There is good news and bad news for sugarbeet growers and the sugarbeet industry resulting from the El Ninõ weather conditions this year. The good news occurs mostly in the south of the state and gets progressively worse in a northward direction. In the Imperial Valley, weather conditions have been relatively mild. The result has been a record average sugar percentage so far this year. The factory has had to reduce its rate of slice because the sugar crystallization end of the plant cannot keep up with beets with such a high sugar content. Most growers in the Imperial Valley are having a very profitable year. Root yields appear to be approximately as high as in the prior two or three years, but sugar percent is larger. At the 60 % stage in the harvest, sugar percent was still 18% (with a few contracts as high as 20%) and tonnage had increased to 30 tons to the acre and was rising as the season progressed. Demand for acreage is high and the industry there seems to be thriving.

Circumstances are very different in the Central Valley. In Kern County, high rainfall reduced the need for irrigation water this year, and conditions have favored good beet growth. Indications are for a very good crop. But harvest will be delayed because of a backlog of overwintered sugarbeets in other areas. The goal is to complete the Kern harvest during the month of August with beets being shipped to Woodland and Tracy to help with the processing. Fall planted beets in the western Fresno county area will be harvested after the Kern crop in September. This is six to eight weeks later than normal. Growers will have to continue to irrigate sugarbeets and concern themselves with pest management of their crop during the growing season, including irrigation, powdery mildew, and insect management.

The overwintered crop in the San Joaquin Valley, currently being harvested from Merced and Fresno counties is averaging approximately 34 tons per acre and 15.5 % sugar. These are high root yields and a good to acceptable sugar percent. In the Tracy factory area the root yield currently is 32 tons per acre from the Collegeville area, and 15.5 % sugar. In the Woodland factory area, overwintered beet yields are averaging approximately 30 tons per acre at 15% sugar currently. Some fields in the central part of the state have produced over 50 tons of roots. Fall harvest beets in Glenn County were planted on very few acres (approximately 1,000 compared to the 5,000 acres that were planned) and harvest is scheduled there for October. It will be a short one and beets from the Upper Klamath Basin will then be processed for the remainder of the fall.

Record rainfall in the winter and spring prevented the planting of most of the proposed sugarbeet acres in Glenn and Butte counties. Several thousand acres intended for fall-harvest beets were lost to the industry. Those that were planted were established late in April and even in May, though mild weather in late spring has allowed young plants to grow well.

Acreage in the state for next year also is uncertain. Next season’s overwintered beet crop has not yet been established. Typically, most of those fields are planted in May and June, but like everything else in the central valley, schedules are seriously disrupted. Late planting may help to minimize the risk of infection with Beet Yellows Virus. The source of this virus is old, over-wintered beets. There are a lot of these fields around this year at the time when new fields must be planted. By early May significant distances between sugarbeet fields would be created allowing for replanting at that time with reasonable isolation of new beets from old beets, for virus yellows control. Late planting this year, however, should reduce the risk of infection despite the presence of old beets because the aphid vectors of the virus do not fly when temperatures reach summertime levels.

In the Upper Klamath Basin, some beet fields were planted later than normal, and there was some frost induced replanting, but most acres are underway. Rainfall in spring has meant that irrigation has been largely unnecessary this spring so far. Potato growers have had difficulty planting all their acres in a timely manner.

Because planting of next year’s overwintered crop has been delayed in Central California, it remains uncertain how many acres of sugarbeets will be produced for the next year in that area. Growers may shift summer crops normally planted into fields with beets into the fields that would have been used for beets for the upcoming crop.

Irrigation. No one can remember a year like the current one, so there is no precedent to use to predict what will happen with overly mature, bolted plants as the summer progresses. Root yields should rise somewhat, but sugar percentage may decline during the hot weather. Some continued crop growth can be expected, so farmers should manage their crops. There are some important considerations to keep in mind. Root rots may begin to be a problem because older crops during periods with hot temperatures and standing water are susceptible to pathogens. Rhizomania resistance, which has become quite good in the newer varieties under normal conditions, may be challenged this year as the summer progresses.

We are at the limit this season of what we know with confidence about sugarbeet irrigation and water recovery at depth. Careful irrigation must be practiced. This is easier to say than to do. It will be difficult to irrigate using furrows because of the trash left after chopping bolted seed stalks. If soils crack too much, it will slow down water movement in the furrow and lead to saturated conditions, especially at the head end of the field. A late June or early July harvest may not need irrigation if the soil profile to six feet deep is reasonably full of moisture. But there may be no alternative to irrigation if the crop must be held late into the summer months.

For root rot control, growers should avoid continuously saturated soil conditions by providing good field drainage and using short irrigations. Excessive dryness may not be beneficial, however. If fine roots are killed in dry surface soil layers, when re-irrigated, water uptake will be slow and soils will remain saturated longer, favoring root rots. In a study conducted in Arizona some years ago on sandy soils and under very high temperatures, more frequent, shallow irrigations reduced disease compared to less frequent, deeper irrigations. It is also true that most crops suffer more severely from plant diseases, including root rots, once stress has occurred. So it would be wise to replace some of the water used by the crop during the next month for late harvested crops.

Sugarbeets are thought to root to six feet deep. On good soils, they may root even deeper after over-wintering and growing for twelve months or more. Clay loam soils hold 1.5 to 2.0 inches of crop available water when at field capacity. After the wet winter we have had, most profiles should be moist to six feet or more. So there may be 9 to 12 inches of moisture available to deeply rooted beet crops in the profile at field capacity. Beets are capable of using that water. Water use in a normal month of July will likely be approximately 7 to 8 inches. We found in a line source trial at WSREC that for overwintered beets, irrigating to 60 to 70 % of potential crop ET was sufficient for maximum sugar yields in mid-July on the deep Panoche loam soil at that location. The crop had rooted to at least nine feet and was able to recover a significant amount of water from deep in the profile by June and July (see figure 1).

Crops absorb the majority of their water, however, from the surface soil layers because most of the roots are nearer the surface. Typically 70 % of seasonal water use is derived from the top half of the rooted profile. Some replacement of surface soil moisture is advisable. But if the soil in a beet field is deep and is moist to 6 feet or more, growers should replace only a portion of the water used by the crop from the top half of the profile, allowing the beets to remove the rest of the water they need from deeper layers. It is difficult to apply small amounts of water using furrow irrigation and long irrigation runs, but it is not necessary to wet the entire profile if moisture is already available at depth. Rather than moistening the entire soil profile, it will be sufficient to replace only the moisture used by the crop in the surface one to two feet. This would reduce the amount of water applied and the need to hold water for a long time in furrows, lessening the chance that root rots will occur, while allowing the beets to continue to grow and make sugar. Towards this end, it may be advisable to irrigate before the surface layers get too dry, and allow the beets to use deeper soil moisture later in the season.

Foliar pests and diseases. The behavior of foliar diseases and insect pests may be difficult to predict. Bolted canopies that have been chopped will regrow new leaves and mildew and cercospora likely will affect these canopies. Bob Lewellen notes that sugarbeet seed crops in Oregon must be managed for powdery mildew control and that bolted beets seem to be more susceptible than non-bolted beets to infection. Since growers have large root yields in most instances and sugar percentages are good, a large amount of money is at risk, especially if fields must be held late into the summer. It would seem unwise not to protect the crop canopy under these circumstances if mildew or severe armyworm damage is observed.

Bolting. The cool winter and spring weather have caused a larger amount of bolting to occur than normal. Bob Lewellen reviewed the biology of sugarbeet bolting very nicely in the last issue (1997) of the California Sugar Beet. Beets are biennial and to flower must be photo-thermally induced. They first require exposure to temperatures around 40 to 42^o F, followed by exposure to increasing day length (12 hours or more). Varieties vary in their sensitivity to bolting so there is no fixed amount of exposure required by all varieties. Easy bolting lines require only a few to 1000 hours of exposure to low temperatures, while bolting "resistant" lines may require 2000 hours or more. Beets can de-vernalize when exposed to high temperatures. In a normal climate year, spring temperatures are warmer and some inhibition or reversal of bolting occurs as warm temperatures occur in May and June. This year, however, there has been less de-vernalization weather than normal, and a larger number of beets have bolted. Current varieties also have somewhat less bolting resistance than older ones. The pressing need to establish rhizomania resistance as quickly as possible meant that some bolting resistance may have been lost in the breeding process. It is difficult to advance a large number of resistance traits simultaneously in a sugarbeet breeding program.

The consequences of increased bolting may have been minor or even somewhat favorable if a normal harvest had been possible. Sugar losses are not large if beets can be harvested before seed stalks mature because much of the sugar content of the roots has been accumulated by the time bolting begins in late spring and beets have a large photosynthetic capacity. Bob Lewellen also suggested that processing can be improved if beets are in the early stages of bolting because impurities like Na and K ions and amino N compounds which interfere with sugar extraction are transferred form the roots to the stalks. Indeed, Roger McEuen, factory manager in Mendota, has commented on how well the crop is processing this year. But as roots age, they will become more fibrous and processing quality will deteriorate.

In a normal year, a large amount of the overwintered crop would be harvested by late May, before bolting became too advanced. However, the start of the spring harvest campaign in the Solano-Yolo-Sacramento area and in the area east of Stockton and in Merced County and the Los Banos-Dos Palos areas was delayed until May, when it otherwise would begin in March. The risk of mature (hard) seed formation and woodiness in beets becomes greater the longer the harvest season progresses. As beet stalks become woody, topping canopies prior to harvest results in some of the woody beets being pulled up and dislodged or cracked and broken with large pieces of root left in the ground unharvested. These losses can affect yield, perhaps significantly. So topping should be done when seed stalks have formed, but before they become woody. This year, that schedule was difficult to meet. Also, some regrowth of seed stalks may occur because high temperatures which retard bolting in the late season have not yet occurred.

Managing bolting. If bolted sugarbeets are allowed to mature, the sugar content of roots falls off, and viable sugarbeet seed is left in the field and field edges. Some of this seed can persist for years and will germinate as a weed in other crops or along field edges. Sugarbeets are not good competitors with other crops, but any that survive and become established may act as a reservoir for the yellowing viruses (Beet Yellows and Beet Western Yellows) and for Beet Mosaic Virus. The most serious disease is Beet Yellows Virus which can only infect seedling beets by being transferred by green peach and black bean aphids from nearby old, infected beets. For this reason, seedling beets growing in other crops or along field edges are a danger to the entire industry. Fields left to set hard seed can harm an entire region’s beet crop. If a large amount of sugarbeet seed is formed this year, the El Ninõ weather conditions may have adverse consequences for many years to come. Aphids have an amazing ability to find host plants, even if they are small, or hidden in a crop like wheat or a hedgerow. It is important that bolted sugarbeets be prevented from forming mature seed. A good sugarbeet seed crop will yield about 4,000 pounds of seed per acre. There are about 40,000 seeds per pound so an unchopped field may produce 160-200,000,000 seeds.

Spreckels Sugar has been very responsible about this problem and is providing a flail mower for growers with a bolting problem.

A few years ago, Bob Sailsbery and Jack Hills conducted some trials analyzing the effects on sugar yield of chopping bolters (Sailsbery and Hills, 1986). About 12 inches of canopy were left after chopping. They reported that chopping bolters had no effect on either root or sugar yield of fall-planted sugarbeets in Tehama County. Bolters were cut either two or three weeks prior to harvest. Harvests occurred in mid-May and mid-June. In both these trials, hard seed and woody stalks had not yet formed.

Gaining experience in the management of bolted crops.

We have an opportunity this year to expand our understanding about the management of bolted sugarbeet crops. I recommend that those of you who work with sugarbeet growers keep track of the performance of the fields after tops are cut. This winter at the sugarbeet workgroup, we can pool our observations and create a report for useful for others in future years. In particular we will be interested in the regrowth of flower stalks after cutting, the occurrence of diseases after cutting, and the yield and quality of the crop being held in the field as the summer progresses.

In summary: El Ninõ conditions are producing a record year in the Imperial Valley, and difficulties everywhere else in California. Harvest schedules in the central valley are delayed by 4 to 8 weeks. Average root yields may set a new statewide average record, but because of delayed harvests and an exceptional amount of bolting, average sugar percent may decline as the summer progresses. Some management of crops waiting for harvest will be necessary, especially if harvest is delayed until late in the summer. Irrigation and some disease and insect control may be necessary to protect growers’ investments in their crops. The planting of fall harvest beets was delayed in the San Joaquin Valley (Tulare and Merced) and delayed, reduced in acreage, or largely abandoned in Glenn and Butte counties. The Upper Klamath Basin beet crop is growing normally and heavy rains in May have reduced the need to irrigate there.

References:

Lewellen, R. (1997). Nonbolting tendency in sugar beet, a continuing plant breeding objective. P 27-29. The California Sugar Beet. 1997 Annual Report. California Beet Growers Association, Stockton, Calif.

Sailsbery, R.L., and Hills, F.J. (1986). Managing overwintered sugarbeets. Calif. Agric. 40(5/6):31.

(FIGURE NEEDED)Fig. 1. Sucrose yield as a function of irrigation amount for a fall-planted crop in western Fresno County. Beets used additional water present in the soil profile to nine feet deep when irrigation amounts were reduced from 85% of crop ET. 14 Mg of sugar per ha equals 12,500 lb per acre.