Cranberry Yellow Vine
| (photo1
and photo2):
Sample
of vines with Yellow Vine Syndrome taken from Washington County, Maine
on Aug. 25, 1999 |
Herbicide Injury (not Yellow
Vine) (photo): Cranberry
leaves damaged by the herbicide, Evital. Notice how the yellow versus green
patterning is reversed from that of Yellow Vine. |
The following 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. 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 YV?
The YV symptoms are most likely due to nutritional
imbalances in the cranberry plants. 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. [Maine Note: Casoron was a likely contributor
for YV found on Maine beds in 1999]. These stress conditions lead to
poor root development. This past spring [2003] many [Massachusetts] bogs
stayed wet due to late ice out and frost protection. This can lead to shallow
rooting. Casoron use can aggravate the problem.
We have previously visited [Massachusetts]
bogs with patches of YV and have found that the soil water content in the
YV areas is 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 YV -- 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 YV -- 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.
Morning 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
Ideally, irrigation water should be applied
as a combination of subirrigation (manipulation of the water table) and
overhead sprinkler irrigation.
If you have comments or questions about this page,
contact Charles Armstrong at: charlesa@umext.maine.edu
Putting
knowledge to work with the people of Maine
