Stephen D. Danielson

The Fatty Acid Compositions of Phospholipids and Triacylglycerols from Two Chinch Bug Species Blissus leucopterus leucopterus and B. iowensis (Insecta: Hemiptera; Lygaeidae) Are Similar to the Characteristic Dipteran Pattern

1. 1. The fatty acid compositions of phospholipids and triacylglycerols prepared from whole chinch bugs Blissus leucopterus leucopterus and B. iowensis were analyzed. 2. 2. The fatty acid profiles from these insects are different from those from all other insect groups so analyzed, except most Diptera. 3. 3. The major components include 16:0 and 18:0, high proportions of 16:1 and 18:1 and low proportions of polyunsaturated fatty acids. 4. 4. The fatty acid profiles were similar for several categories from both species of chinch bugs, including adult males and females, prediapausing and dispausing adults, and nymphs.

Cross-Resistance and Resistance Longevity as Induced by Bean Leaf Beetle, Cerotoma trifurcata and Soybean Looper, Pseudoplusia includens herbivory on Soybean

Cross-resistance, and longevity of resistance, induced by the bean leaf beetle, Cerotoma trifurcata, was studied IN the soybean PI 227687 that exhibited induced response in earlier studies. Bean leaf beetle adults and soybean looper, Pseudoplusia includens, larvae were used to induce resistance and to determine beetle feeding preference. Beetles were collected from soybean fields 2 to 5 days prior to the feeding preference test. The level of cross-resistance induced by soybean looper herbivory to subsequent bean leaf beetle feeding was higher when compared to cross-resistance induced by bean leaf beetle herbivory against subsequent feeding by soybean looper. Further, herbivory by the bean leaf beetle also induced resistance against soybean looper feeding. In the longevity study, leaflets from treated plants were collected 5, 10, 12, 14, 16, 20 and 25 days after initiation of feeding. Pairwise comparisons of leaflets from plants treated by bean leaf beetle herbivory with untreated plants revealed that induced responses were highest 14 and lowest 25 days after initiation of feeding. On other sampling days, levels of induced response varied with the sampling day.

Field resistance of perennial glandular-haired Medicago strains and alfalfa cultivars to the alfalfa weevil

SummaryField plots planted in 1986 to four, perennial, glandular-haired Medicago strains and four alfalfa cultivars were evaluated for alfalfa weevil, [Hypera postica (Gyllenhal)], abundance and feeding damage as well as plant height from 23 April through 21 may 1987 and from 25 April through 26 May 1988. The plots were located near Mead, Nebraska and both sweep and stem sampling methods were utilized. In 1987, M. glandulosa had the fewest larvae present in sweep samples on 1, 9, and 15 May, although on the last date it did not differ significantly from three other entries. The glandular-haired M. glandulosa also was among those entries having the fewest number of larvae present in stem samples on 9 May, 1987. Significant differences in the number of damaged stem tips were observed on 9 and 21 May, 1987, when M. glandulosa was among those entries having the least amount of damage. The other three glandular-haired strains had larval infestations and damage similar to those for the cultivars. Weevil abundance and damage were generally low in 1988. Medicago glandulosa was shortest of the glandular-haired strains, which were shorter than the cultivars.

Effects of Aphid (Homoptera) Abundance and Surrounding Vegetation on the Encounter Rate of Coccinellidae (Coleoptera), Chrysopidae (Neuroptera), and Nabidae (Hemiptera) in Alfalfa

Predaceous insect encounter rate was measured in 21 southeast Nebraska alfalfa fields through weekly sweep net sampling during 2002–03. The most frequently encountered predaceous insect families we...

lnduced Resistance to Bean Leaf Beetle (Coleoptera:Chrysomelidae) in Soybean

Induced resistance in soybean, Glycine max (L.) Merrill, to the bean leaf beetle, Cerotoma trifurcata (Forster), was investigated in greenhouse experiments using the treatments of mechanical injury...

Bean leaf beetle (Coleoptera: Chrysomelidae) abundance in soybean fields protected and unprotected by shelterbelts.

The bean leaf beetle, Cerotoma trifurcata (Forster) (Coleoptera: Chrysomelidae), is a major insect pest of soybean in Nebraska and throughout much of the Midwest. This insect overwinters in the adult stage in litter in wooded areas such as shelterbelts. Historically, crop producers have been unsure of the merits of shelterbelts, especially if nearby crops are more likely to be infested by insect pests as a result. In this study, bean leaf beetle adults were sampled during the season by visually counting the number of beetles found on soybean plants early in the season and by sweep net sampling once plants were at the V4 stage (approximately 0.33 m tall). Sampling was done in 1997 and 1998 at the University of Nebraska Agricultural Research and Development Center in Saunders Co. in east-central Nebraska. Beetle counts were compared between shelterbelt-protected and -unprotected fields. In general. bean leaf beetles were more numerous in 1997 than in 1998, with abundance peaks occurring in late-July and early-September in both years. There were significant differences in bean leaf beetle counts from protected and unprotected fields on only three of the 11 and four of the 13 sampling dates in 1997 and 1998, respectively. On the sampling dates when significant differences were found, two of three in 1997 and three of four in 1998 had higher bean leaf beetle abundance in the protected soybean fields. The results of this study indicate a tendency for more bean leaf beetles in shelterbelt-protected soybean fields when differences are found, but beetle numbers were not significantly different between protected and unprotected fields on the majority of sample dates in the two years of this study. This study also reconfirms the presence of two generations of the bean leaf beetle in Nebraska.

Glandular hair densities in three perennial Medicago species

SummaryBecause a number of insect pests periodically reduce the yields and/or quality of alfalfa, control measures are often required to prevent or limit losses. Physical characteristics such as glandular hairs have been associated with resistance to alfalfa insect pests. This study was conducted to determine the occurrence and relationships of glandular hair density on three perennial Medicago species that can be crossed with alfalfa, M. sativa L. Glandular hairs were visually counted on the stem, leaflet margin, abaxial leaflet surface, leaf midrib, and petiole of M. glandulosa David, M. glutinosa Marshall Von Bieberstein, and M. prostrata Jacquin. Environmental and genotypic correlations were obtained to estimate the relationships between hair densities on different structures of each Medicago species. Erect glandular hairs were present on all the vegetative structures of the plants, but density and distribution varied within species. Mean hair density was relatively high and uniform on stems, petioles, leaflet margins, midribs, and abaxial leaflet surfaces of M. prostrata.Glandular hair densities were more dense on stems and petioles than on the leaflets of M. glandulosa and M. glutinosa. Relatively high genotypic and environmental correlation coefficients were obtained when hair densities on stems, petioles, leaflet margins, abaxial leaflet surfaces, and leaflet midribs were compared. Selection on the basis of glandular hair density on one Medicago structure can lead to correlated responses in glandular hair density on other structures on the plant.