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If you would like to, you can learn more about the cookies we use. One or more of the features that are needed to show you the maps functionality are not available in the web browser that you are using. The first visual symptom of leafhopper feeding is a subtle paling of the veins and curling of the leaflets. Necrosis occurs in tissues distal to the feeding site and is associated with accumulation of photosynthates due to occlusion of the phloem.
In potato, this marginal necrosis of leaves distal to feeding sites is termed 'hopperburn'. Hopperburn usually begins as a triangular lesion at the tip of infested leaflets. Lesions spread progressively back and inward from the margins, finally destroying the leaves; plants may senesce and die prematurely.
The entire leaf may become yellow, and the symptoms often resemble those caused by viruses. The presence of adult and immature leafhoppers on the undersurface of the leaf serves to distinguish leafhopper injury from virus symptoms or mineral deficiencies. Water transport is also disrupted, resulting in wilting. Salivary secretions of the leafhopper are rich in amylase and invertase, and are toxigenic to phloem sieve cells.
Controversy exists as to the relative importance of direct injury by mechanical occlusion of phloem cells, indirect injury by toxigenic secretions, or the induction of abnormal tissue growth surrounding the phloem; however, economic injury occurs at extremely low leafhopper densities indicating that the effect is not merely mechanical Radcliffe and Johnson, Feeding of leafhoppers and nymphs stimulates an elevation in foliage sugar concentration that enhances the nutritional suitability of the host.
This feedback mechanism functions most successfully in leafhopper-tolerant strains and bears directly upon natural evolution of E.
The size of the leafhopper population required to cause economic damage varies according to cultivar, the stage of plant growth and environmental circumstances.
Early-maturing cultivars are generally assumed to be more susceptible to leafhoppers, but these cultivars bulk more rapidly, and their yield may actually be affected less. Another common assumption is that the potato crop is more susceptible to leafhopper injury if it is under stress and hence that it is more important to control leafhoppers under those conditions.
Some studies, however, have shown that the combined effects of leafhopper damage and water stress or certain diseases are less than additive. If leafhopper populations exceed locally accepted action thresholds, insecticides provide the only effective means of controlling these pests on potato. Soil systemics applied infurrow at planting or side-dressed at plant emergence give weeks of control and can essentially prevent the transmission of leafhopper-borne pathogens.
However, for reasons of cost, systemic insecticides are probably seldom used specifically for this purpose. The standard industry practice for leafhopper control on fresh-market potatoes is to apply foliar sprays. Since both the insect and the initial stages of plant injury are inconspicuous, it is common practice in some production areas to spray on a routine schedule.
This approach usually results in unnecessary insecticide applications, which may induce an outbreak in aphid populations and increases selective pressure for insecticide resistance in other pests. Growers in central Minnesota, USA, typically spray every 10 days, but equivalent leafhopper control can be achieved with as few as two applications for the season.
As integrated pest management comes into more common usage in potato production, spray schedules should be based on appropriate action thresholds and actual leafhopper populations determined from field scouting Radcliffe et al.
Most leafhoppers seem to have few effective natural enemies. An insect-pathogenic fungus, Erynia radicans infects the leafhopper in Wisconsin and Minnesota, but it is rarely found in Illinois. Some other leafhoppers are also susceptible to this pathogen. This fungus appears to be very diverse and may actually comprise several species. Most fungal pathogens operate under the limitation that they have strict temperature requirements, need high humidity for spore germination and infection, and are readily disseminated only when the host has a high population density.
At the present time biological control is not a viable management option for leafhoppers. Effective controls for E. Insecticides provide good control of the nymphs and adults. Early season leafhoppers can be controlled with systemic soil insecticides applied at planting time. However, due to the high cost and short protection period of such a treatment as well as the uncertainty of leafhopper infestations occurring, foliar treatments based on economic thresholds may be a preferred management strategy.
Leafhopper populations may persist until the first frost, and fields should be continuously monitored in areas where substantial numbers have been determined.
More than one application may be necessary if season-long control is desired Radcliffe et al. Adequate screening of window and open areas, as well as proper sealing of door edges can reduce infestation by leafhoppers in a greenhouse. Chemical insecticides can provide adequate control in these situations. Host-Plant Resistance Many crops have some levels of physiological resistance to leafhopper that can be classified into one of three categories: tolerance, antixenosis or antibiosis.
Resistance has been documented in Medicago Brewer et al. The causes for resistance glycoalkaloids were examined extensively in potato Schalk et al. Plant resistance workers have long noted an association or susceptibility to this leafhopper species with lack of pubescence and other physical characteristics in original germplasm lines of soyabean, potato and lucerne Broersma et al. In part, this physical resistance is because trichomes impede the normal attachment of individuals to the plant surface.
Studies on glandular trichomes have been well documented by Mackenzie et al. A chemical basis for resistance to feeding is less frequently cited compared with a physical basis. For example, comparisons of closely related Solanum species suggest that trichome presence and not glycoalkaloid content is associated with resistance. Alternatively, Raman et al. Increased glycoalkaloid content was associated with greater resistance among potato cultivars. A larger study of species of Solanum found that leafhopper resistance was associated with both the glycoalkaloid tomatine and glandular trichomes, and that artificial selection led to increased susceptibility to the leafhopper Flanders et al.
These differences are due in part to alkaloids. The alkaloid, leptine-I, extracted from leaves of Solanum chacoense, markedly reduced both the rate of initial imbibition by the leafhoppers and their survival time. Tomatine, solanine, solandine and demissidine reduced initial imbibition, but did not influence survival time, and tomatidine affected neither imbibition nor survival.
Thus, the alkaloids, in relation to their qualitative and quantitative distributions in the plants and their antifeeding properties, probably play decisive roles in the natural interactions of leafhoppers with Solanum species.
The glycoalkaloid contents of foliage were measured in several populations derived from potato crosses that had been improved for resistance to the leafhopper by recurrent selection. These were analyzed for tuber glycoalkaloid content for many years Slessman and Bushnell ; Sanford et al. The trichomes of soyabean influenced the ability of the leafhopper to get to the leaf surface in order to feed on it. Reductions in populations size on pubescent plants are due to interference with feeding.
The potential of using semiochemicals in crop protection has been evaluated by several authors and is reviewed in Canada Pelletier and King, In other crops In sweet potato, there are pubescent clones with glandular trichomes which are a resistance mechanism to E.
Schaafsma et al. Plant lectins affect the survival time of adult female E. Potato E. Earlier investigators reported a strongly negative curvilinear yield response with increasing densities of the leafhopper. However, because it takes so few leafhoppers to cause economic damage, the relationship between yield loss and leafhopper numbers can be considered directly linear Radcliffe and Johnson, Maximum pest population and hopper burn were observed on variety Kufri Chandramukhi and Kufri Bahar and minimum on Kurfri Sindhuri.
Early planted crops suffered the maximum hopper burn Verma et al. Lucerne A negative correlation exists between leafhopper density and the lucerne growth parameters.
Correlation is highest between reduction in percentage crude protein and leafhopper density. Damage is generally more severe on second- than third-harvest lucerne. Plant height was reduced by Lucerne dry weight declined by 7. Economic Threshold Levels Economic thresholds for leafhopper on potato have been extensively documented Cancelado and Radcliffe, ; Johnston ; Walgenbach and Wyman, ; Johnston et al.
If the number of adult leafhoppers in potatoes exceeds an average of one insect per sweep, treatment is suggested. A total of 10 nymphs per leaves is also enough to suggest that control measures be implemented. Johnston found an economic threshold of nymphs per leaves. Careful monitoring is necessary to detect the presence of nymphs on potato leaves. Both nymphs and adults of the leafhopper are toxigenic. Toxicological feeding on potato and lucerne causes a characteristic damage: hopperburn. The economic threshold for leafhoppers in lucerne varies depending on plant height.
As the crop increases in height, the number of leafhoppers required for economic injury also increases. The threshold of one leafhopper per trifoliate leaf should be used to determine if an insecticide treatment is necessary on dry beans and soyabeans.
While soyabeans are susceptible to leafhopper damage, they appear to be more tolerant than dry beans. Under good growing conditions, soyabeans can outgrow moderate leafhopper injury. However, if the soyabeans are under stress, they are less tolerant of leafhopper feeding and the plants should be treated if symptoms are beginning to show.
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Empoasca fabae (soybean)
With globalization, a major entomological threat to food and fiber security is receiving growing attention: the accidental introduction of insects into habitats containing plants unequipped to resist colonization. The recent invasion of eastern North America by the emerald ash borer, Agrilus planipennis Fairmaire, is a prime example that threatens practically all ash trees in the eastern U. Spotted-wing drosophila, Drosophila suzukii Matsumura , a serious fruit pest, was identified in Hawaii in the s. It was first found in California in and had spread throughout the state by Bolda et al. By , D. Soybean aphid, Aphis glycines Matsumura, a native to Asia, was first reported in the U. Haack reported 25 new introductions of exotic bark- and wood-boring beetles into the United States between and
List of symptoms / signs
Tettigonia fabae Harris, a Erythroneura fabae Fitch, a Typhlocyba fabae Walker, F. Tettigonia mali Le Baron, a Chloroneura malefica Walsh, a Empoa fabae Walsh, a
Empoasca (Empoasca) fabae (Harris, 1841)
Empoasca fabae belongs to family Cicadellidae and genus Empoasca within order Hemiptera. Adults have pale to iridescent green bodies with 6 or 8 white spots on their pronotum. They are able to feed and reproduce on at least different plant species across twenty-six families. Empoasca fabae is a seasonal migration species.