Making a Stink About Bugs

The introduction of new insect pests damaging to grapes is an ongoing threat for California’s grape growers.  Light brown apple (LBAM) and European grapevine (EGVM) moths are two recent examples of introduced insects the presence of which has been very costly to growers.  Although safe and effective conventional and organic control methods are available to manage moths, these particular insects are considered ‘quarantine’ pests, so extra special measures must be taken in the vineyard and throughout the fruit distribution and processing network.  Quarantine pests are a particular concern for the trade of fresh fruits, such as table grapes, due to import restrictions in some domestic and international markets.  Exactly how these insects made it to California is not presently known, but past insect introductions have come from contaminated plants and plant products.  Thus, it is critically important that everyone recognize the potential danger of violating plant protection and quarantine regulations.

Just as grape growers learn they have made excellent progress toward eradicating EGVM, officials are expressing concern over a new exotic insect pest, the brown marmorated stink bug (BMSB).  The BMSB is now found in 33 States.  Although not established in California, it has been identified in Los Angeles and Solano Counties.  BMBS can fly, but they primarily move into new areas by hitchhiking on vehicles and equipment.  Native to Asia, its thought that BMSB arrived in packing crates shipped to the Eastern US.  It has a large host range that includes grapes and many of the fruits and vegetables grown in California.  Damage can be substantial when BMSB populations are not identified early and managed appropriately. Apple growers in the Mid-Atlantic States have reported losses of $37 million representing 18% of their fresh apple market.  Growers and wineries are also concerned that the “stink” from any bugs accidentally crushed in wine or juice grapes could taint the product with off flavors. This insect should concern homeowners as well, since people in the Mid-Atlantic States have reported large populations of BMBS overwintering in their homes and becoming a nuisance.  

BMSBs resemble some other California stinkbugs such as the rough stink bug, a beneficial predator of other insects.  If you think you’ve found a BMSB, or any other odd or unique looking insect pest, you should collect it and bring it to your local university advisor, ag commissioner or state ag department entomologist for proper identification.  Early identification of invasive pests is critical for protecting California’s billion dollar agricultural industries.

You can learn more about the BMSB and current research here.

Breeding New Pest Resistant Rootstocks for Grapes

With bloom well underway, grapevine breeders and geneticists, such as Peter Cousins, with the USDA’s Grape Genetics Research Unit, in Geneva, NY, are busy making crosses between pairs of vines having favorable traits.  Cousins is a rootstock breeder, so traits that interest him include resistance to root-knot nematodes, soil-borne pests whose feeding activities can cause extensive damage to grapevine roots, thereby weakening the vines and reducing yields.  Though Cousins, is based in NY, he is cultivating some advanced selections from his rootstock breeding program in a vineyard at the Kearney Agricultural Research and Extension Center in Parlier, California.  By growing the vines at Kearney, Cousins can assess their performance in the San Joaquin Valley, one of the most important grape-growing regions in the world.  Vines that maintain their nematode resistance, grow well, and are easily propagated, may eventually be released as commercial rootstocks, and serve as a genetic resource for future crosses aimed at further strengthening their nematode resistance by incorporating as many resistance mechanisms for resistance as possible.

Some wild grapevine species have unique nematode resistance mechanisms, and are thus used as parents in rootstock breeding.  Cousin’s goal is to incorporate as many different forms of resistance as possible into new rootstocks, so some advanced selections are complex hybrids of several species.  Wild grapevines, and their hybrids, are dioecious; invididual vines bear clusters of either male or female flowers.  Dioecious vines are relatively easy to cross as the flowers do not have to be emasculated; to prevent unwanted crosses, he simply encloses female flower clusters in paper bags prior to bloom. 

As bloom approaches, he periodically he taps on the bags, listening for the rattle of detached petals that signals the blossoms are ready to be pollinated.  Properly prepared, pollen, which Cousins prepares by grinding flowers in a coffee mill, can be stored for a relatively long time, facilitating crosses between vines that might not flower at the same time.  To pollinate, the bags are removed, the appropriate pollen is slathered on with paint brush, and the cluster is labeled, and recovered with the bag.  Cousins will return in the summer, to extract the seeds from the fruit.  Seedlings will then be screened for nematode resistance, and the best selections may eventually end up returning to Parlier, to be evaluated alongside their parents.  To learn more about Dr. Cousin’s research program, and see his rootstock selection vineyard, plan to attend Grape Day at Kearney, August 18, 2011.

Managing fruit set; an important early step in producing quality table grapes

Grapes in the San Joaquin Valley are blooming.  The flowers are not particularly impressive to look at—they bear a superficial resemblance to brocolli—but the have a fresh, clean, invigorating scent.  That’s good, because there’s a lot of work to be done in the vineyard around bloom.  Table grape growers are among the busiest of viticulturists at bloom, as they must take steps to limit the amount of fruit set, so that the remaining berries will have ample room to grow without becoming excessively crowded.  If too many berries are set, the cluster will become excessively compact, full of misshapen and cracked berries that are highly susceptible to rot.  Home growers can thin their grapes by brushing the flower clusters with a scalp brush until about half the flowers are removed, but this approach is impractical for most commercial growers.

Instead, most growers apply a natural plant growth regulator gibberellic acid (GA₃) during bloom to reduce fruit set.  Generally, between 0.5 to 20 grams/acre GA₃ is applied to the vines when 30% to 80% of the flowers have opened, and multiple applications may be needed in some cases.  The proper application timing and dose depends on a variety of factors including the cultivar, environmental conditions at bloom, and cultural practices such as type of trellis and spray equipment used.  The use of GA₃ can reduce return fruitfulness of certain seedless cultivars, and many recently released cultivars require less GA₃ than traditional cultivars to achieve adequate thinning.  Seeded grapes, including wine grapes, may also respond to GA₃  thinning sprays, but seeds are a natural source of GA₃, and seeded varieties are more apt to respond to such sprays with unwanted side effects including reduced shoot and cluster counts the following spring, and increased proportions of tiny “shot” berries that detract from the appearance of table grape clusters. Before applying GA₃, or any other agricultural chemical, be sure to review the label and ensure the instructions are followed. 

Prebloom zinc sprays can improve fruit set

The earliest grapevine varieties are starting to bloom at the Kearney Agricultural Research and Extension Center in Parlier, near Fresno, California.  Some of the grapevines here, as in other parts of the state, are susceptible to mild zinc deficiencies, the only obvious symptom of which may be reduced fruit set.  Varieties having 'Muscat of Alexandria' parentage are particularly prone to zinc deficiency, as are vines on sandy soils, or those grafted to rootstocks having Vitis champinii parentage, including 'Freedom' and 'Harmony'.   All vines at the station are subject to an annual zinc foliar spray during a two-week pre-bloom window that closes when 60 to 70% of flowers have opened.  This year's treatment is scheduled for Monday, May 9. 
Neutral zinc is the most effective product.  Two to three pounds of neutral zinc per acre are suggested to correct moderate deficiencies, though lower rates may be acceptable for minor deficiencies.  Dilute sprays are most effective, using 100 to 150 gallons of water per acre. For more information on the diagnosis and correction of zinc or other micro or macro nutrient deficiencies, review L. Peter Christensen's excellent book chapter Mineral Nutrition and Fertilization.

Too Hot!

It's starting to get hot in the San Joaquin Valley. To comply with the law and help prevent heat-related illnesses, employers must ensure certain safety practices are employed. First, people working outside in hot weather should drink at least 4 cups of water per hour.  Thus, employers must provide a sufficient and readily accessible supply of clean, cool, water.
In California, employers must provide shaded areas that are ready to use once temperatures reach 85 degrees Fahrenheit. Acceptable shaded areas are described in the California Code of Regulation.  When temperature reach or exceed 95 degrees Farenheit, additional high-heat procedures should be implemented.  Such procedures include ensuring that effective communication is maintained; observing employees for alertness and signs or symptoms of heat illness; reminding employees to drink water throughout the workday; and closely supervising new employees.

Dr. Anita Oberholster Joins UC as Cooperative Extension Enologist

The UC Davis Department of Viticulture and Enology will host a welcome reception for Dr. Anita Oberholster, who was recently appointed UC Cooperative Extension Specialist in Enology.  The reception will be held at the Robert Mondavi Institute for Wine and Food Science, UC Davis on May 13^th, from 10:00AM to 3:00PM.  The day's activities will begin with Anita’s introduction by the Department Chair, Andrew Waterhouse.  Dr. Oberholster will discuss her recent research experience and her vision for the Enology Cooperative Extension program. Wine industry representatives will have an opportunity to ask questions and make suggestions for research topics.  Additional Department Faculty will also make presentations, including including Linda Bisson, who will discuss VENSource and the departments new extension program in enology; Jim Wolpert, who will discuss the Community of Practice and viticulture extension; Susan Ebeler, who will talk about the new Agilent Analytical Facility and its implications for future research; and David Mills who will talk about the new Professional Masters’ Program. The event is an opportunity to bring industry issues and questions to the faculty, and to find out how they envision their role in supporting California’s wine industry into the future.

Following the morning presentations, a crowd-favorite Buckhorn-Barbecue lunch will be served to paid participants. After lunch, in-depth tours of the Viticulture & Enology facilities, led by faculty and professional staff, will commence.

Save the Date

When: Friday, May 13, 2011 from 10:00AM—3:00PM

What: Reception to introduce Dr Anita Oberholster, UC Cooperative Extension Enologist

Where:

Cost: $29.00 per person

Seating is limited for this event and early signup is suggested.

Registration for this event is available at:

http://ucce.ucdavis.edu/survey/survey.cfm?surveynumber=6177