GraDe Dhvlloxera in California Jeffrey Granett 0 Austin C. Goheen 0 Lloyd A. Lider
New bioty--poses some risk in coastal vineyards Phylloxera feeding on grape roots cause galls, which are necessary for the insects' nutrition.
Grape phylloxera is an aphidlike pest ing. They molt four times, reaching adult- native to the eastern and southern United hood in about a month. In California, all States, where it lives on wild grape spe- phylloxera are females and may lay up to cies that have varying levels of tolerance 250 eggs. There may be as many as five or resistance to it. This insect, Daktulo- generations a year under favorable condi- sphaira vitifoliae (Fitch), was moved to tions. Europe and California during the last cen- Phylloxera need favorable tempera- tury on cuttings from some of these grape tures, soil type, and hosts for survival. Soil species. It decimated vineyards in those temperatures must be between about 60" areas, because the wine grape, Vitis vini- and 90°F; at levels very much above or fera, is highly susceptible to infestations. below this range, phylloxera do not feed The root-inhabiting form of grape and will die. They grow well on roots in phylloxera can increase rapidly in num- clay soils but do poorly in sandy soils, for bers. In the fall, when temperatures fall reasons that are not known. below 60"F, all forms except the first- Interaction with the host plant is nec- stage crawlers die. When soil tempera- essary. As it attempts to feed, the phyllox- tures rise above about 60°F in the spring, era injects saliva into roots. The saliva these overwintering crawlers start feed- causes a susceptible host to form swell- ings, or galls, and gall formation seems to be required for the insect to feed properly. Some American Vitis species and hybrids of these with V. vinifera do not form galls or do not form them well; these plants are resistant to the grape phylloxera. The technology for using phylloxera- resistant rootstocks (either pure Ameri- can Vitis species or hybrids) was devel- oped over 100 years ago, but selection of rootstocks for use in vineyards depends on many viticultural characteristics in addi-
Phylloxera distribution by counties. Most of this is type A. Type B has thus far been dis - covered only in Napa and Sonorna counties. (From CDFA data)
10 CALIFORNIA AGRICULTURE, JANUARY-FEBRUARY 1987 and dying. Extremely high numbers of phylloxera were found on the roots. After looking at 46 sucker canes of the root- stocks taken from the vineyard in June 1985, we determined that 23 of the root- stocks were AxR-1. The other 23 were an- other V. vinifera X V. rupestris hybrid, XX or 95-3 C, which we kdow to be sus- ceptible in general to phylloxera. Next we brought phylloxera from the AxR-1 plants into the laboratory to test them on genuine AxR-1 root pieces from the Department of Viticulture vineyard at UC Davis. We placed eggs on 1.5-inch root pieces, which we kept moist by wrapping one end with moist cotton. For each phyl- loxera type tested, we used 50 to 120 eggs per experiment and replicated the experi- ment five times, comparing the new phyl- loxera strain with another strain in devel- opment time to the adult stage, generation time, longevity of individuals, and reproductive rates. Analysis of the data with life-table statistics indicated that the phylloxera from the newly infested vineyard differed from the other California population in Grape phylloxera decimated California vineyards during the last century, because the wine having a faster development and rate of grape rootstock, Vifis vinifera, was highly susceptible to infestations. Planting resistant egg laying on AxR-1 (table 1). rootstocks effectively controlled the ipsect. This photo shows damage from type B phylloxera. As a final test to ascertain biotypes, we interplanted a small rootstock trial in the affected vineyard in 1984. (This trial tion to resistance to phylloxera. Trials in size and severity. Growers have been was also used to determine resistance of have been established in several Califor- able to deal with the problem by cultural various rootstocks.) We used a random- nia grape-growing areas with different methods. This situation has been known ized block design with 20 plants of each of scion/rootstock combinations to evaluate for a long time and does not seem to be five rootstocks, and four replications. viticultural characteristics along with re- worsening. These plants were analyzed for vigor in sistance. A third phylloxera problem is new to October 1985 on a scale of 0 to 9, with five California: the recent discovery of phyl- people rating each plant independently. In Phylloxera problems loxera biotypes, or forms of the insect July 1986, the plants were dug and infes- Phylloxera is well distributed in Cali- that are not different species but that dif- tations on the roots determined. fornia’s viticultural regions, but the prob- fer in some important biological charac- The ratings averaged for the five ob- lems it causes vary. teristic. The characteristic of importance servers indicated that AxR-1 was rela- Although the insect infests the coastal to phylloxera is the ability to utilize a re- tively susceptible when compared with valleys, growers occasionally take the sistant rootstock as a food source. Phyl- S04, St. George, and 1202 C rootstocks (ta- risk of planting susceptible own-rooted loxera biotypes able to survive on partial- ble 2). Based on all the data, we concluded vines. Phylloxera are generally found in ly resistant V. vinifera X V. rupestris that there are at least two phylloxera bio- such vineyards within 5 to 10 years of crosses have been known worldwide since types in California and that one (type B) is planting; within another 5 to 10 years around 1915 (as reported by researcher A. able to utilize AxR-1 as a host. after the first discovery, the vineyards de- I. Perold in England in 1927; C. Borner, To date, we have identified three vine- cline to a level of nonproductivity. Cur- Germany, 1943; A.B. Stevenson, Canada, yards in Napa and Sonoma counties that rently, a number of vineyards in Monte- 1970; C.A. De Klerk, South Africa, 1979; are infested with type B. The vineyards rey, Napa, Lake, and Mendocino counties and P.D. King and G. Rilling, New Zea- are grafted primarily onto AxR-1 root- are on susceptible roots and have phyllox- land, 1985). These biotypes, however, stocks, but susceptible root types are in- era populations. Because there are no ac- have not been seen in California before termixed. We do not know the signifi- cepted, reliable chemical treatments for now. We began research to determine cance of this interplanting. We also do not phylloxera eradication, these vineyards whether phylloxera damage observed in a know whether the current finds of type B will eventually have to be replanted on Napa Valley vineyard was caused by a are the limit of type B distribution in Cali- resistant rootstocks. new biotype and, if so, to evaluate root- fornia. Another phylloxera problem exists in stocks against this new form. Central Valley vineyards. Soil tempera- Resistance of other rootstocks tures there tend to be above 90°F to some Biotypes We screened selections of grapes for depth in midsummer, causing phylloxera Our initial observations of phylloxera resistance to type B phylloxera. For these mortality. Some Valley soils are also very biotypes in California came about when a tests we used methods similar to the pre- sandy and therefore not optimal for phyl- Napa Valley grower came to the Univer- viously described life-table tests in the loxera. Although a number of Central Val- sity with a problem: Cabernet Sauvignon laboratory. Each rootstock experiment ley locations have grape phylloxera popu- vines grafted on what he thought was the included 50 eggs, and all experiments lations, the infestations tend to be limited resistant rootstock AxR-1 were declining were replicated three times. The criterion
CALIFORNIA AGRICULTURE, JANUARY-FEBRUARY 1987 11 TABLE 1. Population growth parametersof grape phylloxera on AxR-1 root TABLE 3. Laboratory tests evaluating standard and experimental pieces in the laboratoryt rootstocks for resistance to type B phylloxera Population parameters Parentage Variety Evaluation* (mean ? standard deviation) Paired Pure Vitis species Parameter Type A Type B t-test V. vinifera Cabernet Sauvignon Developmental time V. champini Dogridge V. champini Salt Creek (days). 41 ? 5.2 30 3.5 * V. riparia Riparia Gloire Generation time (days) 54 +_ 5.7 38 rt_ 6.1 Gross reproductive rate V. rupestris St. George (eggdfemale) 63 ? 32 128 ? 25 Hybrids of Vitis vinifera lncreaselgeneration V. rupestris x (individuals/female) 12 * 6.8 22 -t 15 NS V. vinifera AxR-1 S Population doubling time 1202 c ZIR (days) 17 ? 4.6 9 * 1.8 xx (93-5 C) t Phylloxera from vineyards infested with indicated biotype. V. rotundifolia x * Statistical significance at Pt0.05.df=4. NS indicates nonsignificance, P>0.05. df=4. V. vinifera 0 43-43 S 0 39-16 I TABLE 2. Field trial results with rootstocks in vineyard infested with type 0 44-4 I B phylloxera V. rufotomentosa x V. vinifera 171-6 R Vigor Infestation category Complex parentage 1613 C I (number of vines)* Number rating Complex parentage Harmony R Variety of vines (Mean + SD)t None Light Heavy Complex parentage Freedo m I May 1984 plantings: Hybrids with no SO4 20 6.8 rt 1.5 20 Vitis vinifera parentage 1202 c 20 6.1 ? 1.1 5 15 V. berlandieri X St. George 20 6.5 ? 0.9 5 14 1 V. riparia 5A I AXR-1 20 3.1 ? 0.8 8 12 5 00 I Chenin Blanc. 20 1.0 ? 1.2 1 19 SO4 I V. berlandieri x May 1985 plantings: V. rupestris 99 R R 0 39-1 6 15 6.3 + 1.4 13 2 110 R R 0 44-4 6 6.8 * 0.7 5 1 V. riparia x 0 43-43 15 5.5 ? 1.2 3 11 1 V. rupestris 3306 C R 171-6 6 5.2 ? 1.2 6 3309 c I 110 R 10 5.2 ? 1.4 1 8 1 t The evaluation assumes the AxR-l/type A interaction represents minimal resistance t Vigor evaluations are based on a 0-9 scale, with the highest numbers indicating the under California conditions. S, susceptible (doubling time
12 CALIFORNIA AGRICULTURE, JANUARY-FEBRUARY 1987