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Areas identified as escape zones for Pseudocercospora ulei, the causal agent of South American Leaf Blight (SALB), are being sought for the development of profitable rubber growing, as high-yielding Asian clones can be grown there without suffering repeated defoliation caused by epidemics of the disease. A performance trial with 10 clones was set up in 2006 in such an escape zone in Ecuador with non-American clones whose high production potential is acknowledged elsewhere in the world, some of which are recommended on a commercial scale. Production results over seven years, between 2013 and 2019, indicated a very high potential for this material in this new region, reaching average yields of 2.5 t/ha/year for clones PB 280, PB 312 and PB 314, and 1.85 t/ha/year for the control clone RRIM 600, despite a very pronounced 5-month dry season. However, the risks of wind damage and tapping panel dryness were found to be very high for PB 312 and PB 314. Clone PB 280 proved to perform best overall, with 93% of trees in production and one of the lowest Tapping Panel Dryness (TPD) rates. This clone, distinguished by its medium high latex metabolism and a high sucrose reserve, presents a highly promising alternative for the cultivation of rubber trees in escape zones. This is particularly relevant in situations where the phytosanitary risk associated with P. ulei is constrained. [ABSTRACT FROM AUTHOR]

Nutrient management is critical for the development and growth of rubber trees during the immature phase. We present the results of a fertilizer trial during the immature phase of a rubber plantation setup in Cambodia. The main objective of this study was to analyze the response of a specific clone, PB330, in the specific conditions of one of the most important rubber-growing areas of Cambodia. The experiment was arranged in a randomized complete block design with 4 treatments and 4 replications. The four treatments consisted of 3 fertilization treatments with an increasing dose of fertilizers (respectively T1, T2 and T3) compared to a non-fertilized control (T0). The girth of trees was measured every six months from the end of the first year after planting (YAP) to the end of the 6th YAP. Results showed that fertilization had a significant effect on tree girth. At the end of the 6th YAP, fertilization had a significant effect on the number of tappable trees, and stand basal area but not on average tree girth. The most pronounced effect of fertilization was observed from annual increments in girth and stand basal area during the 3rd and 4th YAP. The effect of fertilization on tree growth was evident from all three treatments, although T3 gave the most significant increase compared to T0, increasing doses of fertilizer did not significantly improve the growth parameters. Hence, this study confirmed the importance of mineral nutrition on rubber tree growth during the immature phase even at T1, the lowest level of nutrient inputs. These results can be used to improve the standard fertilizer recommendations for immature rubber trees in Cambodia. We recommend setting up similar trials in different edaphic conditions of the country with the aim to establish nutrient management practices tailored to local biophysical constraints. [ABSTRACT FROM AUTHOR]