Lynn Wunderlich

Electronically controlled delivery system for beneficial insect eggs in liquid suspensions

A mechanical system was developed to meter and discharge liquid suspensions of insect eggs for release of biological pest control agents. The system consisted of a reservoir that was pressurized by compressed air which distended the bottom surface of the reservoir, agitated the suspension and forced it through a liquid supply tube which terminated in a tapered orifice. A pulse-width modulated valve provided intermittent flow which produced large droplets (ca. 2 mm diameter) of suspension. The duration of and intervals between liquid pulses, which determined application rate of and spacing between discharged eggs, respectively, was controlled by a microprocessor. Liquid droplets could be propelled outward to 3 m and at flowrates ranging from 25 to 250 mL/min per orifice. In operation, discharge distance of the eggs was controlled by the reservoir pressure, ranging from 10 to 50 kPa, and the flowrate was controlled by the duty cycle, or relative open time of the metering valve (10 to 100%). The system provided adequate agitation to discharge uniform suspensions of eggs in liquid carriers for 50 min and did not reduce viability of green lacewing eggs as measured by bioassays of larvae emergence from discharged eggs.

Ferrisia gilli (Hemiptera: Pseudococcidae) Transmits Grapevine Leafroll-Associated Viruses

Abstract Several mealybug species are vectors of grapevine leafroll-associated viruses (GLRaV), which cause the economically important grapevine leafroll disease in grape-producing regions worldwide. The mealybug Ferrisia gilli Gullan is a new pest of grapevines in El Dorado County, located in the Sierra Foothill wine-growing region of California. GLRaV species 1, 2, 3, and 4LV have been detected in vineyards with symptomatic vines in the Sierra Foothills. We conducted controlled virus acquisition and transmission experiments using source vine accessions infected with different combinations of GLRaV. We determined that F. gilli acquired GLRaV 1, 2, 3, and 4LV, and transmitted GLRaV-3 and GLRaV-4LV to uninfected recipient vines. Like numerous other mealybug species, in addition to causing direct damage to vines, F. gilli poses a threat to the grape industry as a vector of economically damaging viruses.

Seasonal biology of Ferrisia gilli (Hemiptera: Pseudococcidae) in California Sierra foothill vineyards.

ABSTRACT The mealybug Ferrisia gilli Gullan is an emerging pest of wine grapes grown in Californias Sierra foothills. A relatively new species, it had previously been recorded as a pest of pistachio, almond, and ornamentals. It was first reported on grape in El Dorado County in 2003 and has since established and spread. Nondestructive monitoring of grape vine sections was conducted in untreated vineyard plots and compared with destructive sampling conducted in grower-treated plots in 2008 and 2009 to determine F. gilli life stage seasonal presence, number of generations, location on the vine during the season, and damage potential to fruit clusters. Two generations were observed to be completed during the season. F. gilli overwintered under the bark at the base of the trunk, trunk, and cordon as second and third instars. Adults were found at the base of emerging shoots (spring) or on and under bark of old and new spurs. Live crawlers were born in June (first generation) and late August to September (second generation), and migrated to leaves to feed before moving to protected locations under bark or into fruit clusters. Lower mealybug densities and fruit damage were recorded on vines with than without insecticide treatment (s). Parasitized mealybugs were collected in low numbers and an Acerophagus sp. was the dominant parasitoid.

No evidence of transmission of grapevine leafroll-associated viruses by phylloxera (Daktulosphaira vitifoliae)

Grapevine leafroll disease is associated with several species of phloem-limited grapevine leafroll-associated viruses (GLRaV), some of which are transmitted by mealybugs and scale insects. The grape phylloxera, Daktulosphaira vitifoliae (Fitch) Biotype A (Hemiptera: Phylloxeridae), is a common vineyard pest that feeds on the phloem of vine roots. There is concern that these insects may transmit one or more GLRaV species, particularly GLRaV-2, a species in the genus Closterovirus. A field survey was performed in vineyards with a high incidence of grapevine leafroll disease and D. vitifoliae was assessed for acquisition of GLRaV. In greenhouse experiments, the ability of D. vitifoliae to transmit GLRaV from infected root sections or vines to co-planted virus-free recipient vines was tested. There were no GLRaV-positive D. vitifoliae in the field survey, nor did D. vitifoliae transmit GLRaV-1, −2, −3, or -4LV in greenhouse transmission experiments. Some insects tested positive for GLRaV after feeding on infected source vines in the greenhouse, however there was no evidence of virus transmission to healthy plants. These findings, in combination with the sedentary behaviour of the soil biotype of D. vitifoliae, make it unlikely that D. vitifoliae is a vector of any GLRaV.