Effects of soil enrichment on soil nutrition, and sugarcane physiochemistry, yield, and injury caused by Mexican rice borer (Eoreuma loftini)

Soil enrichment with two rates of compost and chicken litter were compared with conventionally fertilized sugarcane, Saccharum spp., in the subtropical Lower Rio Grande Valley of south Texas for two consecutive seasons.  The high compost rate resulted in the most consistent increases of soil nutrients, including N, P, K, Ca, Mg, S, Fe, Zn, Mn, and Cu.  Analysis of nutrients in sugarcane leaf tissue showed that only N was higher in the high compost treatment, associated with greater abundances of three free amino acids, arginine, histidine, and lysine (each essential to insect growth and development), and of the sugar fructose.   Although the high compost treatment yielded the most marketable sugarcane stalks per stool during the first season, this benefit was offset by greater infestations by the Mexican rice borer, Eoreuma loftini (Dyar), in terms of numbers of entry and exit holes per stalk, and percentages of injured internodes and stalks.  As a result, stalk weight, length, and percentage brix were reduced.  During the second season, numbers of stalks per stool were not greater in the high compost treatment, nor was percentage brix less, but the growth parameter measurements were decreased and Mexican rice borer injury was the worst.  This study demonstrates that changes in host plant biochemistry from enhancing soil nutritional quality can have substantial negative effects on sugarcane production in the presence of Mexican rice borers.  Hence, soil quality should be considered as part of integrated efforts to manage the pest.