Infectivity of Entomopathogenic Fungal Isolates Against Tarnished Plant Bug Lygus lineolaris (Hemiptera: Miridae)

Twelve isolates of entomopathogenic fungi belonging to Metarhizium robertsii, M. pinghaense, M. brunneum, Beauveria bassiana, and Isaria fumosorosea were screened against tarnished plant bug. All isolates were pathogenic, causing mortality from 28.8 ± 3.4 to 96.3 ± 2.7%. The LT₅₀ values ranged from 2.7 to 6.0 d while the LT₉₀ values varied between 6.6 and 15.0 d. Metarhizium robertsii isolate CPD6 (will be under the trade name NoVil) was among the isolates that caused high mortality within shorter times and was selected for study on developmental stages and greenhouse trial. The third-, fourth-, and fifth-instar nymphs, and adults were inoculated with 10⁶, 10⁷, and 10⁸ conidia per ml of NoVil. All the stages were susceptible to fungal infection. However, third and fourth instars were the most susceptible with no significant differences in mortality across the three concentrations. On the other hand, mortality was dose-dependent with fifth-instar nymph and adult stages. The LT₅₀ and LT₉₀ values were also dose-dependent, with higher concentrations having shorter lethal-time values as compared to the lower concentrations. In the greenhouse, pepper plants were sprayed with NoVil and chemical insecticide Flonicamid (as industrial standard), before releasing adult tarnished plant bug. Mortality of 37.3, 75.5, and 76.3% was recorded in the control, NoVil, and Flonicamid, respectively. This study has identified NoVil as a potential mycoinsecticide candidate for the control of tarnished plant bug under greenhouse conditions. Further field testing on juvenile and adults is needed to evaluate the potential for in-field control.     

Hosts of potato spindle tuber virus in suborder Solanineae

Additional hosts for potato spindle tuber virus (PSTV) found in the suborder Solanineae are:Nolana sp. (Nolanaceae);Antirrhinum sp.,Diascia barberae, Nemesia sp., N. foetens, Penstemon sp. (Scrophulariacceae); andBrowallia speciosa (B. major) andSolanum melongena in the Solanaceae. PSTV produced no local lesions upon inoculation of these hosts. Inoculated plants ofS. melongena (eggplant, ‘Black Beauty’) were dwarfed and epinastic. These rarely used genera in the Solanineae can be readily infected with the virus; leaf and floral parts are profuse and the tissues, upon grinding, leave very little residue.     

Experimental host range of the potato spindle tuber ‘virus’

Two hundred thirty-two plant selections (species and varieties) were tested for susceptibility to the potato spindle tuber ‘virus’ (PSTV). One hundred thirty-eight selections were found to be susceptible to PSTV but no ‘virus’ was recovered from the remaining 94. Susceptible plants were found in the families Boraginaceae, Campanulaceae, Caryophyllaceae, Compositae, Convolvulaceae, Dipsaceae, Sapindaceae, Scrophulariaceae, Solanaceae, and Valerianaceae. Most of the susceptible selections were symptomless carriers of PSTV. Visible symptoms were produced by both mild and severe strains of PSTV inLycopersicon esculentum cv. Allerfruheste-frëiland,Scopolia anomala, S. corniolica, S. lurida, S. sinensis,S. stramonifolia, S. tangutica, Solanum aviculare, andS. avicular var.albiforme; and only by the severe strain inGynura aurantica, Petunia hybrida var. Burpee Blue, andSolanum depilatum. Temperature of 21.1-22.8 C (70-73 F) with a light intensity of about 400 ft-c favored local lesion development inScopolia sinensis. S. sinensis appeared to be more susceptible than otherScopolia species.     

Detection of potato spindle tuber viroid by nucleic acid spot hybridization: Evaluation with tuber sprouts and true potato seed

A diagnostic test for the potato spindle tuber viroid (PSTV) that is based on hybridization of highly radioactive, recombinant DNA complementary to PSTV with PSTV bound to a nitrocellulose membrane and autoradiographic detection of the resulting DNA-RNA hybrids has been evaluated with tubers from 20 potato clones maintained at the International Potato Center (CIP) and with true seed obtained from healthy or PSTV-infected potato plants. The nucleic acid spot hybridization test detected PSTV not only in tuber sprouts from 10 clones that had previously tested positive in polyacrylamide gel electrophoretic (PAGE) analysis, but also in tuber sprouts from 9 clones that had previously tested negative in PAGE analysis. Further tests confirmed the presence of PSTV in these clones. The spot hybridization test detected PSTV in mixtures of seed extracts equivalent to as few as one seed from a PSTV-infected plant and 80 seeds from healthy plants. The spot hybridization test was shown to be more sensitive and reliable than PAGE analysis; it is suitable for the testing of large numbers of samples with a minimum expenditure of labor and materials.     

马铃薯纺锤块茎类病毒不同株系及不同接种方法对产量的影响

马铃薯纺锤块径类病毒(Potato spindle tuber viroid)是危害黑龙江省马铃薯生产的一种重要病害。为了查明不同类病毒变株对主栽品种克新1号和4号所引起的产量损失和症状反应,应用往复聚丙烯胺凝胶电泳法(Peturn-Polyacmdegel electophoresis)鉴定类病毒。试验结果表明,接种当年,接种类病毒的处理平均减产37%,按商品产量计算减产达47%。当年表现症状的植株平均为59.6%,块茎产生症状的植株平均为57.4%。用于接种的3个马铃薯纺锤块茎类病毒变株的致病力,以当地的类病毒弱系为最强,其次为北美的类病毒强系,北美的类病毒弱系的致病力较弱。类病毒对产量的影响与马铃薯品种和类病毒变株的组合有极为密切的关系。克新1号接种当地的类病毒弱系时薯块严重畸变,商品产量只为不接种对照的21%。用往复电泳法检测各个试验处理被类病毒侵柴的情况,芽接种处理,于出苗后1周即可检测到类病毒,叶接种处理,于接种后2周即能检测到类病毒。出苗后7周,植株中类病毒浓度达到高峰,随即急剧下降,到出苗后10周,大部分接种植株已检测不到类病毒。块茎直径达1厘米时,即能检测到类病毒,随着块茎膨大,类病毒浓度也相应增高,到收获前,块茎中的类病毒含量只略低于植株含类病毒高峰期的浓度。用于本试验的克新1号、4号无类病毒和主要马铃薯病毒的核心材料,在1988年已交付给省内外的良种场繁殖使用。于当年秋季抽样检测克山第二良种场连续种植二年的种薯,当年种植试管苗生产的种薯,以及试管苗等,均未检测到类病毒。     

Assessing compensation for insect damage in mixed plantings of resistant and susceptible potatoes

Plant mixtures have been proposed for pesticidal transgenic potatoes as a means to reduce selection intensity favoring resistant insect genotypes. Colorado potato beetle,Leptinotarsa decemlineata (Say), defoliation was simulated in mixed plantings of susceptible and resistant potato “mimics” to evaluate yield compensation. Various mixtures of susceptible and resistant potato were planted at two densities and two locations in eastern North Carolina. Resistant plants were undamaged throughout the season whereas susceptible plants were completely defoliated by hand either during early or late bloom. The ability of non-defoliated plants to compensate for neighboring defoliated plants was investigated through single-plant and smallplot field experiments for 2 years. Yield compensation for defoliated plants by neighboring non-defoliated plants was not evident in our studies. Yield of two potato plants, positioned on either side of a defoliated plant, was not different from yield of two potato plants positioned on either side of a non-defoliated potato plant. Compensation in mixtures of resistant and susceptible potato was not evident using several non-linear regression analyses. A negative linear relationship existed between yield and an increasing percent of susceptible plants in the mixture for all planting densities, at each location, every year.     

New disease symptoms observed on field-grown potato plants with potato spindle tuber viroid and potato virus Y infections

Summary Potato spindle tuber viroid (PSTV) and potato virus Y (PVY) were isolated from plants of cultivar Kennebec with severe necrotic symptoms in the field. In the greenhouse, severe necrotic symptoms were reproduced only when potato plants were infected either simultaneously with PSTV+PVY, or with PSTV prior to PVY infection. Thirteen additional potato cultivars were tested in the greenhouse for this synergistic reaction and eight developed necrotic responses similar to cv. Kennebec. PVY concentration was significantly higher in doubly infected plants, compared with those infected with PVY alone.     

PSTV与PVY的互作及其对马铃薯产量影响

本文分别在温室和田间条件下利用人工接种的方法研究了马铃薯纺锤块茎类病毒（ＰＳＴＶ）和ＰＶＹ在克新４号及Ｋｅｎｎｅｂｅｃ两品种上的相互作用．试验结果表明：在温室条件下ＰＳＴＶ和ＰＶＹ的复合接种均能在二品种上不同程度地产生条型坏死症状，而在田间未出现明显症状．ＰＳＴＶ与ＰＶＹ混合接种或ＰＳＴＶ接种一周后再接ＰＶＹ会促进ＰＶＹ增殖，植株内ＰＶＹ的浓度显著高于单独接种ＰＶＹ，但ＰＶＹ侵染后再接ＰＳＴＶ对ＰＶＹ的浓度无显著影响．ＰＳＴＶ和ＰＶＹ的工作对ＰＳＴＶ的浓度无显著影响．ＰＳＴＶ与ＰＶＹ复合侵染的三个接种类型都明显地降低平均单株产量和商品薯率，产量损失最大的处理为ＰＳＴＶ与ＰＶＹ混合接种，可导致克新４号减产４５．４％。     

Albinism of potato spindle tuber viroid-infected Rutgers tomato in continuous light

Potato spindle tuber viroid (PSTV) caused albinism in the new growth of Rutgers tomato under continuous light. The albinism response was obtained with 4 isolates causing severe symptoms in tomato and with 1 mild isolate which is normally symptomless. Rutgers tomato inoculated with the 4 severe strains of PSTV developed typical ‘bunchy top’ symptoms in 12 to 16-hr day lengths. Symptoms developed slower and much less distinctly on plants incubated in 6-hr days. New growth in PSTV-infected plants was green in short days (12-hr illumination) and chlorotic to white in continuous light. Infectivities of extracts from white portions of plants were from 3 to 10 times greater than those from green portions of infected plants. Albino symptoms also developed in other tomato varieties when inoculated with PSTV and kept under continuous light. Albinism was most pronounced under continuous light at 30°C, somewhat less intense at 24°, and at 16°, new growth of infected leaves and stems remained green. Albinism did not develop in otherSolanum species which are symptomless hosts of PSTV nor in seedling potato plants grown in continuous light.     

Feeding behavior of a potential insect pest, Lygus hesperus, on four new industrial crops for the arid southwestern USA

Camelina (Camelina sativa), guayule (Parthenium argentatum), lesquerella (Physaria fendleri), and vernonia (Centrapalus pauciflorus [formerly Vernonia galamensis]) are either under limited commercial production or being developed for production in the southwestern USA. Insect pests are a potential economic threat to all these new crops, with Lygus hesperus, the western tarnished plant bug, among the most prominent due to its regional abundance and propensity to feed on reproductive plant tissue. The objectives of this study were to establish baseline data on the feeding behavior and potential impact of L. hesperus on camelina, guayule, lesquerella and vernonia. Behavioral observations of adult females and males, and nymphs of this insect were made in the laboratory. Insects spent ≈35% of their time either probing (=tasting) or feeding on various reproductive and vegetative tissues of guayule, lesquerella or vernonia, but only 20% on camelina. When insects did probe and feed they preferred reproductive tissues, primarily flowers and siliques/achenes, and there were differences in these behaviors relative to crop but not generally to insect stage or sex. Insects probed and fed more on flower tissue of guayule and vernonia compared with camelina and lesquerella, and more on siliques of lesquerella compared with achenes of vernonia. When probing and feeding on vegetative tissue, there was generally a preference for stems compared with leaves in all crops except guayule. Results show that L. hesperus will readily feed on the economically important tissues of all crops, and although research has shown that this feeding did not consistently affect lesquerella yield, further work will be needed to determine if such feeding poses a risk to commercial production of camelina, guayule or vernonia.     

Evaluation of a vacuum collector for insect pest control in potato

A field scale vacuum insect collector designed for the control of the Colorado Potato Beetle,Leptinotarsa decemlineata (Say) was tested on potatoes in 1990. The vacuum collector was more effective against adults and small larvae than against large larvae. Results suggested that a large proportion of potato aphids can also be removed from plants. The spread of plant diseases PSTVd and PVX, readily transmitted by contact, was not increased by the repeated use of the vacuum collector.     

Effect of green-belly stink bug,Dichelops furcatus (F.) on wheat yield and development

The green belly stink bug, Dichelops furcatus (F.) (Hemiptera: Heteroptera: Pentatomidae) is a pest of corn and soybean in southern Brazil. It also occurs on wheat, but information on its damage to this crop is limited. To determine the need for sustainable IPM programs, the impact of this bug on wheat production should be determined. Studies were conducted in the screenhouse with 1, 2 and 4 bugs caged for 16 days on single plants, cv. ‘BRS Parrudo’. During the vegetative period (plants ca. 25 cm tall), all infestation levels significantly reduced plant height and ear head length, but did not reduce grain yield. Feeding damage caused tissue necrosis on leaves. During the booting stage, grain yield was significantly reduced with 2 and 4 bugs per plant; ear heads were small, discolored and abnormally developed. In 2013 and 2014 field trials, plants were infested for 18 days with 2, 4 and 8 bugs per m² at vegetative, booting, and milky grain stage. At these infestation levels, there was no significant reduction in grain yield. There was a significant decrease in the number of normal seedlings resulting from seeds exposed to 8 bugs per m² at the milky grain stage. Results suggest that, in general, there is no need to control D. furcatus on wheat, unless numbers are ≥8 bugs per m² during reproductive period.     

Transmission ofErwinia carotovora var.atroseptica byDrosophila melanogaster Meig. I. Acquisition and transmission of the bacterium

Drosophila melanogaster acquired the potato blackleg bacterium,Erwinia carotovora var.atroseptica from laboratory cultures and infected potato plants and readily transmitted it to healthy wounded plants under greenhouse conditions.D. melanogaster also carried the bacterium both internally and externally. Transmission to the nearest plants occurred most often. The possibility of at least short term survival of the bacterium inside the body of the insect is postulated.     

The establishment of alfalfa into different maize residues by conservation-tillage and its effect on insect infestation

The effect of management of maize residues on the population of insects inimical to the establishment of alfalfa, Medicago sativa L., was examined 1 month after sowing. Alfalfa was sown in early and late April, and late May for 3 consecutive years in Centre County, Pennsylvania, USA. The sowings were made by conservation tillage (direct drilled into maize residue with minimal disturbance of soil) into three different maize residues after (1) silage, (2) silage-plus-winter rye cover and (3) grain. A fourth sowing was by conventional tillage (spring ploughing and harrowing maize residue) after grain. A pesticide, carbofuran (granular formulation) was applied at sowing to half of the plots. Methiocarb bait, a molluscicide, was applied as a split application to the same plots, one-half at sowing and the remainder 2 weeks later. Alfalfa plots in the silage-plus-rye maize residues were colonized with fewer insects than the other residue treatments. Excessive growth of rye in early spring that was not successfully suppressed by herbicide treatment produced vigorous rye plants and fewer alfalfa seedlings. Consequently, silage plus rye had the lowest yield of alfalfa in early April sowings in 2 out of 3 years. Insects known to feed on alfalfa, such as tarnished plant bugs, Lygus lineolaris (Palsot de Beauvois), the plant bug, Plagiognathus politus Uhler, pea aphids, Acyrthosiphon pisum (Harris), and meadow spittlebugs, Philaenus leucophthalmus spumarius (L.), were collected by sweep net 1 month after sowing and less often in the silage-plus-rye treatment. These species were present in greater numbers in the other maize residues that had significantly more alfalfa forage. The insidious flower bug, Orius insidious (Say), and a damsel bug, Nabis americoferus Carayon, were collected in significantly greater numbers in the early April sowings, which corresponded with the peak populations of pea aphid. The potato leafhopper, Empoasca fabae (Harris), was most abundant in plots sowed in late April or late May. Pesticide treatment applied at the time of sowing had very little effect on numbers of insects collected by sweep net 1 month later in 1986 and 1988. However, pesticide treatment significantly increased yield by 280 kg ha^?1 in 1987, even though sweep net collections of insects were not reduced by the pesticide treatment. Therefore, the beneficial effect of the pesticide could not be explained on the basis of the insects collected. The highest yields of alfalfa were obtained from the early April sowing into maize residues. This coincided with the time when the majority of alfalfa pests were less abundant than in later sowings; fewer pests were found on the sowings into silage-plus-rye residue. Also, when the rye forage yield was combined with the alfalfa yield, this became the most productive system.     

Glandular pubescence,glycoalkaloid composition,and resistance to the green peach aphid,potato leafhopper,and potato fleabeetle inSolanum berthaultii

Fifteen accessions ofSolarium berthaultii Hawkes andS. berthaultii xS. tarijense Hawkes were assessed for resistance to field infestations of the green peach aphid,Myzus persicae (Sulzer), potato leafhopper,Empoasca fabae (Harris), and potato fleabeetle,Epitrix cucumeris (Harris). Accessions bearing both Type A and Type B glandular trichomes were much more resistant to the green peach aphid and potato leafhopper than accessions bearing Type A hairs alone. All accessions had significantly smaller populations of these 3 pests than S.tuberosum cultivars. Total glycoalkaloid (TGA) content of foliage and tubers was not correlated with insect populations. Foliar TGA levels of field-grown plants varied among accessions, ranging from < 2–240 mg/100 g fresh wt. Solasonine and solamargine were the major foliar glycoalkaloids while solamarines predominated in tubers.     

The effect of an alternate weed host,hairy nightshade,Solanum sarrachoides (Sendtner) on green peach aphid distribution and Potato leafroll virus incidence in potato fields of the Pacific Northwest

Hairy nightshade, Solanum sarrachoides (Sendtner) is an annual solanaceous weed prevalent in potato farmlands of the Pacific Northwest. S. sarrachoides is also a reservoir for Potato leafroll virus (PLRV) and its most important vector, the green peach aphid, Myzus persicae (Sulzer). Green peach aphids prefer S. sarrachoides than potato, Solanum tuberosum (L.), and produce more nymphs on S. sarrachoides than on potato. Increased green peach aphid preference for S. sarrachoides and greater fecundity on this plant could lead to overcrowding and movement toward neighboring potato plants. To test our hypothesis, field trials were conducted at Kimberly, Idaho during the summers of 2003 and 2004. A row of S. sarrachoides seedlings was planted in the middle of potato plots and naturally occurring green peach aphid populations were monitored weekly on potato plots with and without S. sarrachoides. More aphids were consistently found on S sarrachoides plants than on potato plants. More aphids were found on potato plants in plots with S. sarrachoides plants than without S. sarrachoides. Targeted insecticide applications on S. sarrachoides rows alone reduced the number of aphids on potato plants in those plots, suggesting that insecticide sprays prevented aphid movement from S. sarrachoides to potato. Testing of potato tuber sprouts 90 days after harvest by double antibody sandwich ELISA indicated a greater PLRV infection rate on plots with S. sarrachoides than plots without S. sarrachoides. Therefore, the presence of S. sarrachoides in potato plots will likely increase aphid populations and PLRV incidence on neighboring potato plants.     

Ion chromatography analysis of phosphite uptake and translocation by potato plants: Dose-dependent uptake and inhibition of Phytophthora infestans development

Phosphite-based fungicides are increasingly used to control fungi-like plant pathogens from the Oomycetes group. A rapid, precise, and cost-effective suppressed conductivity high performance ion chromatography (HPIC) method was developed to assess the concentrations of soluble phosphites (Phi) and phosphates (Pi) in plant samples. This technique was used to determine the amount of Phi and Pi in leaves and tubers of potato plants following foliar applications of the Phi-based fungicide Confine™. High amounts of Phi were determined in both leaves and tubers indicating that potato plants efficiently uptake and translocate the fungicide. The number of applications of Confine™ and its concentration were found to be directly proportional with the amount of Phi detected in potato plants and inversely proportional with the development of Phytophthora infestans (Mont.) de Bary in these plants. Levels of Phi comparable to those determined in plants were found to strongly inhibit the growth of P. infestans in vitro. The simultaneous estimation of the in planta Phi concentration and of the sensitivity of P. infestans to Phi represent the most comprehensive approach of assessing the efficacy of Phi-based fungicides in controlling late blight development in potatoes.     

Carrot Pathogen ‘<Emphasis Type="Italic">Candidatus</Emphasis> Liberibacter solanacearum’ Haplotype C Detected in Symptomless Potato Plants in Finland

‘Candidatus Liberibacter solanacearum’ (CLso) haplotype C, a bacterial pathogen transmitted by the carrot psyllid Trioza apicalis, causes yield losses in carrot production. Due to concerns that this pathogen might also threaten potato (Solanum tuberosum) production, the occurrence of CLso in cultivated and volunteer potatoes in Tavastia Proper and Satakunta regions of Finland was studied. Volunteer potato plants were found in 13 of the 27 inspected carrot fields. Of the 148 potato samples tested by PCR, eight volunteer potato plants and one cultivated potato grown at the edge of a carrot field were found to be CLso positive. The PCR products obtained from these potatoes with primers OA2/OI2c, LpFrag4-1611F/LpFrag4-480R and CL514F/CL514R all showed 100% sequence identity to CLso haplotype C. This is the first observation of CLso haplotype C in field-grown potatoes. In addition, transmission experiments were performed. Attempts to transmit CLso into potato with carrot psyllids were not successful; however, CLso haplotype C was transmitted from infected carrots to potato plants by leaf grafting and by phloem connection formed by dodder, a parasitic plant, and found to survive in the potato plants for several weeks after transmission. However, the bacterial colonisation progressed slowly in the potato phloem and the amount of bacteria detected was low. The plants produced from the daughter tubers of the CLso-positive potato plants were all CLso negative, suggesting that CLso haplotype C was not able to pass to the daughter plants. None of the CLso-positive potatoes inoculated in greenhouse or collected from fields showed symptoms characteristic of zebra chip disease, associated with CLso haplotypes A and B.     

Insect transmission ofErwinia carotovora var.carotovora andErwinia carotovora var.atroseptica to potato plants in the field

Adult fruit flies (Drosophila melanogaster Meig.) artificially contaminated withErwinia carotovora var.carotovora (Jones) Dye (Ecc) and/orE. carotovora var.atroseptica (van Hall) Dye (Eca) readily transmitted the bacteria to plants in the field that had been injured by crushing the stem. Injured, inoculated plants developed disease symptoms when maintained at high relative humidities.Erwinia was transmitted to ten-hour-old injuries and they became infected as frequently as freshly made wounds. Insect transmission ofEca, Ecc, and mixtures was greatest during the afternoon, which was the warmest part of the day.Ecc was transmitted significantly less frequently during the cold morning than during afternoon or evening hours. A potato cull pile placed in a commercial potato field attracted a natural insect population which increased during the season. BothEcc andEca were isolated from uninoculated rotting tubers in the cull pile and from insects associated with the pile from May through September. These naturally infested insects transmittedEcc and/orEca from the cull pile to artificially injured field plants during July and August at distances as great as 183 m from the cull pile. NoErwinia was isolated from injured plants in a neighboring control field, which lacked a cull pile, further than 6 m upwind from the cull pile. We suggest that insects are important agents in the epidemiology of potato blackleg and soft rot even in areas with low relative humidities.     

Prevalence of Endosymbionts in Polish Populations of Leptinotarsa decemlineata (Coleoptera: Chrysomelidae)

Colorado potato beetle (CPB, Leptinotarsa decemlineata Say) (Coleoptera: Chrysomelidae) is one of the most serious insect pest feeding on wild and cultivated Solanaceae plants. This pest poses a significant threat to potato crops. CPB originated from North America but has become widespread and has adapted in new localizations. Currently, it is reported in many countries worldwide. Endosymbiotic bacteria might have an influence on insect adaptation to new conditions. They are known to play a role in invasiveness of insect hosts and to facilitate colonization of new niches; however, information on endosymbionts of the CPB is very limited. In this study, we screened CPB populations collected from 20 evenly distributed locations in Poland for the presence of Arsenophonus, Cardinium, Wolbachia, and Flavobacterium. We found the presence of Flavobacterium in the studied insects. Little is known about CPB–endosymbionts interactions, thus this study may provide a reference for future studies in this subject.