Two are better than one: the combinations of Beauveria bassiana, diatomaceous earth, and indoxacarb as effective wheat protectants

Abstract

The current study evaluates the efficacy of the entomopathogenic fungus Beauveria bassiana (Balsamo-Crivelli) Vuillemin (Hypocreales: Cordycipitaceae), diatomaceous earth (DE) (Protect-It), and the oxadiazine indoxacarb, at single or combined applications on wheat kernels, for the management of the rusty grain beetle, Cryptolestes ferrugineus (Stephens) (Coleoptera: Laemophloeidae), the red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae), the khapra beetle, Trogoderma granarium Everts (Coleoptera: Dermestidae), and the lesser grain borer, Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae). The study was conducted between November 2020 and August 2021 in Faisalabad under a complete randomized block design. The combination of DE + indoxacarb was the most efficient as it caused higher overall mortalities ranging between 59.34 and 100%, and lower overall progeny production ranging between 8.35 and 33.70 individuals per vial, than all other treatments. Beauveria bassiana alone exhibited the lowest mortality rates ranging between 22.33 and 47.76%, and the highest offspring emergence, ranging between 51.33 and 78.55 individuals per vial. Similar pattern was observed when persistence bioassays were conducted. For a period of 120 days, the DE + indoxacarb was the most powerful combination against all tested species, providing overall mortality rates between 17.06 and 63.80%. The overall progeny production was lower for the insect individuals exposed on wheat treated with the DE + indoxacarb combination, ranging between 13.66 and 52.23 individuals per vial, and higher for those exposed to B. bassiana alone, ranging between 44.03 and 107.67 individuals per vial, for the entire duration of storage. However, the efficacy of all treatments decreased gradually during the course of storage. The findings of the current study indicate that the combinations of entomopathogenic fungi, DE, and indoxacarb can be used for the prolonged protection of stored wheat from the tested noxious insect species of stored products. Further research, which will include other inert dusts in combination with entomopathogenic fungi and indoxacarb, may provide additional knowledge towards an effective management of noxious species occurring in storages.

Entomopathogenic Fungus and Enhanced Diatomaceous Earth: The Sustainable Lethal Combination against Tribolium castaneum

“…Furthermore, the combination of two DEs (Sayan and Celite) with B. bassiana almost suppressed the progeny production of T. granarium during a period of eight weeks [60]. The combinations of B. bassiana and DE Protect-It, as well as each formulation alone, provided significantly lower progeny production than controls, even 120 days post-application [14]. The suppression of insect offspring production is a crucial parameter because it reduces grain damage [61,62].…”

“…The performance of DEs and entomopathogenic fungi is slow in comparison to numerous chemical insecticides, thus, insects continue damaging grains and/or move to other treated or untreated areas of the grain mass [14,55]. The persistence of entomopathogenic fungi depends on their inoculum and the contagion from the mycosed dead insects [63].…”

“…Furthermore, the problem of resistance is linked with the continuous exposure of storage pests to chemicals [9,11,12]. Therefore, to delay the development of the resistance of insects and avert the losses of quantity and degradation of quality of stored commodities, integrated pest management (IPM) approaches have focused on the use of insecticides applied at low doses in combination with biocontrol agents [13][14][15].…”

“…Due to diverse insecticidal effects, entomopathogenic fungi can be potentially incorporated in the management of stored-product insects. These pathogenic agents are considered as appropriate alternatives to synthetic insecticides because they are easily combined with other killing agents [13][14][15][16][17][18] and have high efficacy according to their geographical origin [19,20]. Other benefits making entomopathogenic fungi desirable for stored-product protection are short life cycles, being naturally available, being easy to produce due to less nutrient requirements, having a high reproductive potential, and having less chances of resistance development [21][22][23].…”

Natural Warriors against Stored-Grain Pests: The Joint Action of Beauveria bassiana and Steinernema carpocapsae

“…For R. dominica , C. ferrugineus , T. castaneum , S. oryzae , and O. surinamensis , <2 weeks old adults were used. The populations of R. dominica , T. granarium , and S. oryzae were reared on wheat at 30 °C, 65% relative humidity (RH) in complete darkness [ 59 , 60 ]. The populations of C. ferrugineus were cultured on wheat flour.…”