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On-farm trial with a total of 32 farmers in eight villages of Naivasha and Nakuru areas of Kenya was conducted between December 2013 and September 2014 to evaluate hermetic grain storage technologies under farmers' management conditions. The storage technologies evaluated were metal silo and SuperGrain IV-R bag alongside the standard woven polypropylene bag with or without Actellic super dust. Moisture content, insect population, grain discoloration, and weight loss were analyzed 90, 180, and 270 d after storage. Grain moisture content remained stable over the storage period. Both metal silo and SuperGrain IV-R bag suppressed insect population, prevented grain loss and cross-infestation of insects from the surrounding environment. On the contrary, polypropylene bags allowed rapid build up of insect population and re-infestation from the surrounding environment. Grain weight losses were 1.5% in the metal silo and 1.8% in the SuperGrain IV-R bags compared to 32% in the polypropylene bags without Actellic Super dust, 270 d after storage. The present study, therefore, demonstrates that storing grains either in metal silo or SuperGrain IV-R bags would benefit farmers in reducing grain losses and improving quality. The study was of great interest to the farmers, grain storage scientists, and food security experts.

The minimum temperature at which stored-product insects can move inside stored grain bulks with different grain moisture contents is not known. The movement of adults of four stored-product insects, Cryptolestes ferrugineus (Stephens), Tribolium castaneum (Herbst), Sitophilus oryzae (L.), and Sitophilus zeamais (Motschulsky), at low temperatures inside jars or bulks of wheat with 11.1 or 16.0% moisture content was measured. Spontaneous walking stops (SMh), CCT (no movement after shaken), and minimum movement (TMmin, caught in probe pitfall traps) temperatures were determined at stepped-decrease of temperature. The ranges of SMh, CCT, and TMmin temperatures of the four stored-products beetles were 4.0 to 9.0°C, 2.0 to 8.0°C, and 6.0 to 11.5°C, respectively. The TMmin was ∼3°C higher than the SMh for all the tested beetles. C. ferrugineus had the lowest SMh, CCT, and TMmin temperatures, whereas S. zeamais had the highest values of these determined temperatures. C. ferrugineus under a faster stepped-decrease of temperature had higher SMh, CCT, and TMmin temperatures than that under a slower stepped-decrease of temperature, while adults of T. castaneum were not influenced by the temperature decrease rate. The two species of Sitophilus did not survive to the end of the experiment at the faster stepped-decrease of temperature. Two grain moisture contents did not affect these determined temperatures for all tested species.

This study was conducted to examine the activity of stored-product insect pests outside farm storage facilities during the first 2 mo of storage and to relate that activity to colonization of the grain by insects. Environmental parameters describing the grain storage environment also were analyzed to help in explaining the relationship between insect densities inside and outside grain bins. The most abundant species collected were Ahasverus advena (Waltl), Tyhaea stercorea (L.), Rhyzopertha dominica (F.), and Cryptolestes spp. Farms with high numbers of stored-product insects outside of storage facilities had high numbers of insects in 25-bu experimental bins, and farms on which few insects were detected outside also had fewer insects in 25-bu bins. However, this relationship was not true for commercial farm bins, possibly because of the use of insecticide on the grain or residual pest populations in farm bins. Grain moisture and test weight and the presence of livestock tended to affect insect numbers in the untreated experimental bins, but the effects were not always consistent among species. In farm bins, the use of protectants on the grain tended to obscure expected relationships to environmental parameters.

The relationship between sample characteristics and the likelihood of a price discount was examined for samples of farm-stored wheat taken as it was delivered for sale to elevators in Kansas during 1986 and 1987. Lower test weight, as well as increased grain moisture and dockage content, increased the likelihood of a price reduction. The presence of insects, however, was significantly associated with the probability of receiving a discount only at terminal elevators. Although the likelihood and value of price discounts were more predictable at terminal than at country elevators, only about 20% of the overall variability in discounts was explained by sample characteristics. The cost of price discounts risked because of the presence of live insects at the time of delivery to elevators was 73.5¢/metric ton (t) (2.0¢/bu) if 0.1 to 1.0 insects per 1,000 g were present in the sample, 77.2¢/ t (2.1¢/bu) if the insect density was 1.1 to 5.0 insects per 1,000 g, and $1.51/ t (4.1¢/bu) if more than 5.0 live insects per 1,000 g were present. Overall, for 17,730 t (650,000 bu) sold, 24.6¢/ t (0.67¢/bu) was lost because of insect discounts in some lots.

Preventive and remedial actions reported by producers to maintain the quality of grain during storage on the farm was minimal. Application of malathion when the grain was binned was the most frequent action reported in wheat, aeration the most frequent in corn, and fumigation the principal action in oats. Less than 10% of the grain was reported as fumigated during storage periods of 1 to 4 years and high numbers of dead adult insects observed in fumigated grain indicate that damaging populations were already present when the decision to fumigate was made. Liquid fumigant mixtures were the principal type used in corn and oats; phosphine-producing fumigants were the predominant types used in wheat. Malathion was found on only 14.6% of the wheat, 8.2% of the corn, and 4.2% of the oats from more than 8,000 farm bins across 27 states. When malathion was present the incidence, number of different species, and density of most species were generally less than in untreated grain. The effectiveness of malathion decreased significantly at grain moisture levels above 12%. The most frequent species found in malathion-treated grain were Plodia interpunctella (Hubner), Cryptolestes spp., Tribolium spp., Rhyzopertha dominica (F.), and Oryzaephilus surinamenis (L.). Nearly two-thirds of the insects found in malathion-treated grain occurred in grain containing residues of 2 ppm or less.

Results are given of studies conducted to evaluate the protective values of malathion and pyrethrum grain protectants against damage to corn in Louisiana caused by stored grain insects, especially the rice weevil, Sitophilus oryzae (L.). Both shelled and snapped corn were used in the studies. Malathion gave some protection to stored corn from progressive insect damage during storage; however, satisfactory protection was not obtained at any dosage level tested. Malathion was more effective than pyrethrum. Greater protection was obtained in shelled corn than was possible in snapped corn. Failure in Louisiana to protect corn in storage from insect damage with malathion or pyrethrum is very likely due to the high initial infestation incurred in the field and favorable conditions of temperature, relative humidity, and grain moisture for insect development during much of the storage period.

Malathion was applied to grain sorghum from 6 hybrids at the rate of 1.0 pint of 57% emulsifiable concentrate per 1000 bushels. Little hybrid effect on malathion degradation was found during 12 months’ storage at 80°F and 60% relative humidity. Grain moisture content and storage temperature significantly affected residue retention, but foreign material had no effect on the rate of malathion disappearance.

Malathion applied at 2 p.p.m. to wheat of 13.5% moisture content caused 99% mortality of the rusty grain beetle, Laemophloeus ferrugineus (Steph.) at 8 months after treatment; the wheat was stored in airtight containers at 48° F. A dosage of 16 p.p.m. was required for comparable control in wheat of 15.5% moisture content but this dosage was ineffective in wheat of 18% moisture content at 5 months after treatment. Repellency tests in wheat of 12, 15 and 17% moisture content treated at 4 or 8 p.p.m. the test insects being placed in adjoining untreated wheat, showed that adults of L. ferrugineus but not of sitophitus granarius (L.) were repelled from wheat of 12% moisture content treated at 4 p.p.m.: mortalities of both species ranged from 84.8 to 100.0% in treated wheats. Reproduction of L. ferrugineus was reduced more than that of S. granarius in unevenly treated wheat. There was no adverse effete on the milling or baking quality of wheat treated with malathion at 4 or 8 p.p.m.

Research was performed to determine the effects of variations in grain moisture content, temperature, and dockage content on penetration of HCN through a gain mass. Grain sorghum samples with moisture contents of 11%, 13%, and 15% were fumigated at temperature of 65°, 80° and 95° F. Interstitial air samples and grain samples were taken for cyanide residue analyses at sampling level of 3-, 9-, and 15-ft distances from the point of introduction of the gas. Air samples were taken at 4, 8, and 24 hr and grain samples 4 and 24hr after the introduction of the fumigant. All the main variables caused significant difference in gas concentrations in the air and grain residues. Analyses of samples obtained 4, 8, and 24 hr after introduction of the gas disclosed that cyanide concentrations in the interstitial air and residues on the grain decreased as grain moisture content was increased. These were lower under high temperature conditions. The presence of dockage had an effect similar to that of high moisture in that it reduced the cyanide concentration in the interstitial air and the residue on the fumigated grain sorghum.

The rice weevil ( Sitophilus oryza (L.)) is known to infest standing corn in the field in Louisiana. It was not known at what maximum grain-moisture level oviposition followed by complete development occurred. Studies conducted over a 2-year period showed oviposition may occur at a grain moisture of 65%. Eggs laid at this stage of corn maturity required 9 days for incubation. Complete development from egg to emergence of the adult required 42 days, and occurred between a grain moisture change from 65% to approximately 25%.