Peach rootstocks, which should you use?

Traditionally, peach seedlings have been used as rootstocks for peach and propagators used their own local source of seed. Currently there are only a few standard peach seedling rootstocks used throughout the country. The most commonly used rootstocks in the United States are Nemaguard, Nemared, Lovell, Halford, and Guardian. In addition to these, there are four others: Flordaguard, a low-chill, nematode-resistant rootstock developed in Florida, and three peach-almond hybrid rootstocks developed in California. Two of the peach-almond hybrids, Red Leaf Titan Hybrid and Green Leaf Titan Hybrid, are seed propagated and available from Brights Nursery (5246 South Plainsburg Road, Le Grand, California 95333, 209-389-4511). The other, Hansen, is propagated by cuttings and is available from Burchell Nursery (P.O. Box 8200, Fresno, California 93747, 209-834-1681). Guardian is available from several Tennessee nurseries.

Your choice of rootstock depends on weather and soil conditions at your orchard site. These rootstocks differ in five main traits:

    1. Resistance to rootknot nematodes.
    2. Tolerance to calcareous soil conditions.
    3. Tolerance to water-logged soil conditions.
    4. Cold hardiness.
    5. Tolerance to peach tree short life (PTSL) associated with the ring nematode

Rootknot nematodes are small, worm-like organisms that live in the soil and feed on roots. They enter the root to feed and, in doing so, cause the root tissue to swell and form a gall (rootknot). Rootknot nematodes prefer to live in sandy soils (Figure 1). As your soil texture becomes less sandy, the suitability of the soil environment for nematode reproduction decreases and potential nematode problems also decrease. Thus if your soil is sandy it is important to test your soil for nematodes. Instructions for this can be obtained from the Plant Disease Diagnostic Laboratory at Texas A&M University (http://plantpathology.tamu.edu/Texlab/tpddl.html). It is very important to follow sampling instructions carefully in order to obtain reliable results.

Six of the eight rootstocks mentioned above have good resistance to the common races of the rootknot nematode that are found in Texas (Table 1). Of these, the most commonly used are Nemaguard, Nemared, and Guardian. Susceptible rootstocks can be used in heavier soils but if the soil is sandy and nematodes are a problem, nematode resistant rootstocks should be used.

 

 

 

Tolerance to calcareous soils. About two-thirds of Texas has the potential to have problems with lime-induced chlorosis due to calcareous soils (Figure 2). Calcareous soils are characterized by low organic matter, high pH (7.4-8.5) and a high level of bicarbonate in the soil. In these soils, the iron is only available to the plant at very low concentrations. This low level of plant-available iron will cause the development of lime-induced iron chlorosis characterized by interveinal yellowing of the new growth due to lowered levels of chlorophyll. At high levels of stress, the whole leaf turns white. This condition reduces tree growth and may lead to reduced yields and even tree death.

Of the commonly used rootstocks, Nemaguard is the most susceptible to calcareous soils (Table 1) and will require yearly applications of iron chelates (Fe EDDHA) to maintain green foliage. Lovell appears less susceptible than Nemaguard but the most tolerant rootstocks are the peach-almond types: the two Titan Hybrids and the Hansen rootstock. All of these are also resistant to rootknot nematodes, although it should be noted that they tend to induce more vigorous scion growth and are more susceptible to damage due to water-logged soil than are the peach rootstocks. Consequently, care must be taken not to use these peach-almond rootstocks in areas that are prone to water-logged soil conditions.

Water-logged soil conditions. Plum rootstock is the most tolerant to water-logged conditions. Unfortunately, due to graft incompatibility and other problems, these cannot be recommended for commercial peach orchards. Among peach and peach-almond rootstocks, there is not a high level of tolerance (Table 1) to this often-seen condition in Texas orchards. The best advice is not to plant in areas where there are potential problems with soil water-logging. And under no circumstances, use peach-almond rootstocks in soils that are periodically waterlogged.

Cold hardiness. Cold injury to the trees wood during fall or winter periods can cause severe damage or even premature death of peach trees in Texas, especially in northern growing areas. Rootstock trials done in Georgia, Alabama and South Carolina have shown that Lovell and Guardian survive much better than Nemaguard, and somewhat better than Halford under their cold winter conditions. Consequently, in areas where cold injury is a concern, the more cold hardy rootstocks, Lovell, Guardian and Halford, should be used if possible.

Peach Tree Short Life. PTSL is caused by a combination of factors including cold damage, bacterial canker, and ring nematodes and exacerbated by various management practices such as early pruning and insufficient liming of acid soils. It typically causes the sudden collapse of the tree in spring. In recent years this has been a major problem in the southeastern peach growing areas. Guardian is the only PTSL tolerant rootstock that is available. It is available from several of the nurseries in Tennessee and has been heavily planted in since it was released in 1994.

What happens if there are several problems at your site? Which one takes priority when selecting a rootstock? The most damaging and most predictable problem should take priority. For example, if you have a situation where nematodes are at high levels and there also is a possibility of cold damage during an extreme winter, the nematode problem will have to take first priority. Choosing a rootstock is a matter of weighing the importance of each factor in the ultimate goal of growing healthy trees and maximizing profits.

 Table 1. Tolerancez of Peach Rootstocks to Stress.

Rootstock

Rootknot
Nematodes

Calcareous
Soil

Waterlogging

Cold
Hardiness

Peach Tree Short Life

Lovell

S

MS

S

Moderate

S

Halford

S

S?

S

Moderate

S

Nemaguard

R

VS

S

Poor-Fair

S

Nemared

R

S

S

Fair?

S

Guardian

 

R

MS

S

Moderate

R

Flordaguard

R

VS

S?

Poor

S

Titan Hybrids

R

R

VS

Fair-Good

S

Hansen

R

R

VS

Fair-Good

S

zVS = very susceptible; S = susceptible; MS = moderately susceptible; R = resistant.