Mario Viveros
UCCE Farm Advisor, Kern County
Deciduous Tree Fruits and Nuts
April 8, 2002
Bud failure or crazytop is quite prevalent in Kern County almond orchards. It can be found readily in both young and old orchards. The most affected varieties are Carmel and Nonpareil. Severe symptoms can be seen in the Mission variety in few orchards. The bud failure outbreak is due to high temperature accumulation in June of 2001. Bud failure develops during the growing season of the previous year. Dale Kester's work has shown that the accumulation of temperature above 80o F in June increases the bud failure potential whereas bud failure expression is due to high temperature accumulation during the summer.
The principal symptom is bud failure, this is to say that the vegetative buds fail to grow in the spring. Such buds are dead or severely inhibited. In most cases not all the buds in a shoot are affected and some may develop normally. Shoots from normal buds will grow vigorously often at right angles to the older shoot. Buds that fail, drop off 6 to 8 weeks after spring growth begins in the plant. Often only buds on the center part of the shoots are affected, while buds originating both early and late in the season are normal.
Bud failure trees bloom later than normal trees. The bloom can be delayed one to two weeks. Flower buds are not affected as much as vegetative buds. In fact, fruit set can be higher on bud failure trees than on normal trees. Nevertheless, yields are affected by bud failure. Our research has shown that bud failure can reduce yields in Nonpareil from 265 to 860 meat pounds per acre. In the Carmels, the yields can be reduced from 150 to 1200 meat pounds per acre. This yield reduction is due to less shoot growth.
Bud failure is a big problem in our almond orchards in Kern County. The reasons are due to high temperatures during the summer and rapid shoot growth in the spring. Therefore, we will
Always have bud failure problems in our orchards. However, there are things one can do to minimize its incidence in the orchards.
Variety selection is the most important thing to do to minimize bud failure in your orchard. Carmel is the most susceptible variety to bud failure. If you plant this variety, you will see bud failure. Our growers, however, continue to plant this variety because of its high yields and acceptance in the market.
The second thing to do is to select low bud failure potential sources. The University of California has released to the California nursery industry a low bud failure source (FPMS #1). This source, however, has been showing some bud failure. This year 14 percent of the Carmel (FPMS#1) trees in the Regional Almond Variety Plot were affected by bud failure. Carmel source from the original trees has also looked good in our test plots.
The Nonpareil variety is also susceptible to bud failure. The University of California sources under the FPMS program have looked good both in test plots and commercial orchards. This does not mean that they will never show bud failure but for now they have not shown any symptoms.
The third thing to do is to eliminate bud failure infected trees when they are young. Bud failure trees get worse with age. By eliminating bud failure trees in one, two, three and four- year -old orchards; one will eliminate the worse bud failure trees in the orchard.
Topworking is another alternative to manage bud failure. The practice is expensive and will require skillful grafters as well as a low bud failure potential source. Furthermore, to be successful, one must be willing and able to pay close attention to post-grafting care.
Some growers have pruned off the bud failure from the trees. This has not worked at all. This practice just promotes vigorous growth, which with time will express worse symptoms.