Research and IPM

Determine how damaging root-knot nematodes that occur deeper in the soil profile are.

Determine how much damage can be attributed to root-knot nematodes that infect plants later in the crop cycle.

Determine how useful it is to control root-knot nematodes post-plant, after the initial infection has occurred.

In summary, delaying nematode inoculation generally resulted in slightly higher yields and lower root galling, but effects on final nematode populations were generally inconsistent. Inoculating nematodes very close to the seed resulted in significant yield reductions, whereas inoculation of nematodes at greater depths generally did not result in yield losses. Similarly, nematode inoculation in the upper soil layer resulted in higher levels of root galling, and higher nematode populations at harvest. Attempts to eliminate or reduce nematodes at different points in time after seeding of the melons (with Vydate) failed, as there were no significant differences between these treatments.

It is concluded that, in order to prevent major nematode damage in melons, it is important to prevent nematode infection very early on in the crop cycle, and to eliminate the nematodes in the upper soil layer (e.g., 0-25 cm). Nonchemical alternative management strategies such as solarization or biofumigation may achieve this. Effects of such tactics on final nematode populations, however, may not be dramatic, as delayed or "deep" infestations still resulted in significant nematode populations at harvest time.

In this second year, the melon crop at the South Coast Research and Extension Center (SCREC) was a complete failure (poor emergence, complete failure of plants to grow), and no data could be collected. We have not been able to identify the reason for this. In contrast, the trial at the second location (KREC) was very successful. The results were similar to those obtained the previous year and again showed that melon yields were higher, and root galling indices were lower when plants were allowed to grow for two, four, or six weeks before nematode inoculation.

Inoculating nematodes very close to the seed at the time of seeding resulted in a significant yield loss of about 50%, but did not result in significant yield loss when nematodes were inoculated at greater depths.

We did not observe any significant effects of the Vydate treatments on yields, galling or nematode populations.