Mechanisms Underlying Resistance of Strawberry Cultivars to Tarnished Plant Bugs

ReportThe present study investigated mechanisms that underlie resistance of strawberry cultivars to tarnished plant bugs, Lygus lineolaris (Hemiptera: Miridae). Inter-plant distribution of emerged nymphs in cage experiments suggests that females lay more eggs on plants with numerous fruits, although cultivar per se did not influence oviposition behavior of females. A large number of nymphs emerged from the inflorescence of strawberry plants, which suggests that ovipositing females may cause extensive damage to strawberry fruits. Distinct within-plant distribution of emerged nymphs for different cultivars further suggest that the relative damage caused by ovipositing females may vary for different cultivars

Leaf pubescence mediates the abundance of non-prey food and the density of the predatory mite Typhlodromus pyri

Plants with leaves having numerous trichomes or domatia frequently harbor greater numbers of phytoseiid mites than do plant with leaves that lack these structures. We tested the hypothesis that this pattern occurs, in part, with Typhlodromus pyri because trichomes increase the capture of pollen or fungal spores that serve as alternative food. Using a common garden orchard, we found that apple varieties with trichome-rich leaves had 2-3 times more pollen and fungal spores compared to varieties with trichome-sparse leaves. We also studied the effects of leaf trichome density and pollen augmentation on T. pyri abundance to test the hypothesis that leaf trichomes mediate pollen and fungal spore capture and retention and thereby influence phytoseiid numbers. Cattail pollen (Typha sp.) was applied weekly to mature ‘McIntosh' and ‘Red Delicious' trees grown in an orchard and, in a separate experiment, to potted trees of the same varieties. ‘McIntosh' trees have leaves with many trichomes whereas leaves on the ‘Red Delicious' trees have roughly half as many trichomes. With both field-grown and potted trees, adding cattail pollen to ‘Red Delicious' trees increased T. pyri numbers compared to ‘Red Delicious' trees without pollen augmentation. In contrast, cattail pollen augmentation had no effect on T. pyri populations on ‘McIntosh' trees. Augmentation with cattail pollen most likely supplemented a lower supply of naturally available alternative food on ‘Red Delicous' leaves and thereby enhanced predator abundance. These studies indicate that larger populations of T. pyri on pubescent plants are due, in part, to the increased capture and retention of pollen and fungal spores that serve as alternative food

Architecture and consequent physiological properties of the semitendinosus muscle in domestic goats

Morphological and physiological analyses confirm that the semitendinosus muscle of goats contains two separate compartments in series, each with distinct innervation. These compartments of the muscle are in turn composed of short fibers (approximately four fibers in series in the proximal compartment and seven to eight fibers in the distal compartment) which overlap each other for more than 30% of their length, with much of the overlapping portions consisting of slender tails that terminate at one-tenth of the midfiber diameter. Groups of fibers are associated into relatively narrow bands that run end-to-end in each compartment. The data suggest that the maximum length of muscle fibers may be limited; even the fibers of parallelfibered muscles may not scale with the dimension of the animal.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/50284/1/1051990305_ftp.pd

Genotypic Variation in Constitutive and Induced Resistance in Grapes against Spider Mite (Acari: Tetranychidae) Herbivores

We examined genotypic variation in constitutive and induced resistance in grapes against Willamette spider mites, Eotetranychus willametti Ewing, and Pacific spider mites, Tetranychus pacificus McGregor, 2 common species of tetranychid mites found in California vineyards. We found evidence that early-season injury by Pacific mites induced resistance against subsequent Willamette mite populations but early-season injury by Willamette mites did not induce resistance against subsequent Willamette mite populations. Significant levels of induction were detected for several cultivars of the Old World species Vitis vinifera L. as well as the North American species V. calif arnica Bentham. Phylogenetic relationships among grape genotypes explained little of the variation we observed in induced resistance. Phylogenetic relatedness among grapes did help explain patterns of constitutive resistance for Pacific mites; cultivars of V. vinifera L. tended to be susceptible, whereas North American species were resistant. Wi11amette mites, however, performed well on some Old World cultivars and 2 North American species of Vitis that are native to California. We did not find any strong evidence of a negative correlation between constitutive resistance and strength of induction for these grape genotypes. Our results show that several factors contribute to variation in constitutive and induced resistance in grapes against these 2 species of spider mites, including grape genotype, previous history of mite injury (induction), the species of mite causing previous injury, and to some extent, phylogenetic relatedness among grapes. We also suspect that mite genotype has important influence

Biological Control of Spider Mites in Long Island Vineyards

NYS IPM Type: Project ReportThe mite Typhlodromus pyri can, where it is conserved, provide complete biological control of European red mite. We released T. pyri into vineyards on Long Island in 1996 and into an additional two vineyards in 1997. Typhlodromus pyri were recovered from all four release locations. Where the predators were released in 1996, T. pyri numbers were relatively high in early summer during 1997, but then declined in number. At one of these sites T. pyri apparently provided biological control of European red mite. Where T. pyri were released in 1997, the predators were moderately abundant during the entire season. At both of these locations T. pyri provided biological of European red mite. Typhlodromus pyri were also recovered from plots where the predators were not released. This suggest that T. pyri are endemic to Long Island vineyards, but are probably not as resistant to certain pesticides as those predators from Geneva, NY

Impact of Taedia scrupeus (Hemiptera: Miridae) Feeding on Cluster Development in Concord Grapes

Taedia scrupeus (Say) feeds on grape clusters and shoots early in the growing season. The impact of nymphal and adult feeding was assessed at the individual shoot level by confining nymphs within sleeve cages at 4 different times: prebloom, bloom, postbloom, and prebloom to postbloom. Prebloom feeding significantly reduced the number of berries per cluster and average berry weight, resulting in a 68% reduction in cluster weight. When nymphs were allowed to feed from prebloom to postbloom, cluster weight was reduced by 71%.Feeding only during bloom and postbloom did not affect cluster weight. Prebloom feeding reduced the number of florets per cluster, berries per cluster, and berry weight. The whole-vine impact of T. scrupeus was examined in a commercial Concord vineyard, where 3-vine experimental units were treated with carbaryl to remove T Scrupeus or were left untreated. Unsprayed vines, with a mean density of 20 T. scrupeus per vine, yielded 10.4 kg per vine, and sprayed vines without injury yielded 14.1 kg per vine. The yield component most strongly affected was the number of clusters per vine, which averaged 165.4 and 131.8 per vine in sprayed and unsprayed vines, respectively. Each T. scrupeus nymph was associated with 0.18kg of crop loss, suggesting that as few as 0.5 nymphs per vine can cause economic injury. Where treatment of vineyards to prevent T. scrupeus injury is warranted, it must be applied during the prebloom perio

Use of Entomopathogenic Nematodes for Control of Grape Phylloxera (Homoptera: Phylloxeridae): A Laboratory Evaluation

The effectiveness of 2 species of entomopathogenic nematodes was examined in the laboratory against the root-form of grape phylloxera Daktulosphaira vitifolia (Fitch). Our basic unit of measurement was survival of grape phylloxera established on root pieces of the cultivated grape Vitis vinifera L. variety ‘Cabernet Sauvignon' in the presence or absence of nematodes. In petri dish trials, the Oswego strain of Heterorhabditis bacteriophora Poinar reduced survival of attached grape phylloxera by up to 80% relative to the control treatment, whereas Steinernema glaseri Steiner (isolate 326) had no measurable impact and was not used in further experiments. Hb Oswego significantly reduced survival of grape phylloxera on root pieces placed in small cups filled with soil, but only when soil moisture was high (>13% water content wt:wt) and when high densities of infective nematodes were used (>15,000/g soil). Grape phylloxera exposed to Hb Oswego often turned a brick-red color, indicating successful infection. However, we did not detect any evidence that Hb Oswego could successfully reproduce within the bodies of grape phylloxera hosts. Therefore, although Hb Oswego can exert significant mortality in the laboratory, their use in the field in an augmentative release program may be constrained by the need to use high densities, their dependence on moist soils, and their inability to propagate themselves within grape phylloxera host

Genetic Structure in Native Populations of Grape Phylloxera (Homoptera: Phylloxeridae)

Random amplified polymorphic DNA (RAPD) markers were used to study genetic structure and diversity in native grape phylloxera populations growing on Vitis arizonica Englemann in central Arizona and on V. riparia Michaux in New York. RAPD data from the Arizona collections were clustered into 3 subpopulations, whereas data from the New York collections were not clustered, which reflected topographic features and the distribution of the sampled vines. Similarity coefficients of the 2 collection areas had similar ranges (0.89-1.0). The similarity coefficient between the Arizona and New York collections was 0.62. Analyses of molecular variance were used to partition the variance in genetic distances, and confirmed the results of the dendrogram clustering. The clustering of the Arizona populations is likely the result of gene flow restriction caused by geographic isolation. Greater diversity was expected among the Arizona populations. That diversity levels were similar suggests that other factors, such as inbreeding or past population history, must play a role in the relatively low level of diversity found in Arizon

The interaction of phylloxera infection, rootstock, and irrigation on young Concord grapevine growth

Concord roots are moderately resistant to phylloxera, which form nodosities on the fine roots and weaken the root system. Rootstocks and vineyard floor management both have the potential to eliminate or reduce the effect of phylloxera in New York Concord vineyards. Young, container-grown Concord grapevines were used to evaluate the interaction between rootstock (own-rooted, Couderc 3309), irrigation, and phylloxera infection on vine growth. Phylloxera inoculation alone caused a 21 % decrease in vine dry mass and lack of irrigation (mid-day stem water potential: -0.9 to -1.0 M Pa) alone caused a 34 % decrease in vine dry mass. The combination of phylloxera stress and water stress was additive and caused a 54 % decrease in vine dry mass. Because C3309 rootstock is resistant to phylloxera, the grafted vines showed a response to irrigation but not phylloxera inoculation. This container study shows the potential benefits of irrigating own-rooted Concord grapevines or the use of rootstocks without irrigation to withstand phylloxera infection.