Soybean Aphid Insecticide Tests - Preliminary Results

Bryan Jensen, our IPM Coordinator, and Scott Myers, a Ph.D. student in my lab, initiated an insecticide screening trial on 26 July. The beans were R1 and planted in 30 inch rows during early June. We accomplished the 4-day post spray samples on 30 July and I want to share their preliminary data. Remember, these are preliminary data and we have not run any statistical analysis.Originating text in English.Citation: Wedberg, J.L. (2001). Soybean aphid insecticide tests - Preliminary Results. Integrated Pest and Crop Management: News and Resources for Wisconsin Agriculture from the University of Wisconsin. https://web.archive.org/web/20060828144031/http://ipcm.wisc.edu/wcm/pdfs/2001/01-20insect2.htm

Screen Barriers for Reducing Interplot Movement of Three Adult Plant Bug (Hemiptera: Miridae) Species in Small Plot Experiments

Fiberglass screen barriers 1.2 m high were erected around small (7.3 x 3.7 m) plots of birdsfoot trefoil, Lotus corniculatus, to study the effectiveness of screen barriers in reducing adult plant bug migration into small field plots. Screened and unscreened (control) plots were sprayed with an insecticide at the onset of the experiment, and subsequent adult mirid migration into these trefoil plots was measured by sweep net samples during the following 24 day period. Combined adult Adelphocoris lineolatus, Lygus lineolaris, and Plagiognathus chrysanthemi densities were significantly lower in screened versus unscreened plots with 37070, 28010, and 23070 fewer adults at 7, 17, and 24 days, respectively, following insecticide application. Although these barriers were inexpensive and simple to construct, we conclude that they were not practical and effective enough for reducing adult mirid migration in small plot experiments of this type

Survival and Growth of Two \u3ci\u3eHydraecia\u3c/i\u3e Species (Noctuidae: Lepidoptera) on Eight Midwest Grass Species

Grasses play a critical role in the life cycles of both the hop vine borer (Hydraecia immanis) and potato stem borer (H. micacea), two potentially se­rious agriculture pests. Neonate larvae of both species (Noctuidae: Lepidoptera) were reared on eight selected grasses and corn for 14-18 days under greenhouse conditions to determine their survival and growth. These were quackgrass (Agropyron repens), smooth bromegrass (Bromus inermis), orchardgrass (Dactylis glomerata), large crabgrass (Digitaria sanguinalis), barnyardgrass (Echinochloa crusgalli), giant foxtail (Seteria faberii), wild prosso millet (Panicum millaceum), Johnsongrass (Sorghum halepense), and corn (Zea mays). In a separate, concurrent experiment, H. immanis and H. micacea larvae were reared on quackgrass, smooth bromegrass and orchardgrass (narrow-stemmed grasses) and sampled after 7, 10 and 14 days. H. immanis larvae generally grew more slowly and dispersed less quickly than H. micacea larvae. The fewest H. immanis and H. micacea larvae were recovered from giant foxtail. H. immanis larvae reared on quackgrass, smooth bromegrass and orchardgrass (thin-stemmed grasses) outgrew their hosts by the third instar and rapidly dispersed, particularly from quackgrass. Due to the unique internal stem-feeding behavior of these larvae the stem thickness becomes a constraining factor regarding duration of suitability to serve as a larval host. Grass feeding has tremendous significance regarding the geographic spread, local population densities, phenological damage periods, and cultural control methods such as crop rotation for these two noctuid species

Effects of Corn and Selected Weed Species on Feeding Behavior of the Stalk Borer, \u3ci\u3ePapaipema Nebris\u3c/i\u3e (Lepidoptera: Noctuidae)

Experiments were conducted in an outdoor insectary to examine behavioral interactions between fifth instar stalk borers, Papaiperna nebris, and potential host plant species. Plants tested included 6- and 8-leaf stage corn, Zea mays, and ten weed species (six broadleaf and four grass) commonly associated with corn production in southern Wisconsin. Broadleaf plants found to be acceptable hosts included Ambrosia trifida, Arnaranthus retroflexus, Rumex crispus, and Chenopodium album; Asclepias syriaca and Abutilon theophrasti were not acceptable as host plants. Corn and the other grass species (Agropyron repens, Bromus inermis, Dactylis glomerata, and Setaria faberi) were found to be acceptable hosts. All acceptable plants also supported larval development to the pupal stage, though on 6-leaf stage corn and the small-stemmed grasses the majority of larvae dispersed before completing development. Larvae developing on corn, A. triftda, and A. retroflexus pupated within the plant stem, whereas larvae developing on the other plants pupated in the soil near the plant on which they fed. Stalk borer larvae required substantially less time to bore into corn stalks than into the stems of the broadleaf plants. In a limited preference experiment, corn was clearly preferred as a host plant over the three broadleaf and one small-stemmed grass species tested

Suitability of Selected Broad-Leaved Weeds for Survival and Growth of Two Stalk-Boring \u3ci\u3eHydraecia\u3c/i\u3e Species (Lepidoptera: Noctuidae)

Third instar hop vine borer (Hydraecia immanis) and potato stem borer (H. micacea) are new pest species on corn in the Midwest. Early instar larvae feed on small-stemmed grasses, and later instar larvae switch to broad- stemmed hosts to complete development. In order to assess potential suitability of various weeds of corn fields, larvae were reared on seven selected broad- leaved plants for 16-18 days under greenhouse conditions to determine their feeding behavior and performance. Domestic plants included hop (Humulus lupulus) and potato (Solanum tuberosum); weed species included curly dock (Rumex crisp us), redroot pigweed (Amaranthus retroflexus), lambsquarters (Chenopodium album), common ragweed (Ambrosia artemisiifolia) and giant ragweed (A. trifida). Larvae of both species survived best on corn, hop, and curly dock. While potato was an excellent host for the potato stem borer H. micacea, survival was poor for the hop vine borer, H. immanis. Red root pigweed, common ragweed, giant ragweed and lambsquarters were poor hosts for both moth species. While the potato stem borer, H. micacea, larvae were able to grow well and gain weight rapidly on several hosts, the hop stem borer, H. immanis, grew well only on hops. Larval feeding behavior and size, as well as plant phenology, stem thickness, and growth form, are all critical determinants as to whether or not a particular plant species can serve as a final host on which H. immanis and H. micacea can complete development

Survival, Development and Population Dynamics of \u3ci\u3eEmpoasca Fabae\u3c/i\u3e (Homoptera: Cicadellidae) on Three Legume Hosts

Survival and development of potato leafhopper, Empoasca fabae, nymphs were measured on alfalfa (Medicago sativa), birdsfoot trefoil (Lotus corniculatus), and red clover (Trifolium pratense). Survival was not significantly different among host plants (mean = 62%). There was no interaction between sex and host plant for developmental time. Males developed significantly faster than females. Developmental time was fastest on alfalfa, intermediate on trefoil, and slowest on red clover. Plots of alfalfa, trefoil, and red clover were planted to compare the seasonal abundance of the potato leafhopper in the three forages. Nymphs were more abundant in trefoil than in alfalfa and red clover late in July, but no differences occurred on the other sample dates. At their peak, adults were more abundant in alfalfa than in trefoil and red clover

Insect Pests Associated With Birdsfoot Trefoil, \u3ci\u3eLotus Corniculatus\u3c/i\u3e, in Wisconsin

Insect surveys taken during 1984-1986 in Ashland and Bayfield Counties of northern Wisconsin revealed that several potential insect pest species were common in birdsfoot trefoil, Lotus corniculatus. Three plant bug species, including: the tarnished plant bug, Lygus lineolaris: alfalfa plant bug, Adelphocoris lineolatus; and Plagiognathus chrysanthemi were abundant in most sampled fields. P. chrysanthemi was the most abundant species, was only present in the northern locations, and completed one generation per year. A. lineolatus and L. lineolaris were second and third in abundance, respectively, and completed two generations per year. Population levels of the potato leafhopper, Empoasca fabae. exceeded a combined total of 45 nymphs and adults per sweep in a southern Wisconsin location but were uncommon in northern Wisconsin. Present, but less abundant, were the trefoil seed chalcid, Bruchophagus platypterus; meadow spittlebug, Philaenus spumarius; and pea aphid, Acyrthosiphon pisum, all occurring at densities of less than one insect per sweep

Alfalfa weevil pest management program

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