Experimental Evaluation of Arthropod Predation on Pieris rapae (Lepidoptera: Pieridae) Eggs and Larvae in Cabbage

Knowledge of factors causing mortality in herbivorous insects is essential to developing a better understanding of their population dynamics and more effective strategies to manage their abundance in crops. In this study we used 2 methods of predator exclusion to evaluate the effects of arthropod predators on Pieris rapae L. eggs and larvae on cabbages (Brassica oleracea variety capitata L.) in New York State. Survivorship of P. rapae on cabbage plants caged to exclude predators was compared with survivorship on plants in cages that were opened at the bottom to allow access by arthropod predators but not larger predators such as birds. Two cohorts were followed in each of 2 unsprayed cabbage plots in each of 2 yr for a total of 8 cohorts. Estimated mortality of eggs and larvae from arthropod predators ranged from 23 to 80%, averaged 53% for all 8 cohorts, and affected mainly the eggs and 1st instars. Exclusion experiments were also conducted comparing mortality of individual P. rapae eggs protected from predators by rings of Tanglefoot with that of eggs that were left exposed to predators. Mortality attributed to arthropod predators for the entire egg stage among 6 cohorts placed in each of 2 fields ranged from 0 to 44%. Our experiments demonstrate that P. rapae eggs and 1st instars suffer variable, but often quite high mortality from arthropod predators in cabbage fields. Recognizing the important role of these predators is a 1st step toward developing ways to maximize their activity in commercial field

Evidence for multiple structural genes for the γ chain of human fetal hemoglobin

A sequence with a specific residue at each position was proposed for the γ chain of human fetal hemoglobin by Schroeder et al. (1) after a study in which hemoglobin from a number of individual infants was used. We have now examined in part the fetal hemoglobin components of 17 additional infants and have observed that position 136 of the γ chain may be occupied not only by a glycyl residue, as previously reported, but also by an alanyl residue

Feasibility analysis of reciprocating magnetic heat pumps

The conceptual design selected for detailed system analysis and optimization is the reciprocating gadolinium core in a regenerative fluid column within the bore of a superconducting magnet. The thermodynamic properties of gadolinium are given. A computerized literature search for relevant papers was conducted and is being analyzed. Contact was made with suppliers of superconducting magnets and accessories, magnetic materials, and various types of hardware. A description of the model for the thermal analysis of the core and regenerator fluids is included

Superconductivity in a spin liquid - a one dimensional example

We study a one-dimensional model of interacting conduction electrons with a two-fold degenerate band away from half filling. The interaction includes an on-site Coulomb repulsion and Hund's rule coupling. We show that such one-dimensional system has a divergent Cooper pair susceptibility at T = 0, provided the Coulomb interaction $U$ between electrons on the same orbital and the modulus of the Hund's exchange integral $|J|$ are larger than the interorbital Coulomb interaction. It is remarkable that the superconductivity can be achieved for {\it any} sign of $J$. The opening of spectral gaps makes this state stable with respect to direct electron hopping between the orbitals. The scaling dimension of the superconducting order parameter is found to be between 1/4 (small $U$) and 1/2 (large $U$).Comment: 11 pages, Latex, no figure

ARTHROPOD PREDATORS IN CABBAGE (CRUCIFERAE) AND THEIR POTENTIAL AS NATURALLY OCCURRING BIOLOGICAL CONTROL AGENTS FOR PIERIS RAPAE (LEPIDOPTERA: PIERIDAE)

We used three sampling methods to identify the arthropod predators most abundant and active in fields of cabbage, Brassica oleracea L. var. capitata, and determined those most likely to be important predators of the imported cabbageworm, Pieris rapae L., by testing the predators' abilities to forage on cabbage plants and to feed on Pieris rapae in small arenas in the laboratory. Abundance and activity in the field were monitored with pitfall traps, sticky traps applied directly to leaves, and plant samples. Four criteria were used to assess the species' potential value as a predator of Pieris rapae in cabbage: relatively high overall abundance in trap catches and plant samples, occurrence on plant foliage in the field, a high propensity to feed on Pieris rapae eggs and first instars, and the ability to search for larval Pieris rapae on cabbage plants. Four species, the wolf spider Pardosa milvina (Hentz) (Araneae: Lycosidae), the harvestman Phalangium opilio L. (Opiliones: Phalangiidae), and the lady beetles Coleomegilla maculata lengi Timberlake and Hippodamia variegata (Goeze) (Coleoptera: Coccinellidae), demonstrated these attributes, although all four species appeared unable to search for prey on some parts of the cabbage plants, owing to unsure footing on the plants' slippery cuticular wax. Linyphiids (Araneae) and syrphids (Diptera), the most abundant taxa in the plant samples, may prove better at thoroughly searching cabbage plants, but remain to be tested in future laboratory trials. Our results show that only a small portion of the predatory arthropod species that occur in cabbage fields is likely to prey on Pieris rapae on the plants, although important questions remain about the roles of some taxa. Future efforts to enhance biological control of Pieris rapae by naturally occurring predators can now focus on further elucidating and finding ways to enhance the roles of those predators that are effectiv

Ecology of Thysanoptera within Cabbage Fields

The occurrence and species composition of thrips within cabbage fields were studied during 1981 and 1982. Temporal differences in abundance and species composition depended on the spatial relationship of cabbage fields to cereal and forage crops. Sticky traps within cabbage fields recorded peak flights of thrips during maturation and senescence of adjacent wheat or oat fields and cutting of adjacent alfalfa and red clover fields. These data indicate several important findings regarding the ecology of thrips in general and the possible management of Thrips tabaci Lindeman in particular. First, although there are large numbers of thrips in cabbage fields during certain time periods (e.g., maturation or harvesting of crops), most will not be T. tabaci and need not be of concern to cabbage growers. Second, there are significant differences in thrips phenology and species composition in cabbage fields, and these differences appear to be dependent on phenology and management of adjacent field and forage crops. Third, although many other species are present, T. tabaci appears to be present in adequate numbers to infest cabbage at the critical period of head formation. This critical period occurs at different times depending on area, planting date, variety, and weathe

An Effective Theory for Midgap States in Doped Spin Ladder and Spin-Peierls Systems: Liouville Quantum Mechanics

In gapped spin ladder and spin-Peierls systems the introduction of disorder, for example by doping, leads to the appearance of low energy midgap states. The fact that these strongly correlated systems can be mapped onto one dimensional noninteracting fermions provides a rare opportunity to explore systems which have both strong interactions and disorder. In this paper we show that the statistics of the zero energy midgap wave functions in these models can be effectively described by Liouville Quantum Mechanics. This enables us to calculate the disorder averaged N-point correlation functions of these states (the explicit calculation is performed for N=2,3). We find that whilst these midgap states are typically weakly correlated, their disorder averaged correlation are power law. This discrepancy arises because the correlations are not self-averaging and averages of the wave functions are dominated by anomalously strongly correlated configurations.Comment: 13 page latex fil

Advances in Control of Onion Thrips (Thysanoptera: Thripidae) in Cabbage

Onion thrips, Thrips tabaci Lindeman (Thysanoptera: Thripidae), feeding injury results in discoloration and a rough texture on cabbage, Brassica oleracea capitata (L.), leaves, and damage may occur deep inside the head. It has become a key pest of cabbage in the United States and many other countries. Previous studies have indicated poor control using insecticides. The present study identified imidacloprid drenches and sprays of acetamiprid, dimethoate, spinosad, and imidacloprid as insecticides that performed better than the industry standard, lambda-cyhalothrin. However, additional tests with foliar sprays of dimethoate and acetamiprid indicated there was not an ideal crop stage (precupping, cupping, or postcupping) at which either insecticide could be applied for reliable control of T. tabaci, possibly because of multiple flights of thrips into the crop or the asynchrony of flights and susceptible crop stages. In tests in a commercial field, a soil drench of imidacloprid 4 wk after transplanting reduced the number of damaged leaves in the head by 32%, whereas five sprays of acetamiprid reduced damage by 51%. Combining both insecticide regimes reduced damage by 85%, but resulted in a very costly management program. Cabbage varieties varied considerably in susceptibility with some having negligible thrips injury, regardless of being treated with an insecticide. Planting date affected susceptibility of cabbage to some degree, but not as much as other tactics. Overall, these studies indicate that increased emphasis should be placed on breeding cabbages to be resistant to T. tabaci as the foundation for its managemen