Evaluation of three formulations of Beauveria bassiana for control of lesser mealworm and hide beetle in Georgia poultry houses

Initial screening of 12 Beauveria bassiana (Balsamo) Vuillemin isolates against larvae of the lesser mealworm (Alphitobius diaperinus [Panzer]) resulted in the selection of two isolates, GHA and 707, for further testing under field conditions. Three formulations of each strain were prepared: an EC, a ground corn granular formulation, and waste product of fungal propagation containing spent media, mycelia, and unharvested conidia ("residue" formulation). Two field trials were conducted in commercial caged-layer houses in Georgia with 5-6 mo of manure accumulation and established populations of A. diaperinus and hide beetles (Dermestes maculatus DeGeer). In the first trial field, B. bassiana was applied a single time to the manure surface at either 10(9) (EC and granular cornmeal bait formulations) or 10(8) (residue formulation) fungal spores per square meter. In the second trial, two successive weekly treatments were applied, using a total of 6x the rate of application used in the first trial, Significant treatment effects were short-lived and only detected 2 wk after treatment in both trials. The granular formulations of both strains and the residue formulation of the GHA strain provided the greatest degree of suppression (60-90%) of beetle larvae. A laboratory bioassay confirmed that the granular bait was the most effective formulation. More frequent applications made earlier in the manure accumulation cycle may be necessary to achieve satisfactory control of these beetles.     

Suppression of adult lesser mealworm (Coleoptera: Tenebrionidae) using soil incorporation of poultry manure

The effectiveness of manure incorporation in reducing the numbers of adult lesser mealworms emerging from caged-layer poultry manure applied to agricultural fields was examined in summer 2002 and 2004. Incorporation treatments included control (no incorporation), disk (7-cm depth), harrow (15-cm depth), chisel plow (30-cm depth), and moldboard plow (33-cm depth) on silt loam soils in New York state. An estimated 55,192 and 183,500 live adult lesser mealworms were applied to the field in 2002 and 2004, respectively. Mortality due to the action of the manure spreader was 32.4% in 2002 and 6.5% in 2004. No significant differences were observed between treatments in 2002. However, moldboard plowing significantly reduced beetle emergence compared with no tillage in 2004. Peak beetle flight was observed 10 and 17 d after manure application in 2002 and 2004, respectively.     

Evaluation of a barrier to inhibit lesser mealworm (Coleoptera: Tenebrionidae) and dermestidae movement in high-rise, caged-layer poultry facilities

An evaluation of a mechanical barrier to prevent movement of adult and larval lesser mealworm, Alphitobius diaperinus (Panzer); larder beetle, Dermestes lardarius L.; and hide beetle, Dermestes maculatus De Geer was conducted in caged-layer poultry facilities in New York and Maine. The barrier, a plastic collar wrapped around building support posts, proved highly effective at preventing movement of adult lesser mealworms. Significantly more lesser mealworm larvae were recovered from cardboard collar beetle traps placed below both washed and unwashed barriers than from traps placed above washed and unwashed barriers. Similarly, significantly more adult Dermestes were recovered from traps placed below washed barriers than from above both washed and unwashed barriers. The level of fly specking on the barrier was found to have no significant impact on the numbers of adult lesser mealworms and adult and larval Dermestes recovered either above or below barriers. Fly specking level did significantly impact the numbers of lesser mealworm larvae recovered above the barrier. Although washed barriers provided the greatest deterrent to adult lesser mealworms, the presence of the barrier, regardless of the level of fly specking, provided a significant deterrent to beetle climbing success. Washed barriers further reduced climbing success by lesser mealworm larvae by 17%, Dermestes adults by 7-28%, and Dermestes larvae by 33-38%. The high level of climbing observed by adult lesser mealworms suggests that the impact of adult beetle movement toward birds should be considered in its importance in building damage, disease transmission, feed infestation, and bird productivity and health. Observations on cost and maintenance of the barrier are discussed.     

Field assessments of control agents for lesser mealworm (Coleoptera: Tenebrionidae) using litter sampling

Spinosad, diatomaceous earth, and cyfluthrin were assessed on two broiler farms at Gleneagle and Gatton in southeastern Queensland, Australia in 2004-2005 and 2007-2009, respectively to determine their effectiveness in controlling lesser mealworm, Alphitobius diaperinus (Panzer) (Coleoptera: Tenebrionidae). Insecticide treatments were applied mostly to earth or 'hard' cement floors of broiler houses before the placement of new bedding. Efficacy of each agent was assessed by regular sampling of litter and counting of immature stages and adult beetles, and comparing insect counts in treatments to counts in untreated houses. Generally, the lowest numbers of lesser mealworm were recorded in the house with hard floors, these numbers equalling the most effective spinosad applications. The most effective treatment was a strategic application of spinosad under feed supply lines on a hard floor. In compacted earth floor houses, mean numbers of lesser mealworms for two under-feed-line spinosad treatments (i.e., 2-m-wide application at 0.18 g of active insecticide (g [AI]) in 100-ml water/m2, and 1-m-wide application at 0.11 g ([AI] in 33-ml water/m2), and an entire floor spinosad treatment (0.07 g [AI] in 86-ml water/m2) were significantly lower (i.e., better control) than those numbers for cyfluthrin, and no treatment (controls). The 1-m-wide under-feed-line treatment was the most cost-effective dose, providing similar control to the other two most effective spinosad treatments, but using less than half the active component per broiler house. No efficacy was demonstrated when spinosad was applied to the surface of bedding in relatively large volumes of water. All applications of diatomaceous earth, applied with and without spinosad, and cyfluthrin at the label rate of 0.02 g (AI)/100-ml water/m2 showed no effect, with insect counts not significantly different to untreated controls. Overall, the results of this field assessment indicate that cyfluthrin (the Australian industry standard) and diatomaceous earth were ineffective on these two farms and that spinosad can be a viable alternative for broiler house use.     

Responses of susceptible and cyfluthrin-resistant broiler house populations of lesser mealworm (Coleoptera: Tenebrionidae) to gamma-cyhalothrin

Gamma-Cyhalothrin was proposed as an agent for management of lesser mealworm, Alphitobius diaperinus (Panzer) (Coleoptera: Tenebrionidae), in Australian broiler houses. From 2007 to 2009, baseline susceptibility of 20 Australian broiler farm beetle populations plus an insecticide-susceptible laboratory population was determined for gamma-cyhalothrin by using topical application. In addition, repeat testing and regression analyses of specific beetle populations to gamma-cyhalothrin showed that topical application was a very reliable and repeatable testing method. The 21 populations were tested with a cyfluthrin discriminating concentration (based on LC(99.9), 0.0007% [AI]) to identify possible cross-resistance. Across all populations, there was a significant linear relationship between the gamma-cyhalothrin LC50 value and mortality induced by the cyfluthrin LC(99.9). Full cyfluthrin baseline studies of seven populations indicated that gamma-cyhalothrin was twice as toxic as cyfluthrin, even against susceptible beetles and resistance ratios at the cyfluthrin LC50 and LC(99.9), varied considerably, with maxima of 56.6 and 83.6 respectively. Corresponding ratios for gamma-cyhalothrin for the same populations were 8.6 (LC50) and 7.9 (LC(99.9)). There were no significant correlations between beetle weights and gamma-cyhalothrin LC50 or LC(99.9), values. A discriminating concentration of 0.005% (AI) gamma-cyhalothrin was chosen to detect any future changes in susceptibility. Results of this study suggest that cyfluthrin can confer cross-resistance to gamma-cyhalothrin in A. diaperinus, but the magnitude of this resistance is unpredictable. Thus, widespread and frequent cyfluthrin use in broiler houses in eastern Australia, which has selected for cyfluthrin resistance, also has resulted in reduced susceptibility to gamma-cyhalothrin. Due to its higher relative toxicity, gamma-cyhalothrin is still potentially useful for management of lesser mealworm, but due to cross-resistance issues, adoption of gamma-cyhalothrin for broiler house use will require a cautious and judicious approach.     

Lesser mealworm (Coleoptera: Tenebrionidae) emergence after mechanical incorporation of poultry litter into field soils

Lesser mealworm, Alphitobius diaperinus (Panzer), emergence from North Carolina field soils was evaluated in a controlled experiment simulating land application of turkey litter and again in field studies. Adult lesser mealworms were buried in central North Carolina Cecil red clay at depths of 0, 8, 15, 23, and 30 cm and the beetles emerging from the soil counted 1, 3, 7, 10, 13, 17, 21, 24, and 28 d after burial. Beetles emerged from all depths and differences among depths were not significant. Beetles survived at least 28 d buried in the soil at depths < or =30 cm. In seasonal field studies, lesser mealworm emergence from clay soil with poultry litter incorporated by disk, mulch and plow was compared with emergence from plots with no incorporation. Incorporation significantly reduced beetle emergence when poultry litter containing large numbers of beetles was applied to clay field soils during the summer (F = 3.45; df = 3, 143; P = 0.018). Although mechanical incorporation of poultry litter reduced beetle emergence relative to the control, greatest reductions were seen in plowed treatments. Beetle activity was reduced after land application of litter during colder months. Generally, lesser mealworm emergence decreased with time and few beetles emerged from the soil 28 d after litter was applied. Similarly, mechanical incorporation of poultry litter into sandy soils reduced beetle emergence (F = 4.06; df = 3, 143; P < 0.008). In sandy soils typical of eastern North Carolina, disk and plow treatments significantly reduced beetle emergence compared with control.     

Carcinops troglodytes (Erichson) (Coleoptera: Histeridae) preying on Alphitobius diaperinus (Panzer) (Coleoptera: Tenebrionidae) in poultry houses

We first record Carcinops troglodytes (Paykull) as a predator of Alphitobius diaperinus (Panzer) larvae in poultry houses in North and Northwest regions of the state of Paraná. Carcinops spp. are commonly recorded as predators of dipterans, and this record in poultry houses indicates the possibility of exploiting such predator for future studies aiming the development of management strategies for A. diaperinus.     

Effects of temperature and humidity on transpiration in adults of the lesser mealworm,Alphitobius diaperinus (Coleoptera: Tenebrionidae)

Measurements of water loss were made on adults of the lesser mealworm, Alphitobius diaperinus, using a recording micro-electrobalance and a programmable heat circulator bath. This species originates in tropical regions and infests poultry houses in temperate countries. Two routes of water loss were examined: the general cuticle and via the spiracles. Temperature and relative humidity of the ambient air substantially affect the cuticular transpiration in adults (fresh body weights from 12 mg to 22 mg). At near 0% R.H., between 20 and 40 degrees C the rate of body water loss gradually increased; on the other hand, the insects gained weight in an atmosphere close to saturation. Above 40 degrees C transpiration flow abruptly increased coinciding with the start of vigorous locomotor activity. This critical point corresponds to the opening of the spiracles from which the water is expelled from the tracheal system.In dead specimens, killed by cyanide or solvent, the water vapour slowly diffused out of the spiracles and, as in atracheate insects, the transpiration curves did not show a peak as the air temperature was increased.The thermostupor point (TSP) occurred as the insects became motionless; the corresponding temperature is significantly affected by atmospheric relative humidity (TSP=47.4+/-0.6 degrees C at c. 0% R.H.; TSP=46.6+/-0.7 degrees C at c. 100% R.H.).The transpiration flow was about four times as fast in specimens treated with solvent as in the individuals (live or cyanide-killed) that had undamaged water-proof cuticle. This species has to cope with a double challenge: (i) to adapt its physiology and ecology to poultry-house conditions which constitutes an extension of its primary habitats, and (ii) to survive over winter; high drought resistance and heat tolerance may constitute a pre-adaptation to conquer anthropogenic air-conditioned sites.     

Transient gut retention and persistence of Salmonella through metamorphosis in the lesser mealworm, Alphitobius diaperinus (Coleoptera: Tenebrionidae)

Aims: This study was undertaken to determine the retention of Salmonella through Alphitobius diaperinus metamorphosis and its contribution, through defecation, to external contamination. Methods and Results: Insects were exposed to a tagged Salmonella enterica and evaluated for external elimination. (i) Each day for 3 weeks, a filter collected frass from a restrained insect for analysis. (ii) Exposed larvae in a closed container were followed through pupation, and newly emerged adults were examined for their retention of marker bacteria. Conclusions: Exposed adults and larvae produced Salmonella‐positive frass for an average of 8 days, ranging from 6 to 11 days and 6 to 12 days, respectively. Nineteen per cent of the larvae carried Salmonella through metamorphosis and eclosion, with 5% of the pupal exuviae being positive as well. Significance and Impact of the Study: Many sources of foodborne pathogens within the poultry production facilities, including reservoir populations, currently go unrecognized. This diminishes the ability of producers to mitigate the transfer of pathogens between animals, humans and the environment. Poultry management standards accept the reutilization of litter. Alphitobius diaperinus survive between flock rotations on the reutilized litter, and it was demonstrated in this study that the Salmonella they carry can survive with them.     

Effect of temperature and poultry litter in Beauveria bassiana (bals.) Vuill. and Metarhizium anisopliae (Metsch) virulence against the lesser mealworm Alphitobius diaperinus (Panzer) (Coleoptera: Tenebrionidae)

This study was carried out to evaluate the influence of temperature and poultry litter on germination vegetative growth virulence and conidial production of Beauveria bassiana (Bals.) Vuill. and Metarhizium anisopliae (Metsch.) isolates on larvae and adults of the lesser mealworm (Alphitobius diaperinus) (Panzer). The vegetative growth and conidial production were evaluated on culture media. Virulence was studied submerging larvae and adults in a conidial suspension (1 x 10(8) conidia/ml). All the experiments were carried out in growth chamber (26 degrees C and 32 degrees C and 14h photophase). Fungus-killed insects were daily collected and used for microscopic conidial counts. The poultry litter effect was evaluated by submerging the insects in a fungal suspension (10(8) conidia/ml) and then transferring them to cups containing poultry litter (new and used). B. bassiana isolates were more sensitive than M. anisopliae to high temperature because conidia viability, vegetative growth and virulence were negatively affected (P < 0.05). The conidial production was higher to B. bassiana in 26 degrees C (7 to 11 x 10(8) conidia/larval cadaver and 8 x 10(8) conidia/adult cadaver) (P < 0,05). Larval stage was about 10 times more sensitive to M. anisopliae at 26 degrees C than adults stage. Regarding B. bassiana, differences on sensitivity between larval stages and adults were not observed at this temperature. However, at 32 degrees C, larval stage was more sensitive for CB116 and UEL50 isolates. Mortality was higher when larvae and adults (15.7 and 66.7% respectively) were treated by B. bassiana and maintained on new poultry litter at 26 degrees C) (P < 0.05).     

A sexually dimorphic response in supercooling temperature, enhanced by starvation, in the lesser mealworm Alphitobius diaperinus (Coleoptera: Tenebrionidae)

The effect of starvation on supercooling temperature (SCP) distribution was investigated in adults and larvae of Alphitobius diaperinus (Coleoptera: Tenebrionidae).

The mean values for SCPs of adults fed at 20°C were −14.5±2.4°C (31 males) and −10.3±1.3°C (29 females). The distribution of the SCPs of these control adults was unimodal. No significant differences were observed in either mean wet weight or mean dry weight between males and females.

The mean values for SCPs of adults starved for 1 month at 20°C were found to be bimodal due to sexual dimorphism. The mean SCPs for males was lower (−17±2.6°C; 28) than that for females (−11.2±1.8°C; 26). No significant differences were observed in either mean dry weight or wet weight between males and females.

The SCPs of both fed and starved larvae, kept for 1 month at 20°C were −12.3±2.4°C (fed) and −18.0±2.6°C (starved).     

Effect of food shortage and temperature on oxygen consumption in the lesser mealworm, Alphitobius diaperinus (Panzer) (Coleoptera: Tenebrionidae)

Abstract.  Temperature and food availability are limiting factors for the establishment of tropical insects in temperate countries. In the alien pest beetle, Alphitobius diaperinus (Panzer) (Coleoptera: Tenebrionidae), starvation and temperature have a significant impact on metabolic rate with oxygen consumption ranging from 0.5 µmol/g fresh mass (FM)/h at 12 °C to 3.4 µmol/g FM/h at 24 °C. At 12 °C, oxygen consumption decreased continuously during an entire period of starvation. However, at 16, 20 and 24 °C, beetles display a marked hyperactivity that leads to an increase in the oxygen consumption level during the first week of starvation, followed by a steep decrease until the end of the starvation period. Oxygen consumption either does not decline in fed beetles (observed at higher temperatures) or declines at a much shallower rate than in starved beetles (observed at cooler temperatures). During the first week of refeeding, Oxygen consumption rose steeply at 16, 20 and 24 °C before levelling off to the initial value ( t ₀). At 12 °C, no compensation process was observed during recovery. This study reveals that an important threshold in the biology of A. diaperinus lies between 12 and 16 °C, leading to the onset of reduced locomotor activity and the promotion of survival to the detriment of reproduction. This 'sit and wait' behaviour is proposed as an adaptive strategy (i.e. inactivity and lower oxygen consumption coupled with low energetic requirements and high recovery abilities). Such behaviour and the observed hyperactivity were rarely described in insects before the present study. Together, the previous and present results suggest that A. diaperinus populations are likely maintained in temperate regions by immigration from warmer situations.     

Metabolic mechanisms only partially explain resistance to pyrethroids in Australian broiler house populations of lesser mealworm (Coleoptera: Tenebrionidae)

The susceptibility of six Australian broiler house populations and an insecticide susceptible population of lesser mealworm, Alphitobius diaperinus (Panzer) (Coleoptera: Tenebrionidae), to cyfluthrin, beta-cyfluthrin, gamma-cyhalothrin, and deltamethrin was investigated. One broiler house population had equivalent susceptibility to the susceptible to beta-cyfluthrin and beta-cyhalothrin, with higher susceptibility to cyfluthrin and deltamethrin. The remaining five populations demonstrated strong resistance to cyfluthrin (19-37-fold), the insecticide used most widely for management of A. diaperinus in Australia. Each cyfluthrin-resistant population demonstrated reduced susceptibility to beta-cyfluthrin (resistance ratios were 8-17-fold), deltamethrin (2.5-8-fold), and gamma-cyhalothrin (6-12-fold) compared with the laboratory population, but cross-resistance patterns varied considerably between populations. Adding piperonyl butoxide (PBO) had no effect on the susceptibility of the susceptible population to any of the insecticides, but it increased the susceptibility of each of the five cyfluthrin-resistant populations: to cyfluthrin (synergism ratio range, 1.9-5.0-fold), beta-cyfluthrin (1.6-4.1-fold), and y-cyhalothrin (1.7-2.0-fold). PBO had a more variable effect on susceptibility to deltamethrin, with three of the cyfluthrin-resistant populations being more susceptible to deltamethrin in the presence of PBO, but susceptibility of the remaining two populations was unaffected by adding PBO (synergism ratio range, 0.9-2.5-fold). Overall, the addition of PBO to the four pyrethroids had variable effects on their susceptibility. This variability indicated the presence of other resistance mechanisms in beetle populations apart from metabolic resistance. In addition, the relative importance of metabolic resistance in each beetle population varied widely between pyrethroids. Thus, it cannot be assumed that PBO will reliably synergize pyrethroids against cyfluthrin-resistant lesser mealworm populations when using it to mitigate insecticide resistance.     

Survival and chill-coma in the adult lesser mealworm,Alphitobius diaperinus (Coleoptera: Tenebrionidae), exposed to low temperatures

The survival of adult Alphitobius diaperinus (Coleoptera: Tenebrionidae) at low temperatures has been investigated under laboratory conditions: LT₅₀ ranges from 9.5 days at 6°C to 47.6 days at 10°C and LT₉₉ ranges from 20 days at 6°C to 102.2 days at 10°C. Mean survival shows no significant differences between sexes, but at 10°C, all the males are dead after 88 days and all the females after 107 days. Temperature of 6°C is progressively lethal for the beetles: activity ceases, all the insects are in chill-coma after 12 days and died after 22 days. At 10°C, after 1 month, 70% of the insects are still active. Chill-coma is a reversible state but insects which entered chill-coma last did not recover in most cases and also died the last. During winter sanitary disinfections, A. diaperinus is submitted to subzero temperatures: the rate of adult survival is a key factor governing the population dynamics in the poultry houses.     

A comparative toxic effect of Cedrus deodara oil on larval protein contents and its behavioral effect on larvae of mealworm beetle (Tenebrio molitor) (Coleoptera: Tenebrionidae)

Cedrus deodara (deodar) is practically used, as insect repellent, in the northern areas of Pakistan but no data available therefore this study was conducted to evaluate the effectiveness of deodar oil as an alternate of conventional insecticides against the larval pest stage of mealworm beetle (Tenebrio molitor), by feeding method. The aim of the study was to investigate the effectiveness of deodar oil as an alternate of conventional insecticides against the larval pest stage of mealworm beetle (Tenebrio molitor), by feeding method. All tested chemicals showed efficacy against the pests. The LC₅₀ was determined by probit analysis and was found to be 3.41, 0.086 and 0.023% of larvae treated with deodar oil, Carbosulfan and Imidacloprid respectively The LC₅₀ treated larvae were subjected to the evaluation of protein activity, qualitatively and quantitatively. The protein level in tested insects was enhanced when treated with Imidacloprid, Carbosulfan and deodar oil. The electrophoretic profile of treated insects showed more bands in insects treated with Cedrus deodara oil. This electrophoretic profile appeared in 4, 5, 7 and 8 bands for tested chemicals including control. Antifeedant activity was observed for C. deodara as larvae were deterred to feed on the food found in the container.     

Balanced intake of protein and carbohydrate maximizes lifetime reproductive success in the mealworm beetle,Tenebrio molitor (Coleoptera: Tenebrionidae)

Recent developments in insect gerontological and nutritional research have suggested that the dietary protein:carbohydrate (P:C) balance is a critical determinant of lifespan and reproduction in many insects. However, most studies investigating this important role of dietary P:C balance have been conducted using dipteran and orthopteran species. In this study, we used the mealworm beetles, Tenebrio molitor L. (Coleoptera: Tenebrionidae), to test the effects of dietary P:C balance on lifespan and reproduction. Regardless of their reproductive status, both male and female beetles had the shortest lifespan at the protein-biased ratio of P:C 5:1. Mean lifespan was the longest at P:C 1:1 for males and at both P:C 1:1 and 1:5 for females. Mating significantly curtailed the lifespan of both males and females, indicating the survival cost of mating. Age-specific egg laying was significantly higher at P:C 1:1 than at the two imbalanced P:C ratios (1:5 or 5:1) at any given age throughout their lives, resulting in the highest lifetime reproductive success at P:C 1:1. When given a choice, beetles actively regulated their intake of protein and carbohydrate to a slightly carbohydrate-biased ratio (P:C 1:1.54–1:1.64 for males and P:C 1:1.3–1:1.36 for females). The self-selected P:C ratio was significantly higher for females than males, reflecting a higher protein requirement for egg production. Collectively, our results add to a growing body of evidence suggesting the key role played by dietary macronutrient balance in shaping lifespan and reproduction in insects.     

Distributions of lesser mealworm (Coleoptera: Tenebrionidae) in litter of a compacted earth floor broiler house in subtropical Queensland, Australia

Distributions of lesser mealworm, Alphitobius diaperinus (Panzer) (Coleoptera: Tenebrionidae), in litter of a compacted earth floor broiler house in southeastern Queensland, Australia, were studied over two flocks. Larvae were the predominant stage recorded. Significantly low densities occurred in open locations and under drinker cups where chickens had complete access, whereas high densities were found under feed pans and along house edges where chicken access was restricted. For each flock, lesser mealworm numbers increased at all locations over the first 14 d, especially under feed pans and along house edges, peaking at approximately 26 d and then declining over the final 28 d. A life stage profile per flock was devised that consisted of the following: beetles emerge from the earth floor at the beginning of each flock, and females lay eggs, producing larvae that peak in numbers at approximately 3 wk; after a further 3 to 4 wk, larvae leave litter to pupate in the earth floor, and beetles then emerge by the end of the flock time. Removing old litter from the brooder section at the end of a flock did not greatly reduce mealworm numbers over the subsequent flock, but it seemed to prevent numbers increasing, while an increase in numbers in the grow-out section was recorded after reusing litter. Areas under feed pans and along house edges accounted for 5% of the total house area, but approximately half the estimated total number of lesser mealworms in the broiler house occurred in these locations. The results of this study will be used to determine optimal deployment of site-specific treatments for lesser mealworm control.