Agroecological factors impacting stem borer (Lepidoptera: Crambidae) dynamics in Gulf Coast sugarcane and rice
Doctor of Philosophy (PhD)
Diatraea saccharalis (F.) and Eoreuma loftini (Dyar) are stem boring pests of sugarcane (Saccharum spp.) and rice (Oryza sativa L.) crops in the Gulf Coast region. Studies were conducted to determine the role of agroecological factors, including predator disruptions, alternate hosts, and crop phenological conditions, on stem borer populations.
The year after Hurricane Rita storm surge flooded sugarcane in Louisiana, a 71% reduction in the predaceous Solenopsis invicta Buren was recorded. Even with a 2.4-fold increase in the number of insecticide applications used for D. saccharalis management in flooded fields, growers still incurred higher injury.
In two field experiments, October sampling showed that sugarcane planted in early August harbored 4.7 to 19.0-fold greater D. saccharalis infestations than September plantings. Although there is a potential for increased D. saccharalis overwintering populations in early plantings, differences in infestations were not recorded during the spring.
Sentinel plant experiments confirmed that a number of non-crop grasses are stem borer hosts. Subsequently, sampling along transects every 6-8 wk compared stem borer infestations in non-crop grasses adjacent to rice fields. While D. saccharalis densities were relatively low, E. loftini average densities were 0.3 to 5.7 immatures/m2 throughout a 2-yr period. A greenhouse study showed that rice is more preferred for E. loftini oviposition than the primary non-crop hosts johnsongrass [Sorghum halepense (L.) Pers.] and Vasey’s grass (Paspalum urvillei Steud.). In addition, E. loftini larval development duration in degree-days above a threshold temperature is 1.7-fold greater on johnsongrass and Vasey’s grass than on rice.
A 2-yr rice study showed that a lower than traditional harvest cutting height (20 vs. 40 cm) reduced E. loftini infestations by 70 to 81% whereas D. saccharalis infestations were not changed. Furthermore, rice stubble under favorable conditions represents an overwintering habitat in addition to non-crop hosts.
This research showed that predator disruptions, sugarcane planting dates, non-crop hosts, and rice stubble management impact stem borer populations when they are traditionally left unmanaged. Thus, the evaluation of a stem borer management strategy that targets infestations in late season sugarcane and rice, but also in non-crop hosts, is warranted.
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Beuzelin, Julien M., "Agroecological factors impacting stem borer (Lepidoptera: Crambidae) dynamics in Gulf Coast sugarcane and rice" (2011). LSU Doctoral Dissertations. 1675.
Reagan, Thomas E.