Time-Mortality Relationships to Control Tyrophagus putrescentiae (Sarcoptiformes: Acaridae) Exposed to High and Low Temperatures

Mycophagous Mite, Tyrophagus putrescentiae, Prefers to Feed on Entomopathogenic Fungi, except Metarhizium Generalists

(1) Background: The mycophagous mite, Tyrophagus putrescentiae, was found to feed on entomopathogenic fungi (EPF) in our previous experiments, which seriously impacted the culture and preservation of fungal strains. Therefore, it is necessary to investigate the biological characteristics of the occurrence and damage to EPF. (2) Methods: The mite's growth and development and feeding preference were surveyed by comparative culture and observation; also, optical and electronic microscopies were employed. (3) Results: T. putrescentiae could survive normally after being fed on seven EPF species, including Purpureocillium lilacinum, Marquandii marquandii, Cordyceps fumosorosea, Beauveria bassiana, Metarhizium flavoviride, Lecanicillium dimorphum, and Metacordyceps chlamydosporia. The first four fungi were the mite's favorites with their greater feeding amount and shorter developmental duration. Interestingly, the mite could also feed on Metarhizium anisopliae and Metarhizium robertsii, but this led to the mite's death. After feeding on M. anisopliae and M. robertsii, the mites began to die after 24 h, and the mortality rate reached 100% by 72 h. Observation under optical microscopy and scanning electron microscopy revealed that the conidia of M. anisopliae and M. robertsii adhered to the mite's surface, but there was no evidence of penetration or invasion. However, dissection observation indicated that the two Metarhizium species germinate and grow within the mite's digestive tract, which implies that Metarhizium generalists with broad-spectrum hosts and the production of destruxins have acaricidal activity toward the mycophagous mites.

Using liquid smoke to control infestations of the ham mite, Tyrophagus putrescentiae, on dry-cured hams during aging

Eight treatments of edible coatings and nets including liquid smoke (SP and 24P) and xanthan gum (XG) were used to evaluate their effectiveness at controlling mite growth on dry-cured hams. Mite growth was controlled (P < 0.05) in both coating and netting treatments of 1% SP + 1% XG. Increasing SP concentration from 1% to 2% in the SP only treatments without XG did not control mite growth (P > 0.05) in the coating but controlled mite growth (P < 0.05) when infused in the nets. Both coating and netting treatments with 2% 24P + 1% XG controlled mite growth (P < 0.05), and ham cubes with 1% and 2% 24P in infused nets had mite numbers of 4.6 and 9.4, respectively. SP did not impact the sensory attributes of the ham. Results indicate that liquid smoke can potentially be added in coatings or ham nets to control mites and used in an integrated pest management program for dry-cured hams.

Efficacy of Dust and Wettable Powder Formulation of Diatomaceous Earth (Detech®) in the Control of Tyrophagus putrescentiae (Schrank) (Acari: Acaridae)

Tyrophagus putrescentiae (Schrank) (Acari: Acaridae) is a cosmopolite mite species commonly in found food and stored products. In this study, the acaricidal activity of two Turkish diatomaceous earth (DE) formulations (Detech^® WP95 and Detech^® Dust) were applied on a concrete surface at five different concentrations (1, 2.5, 5, 7.5, and 10 g/m²) and dead individuals were counted at 11 different time intervals (1, 3, 6, 9, 12, 15, 18, 21, 24, 27, and 30 h) at a temperature of 25 ± 1 °C and 75 ± 5% relative humidity (RH). Mite mortalities were observed after 6- and 18-hour exposure periods at all concentrations of dust and wettable powder (WP) formulations, respectively. Specifically, 100% mortality for the WP formulation was achieved at the highest concentration of 10 g/m² after 15 h of exposure and after 27 h and 30 h for the lowest concentration. In the case of dust formulation, mortalities were observed after 3 h of exposure at all concentrations except at 1 g/m², while a 100% mortality rate was achieved after 21 h of exposure to all concentrations and after 18 h of exposure for 7.5 g/m² and 10 g/m². This study indicates that both WP and dust formulations of local diatomaceous earth can cause 100% mortality in 24 h on average and can be a promising alternative to conventional chemical acaricides.

Duration of Low Temperature Exposure Affects Egg Hatching of the Colorado Potato Beetle and Emergence of Overwintering Adults

Simple Summary

The Colorado potato beetle is a pest of Solanaceae in China, more than 30 species of Solanaceae as host plants of the Colorado potato beetle, and this beetle can cause yield losses to potato farms. Temperature is one of the main factors that affect the growth and survival of insects. In recent years, due to global climate change, sudden drops in short-term temperatures are also frequent, which will affect insects. This paper studies the influence of short-term low temperature on the Colorado potato beetle. In laboratory experiments, we evaluated the effect of short-term low temperature on the Colorado potato beetle eggs, and the emerged date, the number of Colorado potato beetles, were analyzed in combination with the low temperature conditions. Our results show that low temperature had adverse effects on the development of Colorado potato beetle eggs and the emerged of adults Colorado potato beetles, and the longer the low temperature treatment time, the greater the impact.

Abstract

The Colorado potato beetle is a serious pest of Solanaceae in China. In early summer, cold spells in later spring may occur for brief periods in the field environmental conditions, and temperatures often deviate far below the normal temperature for short periods, such as sudden short-term low temperature, may affect the development of Colorado potato beetle eggs. This paper studies the effects of low temperature stress at 8 °C for 0 d, 1 d, 3 d, 5 d, 7 d, and 10 d on the development of Colorado potato beetle eggs. Our results show that egg survival is significantly affected by short-term low temperature exposure. The percentage of eggs hatched is significantly affected by different treatment times (p = 0.000)—the percentage of eggs hatched decreases with increased treatment time, and Colorado potato beetles will extend the wintering time of their soil to resist the effects of lower temperatures. Thus, exposure of Colorado potato beetles to a short-term low temperature affects their emergence and population growth; this study could provide information for the occurrence, monitoring, and early warning of Colorado potato beetle during short-term temperature.

Comparative assessment of the thermal tolerance of spotted stemborer, Chilo partellus (Lepidoptera: Crambidae) and its larval parasitoid, Cotesia sesamiae (Hymenoptera: Braconidae)

Under stressful thermal environments, insects adjust their behavior and physiology to maintain key life-history activities and improve survival. For interacting species, mutual or antagonistic, thermal stress may affect the participants in differing ways, which may then affect the outcome of the ecological relationship. In agroecosystems, this may be the fate of relationships between insect pests and their antagonistic parasitoids under acute and chronic thermal variability. Against this background, we investigated the thermal tolerance of different developmental stages of Chilo partellus Swinhoe (Lepidoptera: Crambidae) and its larval parasitoid, Cotesia sesamiae Cameron (Hymenoptera: Braconidae) using both dynamic and static protocols. When exposed for 2 h to a static temperature, lower lethal temperatures ranged from -9 to 6 °C, -14 to -2 °C, and -1 to 4 °C while upper lethal temperatures ranged from 37 to 48 °C, 41 to 49 °C, and 36 to 39 °C for C. partellus eggs, larvae, and C. sesamiae adults, respectively. Faster heating rates improved critical thermal maxima (CT_max ) in C. partellus larvae and adult C. partellus and C. sesamiae. Lower cooling rates improved critical thermal minima (CT_min ) in C. partellus and C. sesamiae adults while compromising CT_min in C. partellus larvae. The mean supercooling points (SCPs) for C. partellus larvae, pupae, and adults were -11.82 ± 1.78, -10.43 ± 1.73 and -15.75 ± 2.47, respectively. Heat knock-down time (HKDT) and chill-coma recovery time (CCRT) varied significantly between C. partellus larvae and adults. Larvae had higher HKDT than adults, while the latter recovered significantly faster following chill-coma. Current results suggest developmental stage differences in C. partellus thermal tolerance (with respect to lethal temperatures and critical thermal limits) and a compromised temperature tolerance of parasitoid C. sesamiae relative to its host, suggesting potential asynchrony between host-parasitoid population phenology and consequently biocontrol efficacy under global change. These results have broad implications to biological pest management insect-natural enemy interactions under rapidly changing thermal environments.

Use of Lard, Food Grade Propylene Glycol, and Polysaccharides in Infused Nets to Control Tyrophagus putrescentiae (Schrank; Sarcoptiformes: Acaridae) Infestation on Dry Cured Hams

Tyrophagus putrescentiae (Schrank) is controlled in the U.S. dry cured ham industry with methyl bromide (MB) fumigation. However, MB fumigation is being phased out of use since it is an ozone depleting substance. The objective of this research was to evaluate ham nets that were infused with lard, propylene glycol (PG) and polysaccharide coating for their efficacy at controlling mite infestations on dry cured ham cubes from hams that were aged for 4 to 6 mo. Results indicated that fewer T. putrescentiae (P < 0.05) were on ham cubes with treated nets containing PG when compared to the number of mites on ham cubes with untreated nets over 10 wk of storage. Lard infused nets without PG did not decrease the mite population (P > 0.05). The net without coating slowed the growth and reproduction of T. putrescentiae since net controls had fewer mites (P < 0.05) than controls without nets. Fungi were not present on ham cubes that were treated with PG-containing nets over 10 wk of storage with a few exceptions. In conclusion, lard and xanthan gum, or carrageenan + propylene glycol alginate treated nets containing the medium concentration of PG effectively inhibited mite reproduction and fungal growth on dry cured ham and could potentially be used in an integrated pest management program to control mites on dry cured hams.

Application of Food-Grade Ingredients to Nets for Dry Cured Hams to Control Mite Infestations

Infestations of Tyrophagus putrescentiae (Schrank; Sarcoptiformes: Acaridae), known as the ham mite, may occur on dry cured hams during the aging process. The fumigant methyl bromide is currently used to control mite infestations, but it will eventually not be available for use since it contributes to the depletion of the ozone layer. The use of ham nets treated with xanthan gum, carrageenan, propylene glycol alginate, and propylene glycol food-grade ingredients on mite orientation to or oviposition on treated or untreated ham cubes, and mite reproduction and population growth over a 10-wk period was evaluated. Behavioral tests indicated that more than 95% of the mites oriented to the ham cubes that were wrapped in untreated nets when compared to treated nets and no eggs were laid on the latter. The reproduction assays demonstrated that there were fewer (P < 0.05) T. putrescentiae produced over a 2-wk period on ham cubes covered with both gum and propylene glycol treated nets, when compared to the untreated or gum-only treated nets over the 10-wk storage period of the experiment. Medium and high concentrations of propylene glycol treatments showed the lowest reproductive rates of mites. No more than 4 mites could be found on each of these treatments in comparison to 200 to 300 mites that were recorded on the untreated hams. This study demonstrated efficacy of using the nets treated with food-grade ingredients during ham aging to control mite infestations on a laboratory scale. Further research will be conducted to determine the effectiveness of the same treated nets on whole hams in commercial aging rooms.