Aphid

About: Aphid is a research topic. Over the lifetime, 11380 publications have been published within this topic receiving 229721 citations. The topic is also known as: Aphidoidea & plant lice.

How nutritionally imbalanced is phloem sap for aphids

Abstract: Aphids harbour intracellular symbionts (Buchnera) that provide their host with amino acids present in low amounts in their diet, phloem sap. To find out the extent to which aphids depend on their symbionts for synthesis of individual essential amino acids, we have evaluated how well phloem sap amino acid composition matches the aphids’ needs. Amino acid compositions of the ingested phloem sap were compared to amino acids in aphid body proteins and also to available information about optimal diet composition for other plant feeding insects. Phloem sap data from severed stylets of two aphid species, Rhopalosiphum padi (L.) (Homoptera: Aphididae) feeding on wheat, and Uroleucon sonchi (L.) (Homoptera: Aphididae) feeding on Sonchus oleraceus (L.), together with published information on phloem sap compositions from other plant species were used.

Competition between gall aphids and natural plant sinks: plant architecture affects resistance to galling

Abstract: Gall forming herbivores induce sinks and act as phloem parasites within their host plants. Their performance on the host plant can depend on the sink-source relationship they establish with the plant. Because sink-source relationships within a plant are reflected in its architecture, we examined how architectural differences among cottonwoods might influence the success of the galling aphid, Pemphigus betae. Using cloned cottonwoods in common garden studies, we found three major patterns. First, there is a significant clonal or genetic component to tree architecture; cloned trees grown in a common garden maintain the architecture of parental trees. Second, resistant tree genotypes have more natural sinks (i.e., buds) relative to sources (i.e., stem volume) than susceptible trees. Third, these differences in architecture result in greater competition among sinks on aphid-resistant trees than on aphid-susceptible trees. Sink competition within a tree was estimated by the Gini coefficient which quantifies the size inequality of a shoot population (i.e., competition among sinks is low when shoots are nearly equal in size, and great when a few shoots are large and most are small). Aphid death through gall abortion increased significantly (r 2 = 0.65) on garden-grown trees as competition among sinks within a tree increased. Based on these observations we proposed the "sink competition hypothesis" to account for the performance of gall formers on their host plants. To test this hypothesis, we experimentally reduced sink densities (i.e., buds) on branches of resistant tree genotypes to resemble the bud densities of susceptible genotypes. By reducing the number of competing sinks, we predicted that aphid survival would increase. As predicted, aphid survival significantly increased. For example, in one removal experiment, aphid survival increased from 20% on control branches to 55% on branches with the highest level of bud removal. Similar bud removals on susceptible trees did not increase aphid survival, indicating that competition is relaxed on susceptible hosts. With the exception of the plant vigor hypothesis, most current hypotheses explaining herbivore distributions in nature focus on the importance to leaf-chewing herbivores of variation in chemistry. We believe that a sink competition model is needed to explain the distributions of the diverse group of herbivores that act as phloem parasites. The sink competition model is more mechanistic than the vigor hypothesis, and may account for apparent contradictions because it more clearly quantifies the resource base and the potential interactions that occur when sinks, either herbivore-induced or natural, compete for sources.

Host alternation in aphis fabae scop. i. feeding preferences and fecundity in relation to the age and kind of leaves

Abstract: The feeding preferences and comparative fecundity of laboratory-bred, alienicolae alatae of Aphis fabae were investigated in small leaf cages on spindle and sugar beet leaves, representing a winter and a summer host respectively, both in pots in the greenhouse and while growing naturally outdoors. The aphids' readiness to stay and feed, and their average reproduction rate, both varied between leaves of different ages and kinds, and there was evidence of true fecundity differences among aphids feeding on different leaves. As a general rule, readiness to settle and reproduction rate varied together in the same sense, but they did so significantly less often in comparisons between leaves of different kinds, spindle and beet, than in comparisons between leaves of one kind only. Among the leaves on the same kind of plant, the aphids preferred to feed and reproduced faster, on the whole, on young and early senescent leaves than on mature ones. To a limited extent, this rule seemed to govern also the aphids' comparative readiness to settle and reproduce, as between leaves of the two different kinds of plant. Allowing for age-differences among the leaves, the aphids settled and reproduced better on spindle than on beet leaves. Since the aphids used were alienicolae, this tends to confirm the usual designation of the winter host as primary and the summer hosts as secondary, for a given aphid species. These findings form the basis of a dual discrimination theory of host selection, which assumes that aphids respond behaviourally to at least two main classes of leaf property: one associated with the age of the leaf and the other with the kind of plant. It is suggested that in nature these two sensory requirements of the aphids may be essentially contradictory, and that the shifting patterns of aphid distribution among leaves and plants may depend on the shifting distribution of leaves offering a satisfactory compromise between them. The phenomenon of host alternation is considered in the light of the dual discrimination theory, as a particular instance of a shifting distribution-pattern probably connected with the alternation of the seasons of active growth and senescence in the winter and summer host plants.

Sugarcane Aphid (Hemiptera: Aphididae): A New Pest on Sorghum in North America.

Abstract: In 2013, the sugarcane aphid, Melanaphis sacchari (Zehntner) (Hemiptera: Aphididae), a new invasive pest of sorghum species in North America, was confirmed on sorghum in 4 states and 38 counties in the United States. In 2015, the aphid was reported on sorghum in 17 states and over 400 counties as well as all sorghum-producing regions in Mexico. Ability to overwinter on living annual and perennial hosts in southern sorghum-producing areas and wind-aided movement of alate aphids appear to be the main factors in its impressive geographic spread in North America. Morphological characteristics of the sugarcane aphid include dark tarsi, cornicles, and antennae, allowing easy differentiation from other aphids on the crop. Sugarcane aphid damages sorghum by removing sap and covering plants with honeydew, causing general plant decline and yield loss. Honeydew and sooty mold can disrupt harvesting. The aphid's high reproductive rate on susceptible sorghum hybrids has resulted in reports of yield loss ranging from 10% to greater than 50%. In response, a combination of research-based data and field observations has supported development of state extension identification, scouting, and treatment guides that aid in initiating insecticide applications to prevent yield losses. Highly efficacious insecticides have been identified and when complemented by weekly scouting and use of thresholds, economic loss by sugarcane aphid can be minimized. Some commercial sorghum hybrids are partially resistant to the aphid, and plant breeders have identified other lines with sugarcane aphid resistance. A very diverse community of predators and parasitoids of sugarcane aphid has been identified, and their value to limit sugarcane aphid population growth is under investigation.