological control agent of Lythrum salicaria, on semiartificial diet

Lythrum salicaria L., purple loosestrife, an invasive Eurasian perennial, is degrading wetlands across temperate North America. Chemical, physical, and mechanical methods failed to provide long-term control. Therefore, four host-specific insect species (two leaf feeders, a root feeder, and a flower feeder) were introduced as biological control agents. To increase the availability of adults of the root feeding weevil Hylobius transversovittatus Goeze for field releases, we developed a semiartificial diet. Suitability of different diet formulations (varying vitamin mixes, salt mixes, antimicrobials, water content, root content) and temperatures for larval development were evaluated. We also monitored how rearing on artificial diet and the number of larvae per container affected larval development time, larval survival, adult weight, and incidences of deformities. Rearing larvae on artificial diet reduced development time from 1-2 yr to 2-3 mo. Larval development was fastest and survival rates highest under constant temperatures of 25 degrees C. Hatch rate and larval survival decreased if eggs were surface sterilized. Using FABCO antimicrobials could not prevent fungal contamination; use of methyl paraben and sorbic acid was successful in suppressing fungal and bacterial growth throughout larval development time to <10%. The moisture content of the diet did not significantly affect larval survival, development, or adult weight. Decreasing the proportion of purple loosestrife roots in the diet reduced adult weight and the proportion of larvae completing development, and increased development time; no larvae were able to complete development in root-free diet. With an increase in the number of larvae per cup, survival rates were reduced. The experiments revealed a female biased sex ratio: females consistently developed faster and were heavier than males. Incidence of adult deformities was consistently below 5%. Increased availability of adults for field release as a result of mass production using the semiartificial diet will accelerate the biocontrol program targeting purple loosestrife. We are able to produce several hundred weevils per week and have adapted the diet to rear other root-feeding weevils.     

Growth and development of the knapweed root weevil,Cyphocleonus achates,on a meridic larval diet

Cyphocleonus achates, the knapweed weevil, is an effective biological control agent of the invasive weed, Centaurea maculosa Lam. A meridic diet was developed and tested for the rearing of the larval stage of this insect. Using this diet, C. achates was reared for over three generations, with the adults being offered knapweed plants for feeding and oviposition in greenhouse conditions. Slight or no differences were seen between insects reared on a standard meridic diet formulation and one containing knapweed tissues. The following life history parameters were monitored over the three generations: percent egg hatch (ranging from 42.9 to 59.1%), time to egg hatch (20.0–23.2 days), time to adult emergence (52.0–54.1 days), adult weights 3 days post-eclosion (101.9–117.0 mg), percent adult emergence (48.3–58.6%), and percent mortality/deformity in the different stages (with mortality occurring primarily in the early larval stages). Additionally, a study involving low temperature and short day conditions suggested that C. achates could be maintained for longer periods of time in larval diet cells when placed in growth-retarding conditions, although percent adult emergence was lower. External morphology was also studied in order to distinguish between the sexes to ensure that each adult cage had a similar ratio of females to males. Abdominal features were found to be the most dependable characteristics for use when determining the sex of adult C. achates.     

Effects of the levels of fatty acids and carbohydrates in a diet on the biosynthesis of fatty acids in larvae of the silkworm, Bombyx mori

The effects of varying levels of fatty acids and carbohydrates in the diet on fatty acid synthesis from glucose in the larvae of the silkworm, Bombyx mori, were investigated. Elevation of the level of dietary fatty acids resulted in the decrease of the rate of fatty acid synthesis in the larvae. The addition of palmitate, stearate, or oleate to a diet had an inhibitory effect on fatty acid synthesis. The prolonged feeding of larvae on a diet containing a high level of fatty acid intensified the depression of the synthesis. The inhibitory effect of dietary fatty acid was found in the presence of both high and low levels of dietary carbohydrates. On the other hand, the rate of fatty acid synthesis was greatly accelerated by increasing the level of sucrose in a diet but not by the addition of starch. Furthermore, the fatty acid composition of the larval tissue shows a marked difference between the two groups of larvae fed on a diet containing sucrose and on a diet containing potato starch. Palmitic and oleic acid contents of larval tissue were increased significantly on the sucrose diet.     

Effect of temperature on the development of the West Indian sweet potato weevil, <Emphasis Type="Italic">Euscepes postfasciatus</Emphasis> (Fairmaire) (Coleoptera: Curculionidae) on an artificial diet

The relationship between temperature and the development of the West Indian sweet potato weevil, Euscepes postfasciatus, on an artificial larval diet containing powdered sweet potato root, was examined at different fixed temperatures from 22 to 31°C. The developmental periods for egg, larvae, and pupae stages shortened in correlation with increased temperature. The thermal constant was 769.2 degree-days and the developmental zero for female and male was 11.1 and 11.7°C, respectively. Although we can rear this weevil at temperatures ranging from 22 to 31°C, rearing temperatures should be kept between 25 and 28°C because the developmental stages were too long at 22°C and the larval period was delayed at 31°C. The basis for these developmental data will be a useful key factor in designing a plan to eradicate the weevil by using a mass-rearing system and SIT.     

Effect of dietary carbohydrate type on lipoprotein lipase, hepatic lipase, and lecithin:cholesterol acyltransferase activities in cynomolgus monkeys

The effects of dietary sucrose and starch with and without exogenous cholesterol on postheparin plasma lipoprotein lipase (PHLA) and hepatic lipase (HLA) were studied in cynomolgus monkeys. Serum triglyceride levels were higher in sucrose-fed animals than starch and exogenous cholesterol lowered serum triglyceride levels when added to sucrose diet but not starch diets. Sucrose markedly increased insulin levels, more so than starch; however, dietary cholesterol lowered insulin levels in sucrose diet but increased the levels in starch diet. PHLA activity was increased two- to threefold greater in sucrose than in starch diets. Exogenous cholesterol lowered PHLA activity in sucrose diet but increased PHLA activity in starch diet. HLA activity was increased with sucrose more than starch. Lecithin:cholesterol acyltransferase (LCAT) activity was significantly higher in sucrose diets than in the starch diet. Addition of cholesterol to either of these diets lowered the LCAT activity. These results indicate that PHLA, HLA, and LCAT activities not only are affected by the nature of carbohydrates, but also are related to triglyceride metabolism. The interaction of carbohydrates and cholesterol in the diet by influencing these selected enzymes plays an integrated role in lipoprotein particle interconversion processes.     

Bionomics of the parasitoid Apanteles taragamae as influenced by different diets fed to its host,Maruca vitrata

The parasitoid Apanteles taragamae Viereck (Hymenoptera: Braconidae) has been introduced into Benin by the International Institute of Tropical Agriculture (IITA-Benin station) from Taiwan in an attempt to control the cowpea pod borer, Maruca vitrata Fabricius (Lepidoptera: Crambidae), a serious pest of flowers and pods of cowpea Vigna unguiculata Walp. (Leguminosae: Fabaceae). Both the pest and its parasitoid are currently mass-reared using a cowpea and maize flour-based meridic diet. In this study, the suitability of germinating seeds from three cowpea varieties, Kpodji-guèguè, Tawa and TVX3236, as substrates, was tested for rearing A. taragamae under laboratory conditions. The seeds that were soaked for 48 h were the most suitable for M. vitrata larval rearing with up to 87 % survival. The highest parasitism rate of M. vitrata larvae by A. taragamae was observed on the local variety Tawa. Compared to meridic diet, the development cycle of the parasitoid was shorter on Tawa sprouts which also lead to the highest lifetime fecundity. The parasitoid sex ratio varied significantly between feeding substrates with a higher proportion of female wasps on the improved varieties TVX2336 and local variety Kpodji-guèguè. Rearing M. vitrata larvae on germinating cowpea grains is 4.38 times cheaper than on meridic diet. The data are discussed with emphasis on the effects of feeding substrates quality on life history parameters of insect pests and their parasitoids.     

Dietary carbohydrate source influences molecular fingerprints of the rat faecal microbiota

Background  

A study was designed to elucidate effects of selected carbohydrates on composition and activity of the intestinal microbiota. Five groups of eight rats were fed a western type diet containing cornstarch (reference group), sucrose, potato starch, inulin (a long- chained fructan) or oligofructose (a short-chained fructan). Fructans are, opposite sucrose and starches, not digestible by mammalian gut enzymes, but are known to be fermentable by specific bacteria in the large intestine.     

Response of hexokinase enzymes and the insulin system to dietary carbohydrates in the common carp, Cyprinus carpio

The response of the common carp to diets with varying amounts of digestible starch, provided either as pea meal (LP, HP, 30 and 46% peas, respectively) or as cereal (LW, HW, 30 and 46% wheat, respectively), was studied and compared with the response to a carbohydrate-free protein-rich diet (CF). Here we focused on the utilisation of dietary carbohydrates by examining the relationship between dietary starch intake, hepatic hexokinase activities, circulating insulin and muscle insulin receptor system. Plasma glucose concentration and hepatic high Km hexokinase (glucokinase, GK) activity were not affected by the content of digestible starch, but 6 h after feeding enzyme activity was higher in the fish fed carbohydrate diets. Similarly, low Km hexokinase (HK) activity was also higher in the fish 24 h after feeding. Fat gain and protein retention were significantly improved by increased digestible starch intake, especially in the HP group, which in turn, presented the highest plasma insulin levels. Glycogen stores were moderately increased by the ingestion of digestible starch. The number of insulin receptors was greater in the CF group than in fish on carbohydrates, except the HP group. Our results confirmed that the common carp uses dietary carbohydrates efficiently, especially when there are provided by peas. This efficiency might be related to the enhanced response of postprandial insulin observed in the HP group.     

The effect of site of starch digestion on performance of broiler chickens

A growth trial with 420 broiler chickens (35 per experimental unit) was conducted in order to evaluate whether bird performance (Days 0–38) is affected by site of starch digestion. Two diets were formulated with the same calculated apparent metabolisable energy, digestible lysine, and digestible starch content. The diets contained starch sources with known amounts of rapidly digestible starch (RDS, starch digested until the posterior jejunum) and slowly digestible starch (SDS, starch digested in the ileum). Diets were either high (H) or low (L) in SDS content. RDS and SDS contents were 298 and 52 g/kg for the H diet and 345 and 7 g/kg for the L diet, respectively. Starch in the H diet was supplied by waxy maize, peas and sorghum and starch in the L diet was supplied by tapioca and common maize. Birds receiving the H diet consumed more feed (P<0.10), grew faster (P<0.01) and had a lower feed conversion ratio (P<0.01) than birds receiving the L diet. The results suggest that broiler chickens perform better on diets containing a minimal amount of slowly digestible starch. Future experiments are necessary to investigate the relation between amount of slowly digestible starch and performance of broiler chickens.     

Responses to dietary starch or sucrose on protein and glucose kinetics in goats fed a high-concentrate diet

Responses of whole body protein synthesis (WBPS) and glucose irreversible loss rate (ILR) were compared between dietary starch and sucrose in four male goats. Diets were fed at 1.2 times maintenance requirements of ME and CP with 30% of the ME as starch, starch plus sucrose or sucrose, twice daily. The diets consisted of 33, 32, 11 and 24% of alfalfa hay, corn, soybean meal and the carbohydrates, respectively. The WBPS and glucose ILR during 5-7 h after feeding were determined by an isotope dilution method of [2H5]phenylalanine, [2H2]tyrosine, [2H4]tyrosine and [13C6]glucose. Sucrose elevated ammonia nitrogen and lowered acetate concentrations in the rumen, but did not differ from starch in nitrogen retention. Glucose ILR and WBPS were similar between the carbohydrates. It was concluded that dietary sucrose would have effects similar to starch on WBPS and glucose kinetics in the absorptive state in goats fed a high-concentrate diet.     

Effects of black-eyed pea trypsin/chymotrypsin inhibitor on proteolytic activity and on development of Anthonomus grandis

The cotton boll weevil Anthonomus grandis (Boheman) is one of the major pests of cotton (Gossypium hirsutum L.) in tropical and sub-tropical areas of the New World. This feeds on cotton floral fruits and buds causing severe crop losses. Digestion in the boll weevil is facilitated by high levels of serine proteinases, which are responsible for the almost all proteolytic activity. Aiming to reduce the proteolytic activity, the inhibitory effects of black-eyed pea trypsin/chymotrypsin inhibitor (BTCI), towards trypsin and chymotrypsin from bovine pancreas and from midguts of A. grandis larvae and adult insects were analyzed. BTCI, purified from Vigna unguiculata (L.) seeds, was highly active against different trypsin-like proteinases studied and moderately active against the digestive chymotrypsin of adult insects. Nevertheless, no inhibitory activity was observed against chymotrypsin from A. grandis larval guts. To test the BTCI efficiency in vivo, neonate larvae were reared on artificial diet containing BTCI at 10, 50 and 100 microM. A reduction of larval weight of up to approximately 54% at the highest BTCI concentration was observed. At this concentration, the insect mortality was 65%. This work constitutes the first observation of a Bowman-Birk type inhibitor active in vitro and in vivo toward the cotton boll weevil A. grandis. The results of bioassays strongly suggest that BTCI may have potential as a transgene protein for use in engineered crop plants modified for heightened resistance to the cotton boll weevil.     

Effects of soybean Kunitz trypsin inhibitor on the cotton boll weevil (Anthonomus grandis)

The cotton boll weevil, Anthonomus grandis, is an economically important pest of cotton in tropical and subtropical areas of several countries in the Americas, causing severe losses due to their damage in cotton floral buds. Enzymatic assays using gut extracts from larval and adult boll weevil have demonstrated the presence of digestive serine proteinase-like activities. Furthermore, in vitro assays showed that soybean Kunitz trypsin inhibitor (SKTI) was able to inhibit these enzymes. Previously, in vivo effects of black-eyed pea trypsin chymotrypsin inhibitor (BTCI) have been demonstrated towards the boll weevil pest. Here, when neonate larvae were reared on an artificial diet containing SKTI at three different concentrations, a reduction of larval weight of up to 64% was observed for highest SKTI concentration 500 microM. The presence of SKTI caused an increase in mortality and severe deformities of larvae, pupae and adult insects. This work therefore represents the first observation of a Kunitz trypsin inhibitor active in vivo and in vitro against A. grandis. Bioassays suggested that SKTI could be used as a tool in engineering crop plants, which might exhibit increased resistance against cotton boll weevil.     

Comparative food utilization of coffee bean weevil larvae on a new freeze-dried diet and green coffee beans

A meridic diet for culturing the coffee bean weevil, Araecerus fasciculatus was formulated and freeze-dried into pellets. When exposed to an atmosphere of 80 ± 5%r.h. the diet reached a moisture equilibrium that invoked oviposition and was satisfactory for growth and development of the insect. Larvae ingested larger amounts of the freeze-dried diet than of the natural food, green coffee beans, reaching equivalent weight and pupation in 31.8 ± 0.4 days on the diet as compared to 46.8 ± 0.8 days on the coffee beans. Approximate digestibilities of the two foods were not significantly different. However, the coffee beans were converted more efficiently to body mass than was the diet. Faeces of larvae on the diet contained more uric acid than those of larvae on coffee beans. Continuous culture and mass rearing of A. fasciculatus on the diet is possible.     

Supplemental Feeding Increases the Utilization of a Factitious Host for Rearing Bracon thurberiphagae Muesebeck (Hymenoptera: Braconidae) a Parasitoid of Anthonomus grandis Boheman (Coleoptera: Curculionidae)

Bracon thurberiphagae is a parasitoid attacking Anthonomus grandis thurberiae, the thurberia weevil. Although B. thurberiphagae can be reared on the boil weevil, the host is expensive to maintain in the laboratory and varies greatly in quality. Heliothis virescens was tested as an alternate host for rearing B. thurberiphagae because of their more consistent quality and availability, but after three generations the B. thurberiphagae population was severely reduced. After the addition of several amino acids to an adult wasp diet, a 100% improvement in the fecundity of B. thurberiphagae reared on H. virescens was observed and a 1:1 sex ratio was restored. This resulted in the ability to maintain a strong colony on an otherwise unsuitable factitious host. The rearing of B. thurberiphagae on H. virescens did not alter their response to boil weevil cues. These results are important in that they demonstrate that the selection of factitious hosts does not necessarily depend on whether the host is suitable, but that the suitability may be manipulated to some degree.     

The relative importance of temperature and diet to larval development and adult size of the winter stonefly, Soyedina carolinensis (Piecoptera: Nemouridae)

SUMMARY. 1. Soyedina carolinensis Claassen, a leaf shredding stonefly, was reared in a series of three laboratory experiments from early instar to adult on different species of deciduous leaves and at various constant and fluctuating temperature regimes.
2. Experiment 1, which involved rearing larvae on fourteen different leaf diets at ambient stream temperatures, showed that diet significantly affected larval growth and adult size but did not affect overall developmental time.
3. Experiment 2, which involved rearing larvae on five different leaf diets at each of three fluctuating temperature regimes (viz ambient White Clay Creek (WCC), ambient WCC+3°C, and ambient WCC+6°C), showed that: (i) adding 6°C to the normal temperature regime of WCC was lethal to 99% of the larvae regardless of diet; and (ii) warming WCC by 3°C did not affect developmental time but did significantly reduce adult size relative to adults reared at WCC temperatures on certain diets.
4. Experiment 3, which involved rearing larvae on five different leaf diets at each of five constant temperatures (viz 5, 10, 15, 20, 25°C), showed that: (i) temperature significantly affected the mortality, growth, and development time of larvae whereas diet only affected larval growth and mortality; (ii) temperatures at or near 10°C yielded maximum larval growth and survival for most diets; (iii) at 5°C, larval mortality was high and growth was low resulting in a few small adults for most diets; (iv) larval mortality was at or near 100% at 15°C regardless of diet; and (v) no larvae survived at 20 and 25°C.     

Temperature-dependent development and reproduction of the boll weevil (Coleoptera: Curculionidae)

Abstract Effects of temperature on development, survival, and fecundity of boll weevil, Anthonomus grandis grandis Boheman, were assessed at 10, 11, 12, 15,20,25,30,35,45, and 46 °C; 65% relative humidity; and a photoperiod of 13:11 (L: D) h. The mortality of boll weevil immature stages was 100% at 12°C and decreased to 36.4% as the temperature increased to 25°C. When the temperature increased from 30 °C to 45 °C, the mortality of weevils also increased from 50.1% to 100%. From 15°C to 35°C, the bollweevilpreimaginal development rate was linearly related to temperature. The average development time of total boll weevil immature lifestages decreased 3.6-fold and the preovipositional period decreased 3.3-fold when the temperature was increased from 15°C to 30°C. The lower threshold for development was estimated at 10.9, 6.6, 7.0, and 9.0 °C for eggs, larval, pupal, and total immature stages, respectively, with total thermal time requirement to complete immature stages of 281.8 DD (degree day) (15°C) and 247.8 DD (35 °C). At 1LC and 46°C, weevil females did not oviposit. Longevity of adult females decreased 4.6-fold with increasing temperatures from 15°C to 35°C. Fecundity increased with increasing temperatures up to 30°C and significantly decreased thereafter. These findings will be useful in creating a temperature-based degree-day model for predicting the occurrence of key life stages in the field. An accurate predictor of a pest's development can be very important in determining sampling protocols, timing insecticide applications, or implementing an integrated pest management control strategy targeting susceptible life stages.     

New larval agar-based diet for laboratory rearing of Mediterranean fruit fly <Emphasis Type="Italic">Ceratitis capitata</Emphasis> (Diptera,Tephritidae)

Five larval diets for laboratory rearing of Ceratitis capitata were tested. These diets were based on wheat bran, microcellulose, potato starch and agar. To evaluate the quality of diet, pupal rearing efficacy and pupal weight were checked. The best results were obtained with an agar based diet used for Manduca sexta laboratory rearing. To simplify the preparation and to reduce the cost of this diet, a new formulation was developed. Larvae reared on the new agar-based diet achieved higher pupal rearing efficacy than larvae reared on bran diet recently used in medfly mass rearing facilities. Heat treated medflies reared on the new agar-based diet achieved similar pupal rearing efficacy with heat treated medflies reared on bran diet. When testing population density, higher pupal rearing efficacy was again achieved on new diet. The highest pupal rearing efficacy was achieved with 100 eggs per 25 g of diet, lowest with 500 eggs per 25 g of diet. Concerning pupal weight, there was no difference in results achieved on Petri dishes with different larval population densities. Larvae reared on new agar-based diet reached better results than larvae reared on bran diet. The preparation of the new diet is simple and the cost is low, so it is good for laboratory tests and rearing.     

The effect of sucrose or starch-based diet on short-chain fatty acids and faecal microflora in rats

An investigation was carried out to determine whether variations of dietary carbohydrates could modify the colonic flora in rats. Sprague-Dawley rats were fed with two equicaloric diets based on the AIN-76 diet (American Institute of Nutrition 1977) but differing from that diet in content of carbohydrates, i.e. high sucrose (64%) of high corn starch (64%). Feeding was continued for 9 months ad libitum and no variation in weight gain was recorded among the different diets. A prevalence of aerobes, and a significant reduction in the ratio anaerobes/aerobes in the faeces of rats on the high starch diet compared with the high sucrose diet, was observed. The anaerobe genera identified included Actinomyces, Bacteroides, Bifidobacterium, Clostridium, Eubacterium, Lactobacillus and Propionibacterium. Bacteroides was the most prevalent genus in both dietary groups (51.2 and 29.5% in the faeces of rats fed the sucrose and starch diets, respectively). In contrast, clostridia were prevalent in the starch-fed group (23.8%) and less so in the sucrose diet (11.5%), as propionibacteria were prevalent in faeces of rats fed the starch diet (15.5%), and low in the sucrose diet (3.9%). The remaining genera were scarce in faeces from rats on either diet. Total short-chain fatty acids (SCFA) were significantly higher in the faeces of animals fed the starch diet compared with those fed the sucrose diet. The relative concentrations of acetic, propionic and butyric acids were not significantly different between the two dietary groups. In conclusion, high starch diet can markedly modify the composition of faecal flora and alter considerably the faecal concentration of SCFAs, compound which might have a health-promoting effect.     

Feeding behavior of Ceratitis capitata (Diptera,Tephritidae): influence of carbohydrate ingestion

Experiments were conducted on Ceratitis capitata larvae and adults to determine the influence of sugar (glucose and sucrose) ingestion on some aspects of the feeding behavior of this species. The results indicate that larval choice of a diet containing glucose or sucrose is not influenced by the rearing diet, by carbohydrate deprivation or by previous experience (induction). Carbohydrate deprivation did not alter the discrimination threshold of the larvae for sucrose. In adult females, the discrimination threshold for sucrose was unchanged when the flies were submitted to carbohydrate deprivation during the adult phase although ingestion by deprived females was 35% higher than ingestion by the control group. However, adults submitted to carbohydrate deprivation during the larval phase suffered a profound reduction in discrimination threshold for sucrose.     

Nutritional and developmental factors in larval growth and retrogression of Trogoderma glabrum

Diet is an important determinant of the developmental pattern of Trogoderma glabrum (Herbst). Two nutritionally adequate diets were compared. The average weight of larvae of the same age was greater when cultured on meridic diet than on standard crude diet. The expected pattern of instars, as determined by head capsule widths, was observed for larvae reared on standard diet. On meridic diet, head capsules of each instar were significantly wider, and both sexes pupated after 5 stadia.Survival during retrogression correlated positively with weight at the time of isolation. Larvae reared on meridic diet survived longer than larvae of equal culture age or weight from standard diet. Survival and maintenance of weight were greatly improved by direct contact with nutritional media, some of which were incomplete (powdered cellulose plus 10% lactalbumin, fructose, or glucose). Cellulose alone, however, was more detrimental to survival than no medium.A moult after transfer to isolation tubes produced 3 morphologically distinct forms, determined by the extent of maturation. Immature larvae retromoulted to smaller larvae; fully mature larvae pupated; and larvae that had initiated but not completed pupal differentiation became prothetelic.