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Pieris rapae (L.) an important pest of cole crops in the northeastern United States, is susceptible to a granulosis virus,Pieris rapae GV (PrGV), that has been shown to be an effective control measure by researchers in several countries. As an alternative to weekly applications of virus to protect cabbage, we tested the use of an action threshold of one small (first-third instar) larva per plant. Results were compared with those obtained using the same threshold with permethrin, and with weekly applications of virus. Plots treated weekly with virus received 5 applications but the action threshold was exceeded only once. In all virus-treated plots, numbers of large (fourth-fifth instar) larvae remained below 0.35 per plant, and were lower at the end of the season (0.07 in plots treated weekly and 0.1 in plots treated once) than in either the untreated or permethrin-treated plots (0.5). In late August, numbers of large larvae in the check plots reached almost 3 per plant. At harvest the number of feeding holes over 0.3 cm in diameter in the 4 innermost frame and the 4 wrapper leaves were counted. Check plots differed from treated plots by an average of 124.2±6.5 holes per plant in the frame and wrapper leave; virus-treated plots had 51.1±6.9 holes more than the permethrin plots. The difference in overall damage between plots treated 5 times with virus during the season and those treated once was not significant. Plots treated once with virus had significantly more damage (7.6±2.7) to wrapper leaves than those treated five times and marketability ratings were somewhat lower, based on fresh market standards. There were no significant differences in head weight among the treatments. At harvest, a high proportion of larvae collected from the check plots were diseased (77% versus an average of 46% in the treated plots). Because of the high numbers of large larvae in the check plots in late August and the extensive damage to plants, we assumed that virus did not affect a significant number of larvae in these plots until late in the growing season. These results indicate the usefulness of PrGV in a cabbage IPM program and that the use of action thresholds can be highly effective, particularly when insect numbers only occasionally reach damaging levels. While cabbage treated with permethrin had the least amount of injury, that treated weekly with virus was not significantly different by fresh market standards, and all cabbages treated with virus met processing standards. For the fresh market, in which cosmetic standards are more important, PrGV may have to be used weekly or with an action threshold lower than one small larva per plant.

Original Publication: Webb, Susan. 2002. “Insect Management for Onions, Leek, and Garlic”. EDIS 2002 (1). https://doi.org/10.32473/edis-ig153-2002. Minor revisions: 2006, 2007, 2010, 2013, and 2017.

Calcium signals appear throughout the first 24 hours of zebrafish development. These begin at egg activation, then continue to be generated throughout the subsequent zygote, cleavage, blastula, gastrula, and segmentation periods. They are thus associated with the major phases of pattern formation: cell proliferation, cell differentiation, axis determination, the generation of primary germ layers, the emergence of rudimentary organ systems, and therefore the establishment of the basic vertebrate body plan. When signals need to be transmitted across significant distances they take the form of waves, either intracellular waves when the cell size is large, or later in development when the cell size is reduced, intercellular waves. We will consider both types of calcium signals and their integration into signalling networks, and discuss their possible functions and developmental significance with regard to pattern formation. BioEssays 22:113-123, 2000.

In this study we investigate the influence of Hepatocyte Growth Factor (HGF) on the motility of embryonic forelimb myoblasts. Using Blindwell chemotactic chambers, it was found that HGF at concentrations of 1-50 ng/ml dramatically enhanced the ability of myogenic cells to migrate. This stimulatory effect was elicited in a dose-dependent fashion and the effect was reversed with the addition of HGF neutralizing antibodies. A checkerboard analysis was performed and it revealed that HGF's effect on limb myoblast motility was through both chemokinesis and chemotaxis. HGF was also examined for its ability to stimulate myogenic cell proliferation, using MF20 antibody as the myogenic marker. At all concentrations tested, HGF did not stimulate an overall increase in the numbers of MF20-positive myoblasts in culture. To examine the chemokinetic effect of HGF on cell migration in the limb, cells were isolated from the proximal regions of the limb (areas rich in myogenic cells), exposed to HGF, labeled with DiI and transplanted into 11.5 day mouse forelimbs. After 36 h of culture, it was found that DiI-labeled limb cells, pretreated with HGF, migrated significantly further in the limb than labeled cells that have not been exposed to HGF. The chemotactic effect of HGF was also investigated by implanting beads loaded with and without HGF into the 11.5 day limb. Proximal to the beads, DiI-labeled limb cells were also transplanted. It was found that HGF was able to chemotactically attract and direct the migration of DiI-labeled limb cells. Immunohistological staining was performed with HGF antibodies to determine the distribution of HGF in the 11.5 day mouse forelimb. It was found that HGF was strongly expressed by the apical ectodermal ridge (AER), the ectoderm and the mesenchyme directly beneath the AER. Positive staining was also obtained for the myogenic regions. However, the pattern was heterogeneous--punctuated with myogenic cells expressing and not expressing HGF.

The effect of platelet-derived growth factor (PDGF) isoforms on limb myoblast migration was examined in vitro. Using Blindwell Chemotaxis chambers, the ability of PDGF-AA, -AB and -BB to stimulate the migration of myoblasts, obtained from the proximal region of 11.5 day mouse forelimb buds, was examined. Immunocytochemistry, with the anti-sarcomeric myosin antibody MF-20, was used to identify the myogenic cells in the heterogeneous cell population. Myoblasts, suspended in PDGF-free medium in the upper chamber, migrated across the polycarbonate filter of the Blindwell chamber to 1-10 ng/ml PDGF-AB and 1-100 ng/ml PDGF-BB situated in the lower well. At 1-10 ng/ml of either PDGF-AB or -BB migration increased in a dose-dependent manner. PDGF-AA, however, was unable to elicit a significant locomotory response in forelimb myoblasts. A Checkerboard assay, with various concentrations of PDGF-AA, -AB or -BB in the upper and lower wells of the chamber, indicated that -AB and -BB but not -AA stimulated the random migration of limb myoblasts. The differential effect of PDGF isoforms on myoblast migration was compared with other aspects of skeletal muscle development. At 0.1-10 ng/ml all three isoforms were able to stimulate an increase in the number of differentiated myoblasts, indicated by the expression of sarcomeric myosin, on examination after 48 h when cultured at low density. In high density cultures, however, these isoforms inhibited myoblast fusion when compared to the spontaneous fusion observed in untreated cultures. Immunohistochemical studies of both cultured limb cells and cryosections of 11.5 day whole limbs revealed that myoblasts expressed both PDGF alpha- and beta-receptors which suggests that the action of PDGF isoforms on limb myoblasts is receptor-mediated. Finally, having demonstrated that the PDGF-B monomer stimulates migration in limb myoblasts, by immunohistochemistry, the presence of PDGF-B was confirmed and its distribution examined in the 11.5 day forelimb.

Fibroblast growth factors (FGFs) are believed to be vital for limb outgrowth and patterning during embryonic development. Although the effect of FGFs on the formation of the skeletal elements has been studied in detail, their effect on the development of the limb musculature is still uncertain. In this study, we used Blindwell chemotactic chambers to examine the effect of FGF-2 and FGF-4 on the motility of myogenic cells obtained from the proximal region of the day 11.5 mouse forelimbs. The limb myogenic cells were found to be chemotactically attracted to FGF-2 and FGF-4 at 10-50 ng/ml. Both FGFs increased myogenic cell migration in a dose-dependent manner, with maximal responses attained at 1-50 ng/ml for FGF-2 and at 10 ng/ml for FGF-4; however, FGF-2 was found to be a more potent chemoattractant than FGF-4. It was possible to inhibit the myogenic cells' response to FGF-2 and FGF-4 by the addition of the appropriate neutralizing antibody. The effects of FGF-2 on cell migration were further investigated by loading this cytokine into Affi-Gel blue beads and transplanting them into day 11.5 forelimb buds. The results showed that FGF-2 attracted DiI-labelled proximal cells to migrate toward the implanted beads and that the migration was more extensive than that observed in the absence of FGF-2. A checkerboard assay was performed in which various concentrations of FGF-2 and FGF-4 were introduced to both the upper and lower wells of the Blindwell chambers. The results indicated that both FGF isoforms can stimulate chemokinesis as well as chemotaxis in myogenic cells. In addition, the effect of FGF-2 at 0.1-10 ng/ml stimulated a significant increase in the number of myocytes expressing sarcomeric myosin on examination after 48 hr in culture, but the effect of FGF-4 was negligible at all concentrations analyzed; however, both FGF-2 and FGF-4 inhibited myocyte fusion compared with the spontaneous fusion observed in control cultures. Finally, we used in situ hybridization and immunohistochemical techniques to determine the distribution of myogenic cells and FGF-2 protein in the day 11.5 mouse forelimbs.

The expression of the soluble 170 kDa brain protein (BP170) was studied in the developing human brain. Using immunohistochemical methods, it was possible to demonstrate that BP170 was expressed very strongly in the visual cortex up to approximately 27 weeks of gestation. After this time, the level of expression was reduced so that by adulthood the levels of BP170 were negligible. Similarly, BP170 was expressed in the hippocampus at all stages of development; however, unlike in the visual cortex, this protein was still apparent, albeit at low levels, in the adult. In addition, BP170 was co-expressed with tyrosine hydroxylase which suggests its possible role in the dopamine pathway.

Transgenic mice were used to study the effect of the neural tube on somite myogenesis. These mice express a transgene in which the 1 kb DNA 5' regulatory sequence of the desmin gene is linked to a reporter gene which codes for E. coli beta-galactosidase. In order to determine whether the developmental fate of cells, specifically the prospective myogenic population, in newly developed somites was pre-determined, newly formed somites were isolated from the caudal region of day 9.5 transgenic embryos and transplanted into 8.5 day non-transgenic host embryos. Even though the implanted somites were not oriented in the host embryos, all the specimens examined developed normally at the graft site forming a dermatome, myotome and sclerotome in the correct anatomical positions. The myotome even expressed the desmin transgene. In addition, we isolated the 3 most caudal somites, that is, the most recently developed somites, from day 9.5 transgenic embryos and maintained them on gelatin-coated coverslips in culture for up to 4 days. While these somite explants did not develop myoblasts, it was possible to induce myogenesis by introducing pieces of neural tube into the explant cultures. These results suggest that the developmental fate of cells within the newly formed somite is not predetermined, but is dependent on the microenvironment surrounding the developing somite.

Watermelon was direct-seeded on 30 Mar at the Central Florida Research and Education Center, Leesburg, FL. Each plot consisted of four 35-ft rows, 7 ft apart with plants spaced 2.5 ft apart. Treatments were replicated four times in an RCB design. Fungicide (mancozeb or chlorothalonil) was applied weekly, usually 2 d after insecticides. All materials were applied with a 2-row tractor-mounted boom sprayer with 18 Albuz (lilac) ceramic hollow cone nozzles, spaced 8 inches apart, delivering 178 gpa at 400 psi or 133 gpa at 200 psi (CGA-215944 and Thiodan only). Silwet (0.02% or 0.03%, vohvol) was tank-mixed with Mycotrol. CGA-215944 was tested for aphid control only and was applied when the number of aphids exceeded five per leaf (high rate on 24 May only, low rate on 24 May and 7 Jun). All other treatments were applied on 24 May, 1,7, 13, and 20 Jun except Thiodan which was not applied on 24 May. Small whitefly nymphs (first and second instars) and large nymphs (third and fourth instars, pupae) were counted and summed on three 0.6-inch diam leaf disks cut from each of 20 leaves per plot for 5 weeks, beginning on 29 May and ending on 26 Jun. Aphids were counted on whole leaves. A square root transformation was used to stabilize the variance of counts for analysis. A two-way ANOVA and a mean separation test (Waller-Duncan k-ratio) were used to determine differences among treatments.

A new mathematical formulation is presented for the analysis of eccentrically stiffened plates, subjected to the combined or separate actions of lateral and in-plane loading. The formulation covers angle and tee section stiffeners as well as rectangular flats. Both material and geometric non-linearities are considered and the governing equations are solved numerically by the application of dynamic relaxation to their finite difference equivalents. Plasticity in the plate is assumed to be governed by a full depth yield criterion, while in the stiffeners, a multilayer approach is adopted. Numerical solutions are presented for a series of plates stiffened by flats, for a wide range of panel slenderness ratios and stiffener rigidities. The effects of initial deformation, combined lateral and in-plane loading and the use of hybrid plates are also investigated. (Author/TRRL)

A simulation model of the sterile insect release (SIR) method of population suppression was developed as a modeling exercise by advanced students of integrated pest management (IPM). Objectives were to create an instructional model that would demonstrate the principles and operation of the SIR technique to undergraduate IPM students, and allow users to see the effects of relaxing or violating various assumptions of the basic model. In particular, the influence of dispersal, spatial distribution of wild and sterile insects, uncertainty about the initial population density, and stochastic processes can be examined by simulation. Ease of changing the qualitative structure of the model and quantitative values of parameters, along with rapid execution and graphic display on a microcomputer, enhance the instructional value of the model. Simulations show that adjustment of the number of sterile males released can generally compensate for variations in competitiveness of sterile males and uncertainty about the survival rate, fecundity and sex ratio of wild insects. However, dispersal and spatial heterogeneity of the target population place more severe demands on the technique. Release of sterile males in a buffer zone surrounding an isolated population is necessary whenever dispersal is likely, but high mobility of the target species and economic and practical considerations may limit the feasibility and success of this approach. Release ratios that greatly exceed expected necessary levels may fail to ensure eradication due to variations in local pest density and sampling errors. Inadequate detection methods may add to the difficulty of eradicating mobile pests. Knowledge of emigration probabilities and dispersal distances, carefully designed sampling and release programs that take spatial heterogeneity of density into account, and efficient detection methods are all essential to success of the SIR technique.

One commercial field, located near Avon, NY, was used for this test. The field was divided into 4 sections and each section contained a subsection of 100 plants in the silking stage. On the silks of each of the 400 plants, 15 newly hatched FAW larvae were deposited on 3 Aug. On 5 Aug, each section was sprayed with 1 of 3 insecticides. Additional sprays of each insecticide were applied on 13 and 19 Aug. A spray of Penncap was substituted for the 19 Aug EPN spray because of PHI. A Grumman Air Cat, delivering 3 gal/acre, was used to apply the sprays. At harvest (29 Aug), 50 ears from each treatment were evaluated for damage.