Extended Development Time Research Articles

Responses of production and storage walnut pests to Bacillus thuringiensis insecticidal crystal protein fragments

Abstract Recent advances in genetic engineering have provided the opportunity to induce walnut plants to produce Bacillus thuringiensis Berliner insecticidal crystal protein fragments (ICPFs) for insect control. We studied the effects of two ICPFs CryIA(b) and CrylA(c) previously shown to be encoded by the cryIA (b) and cryIA (c) genes in the B. thuringiensis strains HD-1 and HD-73, respectively. The lethal effects on larvae of codling moth, Cydia pomonella (L.), navel orangeworm, Amyelois transitella (Walker), and the major postharvest pest Indianmeal moth, Plodia interpunctella (Hubner), were investigated. Both proteins were toxic to the three species tested. Indianmeal moth larvae were the most susceptible and navel orangeworm the least; CryIA(b) was generally more toxic to navel orangeworm. Similar relationships resulted when ICPFs were incorporated into the diet. Both ICPFs caused decreased rate of development of navel orangeworm. Effects on pupal weight occurred only at the highest concentration (100 ng/cm 2 ). Neither ICPF affected frequency of mating or fecundity. In addition to the lethal effects, the extended development times observed could have considerable effects on the population dynamics of the navel orangeworm and possibly other species.

Host effects on the development and fecundity of gypsy moth, Lymantria dispar L., reared under field conditions

We reared gypsy moth larvae outdoors under natural temperature and photoperiod regimes on red oak (Quercus rubra L.) and sugar maple (Acer saccharum Marsh). Initiation of the experiment coincident with the peak hatch of the local gypsy moth population assured normal synchrony between foliage quality and larval development. Compared with larvae reared on oak foliage, the mortality of maple-fed larvae is greatest and development slowest in the first instar. Overall, the larvae reared on sugar maple have higher mortality, extended development time, lower pupal weights, and lower fecundity relative to larvae reared on red oak. The mean diameter of individual eggs did not differ between oak- and maple-fed larvae, nor was the rate of increase in egg mass weight with female pupal weight host dependent. The egg masses from oak-fed moths hatched more completely than did those from moths reared on maple. In the interaction between these two abundant potential hosts and gypsy moths, the interspecific differences between the hosts are more important than any effects of seasonal asynchrony between larvae and foliar development. Gypsy moth larval success is much greater on red oak, and survival and reproduction on sugar maple under field conditions are likely to be marginal at best.

Rearing Dictya floridensis (Diptera: Sciomyzidae) in a continuously producing colony and evaluation of larval food sources.

Methods for large-scale continuous propagation of Dictya floridensis Steyskal were developed. A colony originating from 22 specimens of several Dictya species collected in Alachua County, Fla., became a single species colony after several generations because of failure of all but D. floridensis to survive colonization. The colony was maintained as separate generations until the F5, after which new D. floridensis adults were pooled into mass colony cages. During the F7 generation, colony production was in excess of 1,000 neonate larvae per day, the number of adults was continually increasing, and the females had extended longevity and fecundity. At that time, the colony was considered to be continuously producing, and size of the colony was limited only by the availability of food and rearing facilities. Larvae were reared on living, freshly crushed, frozen snails, Physella hendersoni hendersoni (Clench) and Pseudosuccinea columella Say. Larval development and their survival rate to pupariation was the same whether reared on freshly crushed snails or on live food. Larvae reared on frozen snail tissue compared with live snails had the same sex ratio but were lighter in weight and had extended development time to pupariation and lowered survival rates. Larvae fed and developed successfully upon living embryonated snail egg masses but were unable to use egg masses that had been frozen.

Feeding, Longevity, and Development of Pear Psylla (Homoptera: Psyllidae) Nymphs on Resistant and Susceptible Pear Genotypes

One-day-old first-instar pear psylla, Cacopsylla pyricola Foerster, were placed on ‘Bartlett’ (susceptible), NY10352 (moderately resistant), and ‘Bradford’ (resistant) pear (Pyrus spp.) genotypes. Psylla nymphs fed and developed readily on ‘Bartlett’ but fed little, developed slowly, and did not reach the fifth stadium on ‘Bradford.’ Psylla feeding on NYI0352 resulted in an extremely extended development time, with very few reaching the adult stage.

Mammographic film-processor temperature, development time, and chemistry: effect on dose, contrast, and noise.

Six different combinations of film-processor temperature (33.3 degrees C, 35 degrees C), development time (22 sec, 44 sec), and chemistry (Du Pont medium contrast developer [MCD] and Kodak rapid process [RP] developer) were each evaluated by separate analyses with Hurter and Driffield curves, test images of plastic step wedges, noise variance analysis, and phantom images; each combination also was evaluated clinically. Du Pont MCD chemistry produced greater contrast than did Kodak RP chemistry. A change in temperature from 33.3 degrees C (92 degrees F) to 35 degrees C (95 degrees F) had the least effect on dose and image contrast. Temperatures of 36.7 degrees C (98 degrees F) and 38.3 degrees C (101 degrees F) also were tested with extended processing. The speed increased for 36.7 degrees C but decreased at 38.3 degrees C. Base plus fog increased, but contrast decreased for these higher temperatures. Increasing development time had the greatest effect on decreasing the dose required for equivalent film darkening when imaging BR12 breast equivalent test objects; ion chamber measurements showed a 32% reduction in dose when the development time was increased from 22 to 44 sec. Although noise variance doubled in images processed with the extended development time, diagnostic capability was not compromised. Extending the processing time for mammographic films was an effective method of dose reduction, whereas varying the processing temperature and chemicals had less effect on contrast and dose.

The reproductive biology of Euchaeta antarctica Giesbrecht (Copepoda: Calanoida) at South Georgia

The reproductive biology of the predatory calanoid copepod Euchaeta antarctica Giesbrecht was investigated in two interconnected fjord systems at South Georgia. Counts of the number of spermatophores attached to adult females and the number of egg sacs encountered, indicated probable peaks of reproduction in summer and winter. Patterns of spermatophore placement were examined and compared with data for E. norvegica (Boeck) from boreal waters. Elemental analysis indicated a high proportion of carbon and a low proportion of nitrogen in adult females and egg sacs from both sites. High winter carbon levels in adults seem related to their predatory feeding habits allowing high food intake throughout the year whereas in egg sacs it probably reflects extended development times and/or non-feeding naupliar stages. Mean adult female and egg clutch dry weights were higher in Cumberland East Bay during winter than in Moraine Fjord during summer. These differences are discussed in the context of relationships between fjord morphology and production levels.

The Rate of Morphogenesis of Embryos and Seeds in Four Species of Grain Legumes

Comparative embryo development has been studied histologically in Lupinus albus , Lupinus mutabilis , Vicia faba , Pisum sativum and Lathyrus latifolius. The detailed histology of the stages of embryo formation up to the early differentiation of tissues of the seed is reported. The rate of embryogenesis has been timed through 15 stages of development from anthesis and comparative rates of tissue formation established between the species. The main observation was the slow rate of morphogenesis of embryos and seeds in Lupinus albus in comparison with the very rapid rate observed in Pisum sativum. A long period at the globular embryo stage, when embryo morphogenesis was inactive contributed to the extended development time of embryos and seeds in Lupinus albus. Slow differentiation of reproductive tissues in L. albus determines late maturity in seeds and pods.

Metabolite‐mediated density‐dependent sex determination in a free‐living nematode, Diplenteron potohikus

The nematode Diplenteron potohikus (Yeates) (Rabditida: Diplogasteridae) shows facultative parthenogenesis: males occur, but rarely exceed 20% of the population. When reared singly in monoxenic culture with Bacillus cereus the eggs always gave rise to females. When reared at 2–50 eggs per 5 cm Petri dish up to 16% developed as males. At higher densities the proportion of males declined. Male‐determining properties could be transferred from old culture media to new media in an aqueous cell‐free leachate of the old media. The effects of this leachate could be mimicked by several indole compounds though indoles could not be detected in the leachate by thin‐layer chromatography. The addition of either indoles or leachate extended development time at 20°C by about 25%. Further effects attributed to the accumulation of the metabolite in old cultures were the inhibition of hatching of embryonated eggs, and the inhibition of the development of the posterior branch of the female reproductive system and its ovary. Both of these phenomena were reversed by transfer of the eggs, or the mature females to fresh media.Such a pheromone‐like substance may be of value in preventing the production of males when populations are small and the probability of finding a mate is low. Thus the production of males at times when their value is low is avoided.

Competitive Interactions and Ecological Strategies of Sarcophagid and Calliphorid Flies Inhabiting Rabbit Carrion

The Calliphoridae (blow flies) and the Sarcophagidae (flesh flies) are families of Diptera containing many necrophagous species which contemporaneously exploit rabbit carrion during the summer season in central California. Calliphorids are the dominant inhabitants, but small populations of sarcophagids regularly occur on carcasses. The various species of flies are known to partition larval food resources, and we examined experimentally the role that interspecific competition plays in determining niche relationships within the fly guild. When calliphorid population density was artificially reduced by selectively interfering with oviposition, sarcophagid population density increased 6-fold. This suggested that competition from calliphorids was the principal factor limiting the population size of sarcophagids. Carcass-exploiting sarcophagids allocate a greater proportion of their resources to nonreproductive activities than do calliphorids. This is evidenced by their ovoviviparous reproductive habit, larger body size, reduced fecundity, delayed age of 1st reproduction and extended development time. The total life history strategy of sarcophagids is geared to the production of a few off-spring which rapidly utilize fresh carrion prior to exploitation, and often overexploitation, by the opportunistic calliphorids.

Effects of mercury on survival and development of the larval grass shrimp Palaemonetes vulgaris

Effects of 7 concentrations of mercury from 0.0 (control) to 0.056 ppm on survival and development of the larval grass shrimp Palaemonetes vulgaris (Say) were investigated. A concentration of 0.056 ppm Hg was toxic to all larvae within 24 h, but below a threshold level (≤0.0056 ppm) no lethal effect occurred within 48 h. Feeding appeared to increase slightly the resistance of P. vulgaris larvae to mercury, and 48-h TLm's (median tolerance limits) for fed and unfed larvae were 0.0156 and 0.0100 ppm, respectively. Delayed effects of 48-h exposure to sublethal mercury concentrations which appeared in later post-exposure rearing of the larvae included (1) reduced survival to the postlarval stage, (2) delayed molting, (3) extended development time, (4) increased numbers of larval instars, and (5) morphological deforment

A Practical Artificial Diet for Laboratory Rearing of the Alfalfa Weevil, Hypera postica (Gyllenhal)1

The alfalfa weevil, Hypera postica (Gyllenhal), is an important pest in the United States. The development of nonpesticidal control measures and mass-rearing of this species can be facilitated by the use of a practical artificial diet. Several available artificial diets (Huggans and Blickenstaff 1963; Nash and Tombes 1966; Tombes 1966) are unsatisfactory, with a low adult yield and extended development time. One major obstacle is the insect's high degree of host specificity. We studied several aspects of host selection and feeding behavior (Hsiao 1969, a, b; Hsiao, unpublished data) and used our results to formulate a suitable artificial diet for rearing the alfalfa weevil (Hsiao and Hsiao, 1974). The diet, although adequate for rearing this species from egg to adult, contains many ingredients costly and impractical for general use. We therefore tried to formulate a practical rearing medium suitable for a large scale operation. Wheat germ and alfalfa leaf powder were the major constituents of the resultant diet, which we describe here.