“reduced risk” agents such as essential oil, diatomaceous earth, insect growth
regulator and related compounds can be used to enhance the toxicity.
Microbial pesticide formulation based on Bt subspecies kurstaki and Bt subspecies aizawai were found to be effective against a wide range of lepidopteran pests. Bt
subspecies kurstaki (0.2%) in combination with 5% neem oil or citronella oil is
effective against H. armigera. Use of HaNPV 250 LE/ha in combination with
endosulfan 0.035 % and Fenvalerate (0.005%) +NPV; monocrotophos (0.035%) +
NPV; NPV + B.t and HNPV + NSKE (2.5%) were found to be effective against
larvae of H. armigera, S. litura and L. trifolii. B. bassiana and M. anisopliae fungibased pesticides in combination with deltamethrin or dimethoate 0.015% and
acetamiprid 0.004% were effective on various field pests. Combination of
B. bassiana and M. anisopliae + insecticides was successful in controlling yellow
fever mosquito, Aedes aegypti, coleopterans and stored pests. Synergistic effect of
fungal biopesticides and diatomaceous earth in the management of several crops and
stored pests (Kavallieratos et al. 2006; Sabbour et al. 2014) and B. bassiana +
imidacloprid and DE were effective against soil insects such as the southern mole
cricket, Scapteriscus borellii (Sirvi et al. 2013).
11.13 Factors Influencing the Success of Biocontrol Agent
There are several factors both extrinsic and intrinsic factors that challenge the
effectiveness of biopesticides on a large scale. Since they are from biological agents,
they are affected by external factors such as sunlight and UV radiation. Ultraviolet
light is extremely destructive and results in the photodecomposition of biopesticides.
Temperature plays a significant role and extreme temperature results in reduced
efficacy. Maintaining the optimal temperature in the field is difficult. However, for
its survival and multiplication, the environmental conditions must be favourable to
them. Most of the fungi-based formulations are temperature and humidity sensitive
and conidia will not grow above or below 80% relative humidity. In case of NPV and
other viruses, the suspension sprayed when adhere to the soil surface or leaf which is
not consumed by the larvae does not have any effect on the pests. Hydrolysis in
combination with photodecomposition is often involved in the breakdown of various
pesticide active ingredients. The faster the hydrolysis, the less time the pesticide is
available in the environment. Leaching also affects the biopesticides. If an acidic
pesticide is applied to an alkaline surface or vice versa it may breakdown very
rapidly. Thus, the soil pH and soil biota are important which influence the effectiveness of biopesticides. Rain during the application of biopesticides wash off from the
plant and reduces its effectiveness. Some biopesticides are incompatible with chemical pesticides and thus reduce the activity of biopesticides. The compatibility of
biopesticides with predators and parasitoids is also to be considered while releasing
biocontrol agents. Antagonistic effects of phytochemicals on biopesticides are also
to be considered.
11 Biopesticides for Pest Management
263
regulator and related compounds can be used to enhance the toxicity.
Microbial pesticide formulation based on Bt subspecies kurstaki and Bt subspecies aizawai were found to be effective against a wide range of lepidopteran pests. Bt
subspecies kurstaki (0.2%) in combination with 5% neem oil or citronella oil is
effective against H. armigera. Use of HaNPV 250 LE/ha in combination with
endosulfan 0.035 % and Fenvalerate (0.005%) +NPV; monocrotophos (0.035%) +
NPV; NPV + B.t and HNPV + NSKE (2.5%) were found to be effective against
larvae of H. armigera, S. litura and L. trifolii. B. bassiana and M. anisopliae fungibased pesticides in combination with deltamethrin or dimethoate 0.015% and
acetamiprid 0.004% were effective on various field pests. Combination of
B. bassiana and M. anisopliae + insecticides was successful in controlling yellow
fever mosquito, Aedes aegypti, coleopterans and stored pests. Synergistic effect of
fungal biopesticides and diatomaceous earth in the management of several crops and
stored pests (Kavallieratos et al. 2006; Sabbour et al. 2014) and B. bassiana +
imidacloprid and DE were effective against soil insects such as the southern mole
cricket, Scapteriscus borellii (Sirvi et al. 2013).
11.13 Factors Influencing the Success of Biocontrol Agent
There are several factors both extrinsic and intrinsic factors that challenge the
effectiveness of biopesticides on a large scale. Since they are from biological agents,
they are affected by external factors such as sunlight and UV radiation. Ultraviolet
light is extremely destructive and results in the photodecomposition of biopesticides.
Temperature plays a significant role and extreme temperature results in reduced
efficacy. Maintaining the optimal temperature in the field is difficult. However, for
its survival and multiplication, the environmental conditions must be favourable to
them. Most of the fungi-based formulations are temperature and humidity sensitive
and conidia will not grow above or below 80% relative humidity. In case of NPV and
other viruses, the suspension sprayed when adhere to the soil surface or leaf which is
not consumed by the larvae does not have any effect on the pests. Hydrolysis in
combination with photodecomposition is often involved in the breakdown of various
pesticide active ingredients. The faster the hydrolysis, the less time the pesticide is
available in the environment. Leaching also affects the biopesticides. If an acidic
pesticide is applied to an alkaline surface or vice versa it may breakdown very
rapidly. Thus, the soil pH and soil biota are important which influence the effectiveness of biopesticides. Rain during the application of biopesticides wash off from the
plant and reduces its effectiveness. Some biopesticides are incompatible with chemical pesticides and thus reduce the activity of biopesticides. The compatibility of
biopesticides with predators and parasitoids is also to be considered while releasing
biocontrol agents. Antagonistic effects of phytochemicals on biopesticides are also
to be considered.
11 Biopesticides for Pest Management
263