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Multiple factors contribute to the significant challenge of obtaining an accurate assessment of infestations of spider mites under field conditions in field crops and trees. In addition, standard practices for counting spider mites do not provide a historical record of individual numbers. We developed and evaluated a new device, the “leaf inspector”, for sampling spider mites. Adhesive tape was pressed toward the underside of leaves of maize, Zea mays L., and spider mites on pieces of tape were counted later with the aid of a stereoscope (16–25 magnification). Sampling spider mites using the leaf inspector in the field required 30–60 seconds per leaf, and subsequent counting of spider mites with the aid of a stereoscope required 8 minutes per piece of tape. We showed that: 1) absolute numbers of spider mites on maize leaves were positively correlated with those obtained with the leaf inspector, 2) leaf dimensions did not significantly affect performance of the leaf inspector, and 3) a residual but fairly constant percentage (about 20%) of spider mites was left behind after a maize leaf had been sampled with the leaf inspector. Thus, a more accurate estimation of spider mite abundance was obtained by adding 20% to each count based on using the leaf inspector.
This study explores the spatial relationship between abundance of Russian wheat aphid, Diuraphis noxia (Mordvilko), and variation in edaphic and topographic factors within fields of wheat, Triticum aestivum L. Data from six wheat fields in Colorado, Wyoming, and Nebraska were analyzed by multiple regression. Data collected were numbers of Russian wheat aphids, aspect, relative elevation, slope, and percentages of clay and sand of soils at 25 geographically referenced sites in each field. Slope and percentage of sand explained 24.2% of the variation in Russian wheat aphid abundance within wheat fields in a model developed using stepwise regression.
Stink bugs have become important pests of cotton, Gossypium hirsutum L., in the Lower Gulf Coast region of Texas. Common species, damage potential, and insecticide susceptibility of stink bugs were assessed. A survey of stink bugs in commercial cotton fields in six counties in the Lower Gulf Coastal region of Texas during 2004 and 2005 revealed that brown stink bug, Euschistus servus (Say); E. quadrator Rolston; and E. obscurus (Palisot) were the most common species (>95% both years), while southern green stink bug, Nezara viridula (L.); and green stink bug, Acrosternum hilare (Say), were less common. This stink bug complex differs from that reported for other areas of the Cotton Belt. Also, significantly more stink bugs were collected in the northern counties of Calhoun, Refugio, and Victoria than in the southern counties of Kleberg, Nueces, and San Patricio (approximately 7.5 and 4 times more in 2004 and 2005, respectively). The potential of E. servus and E. quadrator to damage cotton bolls was compared by caging individual adults on bolls in the field. Both E. servus and E. quadrator caused significant reductions in yield (seed cotton weight) and fiber quality (length and fineness) of cotton bolls. Feeding by both species caused abscission of 1.8-cm-diameter bolls from the plant. In general, E. servus caused more damage to bolls than did E. quadrator and damaged a wider size-range of bolls. Foliar-applied insecticides were evaluated against E. servus, E. quadrator, and N. viridula in small plots of cotton in the field. Dicrotophos was most effective against all species. Pyrethroids killed all N. viridula, but the number of E. servus and E. quadrator killed varied significantly. Euschistus quadrator was more susceptible than E. servus to organophosphate, pyrethroid, neonicotinoid, and carbamate insecticides.
Liriomyza (Diptera: Agromyzidae) leafminers are polyphagous and important pests of vegetables, field crops, and ornamental plants around the world. Liriomyza cause economic damage to vegetable crops in the Lower Rio Grande Valley of Texas. The current species composition of the leafminers and associated parasitoid species is unknown. Infested foliage and pupae collected from sand-filled trays beneath pepper, Capsicum annum L., plants were sampled in fields in the Lower Rio Grande Valley in fall 2007 and spring 2008. Foliage was stored in ziplocked bags to allow specimen emergence, and sand from the trays was sieved to collect pupae. All specimens that emerged as adults were identified and recorded. Liriomyza trifolii (Burgess) was the dominant species in peppers in the Lower Rio Grande Valley, accounting for 99% of the specimens identified. Our survey showed 20 species of parasitoids from four families (Eulophidae, Braconidae, Figitidae, and Pteromalidae) to be associated with L. trifolii. Neochrysacharis formosa (Westwood) was the most abundant parasitoid during both seasons, accounting for ≈60% of the specimens.
Surveys of onion, Allium cepa L., fields in Colorado during 2004–2005 found that a complex of thrips species, comprised of onion thrips, Thrips tabaci Lindeman, and three Frankliniella species, were present in almost every location. Onion thrips predominated, averaging between 82.6 and 84.9% of the thrips recovered during the two seasons. Second in abundance was western flower thrips, F. occidentalis Pergande, that averaged 12.6 and 12.2% of the total thrips found during the two years, respectively. Two additional plant-feeding species, F. tenuicornis (Uzel) and F. schultzei (Trybom), also were recovered from the onion fields, and the latter comprised as much as 42% of the thrips in one southeastern Colorado field survey. The relative proportion of the thrips species in fields varied between sites and during the season, differences that might need to be considered when managing thrips on the onion crop. Three species, F. tenuicornis, F. schultzei, and a predatory species, the vespiform thrips, Franklinothrips vespiformis (Crawford), recovered during this study constitute new state records.
Lantana stick caterpillar, Neogalea sunia (Guenée) (Lepidoptera: Noctuidae), can be a serious, often undetected pest of Lantana, a landscape plant commonly grown for its heat and drought hardiness across the southern United States. This insect is often responsible for loss of flowering by Lantana plants in late summer and early autumn. Replications of 22 cultivars of Lantana plants in containers were evaluated for resistance to the lantana stick caterpillar in a greenhouse at Dallas, TX. A natural infestation of the pest developed in mid-July and dispersed through all the plantings. Larvae were sampled during autumn 1996. Most larvae (2.4 to 4.1) per plant were on ‘Lemon Swirl’, ‘New Gold’, ‘Golden King’, ‘LSG Red Orange’, ‘Dallas Red’, ‘Pink Caprice’, ‘Gold Mound’, and ‘Samantha’. No larvae were found on ‘Weeping Lavender’ or ‘White Lightning’ and only means of 0.1, 0.3, and 0.3 larva per plant were recorded on ‘Imperial Purple’, ‘Weeping White’, and ‘Confetti’, respectively. Additionally, 0.5 or fewer larva was found per plant of ‘Patriot Fire Wagon’ and ‘Patriot Rainbow’. All four cultivars of L. montevidensis (K. Spreng.) Briq. (mean of 0.1 larva per plant) were very resistant, whereas all cultivars of L. camara L. (except Lemon Drop', mean of 0.8), and all L. hybrida hort were susceptible and exceeded one larva per plant. Cultivars with purple, white, or red/yellow flowers were infested with fewer larvae than were cultivars with gold, red, orange/red, yellow, or bicolors of yellow with another color other than red.
A new crane fly species is reported from western Michigan. Adults of Tricyphona (Pentacyphona) michiganensis Taber appear in late summer in the bracken fern understory of aspen-birch-red maple forest. The most remarkable feature of the new species is the wing of the female, which is not reduced like that of its presumably closest relative Tricyphona (Pentacyphona) autumnalis Alexander, but of a length similar to that of the male and sometimes longer. Additional characteristics of both sexes distinguish this crane fly from its consubgeners, most of which are restricted to the southwestern and western United States.
There have been major changes in the availability of over-the-counter insecticides in recent years as older products (e.g., organophosphates and carbamates) have been largely supplanted by pyrethroids. To better understand how these newer materials may work in management of European earwig, Forficula auricularia L., a systematic evaluation was done of formulated pyrethroid insecticides that are currently marketed, comparing them to an established standard, carbaryl. Two of the tested insecticides, esfenvalerate and betacyfluthrin, did not produce significant mortality compared to the water check. Three active ingredients - permethrin, deltamethrin, and bifenthrin - produced significant mortality when tested at the marketed concentration but failed to provide significant mortality at 0.2X dilution. Carbaryl provided irregular control that was significant in only one of the two experiments. These data suggest that the concentration of the insecticides in these over-the-counter products presently sold at retail seems to be at or near the lower amount where earwigs can be controlled. Pre-mixed products containing lambda-cyhalothrin and bifenthrin provided significant mortality of European earwig at the marketed concentration and the lesser diluted rate.
The efficacies of a Beauveria bassiana (Bals.-Criv.) Vuill. native strain (BbPM) and B. bassiana (Bea-Sin™) and Metarhizium anisopliae (Metchnikoff) Sorokin (Meta-Sin™)-based commercial products were evaluated against the imported cabbageworm, Pieris rapae (L). Three concentrations (1.2×1012, 1.2×109, and 1.2×106 conidia per hectare) of BbPM, Bea-Sin™, and Meta-Sin™ were applied to commercial cabbage, Brassica oleracea var. capitata L., to evaluate larval mortality during 2005 and 2006. Sampling was done weekly during a 28-day period. Native strain BbPM (92.7%) and Bea-Sin™ (91.8%) killed significantly more larvae than did Meta-Sin™ (62.6%) during both years. The bioinsecticides were most effective early (on sampling days 7 and 14). In general, viability of B. bassiana conidia ranged between 90 and 93% while that of Meta-Sin™ was 52%. The native strain BbPM provided similar control as Bea-Sin™, and both killed significantly more imported cabbageworm larvae than did Meta-Sin™.
Laboratory bioassays were conducted to evaluate mortality and development of the corn earworm, Helicoverpa zea (Boddie), fed on meridic diet with different incorporated concentrations of the Cry1Ac endotoxin of Bacillus thuringiensis. The basic insect colony was obtained from maize of the Colombian “Piedemonte” eastern plains. LC50 calculated by Probit analysis seven days after starting the experiments with neonate larvae, varied from 3.45 to 6.12 and LC80 from 7.12 to 10 µg/ml. Toxin concentration had a marked influence on larval and pupal development, expressed as weight decrease as toxin concentration increased in the diet. Concentrations near or higher than 1.0 ppm caused high larval mortality and a high percent of deformed pupae. No significant difference between the weights obtained with low dosages and the check was obtained. However, a significant increase of the developmental time of both stages was observed when larvae were fed on diet with concentrations higher than 0.01 µg/ml, meaning a longer feeding period and fever annual generations of this polyphagous insect. It is considered that these basic data represent valuable information on the developmental responses of the insect exposed to transgenic cotton and corn, expressing the Cry1Ac toxin.
The study was conducted to know the host plants of adult insects of lamellicorn beetles related to agricultural areas, such as tropical deciduous forest, spiny forest, and xerophilous brush from the northern region of Sinaloa state, México. The data were collected in the morning and evening from August to October 2008. The 18 adult species collected were included in the genera: Diplotaxis, Phyllophaga, Pelidnota, Cyclocephala, Oxygrylius, Cotinis, Euphoria, and Hybosorus, of which Phyllophaga was the genus with the highest number of host species, with 15 species of plants in total, belonging to 10 plant families. The plants used as food by lamellicorn beetles belong to 26 species and 15 families, of which the Fabacea family was the most visited. Within this family the “bacaporo”, Parkinsonia aculeate was preferred by a total of 11 species of beetles.
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