Evaluation of chemical repellents for reducing crop damage by Dickcissels in Venezuela

Abstract

In Venezuela, lethal control of wintering Dickcissels (Spiza americana) is considered a threat to the species survival. To help farmers protect their rice and sorghum crops from depredations by Dickcissels and to minimize the killing of large numbers of these birds, alternative non-lethal crop protection measures are needed. To that end, the responses of captive Dickcissels to three bird-repellent chemicals applied to rice seed were evaluated. In one-cupfeedingtrials, treatments ® of methiocarb (0.05% g g-1, applied as Mesurol 75% wettable ® powder) and anthraquinone (0.5%, applied as Flight Control) reduced consumption of rice by 70% relative to pretreatment consumption. Other anthraquinone treatments (0.05, 0.1%) and methyl anthranilate (0.05%) were ineffective. In two-cup trials, with untreated millet as the alternative food, consumption of rice treated with0.05 and 0.1% anthraquinone was reduced by 90% relative to pretreatment levels. Overall, Dickcissels responded to the repellents similarly to the red-winged blackbird ® (Agelaius phoeniceus). Because Flight Control has been used successfully to reduce blackbird use of rice fields in the USA, the prospect is good for successful reduction of damage to ripening rice by Dickcissels in Venezuela, particularly if repellent use is coupled with the establishment of alternative feeding sites.