The Lower Rio Grande Valley (LRGV) in Texas has an abundance of host crops that can support significant populations of corn earworm (Helicoverpa zea). Adults migrate into the Valley in early March and the following generation emigrates in June. Favourable meteorological conditions can transport migrants over 400 km in one night. Field surveys and trapping are useful to establish identity and emergence trends, but provide little insight into population movements. ARS have used scanning, tracking and vertical-looking radars to study these migration flights over several seasons.
In 1996, these radar studies were supplemented with a UNSW Insect Monitoring Radar (IMR). The IMR is vertical-pointing and combines a nutating beam with rotating linear polarisation. Special algorithms allow it to automatically measure characteristics of over-flying insects that simpler vertical-looking radars cannot determine. As well as insect track, heading, and speed, the IMR can be used to estimate size, body shape and wingbeat frequency. These additional parameters improve the IMR’s ability to reliably classify over-flying targets, thus providing an improved capability for monitoring population movements.
The IMR was operated from Moore Air Base near Edinburg in the LRGV in March and June of 1996. ARS deployed a network of scanning, tracking and vertical-looking radars in and north of the Valley to monitor migration from the LRGV and sources from within Mexico. Each campaign allowed the IMR to compile vertical profiles of migration intensity, speed, direction, heading, and wing-beat frequencies. All radars operated when H. zea were the predominant species emerging.
An overview of data obtained by the IMR during these exercises will be presented. Comparisons and contrasts with participating ARS entomological radars will be made. The utility of the IMR for research and operational applications in this region will also be discussed.