However, in the areas that had high early rainfall and continued to receive frequent
rainfall throughout the season, there were more insecticide applications and frequently a higher
percentage of end-of-season bored internodes. Additional observations in 2003, support our
findings. Heavy infestations of sugarcane borer populations were encountered this year
following early rains in April and May. Continued rainfall in the months of June, July, and
August further intensified problems. Many growers averaged between one and two applications,
with a few growers requiring three applications.
Hensley (1971) documented that dry weather, especially in May and June when first
generation larvae are infesting young tillers, can cause 50% mortality of sugarcane borer larvae.
The biology of the sugarcane borer is well synchronized to that of sugarcane. Weather
conditions favorable to rapid growth of the sugarcane plant (warm temperature and abundant
rainfall) invariably result in rapid increase in populations of the sugarcane borer.
Holloway et al. (1928) stated that there was an inverse relationship between rainfall and
sugarcane borer abundance in Louisiana and Puerto Rico. Heavy rainfall, and particularly winter
rainfall result in flooding and depresses borer survival. Prolonged emersion of stalks kills over
wintering larvae (Capinera 2001). Young larvae living in the whorl of sugarcane and corn are
quite tolerant of short-term emersion, but heavy rainfall while they are dispersing could lead to
death because they are washed from the plants. Wolcott (1915) also demonstrated that there was
an inverse relationship between increased rainfall and the sugarcane borer instars found in the
field, presumably because the larvae drown in the flooded tunnels. In addition to rainfall, cold
winter temperatures are reported to depress larval survival rates in Louisiana (Capinera 2001).
Another important finding from this survey is that many growers do not budget for
supplemental insecticide applications for sugarcane borer control. Our survey suggests that
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growers should budget for a minimum of two applications of insecticide for sugarcane borer
control per hectare each production season. This would allow the grower flexibility in their
overall farm budget during heavy sugarcane borer infestation production seasons to make needed
applications and thus avoid severe economic losses due to the sugarcane borer. This is important
in years like 2003 when growers needed to make two or greater insecticide applications.