Incorporation of Soil Amendments of Molasses for Management of Plant Parasitic Nematodes in Pineapple and Papaya
The project seeks to reduce the use of soil applications of nematicides by using molasses soil amendments. Molasses has been used for many years as a fertilizer in the sugarcane industry to promote increased plant growth and vigor. Sugarcane growers found that during the process of decomposition, molasses also reduced damage to roots caused by nematode root parasites. The project proposed two test sites for pineapple and two sites for papaya. For the pineapple trials, the use of post-plant applications of molasses were to be tested alone and in combination with pre-plant use of a nematicide. For the papaya trials, treatments with molasses were to be compared to no treatments with molasses.
NOTE: Pineapple was abandoned in favor of vegetable crops: onions, Chinese cabbage and Romaine lettuce.
Project goals and objectives
1) Reduce damage in pineapples and papaya from the reniform and root-knot nematodes by incorporating molasses soil amendments
2) Measure the increase in yield from molasses and estimate the reduction in nematicide use needed when molasses is applied.
Molasses was applied to soil through sprinkler irrigation system or by overhead boom sprayer. In a papaya plantation on Maui where high and damaging populations of reniform nematodes had caused a reduction in fruit yield and quality, the molasses applications lowered nematode soil populations and resulted in marked improvement in the tree growth and harvestable fruit. When applied to Chinese cabbage, the numbers of Herodera nematode cysts decreased following harvest. Preplant applications of molasses to onions improved plant color and onion yield although no difference in soil nematode populations or in cyst number was observed. Molasses soil amendments supply carbohydrates and alter the C/N ratio. This affects the soil microbial ecology, usually resulting in lowered populations of plant parasitic nematodes as well as having other favorable effects on plant growth. The specific mechanisms involved are not well understood and vary with the crop, soil conditions and nematode species present.