FIELD AND FORAGE CROPS Attractiveness of Stages of Rice Panicle Development to Oebalus pugnax (Hemiptera: Pentatomidae) L. ESPINO 1 AND M. O. WAY 2 J. Econ. Entomol. 101(4): 1233Ð1237 (2008) ABSTRACT Greenhouse experiments were conducted during 2004 and 2005 with male and female Oebalus pugnax (F.) (Hemiptera: Pentatomidae) caged on rice plants at different stages of panicle development with the objective of determining the most attractive stage to O. pugnax. Field-collected insects were released inside cages containing potted plants and observed during morning and after- noon hours for 5 d. Results showed that attractiveness of male and female O. pugnax to plants with panicles at milk and soft dough stages was greater than plants at preheading and heading stages. Preheading plants were the least attractive to the insects, conÞrming Þeld observations. Results imply that insecticide applications during the preheading stage are likely ineffective and that monitoring efforts during the milk and soft dough stages of panicle development should be intensiÞed. KEY WORDS Oebalus pugnax, Oryza sativa, rice stink bug, rice panicle stage, attractiveness The rice stink bug, Oebalus pugnax (F.) (Hemiptera: Pentatomidae), is a serious pest of rice, Oryza sativa L., in the southern United States (Way 2003). This insect reduces rough (unprocessed rice that includes hull and caryopsis) and head (milled kernels at least three fourths the length of whole kernels) rice yields. It also reduces grain quality by feeding on developing kernels, introducing pathogenic fungi and causing a discoloration of the grain known as “peck” for which growers are penalized (Douglas and Tullis 1950, Swan- son and Newsom 1962, Bowling 1963, Harper et al. 1993, Tindall et al. 2005, Patel et al. 2006, Espino et al. 2007). O. pugnax is a polyphagous insect (McPherson and McPherson 2000) on host grasses in and around rice Þelds and levees (Douglas 1939, Odglen and Warren 1962, McPherson and McPherson 2000). Vasey grass, Paspalum urvillei Steud., has been recognized as one of the preferred wild hosts (Douglas 1939, Douglas and Ingram 1942, Naresh and Smith 1984) as well as barnyardgrass, Echinochloa crusgalli (L.); broadleaf signal grass, Brachiaria platyphylla (Griseb.); southern crabgrass, Digitaria ciliaris (Retz.); jungle rice, Echi- nochloa colona (L.); and Dallis grass, Paspalum dila- tatum Poir. (Naresh and Smith 1984; Tindall et al. 2004, 2005; Rashid et al. 2005). Rice is a preferred cultivated host (Naresh and Smith 1984). Other cultivated crops attacked by this insect are corn, wheat, barley, rye, oats, and sorghum (Odglen and Warren 1962). Adult O. pugnax typically move to rice Þelds from weeds or sorghum Þelds when the rice crop starts to head (Way 2003). However, rice can become infested at any stage of panicle maturity (Way and Bowling 1991), and Þeld populations can increase dramatically in a very short time (Douglas 1939). Numerous Þeld studies have determined that O. pugnax move to head- ing Þelds regardless of calendar date of heading (In- gram 1927, Douglas 1939, Douglas and Tullis 1950, Odglen and Warren 1962, Jones and Cherry 1986, Rashid et al. 2006). Bowling (1967) suggested a re- duction in the suitability of wild hosts as food source due to aging that may trigger O. pugnax movement to rice, whereas Rashid et al. (2006) conjectured stron- ger attractiveness of rice panicles over weed hosts. However, the relative attractiveness of different stages of panicle development has not been reported. In the current study, we aim to identify the relative attractiveness of various stages of rice panicle devel- opment to O. pugnax. Previous research has shown that milk and soft dough are more susceptible than other stages to peck (Espino et al. 2007), and the heading stage may be more susceptible to yield re- ductions by O. pugnax (Swanson and Newsom 1962, Bowling 1963, Rashid 2003, Patel et al. 2006). Inte- grating the knowledge of susceptibility and attraction may help growers improve monitoring and manage- ment timing of this pest. Materials and Methods Greenhouse experiments were conducted during 2004 and 2005 at the Texas AgriLife Research and Extension Center at Beaumont (Beaumont Center, Jefferson County, TX). Seeds of ÔCocodrieÕ rice were planted on 15, 21, and 30 June and 6 July 2004, and 4 and 24 May, and 3 and 13 June 2005 in pots (15-cm lip diameter, 10-cm base diameter, and 15-cm depth) 1 Corresponding author: University of California Cooperative Ex- tension, Colusa, CA 95932 (e-mail: laespino@ucdavis.edu). 2 Texas AgriLife Research and Extension Center at Beaumont, Beaumont, TX 77713. 0022-0493/08/1233Ð1237$04.00/0  2008 Entomological Society of America Downloaded from https://academic.oup.com/jee/article/101/4/1233/2198973 by guest on 27 September 2022