Discovery Research

Consortium for Integrated Management of Stored Product Insect Pests

Discovery Research

The CIMSPIP team has generated a significant number of research outcomes to manage stored product insect pests. The discoveries are listed below under each of the objectives listed above. The outcomes are available in greater detail in the publications listed below and also at: outcomes

a. Reduced Risk Insecticides: Alternatives to Organophosphates as Grain Protectants and for Food Processing Facilities.

	The efficacy of the bacterial insecticide, spinosad, was evaluated. Spinosad at 1 mg/kg was effective against the lesser grain borer on hard red winter, soft red winter, hard white winter, durum, and hard red spring wheats. On hard red spring, hard red winter, and soft red winter wheat, spinosad was effective in killing and suppressing progeny production of the lesser grain borer, Indianmeal moth, rusty and flat grain beetles, and the confused flour beetle. Effectiveness against the rice weevil, sawtoothed grain beetle, and red flour beetle varied with the wheat class and spinosad rate. Activity of spinosad against lesser grain borers, on 12.5 or 14.5% moisture wheat stored at 22, 28, and 34oC for 4 months, was not affected by wheat temperature and moisture.
	Spinosad at 1 mg/kg was stable on hard red winter wheat and provided 100% mortality of the lesser grain borer for 12 months. A six-month study in bins showed that treated grain had no insects, whereas grain subjected to controlled aeration and untreated wheat had measurable infestations of the lesser grain borers, rusty grain beetles, and red flour beetles.
	Spinosad exhibited contact toxicity against adults of the lesser grain borers, red flour beetles, and rice weevils. The performance of spinosad was greater on whole wheat than on cracked wheat or flour. Spinosad controlled eight stored-product beetles on concrete, galvanized steel, waxed tile, and unwaxed tile.
	An Actellic (pirimiphos-methyl) resistant field strain of the rice moth larvae was highly susceptible to spinosad on both corn and sunflower seeds at 0.5 and 1 mg/kg. The rice moth strain was completely controlled on corn treated with 1.5 mg/kg of pyrethrins synergized with 15 mg/kg of piperonyl butoxide.
	Spinosad was tested in combination with other control tactics.It was not compatible with parasitoids of stored-product insects, but was compatible with the warehouse pirate bug, Xylocoris flavipes yes However, spinosad alone was as effective as the spinosad + X. flavipes combination treatment.The combination of spinosad with the organophosphate chlorpyrifos-methyl (Reldan) gave no or little added activity over spinosad alone.
	Actellic (pirimiphos-methyl) alone at 4 mg/kg on wheat and sunflower seeds could be used as a grain protectant against major storage insects except the lesser grain borer.
	A commercial neem extract was highly active against larvae of external grain feeding insects in laboratory bioassays, but internal feeding insects were not affected by similar doses.
	Natural pyrethrins, applied without the synergist PBO, were active against storage insects, and this activity was enhanced by the addition of diatomaceous earth (DE).
	Essential oil form cedar had low activity, as did dried and powdered plant parts of marigolds.
	The insect growth regular pyriproxyfen gave effective control of storage insect larvae when applied to three different surfaces for up to 2 months, slightly better than the currently used hydroprene.
	The combination of Reldan and cyfluthrin (Tempo) at reduced doses was very effective as a grain protectant, and the combination of a low dose of DE with low doses of certain botanical and or synthetic insecticides resulted in very good control of insects in grain. Field trials with the combination of cyfluthrin+Reldan in one-bu drums, and of spinosad applied to 170 bu bins of wheat demonstrated that these materials could protect grain from insect infestation for up to one year.
	The influence of different surface layer treatments of wheat with diatomaceous earth (DE) (Protect-it®) on the distribution, mortality, and reproduction of lesser grain borers at two different temperatures was tested.There was greater mobility and survivorship at the higher temperature, increased beetles numbers and distributionin the controls compared to treatments, and increases in DE depth corresponded to increased mortality, decreased movement, and decreased progeny production.
	Insect mortality increases when the concentrations of DE increase. Methoprene causes little insect mortality.Combinations of the two do not cause any more mortality.

b. Behavior and Genetics

	Toxicity trials showed that even subtle contact of Plodia interpunctella males with attracticidal gel containing 3-18% permethrin and sex pheromone (Last Call) caused a significant reduction in mating and killed male moths within 24 h. Upwind flight studies in a wind tunnel showed that male flight response to the attracticidal gel was significantly lower when the ZETA concentration was 0.32% compared to 0.16%, but P. interpunctella males showed no signs of repellency at any permethrin concentration tested. Field trials in small metal buildings revealed that the attracticidal gel provided efficient control by suppressing reproduction through lack of mating when the moth density was about one mating pair per 10 m3.
	Indianmeal moth oviposition on whole-wheat kernels treated with one of 18 different oils diluted in hexane (oil-treated) was compared to oviposition on whole-wheat kernels treated with hexane only (control). Total oviposition was significantly lower when food dishes were screened compared to experiments with unscreened dishes, using unscreened food dishes, P. interpunctella females laid significantly more eggs in 17 types of oil-treated wheat compared to dishes with control wheat kernels, and using screened food dishes, P. interpunctella females only laid significantly more eggs in walnut oil-treated wheat compared to dishes with control wheat kernels. This study provides the basis for chemical identification of oviposition stimulants for P. interpunctella from food oils.
	Multiple years of monitoring data were collected from a flour mill and the relationship between insects captured in the product, indoor pheromone traps, and outdoor pheromone traps and the effectiveness of fumigations was evaluated. DNA fingerprinting techniques were developed to evaluate the population structure of the red flour beetle. Experiments were conducted to evaluate the effectiveness of traps baited with pheromone are at identifying the sources of red flour beetles.
	Preliminary experiments have demonstrated the occurrence of fractions in dog food that are attractive to sawtoothed grain beetle. Efforts are under way to identify the chemical nature of these compounds. The presence of a female produced sex pheromone that triggers male copulation behavior was also detected.
	An ultrasonic emitter that produces sound frequencies and sound durations at each frequency at random was developed and tested in the laboratory to suppress reproduction of the Indianmeal moth, Plodia interpunctella. The emitter uses a computer, arbitrary waveform generator and custom electronics to generate ultrasonic pulses in 20 to 100 kHz frequency range with randomized pulse length, frequency, and quiet time between pulses across the entire frequency range.

c. Sampling and IPM Decision-Making

	The accuracy of contour mapping of insect trap catch data sets was tested. The accuracy of contour maps for data sets with a random spatial structure was low, while there was a significant correlation between observed and predicted trap catches for re-arranged data sets with spatial auto-correlation. Consequently, our analysis suggests that contour mapping is not appropriate for data sets with a random spatial structure; instead we recommend that such data sets be visualized as scale-sized dots. General recommendations were developed for semi-variogram analysis of data sets’ spatial structure that are of particular relevance to spatial studies of small data sets like those generated in population assessments of stored-product insects.
	A device for the electronic detection, identification and enumeration of pests in grain was evaluated. Manual counts of the contents of the probe tips were made to evaluate the accuracy of the electronic counts. Insect species counts were compared with mean pulse peak amplitudes of known insect species determined in a laboratory setting. The total electronic count overestimated the total manual count by only 5.8%; 658 for the electronic count compared to 622 for the manual count. The mean amplitude for size discrimination for rusty grain beetles is 8. The sum of amplitude counts from 1 to 10 was 472 compared to the actual count of rusty grain beetles of 459. Electronic counts and size discrimination were fairly accurate for our stored wheat test. Having accurate insect counts and knowing the species present in stored grains by using electronic probe traps are important for making informed IPM decisions.
	Early detection and management of these infestations is critical for maintaining quality and integrity of pet food products sold in the pet stores. In a survey of pests in8 retail pet stores in Kansas, a total of 12 to 19 stored-product species per store were captured in traps, and seven out of the eight stores had relatively high species diversity. Except for one store, the insect species presentwere similar. The density of insects in infested bulk-stored and bagged pet food products removed from a store ranged from 2 to 2,270 adults/kg. The types and numbers of insect species captured in traps indicated that infestations were well established in the surveyed stores. Sanitation in conjunction with hydroprene or cyfluthrin applications on targeted floor areas reduced beetle numbers but they did not greatly impact Indianmeal moth numbers.
	Sequential sampling plans based on 30 traps provided higher than the preset type I and type II error rates for classifying infestation levels of weevils captured in traps in retail pet stores.
	The Spatial Analysis of Distance IndicEs (SADIE®) software was used to characterize spatial patterns of three insect species from two retail pet stores before and after sanitation.

d. Biological control

	The efficacy of entomopathogenic nematodes against stored-product pests was evaluated under laboratory conditions. In tests on the pathogenicity of three entomopathogenic nematode species (Steinernema carpocapsae, S. feltiae and S. riobrave) against seven stored product pests (Sitophilus oryzae, Ryzopertha dominica , Tribolium castaneum, Oryzaephilus surinamensis, Trogoderma variabile, Plodia interpunctella , and Ephestia kuehniella, the most pathogenic species was S. riobrave, and it will be used for field experiments.
	The red flour beetle, Tribolium castaneum, is a notoriously difficult to manage pest of grain and grain products. Our previous studies identified synergism in the combination of the desiccant dust, diatomaceous earth, and the insect pathogenic fungus, Beauveria bassiana for controlling several other stored-product beetles. Now we have found that similar synergism occurs with the red flour beetle. Only adult red flour beetles had been previously tested with fungi or desiccant, and we confirmed that they are highly tolerant of both. Against larvae, however, diatomaceous earth at the suggested use rate enhanced the efficacy of B. bassiana across a wide range of doses. The presence of diatomaceous earth resulted in 17- and 16-fold decreases in the median lethal doses for beetles at selected humidities. We identified two factors that contribute to the synergism. Spore attachment to larvae was significantly greater in the presence of diatomaceous earth than without it, and the lipids that were taken up by diatomaceous earth included phospholipids, confirming that damage to the insect cuticle makes subcuticular nutrients available to the fungus for germination and growth.
	Oil and surfactant carriers were also evaluated for their impact on the efficacy of B. bassiana conidia against T. castaneum larvae. In addition to quantifying the dosage of liquid treatments by conidia concentration in the spray volume, conidia deposition on the target surface was quantified for comparison with dry conidia. The median lethal concentration was approximately two-fold lower for B. bassiana conidia in mineral oil than for conidia in Silwet L-77 or without a carrier. The higher efficacy of mineral oil suspension corresponded with greater deposition of conidia in the target area. The lower efficacy of conidia in Silwet L-77 may result because of its better spreading causing loss of conidia from the larval surface. In preliminary trials, the pretreatment of larvae with two botanical insecticides, neem oil, and essential oil of rosemary, did not have a significant interaction with B. bassiana.

e. Aeration Management

Insect populations in bins with no aeration were significantly higher than in bins with ambient and chilled aeration (July to September). Chilled aeration provided better control of insect pests than ambient aeration in stored corn. Crusting and condensation were observed on the grain surface in the relatively warm non-aerated bins while the use of aeration (ambient and chilled) prevented this phenomenon in the relatively cooler bins.

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f. Methyl Bromide Alternatives

f.1. Fumigant Alternatives

We investigated the use of low pressure (vacuum) to kill stored product insects. Additionally, we investigated the effects of temperature and exposure time on mortality of stored-product insects (red flour beetle, lesser grain borer, and Indian meal moth) exposed to low pressures in the laboratory. Life stages of three insect species along with food substrate were kept in glass vials with ventilated lids. The vials were enclosed in side-arm conical flasks. The conical flasks were sealed at the top with rubber stop provided with vacuum pressure gauges to measure the pressure and air was evacuated from the side-arm using vacuum pump. The exposure times varied from few hours at 50 mm pressure to more than a week at higher pressures. Data were analyzed using probit-analysis and exposure times to achieve 99% mortality were compared using the lethal-dose ratio test. For all species, mortality of all life stages increased with increasing temperature. Eggs were the most tolerant life stage, and lesser grain borer was the most tolerant species tested at low pressure.Low pressure treatment offers a chemical-free method of control and an alternative for methyl bromide, a fumigant that may be phased out by 2005 in the US.

Modeling of fumigant gas flow is underway to improve the application precision and efficacy of future fumigants. This holds the potential for using lower amounts of fumigants for shorter durations.

f.2. Temperature Management and Sampling for IPM of Stored Grains

	Maintaining the grain bulk temperature at 11.5oC (52.7oF) to 17.1oC (62.8oF) was most effective in controlling insect populations (both natural infestation and caged insects) during the hot summer months in stored corn. Insect population per day estimated from probe trap catches in the grain bulk indicated that insect numbers increased as temperature increased from spring into the summer months and then dropped during the fall. Indianmeal moth population per day estimated from pheromone-baited sticky flight traps indicated an increase as a function of headspace air and grain surface temperatures
	Two separate three parameter nonlinear regression models satisfactorily described temperatures and relative humidity profiles recorded during heat treatment of mills.
	First instars of red flour beetlr possessed [JC3] two distinct HSPs with molecular masses of 72.8 ± 1.7 and 17.2 ± 0.7 kDa, both were recognized by the HSP70 antibody.
	Traps captures of insects before and after heat treatment of mills indicated that the heat treatment was effective for about 2-4 weeks after which insect populations reached levels similar to pre-heat treatment period. Understanding the sources and dynamics of insects within and outside the mill environment is essential to determine reasons for this population rebound following an intervention.
	A simple degree-minute and a complex thermal death kinetic models were developed to predict mortality of the red flour beetle exposed to elevated temperatures.
	A Heat Treatment Calculator to make heat loss calculations was developed in the Visual Basic environment to determine heat energy required to heat-up a facility.
	Heat sterilization trials of empty farm steel bins were conducted. In the first trial, the temperature at the burner inlet rose to about 65-68oC but the temperature in the plenum never rose above 50oC. The rise in temperature of the bin plenum and samples located on the concrete floor and perforated floor was relatively slow. At steady state conditions, temperatures in most of the insect-flour pouch samples reached only the mid-30s and 40s Celsius. Much of the hot air was lost through the roof vents and up the downspout. In the second trial, the bin vents were blocked with foam insulation and sufficient back pressure was created on the fan to cause the temperature in the plenum to rise to 64.5oC. Heat loss was further reduced by blocking the downspout and manhole. This increased the plenum temperature to 70oC and back pressure from 0.85” to 1.1”. Sensors in the center of the insect-flour pouches at several locations increased toward and above 50oC. However due to the harvest rush, the temperatures were not maintained for a sufficiently long period of time and so no reasonable insect mortality data was obtained. A more comprehensive experiment is planned for next season. It will include laboratory experiments to determine heat transfer rates into corn and flour pouches, and on-farm applications of heat treatment at two sites of collaborating stakeholders.

g. Outreach and Technology Transfer

See Educational Programs in Technology Transfer. [provide link here]

h. Economic Analysis of Stored Product IPM Strategies

Costs of several IPM strategies compare favorably with costs of non-IPM (insecticide-based) strategies. Closed-loop fumigation has lower costs and is likely more effective than conventional fumigation, even though it has higher initial investment costs. Strategies using grain protectants are the most expensive of those considered. The biggest cost of IPM strategies is the cost of sampling grain for insects to determine if treatment is needed. Electronic fumigation monitoring devices are likely the best choice for most grain storage facilities. One brand in particular ranked highest in most criteria considered. Software developed can be adapted for alternative insect management situations, so grain managers can compare costs of alternative insect control strategies. Since costs of IPM strategies compare favorably with costs of non-IPM strategies, these results should encourage adoption of IPM strategies. Evaluation of phosphine monitoring devices should encourage managers of stored grain to adopt safe and effective phosphine monitoring practices, and will help industry to adjust to recent changes in EPA regulations on phosphine applications. This will preserve the availability of phosphine for situations and locations where non-chemical methods have not been effective in managing insects.