RNA interference (RNAi) has previously been shown to be effective in western corn rootworm (WCR, Diabrotica virgifera virgifera LeConte) larvae via oral delivery of synthetic double-stranded RNA (dsRNA) in an artificial diet bioassay, as well as by ingestion of transgenic corn plant tissues engineered to express dsRNA. Although the RNAi machinery components appear to be conserved in Coleopteran insects, the key steps in this process have not been reported for WCR. Here we characterized the sequence of events that result in mortality after ingestion of a dsRNA designed against WCR larvae. We selected the Snf7 ortholog (DvSnf7) as the target mRNA, which encodes an essential protein involved in intracellular trafficking. Our results showed that dsRNAs greater than or equal to approximately 60 base-pairs (bp) are required for biological activity in artificial diet bioassays. Additionally, 240 bp dsRNAs containing a single 21 bp match to the target sequence were also efficacious, whereas 21 bp short interfering (si) RNAs matching the target sequence were not. This result was further investigated in WCR midgut tissues: uptake of 240 bp dsRNA was evident in WCR midgut cells while a 21 bp siRNA was not, supporting the size-activity relationship established in diet bioassays. DvSnf7 suppression was observed in a time-dependent manner with suppression at the mRNA level preceding suppression at the protein level when a 240 bp dsRNA was fed to WCR larvae. DvSnf7 suppression was shown to spread to tissues beyond the midgut within 24 h after dsRNA ingestion. These events (dsRNA uptake, target mRNA and protein suppression, systemic spreading, growth inhibition and eventual mortality) comprise the overall mechanism of action by which DvSnf7 dsRNA affects WCR via oral delivery and provides insights as to how targeted dsRNAs in general are active against insects.

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Finished water storage facilities play a key role in maintaining the quality of drinking water ultimately received by consumers. Without proper design, operation, and maintenance of these facilities, stored water may easily become stagnant and subject to loss of chlorine residual, as well as bacterial regrowth, contaminant entry, and a host of other water quality problems. Given that finished water storage facilities are part of the country's problem with aging infrastructure and that distribution system water quality is increasingly becoming a focus of regulators and customers, water utilities need all the tips they can get to better maintain these facilities. This paper outlines a five‐step approach to developing an operations and maintenance program for finished water storage facilities. The five steps are: understand your facility; define the water quality problems; evaluate alternatives to address water quality issues and select the best solutions; implement good management practices and monitor effectiveness; and, develop standard operating procedures. If utility managers implement this stepwise approach, the quality of water in the distribution system will most likely improve, which will improve public health protection and regulatory compliance. To be successful, though, this approach needs support from utility management to provide the resources operations staff will need to perform the work. For utilities that do not have a tank operations and maintenance program, this paper explains the need for such a program, and it offers a practical approach to setting it up. Utilities that already have a program in place may find additional ideas in this paper to refine their program.