Sitophilus oryzae is one of the most destructive pests of stored grains. It leads to significant quantitative and qualitative losses, resulting in food and income insecurity among farmers. Chemical pesticides are the most common methods used by farmers and other grain value chain actors to manage this pest. However, pesticides are increasingly becoming unattractive for pest control due to health hazards posed to applicators, consumers, the environment, and insect resistance. Modified atmospheres have the potential to manage stored insect pests as an alternative to pesticides. There is limited understanding of when insect pests die when grain is stored in airtight containers. This experiment was conducted to assess the time required to reach mortality of adult S. oryzae when exposed to 1, 3, and 5% oxygen levels. Results revealed that the LT50 for 1, 3, and 5% of oxygen were reached after 69.7 h, 187.8 h, and 386.6 h of exposure, respectively. No adult emergence was observed on infested grains following exposure to 1 and 3% oxygen levels. This result provides vital rationale for storing grain in hermetic storage conditions for at least 39 days to achieve adult S. oryzae mortality and minimize grain reinfestation.

Purdue Improved Crop Storage (PICS) bags were designed to reduce grain storage losses on smallholder farms. The bag consists of three layers: two high-density polyethylene liners fitted inside a woven polypropylene bag. Recently, farmer groups, development relief programs, and government food security agencies have shown interest in PICS bags for large-scale use. PICS bags are conventionally closed by a twist-tie (TT) method, which involves twisting, folding, and tying the lip of each layer individually with a cord. This is not only time and labor intensive, but also may affect the integrity of the liners. We evaluated three new bag closure methods: i) inner liner rolled onto itself and middle liner fold-tied (IR), ii) both liners folded together and tied (FT), and iii) both liners folded and tied separately (FS), along with the conventional twist tie (TT) method. The time to close partially or fully filled 50 kg-capacity PICS bags filled with maize grain was assessed. Results showed that FT was the most time-saving method, reducing bag sealing time by >34% versus the usual TT method. The average internal oxygen levels reached 5% levels for less-infested bags. In both cases, insect population growth was suppressed. Oxygen depletion rates among tying methods remained the same regardless of the closure method used. When large numbers of bags need to be closed, the time-saving FT method is a good alternative PICS sealing method over the conventional twist-tie approach.

Studies were conducted to develop a pheromone-trap monitoring system for sweetpotato weevil, Cylas formicarius (Fabricius), in the southern United States. Effects of trap type and pheromone dose on weevil collections in traps baited with synthetic sex pheromone were studied in four states: Florida, Texas, North Carolina, and Louisiana. A plastic funnel trap and the Universal moth trap (Uni-trap) were more efficacious at collecting C. formicarius males than a screen-cone boll weevil trap. More weevils were consistently caught in the former two trap types than in the latter trap when trap counts were high (x⁻ > 60 weevils per trap per night for both the Uni-trap and the plastic funnel trap) than when trap counts were low (x⁻ < 60 weevils per trap per night). The plastic funnel trap was more efficient (72.8%) than the Uni-trap (58.0%) at capturing marked male weevils released at the base of the traps; however, these traps were equally effective at preventing adults from escaping (2% escape) and were superior to the screen-cone boll weevil trap (43% escape). Trap counts increased (although not consistently significantly) with an increase in pheromone dose between 1 μg and 1 mg. The importance of these data for monitoring C. formicarius in the southern United States and the Caribbean basin is discussed.