Pseudococcus Maritimus Research Articles

Pathogen‐tested material of grapevine varieties and rootstocks

Pathogen‐tested material of grapevine varieties and rootstocks

Leafroll disease is spreading rapidly in a Napa Valley vineyard

In the 1930s and 1940s, little was known about viruses, and information on plant diseases caused by viruses was just beginning to appear in the scientific literature. Problems with grapevines in California, first referred to as “red leaf,” were initially attributed to inexperience in viticultural techniques and poor growing conditions. However, the problem was later identified as leafroll disease, which causes red leaves, and poor yields and fruit quality. We evaluated its rate of spread for 5 years in a Napa Valley vineyard, and found an average rate of more than 10% per year. Leafroll disease can be vectored by low-level populations of grape mealybugs, and is now spreading rapidly in at least one Napa Valley vineyard for unknown reasons. Using stock for planting vines that is certified as virus-free is a key strategy in preventing the spread of grapevine leafroll disease.

Impacts of Argentine ants on mealybugs and their natural enemies in California’s coastal vineyards

Abstract 1. The Argentine ant, Linepithema humile, tends honeydew‐excreting homopterans and can disrupt the activity of their natural enemies. This mutualism is often cited for increases in homopteran densities; however, the ant’s impact on natural enemies may be only one of several effects of ant tending that alters insect densities. To test for the variable impacts of ants, mealybug and natural enemy densities were monitored on ant‐tended and ant‐excluded vines in two California vineyard regions.2. Ant tending increased densities of the obscure mealybug, Pseudococcus viburni, and lowered densities of its encyrtid parasitoids Pseudaphycus flavidulus and Leptomastix epona. Differences in parasitoid recovery rates suggest that P. flavidulus was better able to forage on ant‐tended vines than L. epona.3. Densities of a coccinellid predator, Cryptolaemus montrouzieri, were higher on ant‐tended vines, where there were more mealybugs. Together with behavioural observations, the results showed that this predator can forage in patches of ant‐tended mealybugs, and that it effectively mimics mealybugs to avoid disturbance by ants.4. Ant tending increased densities of the grape mealybug, Pseudococcus maritimus, by increasing the number of surviving first‐instar mealybugs. Parasitoids were nearly absent from the vineyard infested with P. maritimus. Therefore, ants improved either mealybug habitat or fitness.5. There was no difference in mealybug distribution or seasonal development patterns on ant‐tended and ant‐excluded vines, indicating that ants did not move mealybugs to better feeding locations or create a spatial refuge from natural enemies.6. Results showed that while Argentine ants were clearly associated with increased mealybug densities, it is not a simple matter of disrupting natural enemies. Instead, ant tending includes benefits independent of the effect on natural enemies. Moreover, the effects on different natural enemy species varied, as some species thrive in the presence of ants.

Trans-α-Necrodyl isobutyrate, the sex pheromone of the grape mealybug, Pseudococcus maritimus

Headspace volatiles of virgin female grape mealybugs contained a single compound that elicitited responses from antennae of males in GC–electroantennogram analyses. The structure, identified as ( R ∗, R ∗)- trans-(3,4,5,5-tetramethylcyclopent-2-en-1-yl)methyl 2-methylpropanoate, an irregular, non-head-to-tail monoterpenoid, was confirmed by synthesis.

Ethyl Formate As a Postharvest Fumigant for Selected Pests of Table Grapes

Ethyl formate (EF) in combination with CO2 was tested for control of arthropods commonly infesting California table grapes. In addition, table grape tolerance to EF exposure was evaluated. LC99 estimates were developed for target pests by using a range of EF concentrations (0.04–4.7% EF). Response to treatments varied greatly between species, as well as life stages within species. Western flower thrips, Frankliniella occidentalis (Pergande), and adult and crawler stages of grape mealybug, Pseudococcus maritimus (Ehrhorn), were most susceptible to EF treatments. Least susceptible were grape mealybug eggs; Pacific spider mite, Tetranychus pacificus McGregor; and omnivorous leafroller, Platynota stultana Walsingham. The LC99 for target pests fell within the range of EF concentrations tolerated by table grapes with the exception of 1-, 3-, and 5-d-old omnivorous leafroller pupae.

Ethyl Formate As a Postharvest Fumigant for Selected Pests of Table Grapes

Ethyl formate (EF) in combination with CO2 was tested for control of arthropods commonly infesting California table grapes. In addition, table grape tolerance to EF exposure was evaluated. LC99 estimates were developed for target pests by using a range of EF concentrations (0.04-4.7% EF). Response to treatments varied greatly between species, as well as life stages within species. Western flower thrips, Frankliniella occidentalis (Pergande), and adult and crawler stages of grape mealybug, Pseudococcus maritimus (Ehrhorn), were most susceptible to EF treatments. Least susceptible were grape mealybug eggs; Pacific spider mite, Tetranychus pacificus McGregor; and omnivorous leafroller, Platynota stultana Walsingham. The LC99 for target pests fell within the range of EF concentrations tolerated by table grapes with the exception of 1-, 3-, and 5-d-old omnivorous leafroller pupae.

First Report of Grapevine leafroll associated virus-3 in American Vitis spp. Grapevines in Washington State.

Washington State is the largest producer of juice grapes (Vitis labruscana 'Concord' and Vitis labrusca 'Niagara') and ranks second in wine grape production in the United States. Grapevine leafroll disease (GLD) is the most wide spread and economically significant virus disease in wine grapes in the state. Previous studies (2) have shown that Grapevine leafroll associated virus-3 (GLRaV-3) is the predominant virus associated with GLD. However, little is known about the incidence and economic impact of GLD on juice and table grapes. Because typical GLD symptoms may not be obvious among these cultivars, the prevalence and economic impact of GLD in Concord and Niagara, the most widely planted cultivars in Washington State, has received little attention from the grape and nursery industries. During the 2005 growing season, 32 samples from three vineyards and one nursery of 'Concord' and three samples from one nursery of 'Niagara' were collected randomly. Petiole extracts were tested by single-tube reverse transcription-polymerase chain reaction (RT-PCR; 3) with primers LC 1 (5'-CGC TAG GGC TGT GGA AGT ATT-3') and LC 2 (5'-GTT GTC CCG GGT ACC AGA TAT-3'), specific for the heat shock protein 70 homologue (Hsp70h gene) of GLRaV-3 (GenBank Accession No. AF037268). One 'Niagara' nursery sample and eleven 'Concord' samples from the three vineyards tested positive for GLRaV-3, producing a single band of the expected size of 546 bp. The 'Niagara' and six of the 'Concord' RT-PCR products were cloned in pCR2.1 (Invitrogen Corp, Carlsbad, CA) and the sequences (GenBank Accession Nos. DQ780885, DQ780886, DQ780887, DQ780888, DQ780889, DQ780890, and DQ780891) compared with the respective sequence of a New York isolate of GLRaV-3 (GenBank Accession No. AF037268). The analysis revealed that GLRaV-3 isolates from 'Concord' and 'Niagara' share nucleotide identities of 94 to 98% and amino acid identities and similarities of 97 to 98% with the Hsp70h gene homologue of the New York isolate of GLRaV-3. Additional testing by double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) using antibodies specific to GLRaV-3 (BIOREBA AG, Reinach, Switzerland) further confirmed these results in the 'Niagara' and two of the 'Concord' isolates. GLRaV-3 has previously been reported in labrusca cvs. Concord and Niagara in western New York (4) and Canada (1), but to our knowledge, this is the first report of GLRaV-3 in American grapevine species in the Pacific Northwest. Because wine and juice grapes are widely grown in proximity to each other in Washington State and grape mealybug (Pseudococcus maritimus), the putative vector of GLRaV-3, is present in the state vineyards, further studies will focus on the role of American grapevine species in the epidemiology of GLD.

Effect of high-pressure hot-water washing treatment on fruit quality, insects, and disease in apples and pears: Part III. Use of silicone-based materials and mechanical methods to eliminate surface pests

Surface arthropods on pome fruits can cause export problems and disrupt commercial markets. Eliminating insects and mites on the packing line would be the last opportunity to provide for pest-free produce. In this study, an experimental packing line was used to evaluate techniques using different surfactant baths, pressurized water sprays, and styles of rotating brushes to remove field-collected and laboratory-reared grape mealybug, Pseudococcus maritimus (Ehrhorn) (Homoptera: Pseudococcidae), the diapausing two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae) and the woolly apple aphid, Eriosoma lanigerum (Hausman) (Homoptera: Aphididae). The organosilicone Silwet L-77 was no more effective than a silicone-based food grade defoamer in aiding removal. Mechanical methods, such as the style of rotating brushes and pressurized sprays, were significantly effective in removing surface arthropods. No improvement in removal occurred when pressure was increased beyond 420 kPa. These techniques can be easily adapted to commercial facilities and will reduce the incidence of surface arthropods on marketed fresh fruits.

Survey for Viruses of Grapevine in Oregon and Washington.

Grapevines (Vitis spp.) in Washington and Oregon were surveyed for the prevalence of key grapevine viruses. Samples collected from 1,522 vines in Washington were tested for Rupestris stem pitting associated virus (RSPaV), Grapevine fanleaf virus (GFLV), Arabis mosaic virus (ArMV), Tomato ringspot virus (ToRSV), and Grapevine leafroll associated virus-3 (GLRaV-3). Tests were also conducted for GLRaV-1 and -2 on 420 samples from Washington. Two hundred forty samples collected from wine grape vineyards in Oregon were tested for GLRaV-1, -2, and -3, and an additional 2,880 samples were collected from 40 vineyards known to have high populations of Xiphinema americanum nematodes. The latter were tested for ArMV, ToRSV, and GFLV. GLRaV-1, -2, and -3 were detected in 2.6, 0.2, and 6.5% of the Washington samples and in 3.0, 0.4, and 4.4% of the Oregon samples. RSPaV was detected in 4.6% of the samples from Washington. No ToRSV, ArMV, or GFLV was detected in any of the samples from Oregon or Washington. Transmission of field isolates of GLRaV-3 from Washington by the grape mealybug also was demonstrated.

Efficacy of Silwet L-77 Against Several Arthropod Pests of Table Grape

Silwet L-77, an organosilicone surfactant, was applied to several arthropod pests of California table grapes. Eggs of grape mealybug, Pseudococcus maritimus (Ehrhorn), and omnivorous leafroller, Platynota stultana Walsingham, were tolerant to 0.1, 0.25, and 0.5% treatment solutions; however, eggs of Pacific spider mite, Tetranychus pacificus McGregor, were highly susceptible with mortality >99.4% (0.1% Silwet L-77). Mortality of immature and adult stages of cotton aphid (Aphis gossypii Glover), Western flower thrips (Frankliniella occidentalis Pergande), and Pacific spider mite (Tetranychus pacificus McGregor) was ≥93.8, ≥98.5, and ≥99.4% for 0.1, 0.25, and 0.5% Silwet L-77, respectively. Grape mealybug crawlers had 100% mortality when treated with 0.5 and 1.0% Silwet L-77 solutions; however, mortality was only 6.7% when 0.1% Silwet L-77 was applied. ‘Thompson Seedless’ table grapes were not damaged when treated with up to 1% Silwet L-77; however, grapes treated with the 0.5 and 1.0% solutions appeared wet after removal from cold storage because of the effect of the surfactant spreading the water condensation. Grapes dried with the normal bloom on the berries when they reached room temperature.

Efficacy of Silwet L-77 against several arthropod pests of table grape.

Silwet L-77, an organosilicone surfactant, was applied to several arthropod pests of California table grapes. Eggs of grape mealybug, Pseudococcus maritimus (Ehrhorn), and omnivorous leafroller, Platynota stultana Walsingham, were tolerant to 0.1, 0.25, and 0.5% treatment solutions; however, eggs of Pacific spider mite, Tetranychus pacificus McGregor, were highly susceptible with mortality >99.4% (0.1% Silwet L-77). Mortality of immature and adult stages of cotton aphid (Aphis gossypii Glover), Western flower thrips (Frankliniella occidentalis Pergande), and Pacific spider mite (Tetranychus pacificus McGregor) was > or = 93.8, > or = 98.5, and > or = 99.4% for 0.1, 0.25, and 0.5% Silwet L-77, respectively. Grape mealybug crawlers had 100% mortality when treated with 0.5 and 1.0% Silwet L-77 solutions; however, mortality was only 6.7% when 0.1% Silwet L-77 was applied. 'Thompson Seedless' table grapes were not damaged when treated with up to 1% Silwet L-77; however, grapes treated with the 0.5 and 1.0% solutions appeared wet after removal from cold storage because of the effect of the surfactant spreading the water condensation. Grapes dried with the normal bloom on the berries when they reached room temperature.

California mealybugs can spread grapevine leafroll disease

UC Davis's Foundation Plant Materials Service (FPMS) maintains the disease-tested, professionally identified collection of grape scion and rootstock varieties, which is the core of the California Grapevine Registration and Certification Program. In 1992; newly developed serological testing techniques revealed the presence of grapevine leafroll-associated viruses (GLRaVs) in previously healthy vines in an older foundation propagating block, indicating active and recent virus spread. FPMS responded by increasing isolation distances and implementing a comprehensive virus screening program using the new methodology. The critical problem was the lack of information on leafroll virus epidemiology. When the distribution of infected plants in the old vineyard was mapped, new infections were frequently adjacent to known diseased grapevines. This study examined the ability of mealybugs, a putative leafroll vector, to transmit this group of viruses. We were able to confirm that four species found in California — obscure, longtailed, citrus and grape mealybug — can transmit GLRaV-3 isolates. This is the first experimental evidence of grapevine leafroll virus transmission by obscure and grape mealybug. In addition, we report for the first time that GLRaV-5 can be transmitted by longtailed mealybug.

Pest response in packed table grapes to low temperature storage combined with slow-release sulfur dioxide pads in basic and large-scale tests.

The effect of low temperature storage combined with slow release sulfur dioxide pads was determined in basic laboratory and large-scale commercial tests on western flower thrips, Frankliniella occidentalis Pergande; grape mealybug, Pseudococcus maritimus (Ehrhorn); Pacific spider mite, Tetranychus pacificus McGregor; twospotted spider mite, Tetranychus urticae Koch; and omnivorous leafroller, Platynota stultana Walshingham. Temperatures within the foam containers among the packed clusters decreased from ambient to 2 degrees C within approximately 1 d and ranged from 0.4 to 1.7 degrees C in all tests. Sulfur dioxide concentrations in the foam containers ranged between 0.2 and 1.6 ppm during the 1- to 6-wk storage period in basic tests and 0.5-1.1 ppm during the 1- to 8-wk storage period in the large-scale test. Western flower thrips was completely controlled by a > or =1-wk exposure. Grape mealybug mortality was > or =93% after 2-5 wk exposures and 100% after a 6-wk exposure in basic tests. Pacific spider mite and twospotted spider mite mortality was 98.0 and 99.6%, respectively, after a 6-wk exposure. Mortality of grape mealybug and twospotted spider mite increased significantly at > or =3-wk exposures and Pacific spider mite mortality increased significantly at > or =4-wk exposures. Mortality of the spider mites in general was directly related to the duration of exposure. An 8-wk exposure to low temperature storage combined with slow release sulfur dioxide pads in the large-scale test resulted in 100% mortality of western flower thrips, twospotted spider mite, and omnivorous leafroller. The treatment resulted in <8% survival of grape mealybug and <1% survival of Pacific spider mite in the large-scale test. The combination treatment offers an economical method to attain quarantine control of certain insects and mites.

Sampling program for grape mealybugs improves pest management

The results of a mealybug study in Central Valley vineyards, designed to develop sampling guidelines, reveal that mealybug distribution on vines varies greatly through the season and that mealybugs usually prefer concealed locations, such as under bark. This combination makes sampling difficult. A number of sampling techniques were compared. Three- or 5-minute timed counts were most efficient because samplers could follow the mealybugs' movement over the season. Midseason counts were much better predictors of damage at harvest than early season counts. This research confirms past control guidelines and opens new control options. Grape bunches touching vine trunks or spurs will have higher damage. Removing these bunches or using barriers between bunches and mealybug oviposition sites can also reduce damage.

Seasonal movement and distribution of the grape mealybug (Homoptera: Pseudococcidae): developing a sample program for San Joaquin Valley vineyards.

The grape mealybug, Pseudococcus maritimus (Ehrhorn), is an important pest of table grapes in California's San Joaquin Valley. The mealybug causes direct damage by infesting grape bunches, resulting in very low economic injury levels. To develop a sampling program to help growers predict damage and make control decisions, we destructively sampled six entire grapevines each month to determine mealybug abundance and within-vine distribution. These absolute counts were then used to evaluate several relative sampling methods: sticky tape barriers on canes, excised spur samples, standard-sized pieces of bark, timed counts, and nondestructive counts on spurs. At midseason we sampled additional vines to correlate mealybug numbers with economic damage at harvest. Finally, mealybug life stages and natural enemies were recorded throughout the study. Timed 5-min counts show the strongest correlation with total mealybug numbers, and a simple count of mealybugs on three spurs per vine at midseason is the best predictor of economic damage. Mealybugs completed approximately equals 2.5 generations in 1998. Comparison to data on mealybug development suggests that exceptionally long growing seasons could exacerbate infestations by allowing the completion of a third generation. No mealybugs were found on bunches before early August, when second-generation crawlers moved out of the bark. Grape bunches that touched old wood had significantly higher damage and mealybug densities. The majority of mealybugs were always found in protected locations (under the bark of the trunk, spurs or canes), indicating the need for chemical or biological controls that can penetrate these refugia.

Effect of native natural enemies on the population dynamics of the grape mealybug,Pseudococcus maritimus (Hom.: Pseudococcidae), in apple and pear orchards

The impact of native natural enemies on populations of the grape mealybug,Pseudococcus maritimus (Ehrhorn) in apple and pear orchards was assessed using a combination of techniques, including exclusion cages, limb-banding, and visual inspection of shoots and fruits. The complex of native natural enemies (which included two encyrtid parasitoids, (Pseudaphycus websteri Timberlake andMayridia species), a coccinellid beetle (Hyperaspis lateralis Mulsant), and a chamaemyiid fly (Leucopis verticalis Malloch), provided reasonably good control in orchards that had not been treated with insecticides for one to two years. However, surveys indicated that most of these species were absent from orchards regularly sprayed with pesticides.

Influence of constant temperatures on the developmental rate, progeny production, sex ratio and adult longevity of the grape mealybug parasitoid, Anagyrus dactylopii (How.) (Hymenoptera: Encyrtidae)

The effects of six constant temperatures ranging from 15 to 40°C on the rate of development, progeny production, sex ratio and adult longevity of the grape mealybug parasitoid, Anagyrus dactylopii (How.) were determined. It was found to complete the development in the temperature regimes of20–35°C but neither sex emerged as adults at 15 and 40°C. Developmental time of male and female decreased from 32.75 to 10 days, and from 34.50 to 11.75 days respectively, as the temperature increased from 20–35°C. Progeny production increased with the rise in temperature up to 30°C, and a maximum of 182 offspring emerged at 30°C. Sex ratio was altered considerably by different temperatures. Maximum female progeny was also obtained at 30°. Adult longevity of both sexes declined with increasing temperature. Mean longevity of male reduced from 2730 days at 15°C to 2.75 days at 40°C. The findings on the effects of temperature in relation to the rearing in the laboratory and the activity of Anagyrus dactylopii in the field are also discussed.

Phylogenetic relationships of the endosymbionts of mealybugs (Homoptera: Pseudococcidae) based on 165 rDNA sequences

A portion of the gene coding for the 16S ribosomal RNA from the endosymbionts of three species of mealybugs [ Pseudococcus longispinus (Targioni-Tozzetti), Pseudococcus maritimus (Ehrhorn), and Dysmicoccus neobrevipes (Beardsley)] was cloned, sequenced, and compared to a homologous fragment from bacteria representative of aphid endosymbionts as well as major subdivisions of the Proteobacteria. Parsimony analysis of the sequences indicated that the mealybug endosymbionts are related and belong to the γ-subdivision; in contrast, previous studies showed that aphid endosymbionts are part of the -1-subdivision. These findings suggest that the endosymbiosis of mealybugs is a consequence of a single bacterial infection and indicate that this ancestor was different from the ancestor involved in aphid endosymbiosis.

Field Evaluation of Cryptolaemus montrouzieri Muts. in the Suppression of Maconellicoccus hirsutus (Green) on Grapevine

The coccinellid predator, Cryptolaemus montrouzieri (Muls.) was multiplied in large numbers and adult beetles were released against Maconellicoccus hirsutus in three localities in Karnataka. The release of predatory beetles gave excellent control of the grape mealybug within 75 days.

Development and feeding potential of coccinellid predator, Cryptolaemus montrouzieri Muls. on the grape mealybug, Maconellicoccus hirsutus (Green).

Development and feeding potential of the coccinellid predator, Cryptolaemus montrouzieti Muls. was studied on the eggs, nymphs and adult females of the grape mealybug, Maconellicoccus hirsutus (Green). The life cycle of the predator was prolonged when it was reared on eggs of mealybugs. Incubation period ranged 4 to 5 days. The grub took 22.80, 13.85 and 13.45 days when reared on eggs, nymphs and adult of male mealybugs, respectively. The prepupal and pupal periods averaged 2.15 and 8.50 days, respectively. Adult longevity averaged 55.90 days for males and 61.40 days for females. The mean fecundity of a mated female was 210.52. The coccinellid grub consumed a total of 881.30 eggs or 259.00 nymphs or 27.55 adult females of M. hirsutus under laboratory conditions.