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Sorghum midge, Stenodiplosis sorghicola (Coquillett), and corn earworm, Helicoverpa zea (Boddie) are important insect pests of sorghum, Sorghum bicolor (L) Moench. Both pests feed on the developing kernel and directly reduce grain yield. Economic injury levels (EIL) that respond to pest management costs, commodity values and pest density are developed for each pest based upon published reports on grain loss per insect stage and stage-specific mortality. The economic injury level for sorghum midge is M = C 33,256 / V F where M = mean number of adult sorghum midge per flowering panicle, C = cost of management to control sorghum midge per unit area ($/acre), V = market value per unit of production ($ per 100 lbs of sorghum grain), and F = number of flowering panicles per acre. The EIL for sorghum midge is expressed as the number of adult sorghum midge per flowering panicle because only flowering panicles are susceptible to oviposition by sorghum midge females. Corn earworm larval stage must be considered in the EIL because grain consumption per corn earworm larva increases and larval mortality rate decreases with increasing larval size. The EIL for 5–6th instar corn earworm is L = C 9,754 /VP where L = mean number of corn earworm larvae per panicle, P = number of panicles per acre and C and V are as above. The EIL for 3rd–4th fourth instar larvae is calculated by dividing the EIL for 5–6th instar larvae by 0.19 to adjust for the 81 % mean mortality reported for this stage. First and 2nd instar corn earworm larvae consume very little grain and experience high mortality. These stages contribute little to economic loss and are not included in calculating the EIL. Economic thresholds are presented for each pest for a range of typical treatment costs/acre (C), market value per 100 lbs of grain (V) and number of flowering panicles (F) or all panicles (P) per acre.
Performance of pitfall traps using a mixture of propylene glycol and water or water alone as a preservative/killing agent was compared to investigate the selectiveness of these two agents for sampling/preserving ants. Results indicated that traps with a propylene glycol/water mixture collected significantly higher numbers of ants compared to traps with water only. The abundance of Solenopsis invicta Buren, Paratrechina sp. and Diplorhoptrum sp., was significantly higher when propylene glycol was used as the preservative. Results indicate this common preservative affected the behavior of several ant species.
Research was conducted to evaluate the potential of using remote sensing technology to assess feeding damage on the invasive woody plant species, saltcedar, Tamarix ramosissima Ledeb., by a leaf beetle, Diorhabda elongata (Brulle). Field reflectance measurements showed that saltcedar plants exhibiting feeding damage had lower visible green reflectance than healthy plants, and could be distinguished from healthy plants on conventional color aerial photographs. Accuracy assessments performed on supervised classification maps of aerial photographs from two years showed that damaged and healthy saltcedar plants had producer and user accuracies ranging from 88% to 100%.
Seasonality of Xyleborus ferrugineus (F.) and other coleopteran borers of pecan trees was determined weekly in 15 ethanol-baited traps in commercial orchards of five counties of northern Coahuila, Mexico, from 2000 to 2004. Simple and inexpensive traps were made of 600-ml plastic water bottles filled with 300 ml of 50% ethanol, which caught as much as 10 times more insects than yellow sticky traps in preliminary observations. The most abundant beetle was X. ferrugineus, with 93% occurring from July to October, suggesting a multivoltinism for this species. Ocurrence of X. ferrugineus from December to May was practically zero, indicating a dormancy of the insect during this period. Abundance of X. ferrugineus was greater in 2000, decreased during 2001–2003, and increased again in 2004. Temperature and rainfall were not associated with these fluctuations. Captures of X. ferrugineus were significantly more abundant in Nava County than in the remaining counties. Other coleopterans caught in the traps less frequently included the buprestids Chrysobothris sp. and Agrilus sp.; the cerambycids Neoclytus acuminatus (F.), Megacyllene caryae (Gahan), Oncideres cingulata (Say), and Saperda sp.; and the bostrichid Xylobiops sp.
A greenhouse study was initiated to investigate the interactions between the native competitive ant Monomorium minimum (Buckley) and incipient red imported fire ant, Solenopsis invicta (Buren) colonies with 30 workers. The effect of two factors on S. invicta density, distance to the competitor's nest and feeding status (fed vs. starved), were investigated. Results suggest that distance had a significant effect on S. invicta density in the presence of M. minimum; whereas, feeding status did not. The effects of distance and feeding status were also studied on the probability of invasion by either species and the probability of interaction between the two colonies. Results indicate distance had a significant effect on probability of both invasion and interaction. The invasion of incipient S. invicta colonies occurred only at a distance of 0.2m; however, interactions between the two species occurred even at the farther distances of 3.2m and 6.4m. Interactions were greater near the foraging arena under fed conditions and greater near the S. invicta nest under starved conditions.
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