Annual Reports

• Sunflower moths studied as a potential alternate host for oriental fruit moth parasites
• Avocado thrips in California orchards
• New monitoring program helps reduce pesticide use in vegetables
• Reducing the impact of insecticide sprays for San Jose scale in orchards
• Fitting new insecticides into IPM systems for cotton
• Reducing pesticide use in North Coast pears

• UC IPM funds special project on mosquitoes in rice
• Helping to solve water quality problems along the South Coast
• Sustainable management of codling moth with pheromones
• Weed management to mitigate environmental pollution and resource conservation
• Curbing the spread of vine mealybug
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Oriental fruit moth, Grapholitha molesta, is a key pest in many stone fruit crops and a major target of insecticide sprays. Where established, the parasite Macrocentrus ancylivorus can be effective against this pest with up to 80% parasitism in some situations.

Prior to the development of modern insecticides such as DDT, federal and state agencies reared and released Macrocentrus in several areas of the country. However, when effective insecticides were developed, the use of Macrocentrus fell out of favor, except in western Colorado, where the Colorado Department of Food and Agriculture still rears and releases the parasite.

The weakness with Macrocentrus is that it does not overwinter on oriental fruit moth and must be reared and released in orchards each year. However, it does overwinter on other hosts. One such host is the sunflower moth, Homeosoma electellum. The sunflower moth attacks sunflower as the flowers develop.

With support from the Speciality Crops Grant Program, UC IPM Advisor Walt Bentley has established a planting of sunflower at the Kearney Research and Extension Center next to a peach orchard infested with oriental fruit moth. Macrocentrus parasites, collected from Colorado, have been released on the sunflowers, which are heavily infested with sunflower moth.

If the parasite can winter on this alternative host, Walt hopes it can be integrated into an IPM program that combines mating disruption and biological control to reduce late-season sprays for oriental fruit moth.

The avocado thrips is the most serious established invasive pest of California avocados to date. During his sabbatical leave in 2002, Area UC IPM Advisor Phil Phillips studied this insect in Mexico and Guatemala, its native home area, where it is not a pest of avocado.

His studies partially confirmed his theory on why this insect is not considered a pest in these countries. He had supposed that high temperatures during the bloom and fruiting periods coupled with a shift in the host’s phenology would preclude the thrips from attaining population levels necessary to damage young fruit.

He found that temperature is not the key reason for this insect’s shift in pest status but that a shift in the host’s phenology plays a key role. In its native home, the commercial Hass avocado sets its fruit two to four months earlier than when grown in a temperate climate.

This places the sensitive fruit set and early fruit development periods (when thrips fruit scarring would occur) in the middle of the growth flush, the preferred feeding substrate for avocado thrips. This continued availability of succulent foliage prevents fruit scarring from occurring, since the thrips remain on the foliage.

The delay in the tree’s fruit set period when grown in a temperate climate allows this insect to be a significant pest in California avocados where, after building large populations on the growth flush, the avocado thrips migrates to the tender tissue of the fruit peel as the flush ends and the foliage hardens.

Phil plans future trips to Mexico with UC Riverside Entomologist Mark Hoddle to collect live predaceous thrips that will be introduced through quarantine into California avocados for biological control.

Caterpillars in the noctuid family—such as tomato fruitworm, armyworms, loopers, and cutworms—cause significant damage each year in row and vegetable crops throughout California. Treatment thresholds and monitoring programs developed in the past to help growers reduce sprays have simply been too time-consuming to be readily adopted.

UC IPM Advisor Carolyn Pickel and cooperating Farm Advisors have been developing methods that combine use of pheromone traps and degree-day calculations to reduce the amount of monitoring time required to an acceptable level.

A first step was making sure that existing data on how fast the caterpillars developed at various temperatures (or phenology models) was correct and that pheromone traps were an effective monitoring method. Six Central Valley counties were included in the study and the program was tested on processing and fresh market tomatoes as well as on melons.

The research suggested that weekly trap counts of moths taken on a regional basis could be useful in very clearly determining when PCAs and growers need to sample for worms. Sampling of individual blocks for caterpillars or eggs is still required because worm levels vary among fields and not all fields need to be treated.

This program promises to have many benefits. Better timing of pesticide applications will improve control with fewer sprays, reducing costs, improving produce quality, and enhancing environmental protection. This project was originally funded for just Sutter County; however, after initial field results were presented to industry research boards, professional crop advisers, and other UC farm advisors, many additional groups wanted to become involved.

As a result, the project expanded into the San Joaquin Valley and seven farm advisors participated in the research. Impressed with the results, the Department of Pesticide Regulation provided additional funding for demonstrations and training sessions for PCAs. Information on how to use pheromone traps and degree-days is being incorporated into the UC IPM Pest Management Guidelines for processing tomatoes and melons.

Contamination of surface water by dormant sprays containing organophosphate and carbamate insecticides is a critical issue facing California. For many years, these insecticides have been used in combination with horticultural mineral oils to manage San Jose scale, Diaspidiotus perniciosus, in orchards.

Results from three years of research by UC IPM Advisor Walt Bentley have shown that the problem insecticides can be eliminated from the dormant spray, with no loss in efficacy, if higher rates of oil (e.g., 8 gallons per acre) are used. This work has been performed on multiple varieties of plums that have been heavily infested with San Jose scale.

In a related program, a new presence-absence sampling plan may eliminate many unnecessary dormant sprays for San Jose scale and other insects in plums. This program, being developed by Walt, Carolyn Pickel, and other UCCE personnel, involves sampling fruiting spurs during the winter and examining them for scales and other pests.

The relationship between spur infestation and fruit infestation later in the season is significantly and closely correlated. This sampling program and sampling forms are now included in the Pest Management Guidelines for Prunes on the UC IPM Web site and have been promoted in several grower workshops

For several years, South Coast UC IPM Advisor Cheryl Wilen has promoted IPM as a tool for nursery and landscape professionals to help solve water quality problems.

Public employees working in cities and counties have been a key audience for this message and are very receptive. In collaboration with Darren Haver, Water Quality Advisor for San Diego and Orange Counties, and John Kabashima,

Environmental Horticulture Advisor for Orange County, Cheryl has produced pesticide and fertilizer guidelines for cities in Orange County that emphasize IPM in landscape maintenance. Cheryl’s IPM meetings in the Port of San Diego have been a sold-out success; the 2003 meetings focused on rat and gopher control and landscape IPM.

In the research arena, Cheryl is also pursuing the water quality issue. She is conducting trials to reduce runoff from nurseries by adapting irrigation scheduling, potting media, and use of specialized pots. In addition to reducing runoff, these changes to conventional systems have often resulted in improved weed control and reduced need for herbicides or hand-weeding.

Seedling identification and knowledge of its biology is the most important step in weed management.

To increase growers’ ability to identify weeds, UC IPM Advisor Anil Shrestha co-organized a "Weed School" with UC Farm Advisors Kurt Hembree and Richard Molinar that was held at the Kearney Agricultural Center in September 2002.

In addition to classes on weed identification and biology, a technique for weed management using soil solarization was demonstrated by UC IPM Advisor Jim Stapleton. The success of the "Weed School" led to an invitation by the Winegrape Pest Management Alliance for the co-organizers to run a series of weed identification sessions in several Central Valley, North Coast, and Central Coast vineyards.

Anil also conducted additional weed seedling and seed identification demonstrations at the Fresh Market Tomato Field Day in Merced County in collaboration with UC Farm Advisor Kurt Hembree.

Vine mealybug, Planoccus ficus, became an issue of major concern in summer 2002 when it spread from an initial southern California infestation to nine additional northern California counties. A problem only in grapes, the pest causes cluster contamination and yield loss and can transmit viral diseases.

Because of the serious threat posed by this insect, in November 2002 the UC IPM Program funded a special effort, coordinated by UC IPM Advisor Walt Bentley, to develop new methods to detect and manage the pest in grape nurseries. The team included Kent Daane (UC Berkeley and Kearney Agricultural Center, Cooperative Extension Entomologist), Lucia Varela and Jim Stapleton (UC IPM Advisors), David Haviland (Kern County IPM Advisor), and Farm Advisors Rhonda Smith (Sonoma County), Jennifer Hashim (Kern County), and Steve Vasquez (Fresno County).

As the team visited infested vineyards and questioned grape growers, the pattern of spread became evident. Infestation was occurring on young vines in several wine grape varieties planted within the last 4 to 5 years. The few nurseries that supply grape farmers were contacted. They were interested in a nontoxic treatment that would not put fieldworkers handling either dormant plant material or green container plants at risk.

Hot-water treatment of dormant nursery stock was identified as a likely management strategy. The research team initiated a series of laboratory and field studies to determine what temperatures were required to effectively control all life stages of vine mealybug without damaging dormant vines or cuttings. Testing showed temperatures at or above 125°F resulted in 99.99% mortality.

In less than 12 months, this IPM research effort produced a safe and effective management method that was adopted by a number of nurserymen. Commercial nurseries treat their planting stock by immersing materials for 5 minutes into each of three tanks: a warming tank, a treatment tank of water above 125°F, and then a cooling tank. Cooperating nurserymen are optimistic about this technology; four primary providers of dormant grape nursery stock have already invested in full-scale treatment and are now utilizing this technique to ensure planting material is free of vine mealybug.

The UC IPM vine mealybug team is already at work taking the new information out to the field. In addition to reaching nurserymen with the hot-water treatment technique, the IPM Advisors are delivering information to growers and PCAs.

In the Central Valley, Walt Bentley and David Haviland have been actively getting the word out to nurseries and growers. Along the North Coast, Lucia Varela and Rhonda Smith have initiated an educational program and trapping program in collaboration with growers, vineyard managers, and pest control advisers. Thousands of traps have been deployed and are being checked regularly. Meetings and workshops have been offered in both English and Spanish.

The goal of the outreach programs is to identify infestations as early as possible so measures can be taken to limit the pest’s spread to additional vineyards. Control of vine mealybug can be accomplished currently only with the use of insecticides; thus, if this insect becomes widespread, insecticide use will increase, disrupting excellent IPM and biological control programs being implemented for other pests in California’s vineyards.