Yellow Vine Syndrome
[An abnormal physiological condition believed to be due to an imbalance of nutrients in the plant usually due to water stress–from too much water or too little]
The following text is excerpted and adapted with permission from the UMass Extension’s Cranberry Station Newsletter — July 2004 issue (pp 1 – 2 — by Carolyn DeMoranville):
Yellow Vine (YV) shows up as a yellowing along the leaf margins (edges) with the areas along the leaf veins remaining green (see photos below). Usually the symptoms show up first in the old leaves and then move up the stem into the new growth. The most common time for the symptoms to become severe is around fruit set when demand for resources in the plants is high and dependence on sprinkler irrigation is greatest.
What causes Yellow Vine? The YV symptoms are most likely due to nutritional imbalances in the cranberry plants [potassium and magnesium in particular]. But fertilizer management is not the cause of the problem. Instead, we believe that the nutrient imbalance is secondary to root problems caused by stress. The stress involved is most often water stress (too much OR too little) but may also involve herbicide stress on some bogs. These stress conditions lead to poor root development. [Very wet conditions] can lead to shallow rooting. Casoron® use can aggravate the problem and it has often shown up in Maine cranberries where Casoron® was used.
Massachusetts bogs with patches of YV have had soil water content in the YV areas that was either much higher or much lower than that in the surrounding green areas. The consistent finding has been that the rooting depth in YV areas is shallower than that in unaffected areas. In drought conditions, common most years during July and August, uneven distribution of water occurs due to reliance on sprinkler irrigation and varying distance to the underlying water table. Put this together with the high nutrient demand during early fruit development and nutritional problems may be the result. Fertilizer tends to be washed away from the roots during irrigation and areas with poor rooting may not be able to move enough minerals and water to meet the demands of both shoots and fruit. This sets up a competition for resources in which the developing fruit and the youngest leaves (at the top of the shoot) are the best competitors, leaving the older leaves showing symptoms of nutrient stress, in this case, YV.
Treating Yellow Vine (short-term fixes): YV plants are not doing well at taking in nutrients from the roots. For this reason, adding more fertilizer to the soil most likely will do little to arrest or reverse YV. Instead, foliar feeding should be considered. Providing nutrients through the leaves, bypassing the roots, can help to bring the plants back into nutritional balance. Based on tissue testing in YV bogs over a period of years, and based on field research and grower experiences, the most likely foliar feeds to be helpful are magnesium (Mg) and urea. These should be used separately. If you have had success with Mg in the past, try it first, otherwise try the urea first. Apply at dawn or dusk (preferred) as you would a pesticide (minimize washoff). The aim is to have the plant stay wet for several hours after the material is applied so that it may penetrate into the leaves. Use urea at 2-4 lb/A (to give approximately 1-2 lb/A nitrogen). For Mg applications, use a commercial foliar feed (3% Mg) at 1-2 qt/A or apply 2/3 lb/A Epsom Salts (magnesium sulfate). Urea and Epsom Salts should be dissolved in water prior to application as a foliar feed.
Treating Yellow Vine (long-term solutions): In the long term, changes in water management may be needed. In most cases, YV appears in areas that were too wet early in the season. This leads to limited root development and these same areas are then the most susceptible to YV and water stress later in the season. Rooting depth can be improved by keeping the bed well drained early in the season. This is particularly important in years with frequent frost nights requiring sprinkler operation or in years with heavy rainfall. When the water table is closer than about 6 inches below the surface, root development and root function is impaired. A float device, designed by Bruce Lampinen, mounted in a perforated pipe (directions for constructing and installing these are available from the Station) is useful to monitor the depth to the water table and to minimize times when the water table is too close to the root zone. Water can move up from a water table at a depth of up to about 15 inches by the process of ‘capillary rise’. With a water table below 15 inches, capillary rise may be unable to keep up with plant water demands, particularly at midday under stressful conditions (hot, dry, windy). A tensiometer can also be used to monitor moisture in the root zone. A water table varying from 6 to 15 inches in depth (as recommended above) will result in tensiometer readings between 1.5 cbar (at 6″ water table depth) to about 4 cbar (at 15″ water table depth). Therefore, tensiometer readings can be used to assess water status and irrigation can be scheduled based on an early morning reading of the tensiometer (see below). Ideally, irrigation water should be applied as a combination of subirrigation (manipulation of the water table) and overhead sprinkler irrigation.
Morning tensiometer readings:
- 0 – 1.5 cbar soil is too wet
- 1.5 – 4.0 cbar adequate water is available
- 4.0 – 7.0 cbar adequate water for mild conditions, but if hot and/or dry conditions are forecast, irrigation should be applied
- >8.0 cbar irrigation is needed, regardless of weather conditions