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We examined insect herbivores associated with Heteranthera dubia from surveys conducted from 2006 to 2009. Plants were collected, invertebrates were removed, and signs of feeding damage were noted. Herbivores were quantified, and geographic regions were compared based on herbivore density, taxa richness, evenness, and diversity. The greatest density of herbivores occurred at Parker Pond, Washington, which was largely influenced by an abundance of aphids (Rhopalosiphum spp.). Density, richness, and evenness were not significantly different among regions. At least 23 potential insect herbivores were recorded from 15 sites in Texas, Washington, Minnesota, Wisconsin, Vermont, and New York. Of these, five taxa were collected from the order Lepidoptera, one from Coleoptera, six from Diptera, and at least 11 from Trichoptera. The majority of the herbivores were generalists; several had unknown diets. Damage observed to H. dubia included extensive tunneling in the stems of the plant and, in some cases, substantia...

We applied DNA sequence analysis to Rhopalosiphum aphids, which we had previously characterised by random amplified polymorphic DNA (RAPD) PCR. By comparing two gene sequences, we confirmed that Rhopalosiphum sp. T was a species previously undescribed from New Zealand. Significant differences were also observed between a DNA sequence from New Zealand R. near insertum and a European R. insertum sequence deposited in GenBank. The ribosomal ITS proved to be a more robust marker for aphid identification than suggested by previous studies, and intraspecies variation within the ribosomal ITS sequences appeared to be extremely low. Specific PCR primers based upon differences in the ITS sequence were used to rapidly distinguish R. padi from other Rhopalosiphum species found on New Zealand grain crops.

Theoretical studies have suggested that New Zealand populations of Rhopalosiphum padi should consist of genetically separate lineages. We applied random amplified polymorphic DNA (RAPD) PCR to genetic material of Rhopalosiphum aphids from cereal crops and pastures. Several putative R. padi lineages were detected by RAPD PCR in 1995 samples. Subsequent RAPD analyses produced good evidence for the presence of distinct R. padi lineages in New Zealand but reduced the number of predominant lineages to two and revealed low overall genetic variability. One aphid grouping yielded substantially different RAPD patterns from the other aphids, suggesting the presence of a cryptic New Zealand Rhopalosiphum sp.

Experiments were carried out in wheat fields of Economic Entomology Department, Faculty of Agriculture, Mansoura‐University, during two successive seasons 1997 and 1998. The cereal aphids, Schizaphis graminum (Rond.), Sitobion avenae (Fabr.), Rhopalosiphum padi (L.) and Rhopalosiphum maidis (Fitch.) are the serious pests of the wheat crop at Mansoura district. Four hymenopterous parasitoid species, namely Aphidius uzbekistanicus Luz., Aphidius matricariae Hal., Praon gallicum Hal. and Aphidius rhopalosiphi De Stefani, were recorded as primary parasitoids on the cereal aphid species. The numbers and ratios of these species were as follows: A. uzbekistanicus 516 individuals (40.8%) in 1997 and 488 individuals (44.2%) in 1998, A. matricariae 350 individuals (27.6%) in 1997 and 286 individuals (25.9%) in 1998, Praon gallicum 231 individuals (18.3%) in 1997 and 192 individuals (17.4%) in 1998, A. rhopalosiphi 168 individuals (13.3%) in 1997 and 139 individuals (12.6%) in 1998. The dominant aphid parasitoids sp...

Observations were made in a wheat crop to determine the effects on cereal aphids and their natural enemies of an adjacent crop of flowering canola (Brassica napus L.). More hoverflies (Diptera: Syrphidae) were caught adjacent to the canola than within the wheat crop, and apterous Rhopalosiphum padi (L.) (Hemiptera: Aphididae) were less numerous in the margin than at distances of64 m or more into the wheat. Large amounts of canola pollen were presentin hoverfly guts, especially for insects caught close to, or within, the canola. Earlier tests determined optimal colour, design and position of traps. Yellow traps caught most hoverflies in two six-colour comparisons of water pan traps conducted on grassed areas. In wheat, yellow water pan traps atground level caught as many hoverflies as did yellow sticky traps laid horizontally on the soil surface or vertically oriented yellow sticky traps placed at either ear height or at soil level. Only water pan traps caught large numbers of hoverfly larvae. Significantl...

Aphis gossypii Glover (Hom.: Aphididae) is a damaging pest of protected cucumbers in the UK, and control measures are required which are compatible with other components in the overall cucumber integrated pest management programme. Two methods of establishing the parasitoids, Aphidius colemani Viereck (Hym.: Braconidae), in cucumber crops prior to invasion of the aphids were developed. The first involved weekly releases of small numbers of parasitoids beginning before A. gossypii became established on the plants. The second method used open-rearing units based on maize, wheat and rygrass plants infested with Rhopalosiphum padi L (Hom.: Aphididae), which is a common host to many natural enemies of A. gossypii but not a threat to the cucumber crop. Both methods were found to be more efficient in summer than in late spring. Parasitoid release rates were established for the two control methods at both of these times of the year. Like all biological control measures, these methods will require careful manageme...

Predatory species that are considered beneficial in the limitation of cereal aphids might be expected to display a high preference for aphids. Experiments with several potential generalist aphid predators have revealed a low preference for the aphid Rhopalosiphum padi and a low tolerance limit to the consumption of aphids. In these experiments, the limited tolerance of some carabid beetles and linyphiid spiders to Rhopalosiphum padi is demonstrated. Twenty four h food consumption (mg dw mg−1) of two prey types, R padi and Drosophila melanogaster, was determined in both satiated and starved predator individuals. In most cases the feeding capacity for aphids was found to be consistently lower than for fruit flies. Aspects of the natural control of a pest that is of low preference and is not well tolerated by its predators are discussed.

Flight activity of Rhopalosiphum spp. was recorded in a suction trap between 1981 and 1987. Field studies on cereals in Canterbury during the period 1984–1987 showed that Rhopalosiphum padi L., the most frequent species, was usually present at low densities and only occasionally reached maxima greater than 10 aphids per tiller on wheat (Triticum aestivum L.) or barley (Hordeum vulgare L.). Greater numbers of R. padi were found on rye (Secale cereale L.) than on wheat, barley, oats (Avena sativa L.), or ryegrass cv Tama (Lolium perenne × multiflorum). Rhopalosiphum maidis (Fitch) was frequent on barley in 1985 and 1986 but was rare in other years. Rhopalosiphum insertum (Walker) and R. rufiabdominalis (Sasaki) were recorded on cereals in autumn 1987. Comparison of suction trap catches and numbers of winged aphids landing on cereals showed that R. padi concentrated on barley crops to a lesser extent than did R. maidis or Metopolophium dirhodum (Walker).