Sustainable Controls for Vine Mealybug: Biological Control

AVF Proj. ID: 363 / /Cat.: ,
Primary Investigator(s): Kent Daaneby

As part of an ongoing foreign exploration and importation initiative for vine mealybug (VMB), Planococcus ficus Signoret, parasitoids have been collected in the Mediterranean regions of Europe, northern Africa, and South Africa. Natural enemies were either sent first to the USDA-ARS laboratory in France, and then to the UC Berkeley Quarantine Facility (collections by Sforza) or sent directly to UC Berkeley Quarantine (collections by Daane). Our goals were to screen the imported natural enemies for their potential to lower VMB populations in California, and for their possible non target impacts. In 2007, new material was collected in Portugal, but has not yet been screened in Quarantine. From previous collections, we identified populations of the parasitoids Anagyrus pseudococci from northern Italy and Coccidoxenoides perminutus from South Africa. These populations have been approved for release in California. C. perminutus was studied in the laboratory to help determine its potential. It has high lifetime fecundity (149 ± 21 adult offspring per female) and will attack all VMB life stages. The high reproductive rates of C. perminutus observed in the laboratory may not be duplicated in the field. However, C. perminutus may be expected to perform better than A. pseudococci in vineyards with high densities of Argentine ants.

In 2007, releases of A. pseudococci and C. perminutus were made in vineyards the in San Joaquin Valley (SJV), the Northern Interior Winegrape Region (Solano and Sacramento Counties), the North Coast (Sonoma and Napa Counties), and Central Coast (San Luis Obispo County) regions. There were nearly 75,000 female A. pseudococci produced and released. A. seudococci ?northern Italy? was produced in the UC Berkeley Insectary (11,750 females released) as well as the commercial ?Sterling Insectary? (58,500 females released). A small colony of A. pseudococci Sicily was maintained at the UC Berkeley insectary and field production of this strain was directed by CDFA Insectary. The more easily reared C. perminutus, of which approximately 143,000 were released, were produced at the UC Berkeley Insectary.

To date, we have recovered A. pseudococci at all sites, however, we have not yet completed the molecular work on samples to determine if the recovered material was from our release (northern Italy) or the A. pseudococci strain resident in California (Israel). We have recovered C. perminutus at some Central Coast, North Coast, Sacramento, and Central Valley release sites. We also recovered Leptomastidea abnormis in Fresno County (from 2005 releases), where we now consider this species to be established, and Sacramento County. Leptomastix dactylopii was recovered in Sacramento County. VMB parasitism levels range from 0 ? 80%of the collected mealybugs per sample date ? lower in the early summer, higher in the fall and on the exposed vs. protected VMB. As mentioned previously, VMB density and percent parasitism will be presented in the report on mating disruption.

Spider mites in California vineyards: temperature tolerance, effects of plant waterstatus through leaf temperature, impact of novel pesticides and resistance management.

AVF Proj. ID: 370 / /Cat.: ,
Primary Investigator(s): Nicholis Millsby

The preliminary results of two years of field studies in Lodi and Madera vineyards link Pacific spider mite (Tetranychus pacificus – PSM) outbreaks to water stress and the frequency of high temperatures on south-facing leaves. We found a positive relationship between water stress and leaf temperature, with water stressed plants having warmer leaves with higher PSM populations. However, we found no relationship between high leaf temperatures and Willamette spider mite (Eotetranychus willamettei – WSM). Grape growers should use deficit irrigation with caution, especially in vineyards with significant risk of PSM outbreaks.

We also carried out a study on the effects of temperature on development of PSM, WSM and western predatory mite (Galendromus occidentalis – WPM). Preliminary results suggest that 15° C slightly favored WSM over PSM, although PSM laid more eggs. At 22° C development time of the two mites did not differ. However, at 28° C PSM developed faster, lived longer and laid more eggs than WSM, which experienced higher immature mortality. At both 15 and 28° C WPM developed faster than PSM or WSM. Nevertheless, PSM laid 2.5 times as many eggs as WPM at 28° C suggesting that PSM may escape control as temperature rises. Prey type (WSM or PSM) at 28° C did not affect development or longevity of WPM. However, a greater number of WPM immatures escaped from grape leaf disks with WSM as prey compared to PSM as prey suggesting that WPM may be retained more effectively on PSM infested leaves in vineyards.

In addition, we ran a study on the effects of three pesticides on biological control of PSM using grape plants in the laboratory in a fully-crossed, two factor design: Presence and absence of WPM crossed with presence and absence of pesticide. The insecticide imidacloprid (Provado) did not affect PSM population growth, but drove WPM close to extinction, such that PSM densities were 70%lower on grape plants treated with WPM alone than with WPM and imidacloprid. In contrast, the fungicide wettable sulfur (Thiolux Jet) significantly decreased PSM populations by about 50%, and had no effects on WPM, such that PSM densities were about 40% less in the WPM and sulfur treatment than in the WPM alone treatment. The insecticide buprofezin (Applaud) had no effect on PSM, but it reduced WPM populations by 70%}, indicating its potential for long term disruptive effects. Our study demonstrates that use of pesticides such as imidacloprid and buprofezin may facilitate the development of PSM outbreaks, while other pesticides such as wettable sulfur may help WPM to suppress PSM.

Furthermore we tested the resistance of PSM populations to the miticides bifenazate (Acramite) and pyridaben (Nexter). We found that PSM from vineyards that reported miticide failures in south Salinas Valley and Lodi showed 10 times higher resistance to pyridaben than a susceptible population. In addition, PSM from Sonoma and Lodi demonstrated seven- and fourfold resistance to bifenazate respectively. Our results underline the dynamic nature of resistance evolution in PSM and point to the need for alternating miticides from different chemical groups to minimize resistance problems.

Pheromones for Sampling Major Mealybug Pests in California Vineyards

AVF Proj. ID: 332 / /Cat.: ,
Primary Investigator(s): Jocelyn Millarby

We have made major progress towards identifying the sex pheromone of the grape mealybug, the last of the four mealybug species of importance to the wine and grape industries in the western United States that we had targeted for pheromone identification and development. Key advances included:

  • Development of coupled gas chromatography-electroantennogram detection techniques that allowed us to use the antennae of male grape mealybugs as living detectors has clearly shown that extracts from virgin females contain a single pheromone component that elicits strong and consistent responses from the antennae of males. Thus, we have unequivocally located the pheromone compound in the extracts.
  • A combination of microchemical tests, mass spectrometric analysis, and gas chromatographic analyses have shown that the compound is an ester of a previously unknown monoterpene alcohol.
  • By combining pheromone extracts collected over several years, we have a few micrograms of the pheromone. After purification by preparative gas chromatography, this should be provide sufficient material for final, unequivocal identification of the pheromone within the next few weeks.

Thus, the pheromone of this worldwide pest, which has eluded us for five years, if finally within reach, and should be identified and synthesized, with field tests underway, during the 2007 crop year.

Ongoing field trials with the longtailed and obscure mealybug pheromones in California, South America, New Zealand, and Australia, in vineyards, nurseries, and cotton, have demonstrated that these pheromones are highly attractive to male mealybugs, as with the pheromone of the vine mealybug that we identified earlier in this project. There are indications that trap catches of longtailed mealybug show some degree of seasonality, with better catches during the cooler fall months in California.

Sustainable Controls for Vine Mealybug: Biological Control

AVF Proj. ID: 298 / /Cat.: ,
Primary Investigator(s): Kent Daaneby

Research on the vine mealybug (VMB) and natural enemy populations was conducted in San Joaquin Valley (SJV), the Northern Interior Winegrape Region (Sacramento County), the North Coast (Sonoma/Napa Counties), and Central Coast (San Luis Obispo County) vineyards. Our goals are to determine the biological traits of VMB and its natural enemies that influence the success of biological controls, to promote resident natural enemy effectiveness by periodic release of parasitoids, and to import and release novel natural enemies.

Field studies show low levels of resident parasitoid activity in the Northern Interior, North Coast and Central Coast winegrape regions, as compared with the relatively high levels of parasitism in the SJV. Only Anagyrus pseudococci was recovered (Sacramento County). Low parasitism levels were a product of low VMB levels resulting from multiple insecticide applications. To improve resident parasitism, we released Anagyrus pseudococci, Leptomastix dactylopii and Leptomastidea abnormis in vineyards in the North Coast and Central Coast regions. L. dactylopii and L. abnormis were recovered, although at low levels. In augmentation trials, in which we released A. pseudococci, mealybug densities were lower in the release than control plots. Theseresults suggest that mass releases of A. pseudococci aided in economic control of VMB and could be a viable alternative to chemical control (pending cost evaluation).

As for novel natural enemies, we completed quarantine studies of a parasitoid (Coccidoxenoides peregrinus) imported from South Africa and, in 2005 began field releases in Central Coast vineyards. We conducted laboratory trials with VMB on grape and alternate host plant species. Here, we present results of VMB development on grapes. Temperature-related developmental studies were conducted at seven temperatures ranging from 12?34°C. The optimal, lower and higher threshold of fecundity were estimated at 22.6, 11.6 and 34.1°C, respectively The mealybug?s intrinsic rate of increase (how fast the population can grow) and the net reproduction rate (how many offspring it can produce) reached a maximum at 26°C and 433.4 degree days (a measurement of temperature development). The lower and upper threshold temperatures and optimum temperatures for development were estimated at 14.5, 35.4 and 22.2°C, respectively, and the thermal constant at 276.31 degree days.

What do all these developed temperature parameters mean for California and VMB control? These thresholds and constants were used in a degree-day model to estimate the number of generations that could develop in different grape growing regions of California and compared with development in the some of the world?s known infested regions. Four and six generations were estimated for the SJV and the North Coast region, respectively. There was also a higher reproductive rate in California as compared with studies in South Africa. Unfortunately, in comparison to other regions (e.g., Europe, South Africa), VMB is well adapted to both hot summer temperatures found in the both the SJV as well as cooler temperatures found in the coastal regions.

Investigation of the grape mealybug complex and its natural enemies to improve biological control

AVF Proj. ID: 259 / /Cat.: ,
Primary Investigator(s): Kent Daane, Mark Battanyby

The grape, obscure, and longtailed mealybugs belong to the Pseudococcus maritimus-malacearum complex, a group of closely related and biologically similar species that overlap in their host ranges and natural enemies. Economic losses from these pests have increased in West Coast vineyards and some pear orchards over the past decade. Our previous research showed that natural enemies can control obscure and grape mealybug populations in the absence of tending ants (particularly Argentine ants) and insecticide treatments. Unfortunately, most of the insecticides that effectively control ants are more toxic than those used to control mealybugs. We have therefore investigated the use of less toxic ant controls suitable for IPM systems.

In field studies conducted in commercial winegrape vineyards in the Central and North Coast regions, baits consisting of 25%sugar-water and small amounts of pesticides (boric acid at 0.5%; thiamethoxam or imidacloprid at 0.0001%) were dispensed from 250-ml plastic tubes, at a rate of 50 tubes per acre. Plots treated with either boric acid or thiamethoxam showed significant, season-long reductions in ant activity. The reduction in ant activity was associated with significant reductions in mealybug populations and decreased crop damage. One vineyard proved to be more heavily infested with European fruit lecanium scale than mealybugs; we found that ant control allowed natural enemies to lower the densities of the scales as well. In a step toward extending this information, and developing a commercially available baiting system, we established larger plots in the Central Coast region. In these plots, the chosen toxicant was imidacloprid, because it is already labeled for use in grapes. Unfortunately, results at these sites were not conclusive due to the high ant densities at these sites, the late start to the season, and possibly to the instability of imidacloprid when exposed to UV light. In similar experiments employing a sugar-protein bait, we tested the effects of an entomopathogenic fungus, Beauvaria bassiana, on ant activity. To date no significant reduction of ant densities has been detected in this treatment.

Finally, we released a grape mealybug parasitoid (Pseudaphycus angelicus) in combination with ant controls in one of the North Coast vineyards. Parasite recovery rates were very low, however, and the results showed no difference in the level of parasitism between areas with and without ant controls.

Investigation of the Grape Mealybug Complex and its Natural Enemies to Improve Biological Control

AVF Proj. ID: 195 / /Cat.: ,
Primary Investigator(s): Kent Daaneby

Vineyard blocks in which we released Pseudaphycus angelicus, an important grape mealybug parasitoid, in 2000 were monitored in the 2001 season. In the Tulare County table grape block, lowered levels of mealybug damage and elevated levels of parasitism (compared to 2000) were found throughout the release and control plots, suggesting that overwintered parasitoid had moved from the initial release location. Releases planned for the 2001 season were less successful because of low insectary production of P. angelicus. Mid-season releases with a small number of parasitoids did not show any affect on mealybug density or damage ratings. Similarly, releases of green lacewing eggs did not show a reduction of mealybugs or economic damage. Studies testing alternative bait-control for the Argentine ant were tested. A 25%sugar solution and small amounts (0.001-0.0001%) of either imidacloprid, fipronil or thiomethoxam were placed in bait traps throughout a heavily infested Napa Valley wine grape vineyard. Results show a significant late-season reduction of ant activity at the fipronil and thiomethoxam treatments. However, there was no reduction in mealybug density or increase in parasitoid activity. While results showed no economic reduction of Argentine ants, we are encouraged by new information gained and will make the needed adjustments for study in the 2002 season. Finally, we tested the effect of nitrogen fertilization (0, 25, 50, 100, 200 and 400 lbs/ac) and girdling and gibberellic acid practices on mealybug populations. Results from field trials showed no difference between N fertilization treatments or berry sizing practices in mealybug density or egg deposition. We believe these field results were influenced by resident natural enemies, which lowered mealybug densities. In controlled greenhouse trials, mealybug densities and egg deposition on potted plants were greater in higher N fertilization treatments. We conclude that more vigorously growing vines can increase mealybug pest status. There is less evidence that berry-sizing practices have any influence on mealybug pest densities.

PDF: Investigation of the Grape Mealybug Complex and its Natural Enemies to Improve Biological Control

Population Dynamics of the Vine Mealybug and its Natural Enemies in Coachella and San Joaquin Valley Grape Growing Regions

AVF Proj. ID: 132 / /Cat.: ,
Primary Investigator(s): Kent Daaneby

The vine mealybug (VMB) was first identified as a new pest in the Coachella Valley (CV) and shortly thereafter moved north into the San Joaquin Valley (SJV). We report on VMB population dynamics and parasitoid effectiveness in these two different regions. In CV vineyards, VMB density followed a well-known pattern, increasing from spring through early summer, followed by a dramatic decline in May and June. Two parasitoids were recovered ? Anagyrus pseudococci and Leptomastidea abnormis. Both parasitoids increased with VMB densities, however, Anagyrus appeared before Leptomastidea. In SJV vineyards, VMB similarly concentrated on the lower trunk and roots in winter and progressively moved from these protected areas during spring. However, comparison of CV and SJV data showed important differences in VMB seasonal abundance, distribution, and parasitism. In CV, there were 2 distinct adult VMB peaks, while 3 occurred in SJV ? with adult and crawler densities highest in June. In SJV there were also all VMB life stages found on roots, trunk, canes, leaves and fruit in summer and fall samples. Factors leading to VMB decline most sharply contrast the 2 regions. In SJV samples, Anagyrus killed >80% of exposed VMB by August, resulting in lower VMB densities (Leptomastidea was not recovered). Parasitism in the CV never exceeded 25%, and VMB decline came 2 months earlier and was more clearly associated with increasing temperatures than parasitism. The more exposed locations of VMB (e.g., leaves) in the SJV may have resulted in higher parasitism. Laboratory studies on VMB and parasitoid biology are being conducted.

PDF: Population Dynamics of the Vine Mealybug and its Natural Enemies in Coachella and San Joaquin Valley Grape Growing Regions

Population Dynamics of the Vine Mealybug and its Natural Enemies in Coachella and

AVF Proj. ID: 35 / /Cat.: ,
Primary Investigator(s): Kent Daaneby

The vine mealybug (VMB) was first identified as a new pest in the Coachella Valley (CV) and shortly thereafter moved north into the San Joaquin Valley (SJV). We report on VMB population dynamics and parasitoid effectiveness in these two different regions. In CV vineyards, VMB density followed a well-known pattern, increasing from spring through early summer, followed by a dramatic decline in May and June. Two parasitoids were recovered – Anagyrus pseudococci and Leptomastidea abnormis. Both parasitoids increased with VMB densities, however – Anagyrus appeared before Leptomastidea. In SJV vineyards, VMB similarly concentrated on the lower trunk and roots in winter and progressively moved from these protected areas during spring. However, comparison of CV and SJV data showed important differences in VMB seasonal abundance, distribution, and parasitism. In CV, there were 2 distinct adult VMB peaks, while 3 occurred in SJV – with adult and crawler densities highest in June. In SJV there were also all VMB life stages found on roots, trunk, canes, leaves and fruit in summer and fall samples. Factors leading to VMB decline most sharply contrast the 2 regions. In SJV samples, Anagyrus killed >80% of exposed VMB by August, resulting in lower VMB densities (Leptomastidea was not recovered). Parasitism in the CV never exceeded 25%, and VMB decline came 2 months earlier and was more clearly associated with increasing temperatures than parasitism. The more exposed locations of VMB (e.g., leaves) in the SJV may have resulted in higher parasitism. Laboratory studies on VMB and parasitoid biology are being conducted.

Biological Control of Obscure Mealybug, Pseudococcus Viburni, in the North and Central Coast Regions

AVF Proj. ID: 9906 / /Cat.: ,
Primary Investigator(s): Kent Daaneby

Obscure and longtailed mealybug pest status and the effectiveness of natural enemies were studied in five vineyards in the Central Coast regions (San Luis Obispo and Ventura Counties) and one vineyard in Napa County. In all of these vineyards, samples were taken to determine the seasonal abundance of mealybugs and their natural enemies in order to estimate levels of natural control. In three of these vineyards (two in San Luis Obispo County and one in Napa) plots were established to investigate the role of ants on mealybug and beneficial insect abundance. Results showed mealybug populations, when left unchecked, can build to damaging levels because there are few efficient natural enemies resident in vineyards. The most common natural enemies resident in the vineyards were predatory beetles. Results also showed that ants tending mealybugs are quite disruptive to biological control; however, predatory beetles were present on vines with and without ants. In plots where ants were excluded, mealybug densities dropped significantly throughout the season and regardless of the levels of parasite activity (see below).

Seasonal Development and Control of Mealybug Species in Central Coast Vineyards

AVF Proj. ID: 9531 / /Cat.: ,
Primary Investigator(s): Mary Lee Bianchi, Phil Phillips, Kent Daane, Walt Bentleyby

Survey sites were established and monitored for mealybug, ant, and beneficial species. Obscure and long-tailed mealybugs were identified at all survey locations. No positive identification of grape mealybug has been made from any affected vineyards, although its presence is suspected due to recovery of parasite species known to parasitize grape mealybug. There does not seem to be a pattern of conditions that preselect the predominance of mealybug or ant species at any of the survey sites. Although predation was found at all sites it was not important as a control factor. Parasitism was found at three of the five sites, in very low levels. Determination of the seasonal development of each species under coastal conditions was not achieved during the 1995 growing season for three reasons. It was not considered prudent to release these species until positive identification of each was made. Obscure and long-tailed have been positively identified. In addition, pure colonies of the mealybug species were not available for release. Wet, cold weather conditions during the spring and early summer in the Edna Valley were also not conducive to a successful release. Due to the inability to complete objective 2 in 1995 the trial was amended to look at the efficacy of delayed dormant applications and inseason applications of short and long residual insecticides as well as a newly registered material reported to be effective in controlling mealybugs (Table 1). Timing of insecticide applications may be more critical than type of insecticide used when working with multiple species having different developmental cycles during the season. Dormant applications of chlorpyrifos have been successful in controlling grape mealybug populations in the San Joaquin Valley because it overwinters either as eggs or as newly hatched crawlers (Walt Bentley personal communication May 1996). In severely infested vineyards some in-season applications are also necessary. The most successful in-season treatments have been timed to a predominance of the early crawler stage of grape mealybug. In this trial monitoring of sticky tapes on canes indicated an early peak of crawler emergence in the first week of July. Treatments were applied the last week of June. Pre and post counts of leaves indicated significant reductions in mealybug numbers immediately after treatment with dimethoate and methomyl. Only dimethoate was consistent in being significantly different from the control in the number of crawlers captured on sticky tapes during the remainder of the season, and in significantly reducing the infestation of mealybugs in the clusters at harvest as compared to the unsprayed control.