 |
| Photo of a strawberry plant suffering from crown rot. |
Baton Rouge, La. – Southern University Ag Center Agriculture and Natural Resources Agent
Ahmad Robertson, Sr., along with state plant pathologists Drs. Raj Singh,
Melanie Ivey and LSU Ag Center vegetable specialist Dr. Kiki Fontenot, recently
visited several strawberry farms in St. Helena and Tangipahoa Parishes to
assist farming operations suffering from crown, root and stem rots this winter.
The specialist
provided the farmers with an action plan with control recommendations for
insect and disease management.
Last year Southeast
Louisiana received 12 inches of rainfall in late October. This excessive
soaking after rain showers and storms can ruin a plants’ roots, which in turn
affects how plants grow. Strawberries
are among the most challenging horticultural crops to grow in the South due to
high levels of soil borne pathogens, such as phytophthora.
When the soil becomes
saturated with water, this pathogen can produce and release zoospores, which
swim through water-filled pores to infect plant tissue. Infections can occur
during cool to moderate temperatures, which are typical throughout Southeast
Louisiana fruit and vegetable production cycles.
Symptoms:
Symptoms of phytophthora
usually begin in the upper part of the plant's crown and spread downward. The
youngest leaves wilt suddenly and often turn a bluish green color. Wilting
spreads quickly throughout the plant, and complete collapse occurs within
days. When infected plants are cut open,
a brown discoloration can be seen in the crown's vascular tissue or throughout
the crown's tissue.
Field Management:
The pathogen can be
controlled in production fields by using soil fumigation and good cultural
practices. These practices include the use of certified transplants, avoiding
poorly drained soils, and preparing fields to provide good soil drainage during
wet weather.
Soil Preparation:
Good surface drainage
is absolutely necessary for a successful vegetable garden. Water standing in
the garden for long periods of time is fatal to the growth of vegetables. Low
and wet areas can be improved by adding eight inch layers of top soil
(two-three yards of topsoil per 100 square feet) to raise the garden site. Also
make sure to put in drains to carry water away from the garden and plant crops
on high rows. All vegetable crops in
Louisiana should be grown on raised beds at least 10 inches high. High rows
encourage good drainage, especially during times of heavy rains.
Cultural Control:
Use raised beds and
carefully managed drip irrigation; plant in non-infested soils that have good
drainage. Soil solarization has been shown to be effective for the control of
soil borne pathogens and weeds. Solarization is a method of using the natural
energy of the sun to sufficiently heat the soil to temperatures high enough to
kill many soil pests. To use this method, a clear plastic tarp is used to cover
the soil, trapping heat beneath it. Pests that may be killed during
solarization includes nematodes, plant diseases, and weeds. Most nematodes are
killed when the soil temperature goes above 118 degrees. The hottest months, June, July, and August,
are the best times for solarization. Adequate moisture should be present in the
soil to irrigate it, if necessary before treating. If conditions are dry it’s
advisable to run some type of irrigation or soaker hose under the plastic to
water the soil during the course of the treatment. The plastic tarp should be
left on the area for eight weeks.
Control Management:
Commercial farmers
should use fungicides, such as Ridomil Gold SL or Aliette WDG, to manage crown
rots. Begin a fungicide application at
the first sign of disease and repeat applications according to the product’s directions.
Maintaining good sanitation
of planting beds, inspecting plants, handling plants carefully, using crop
rotation and planting resistant cultivars are great practices for disease
management.
For more information,
contact Ahmad Robertson, Sr. in the Tangipahoa Parish Extension Office at
985.748.9381, or in the St. Helena Parish Extension Office at 225.222.4136.
###
No comments:
Post a Comment