Nematode Damage (R)
Prior to the 1950s farmers of orchard crops in California had plenty of new land available as an alternative to replanting land that had previously been in production. However, with growing population and increased land values, a greater proportion of fruit and nut production has been on land where older orchards have been removed. Farmers frequently encounter growth problems when they replant. In severe situations, new plants die. Plant parasitic nematodes that are present on old roots are a common cause of the replant problem.
“Orchard removal and site preparation for walnuts can be extensive and expensive, but worth the time and expense to get new plantings off to the best start, according to Joe Connell, University of California Cooperative Extension farm advisor for Butte County.
Nematodes are a main concern, and the first thing that a grower should do is collect a soil sample from the feeder roots in the old orchard and have a nematode analysis done, Connell said.
After the soil testing, the next step is to cut down the trees, and then treat the stump with a herbicide, Connell said. Treating the stumps kills the entire root system, and it will kill out the nematode population that is attached to that root system, he added.”
Author: Coatney, K.
Title: Walnut site preparation is essential for healthy orchards.
Source: Ag Alert. January 30, 2013.
Rice Field With Sheath Blight
Sheath blight is a disease of rice plants which is caused by a fungus that lives in the soil. When rice fields are flooded, the fungus floats to the top of the water and contacts rice plants; the fungus grows out and moves into the rice leaf. The fungus spreads across the water to adjacent plants. The fungus grows across touching plant parts. The flow of water and nutrients in the rice plant is interrupted and the leaf dies, reducing rice yield. Development of resistant cultivars has been slow, because resistance is linked to undesirable traits such as tall plant stature, late maturity, and poor milling quality. Research has shown that a single application of a fungicide provides almost season-long control of sheath blight.
“Sheath blight of rice, caused by the fungus Rhizoctonia solani, is an economically important rice disease that is occurring throughout the rice-producing areas in the world, including the southern United States. Significant losses in grain quality and yield may occur in severely infected rice fields. Despite its economic importance, there are no completely resistant rice cultivars against this fungal rice disease and control methods for sheath blight are limited to heavy usage of fungicides.”
Authors: Shrestha, B. K., et al.
Affiliation: Louisiana State University Agricultural Center, Baton Rouge
Title: Suppression of sheath blight development in rice and sclerotia germination of Rhizoctonia solani by rice-associated strains of Bacillus spp.
Source: Phytopathology. 2013. 103(Supplement 1)(5):S1.9