Natural occurrence of Lecanicillium spp. on different sucking insect pests.
Lecanicillium spp. are potential microbial bio-control agent mainly used for the management of sucking insect pests such as aphids, whiteflies, scales, mealy bugs etc. and gaining much importance at present for management of pests. Due to indiscriminate use of chemical pesticides which results in development of resistance, resurgence, outbreak of pests and residue problem, the farmers/growers are forced to use bio-pesticides for sustainable agriculture. Lecanicillium spp. is promising biocontrol agent against sucking insect pests and can be used as one of the components in integrated pest management (IPM). However, optimum temperature and relative humidity are the major environmental factors, for the performance of Lecanicillium spp. under protected/field conditions. The present review is mainly focused on nomenclature of Lecanicillium spp., mode of infection, natural occurrence, influence of temperature and humidity on the growth, factors influencing the efficacy, virulence/pathogenicity to target pests, substrates used for mass production, safety to non-target organisms, compatibility with agrochemicals and commercially available products. This review is mainly useful for the researchers/students to plan their future work on Lecanicillium spp.
- entomopathogenic fungus
- mass production
The increased use of conventional chemical pesticides over the years has not only contributed to an increase in food production, but also has resulted in adverse effects on the environment and non-target organisms. In view of these side effects, the necessity for sustainable crop production through ecofriendly pest management technique is being largely felt in the recent times. Few biopesticides are available in the market, among them Lecanicillium spp. based microbial bio-pesticide gaining much importance for sucking pests for organic and sustainable agriculture [1, 2, 3, 4]. Myco pesticides are potential microbial alternative to chemical pesticides and offer a number of benefits such as facility of growth on a variety of substrates, high virulence, trans cuticular penetration, broad host range, less expensive, safe to humans, animals and the environment. Therefore, this review is prepared by compiling the research work done on Lecanicillium spp. by various research groups on various aspects viz., nomenclature, mode of infection, natural occurrence, effect of temperature and humidity for the growth, factors influencing its efficacy, virulence and pathogenicity against target pests under laboratory/greenhouse/field, substrates used for mass production, safety to non-target organisms, compatibility with agrochemicals and commercially available products were discussed and presented.
2. Nomenclature of Lecanicillium spp.
The genus Verticillium contains diverse host ranges including arthropods, nematodes, plants and fungi . The genus has been redefined using rDNA sequencing, grouping insect pathogens into the new genus Lecanicillium which includes L. attenuatum, L. lecanii, L. longisporum, L. muscarium and L. nodulosum, which were all formerly classified as V. lecanii [5, 6, 7].
3. Mode of infection
When L. lecanii conidia comes in contact with the host integument, it gets adhere to the epicuticle and germinate. Germinated conidia form germ tubes that penetrate cuticle directly or grow over the surface of the epicuticle. The germ tube penetrates by lysing both the epicuticle and the procuticle [8, 9]. This is accomplished by the mechanical pressure exerted by appresorium (penetration peg) and secretion of enzymes viz., proteases, chitinases and esterase’s which plays an important role during cuticle penetration of insect host and also serve as cuticle degrading enzymes. The fungus proliferates throughout the insect’s body, draining the insect of nutrients, and eventually killing it in around 48–72 hours. The mycotoxins produced by L. lecanii are bassianolide [10, 11], vertilecanin-A1, decenedioic acid and 10-hydroxy-8-decenoic acid) [12, 13, 14]. As the host nutrients are depleted, the blastopores’ differentiate into elongated hyphae which extend outward from the body forming a mycelial mat of conidiophores over the surface of the integument resulting in mummification. Under favourable environmental condition, conidiophores mature giving rise to conidia which continues the disease cycle further.
4. R & D publications on different aspects of Lecanicillium spp.
The number of publications related to Lecanicillium spp. from 1971 to 2020 was presented in the Figures 1 and 2. The data clearly indicated that, during 1971–80s the publications were completely nil, but during 1981–91s, the R&D work has been initiated in the entire world and the publications were increased gradually reaching 58% during 2001–2020 (Figure 2). While, considering the number publications on various aspects of Lecanicillium spp., more research work has been done on virulence and pathogenicity (Figure 3) followed by biotechnology and biochemistry as compared to morphology, diversity, ecology, mass production. The number of publications was meagre on effect of environmental factors (temperature and humidity), safety to natural enemies and compatibility with pesticides .
5. Natural occurrence of Lecanicillium spp.
Lecanicillium spp. is the most widely distributed and generally found on infected insects both in temperate and tropical areas throughout the world. There are number of reports on natural infection of Lecanicillium spp. on different insect pests but out of the reported insects and pests, maximum are sucking pests belonging to Hemiptera, Thysanoptera and Acarina which indicates its possible spectrum for use as a biocontrol agent for pest management. Reports of natural occurrence of Lecanicillium spp. on sucking insects presented in the Table 1.
|L. lecanii (Is-2, Is-5)||M. persicae||Israel|||
|L. lecanii (Is-6)||Acrithosiphon pisum||Israel|||
|L. lecanii (R-1)||T. vaporariorum||Russia|||
|L. lecanii (Vl6063)||T. vaporariorum||Halifax, Canada|||
|L. lecanii (V0175)||B. tabaci||Guangdong, China|||
|L. lecanii (Vp28)||Pseudococcus sp.||Guangdong, China|||
|L. lecanii (ICAL4)||Nasonovia ribisnigri in lettuce||Madrid|||
|L. lecanii (ICAL6)||M. persicae in pepper||Madrid|||
|L. lecanii (41185)||M. persicae, T. vaporariorum||Korea|||
|L. longisporum (6541)||Aphis gossypii||UK|||
|L. longisporum (6543)||M. persicae||UK|||
|L. longisporum (4078)||M. persicae||Denmark|||
|L. longisporum (HRI 1.72)||Macrosiphoniella sanbornii||UK|||
|L. lecanii (ARSEF 7207)||T. vaporariorum||Argentina|||
|L. longisporum (ARSEF 7461)||T. vaporariorum||Argentina|||
|L. muscarium (ARSEF 7460)||T. vaporariorum||Argentina|||
|L. lecani (ICAL3)||Macrosiphum euphorbiae in tomato||Madrid, Spain|||
|L. lecanii (ITEM 3757)||Brevicorne brassicae in Cabbage||Bari, Italy|||
|L. lecanii||S. bispinosus on tea||Tamil Nadu, India|||
|L. sabanense sp. nov||Pulvinaria caballeroramose||Bogota (Columbia)|||
|L. attenuatum ZJLSP07 and L. psalliotae ZJLA08||Diaphorina citri||Taizhou (Zhejiang Province, China|||
|L. lecanii (FI 2482) and L. muscarium (FI 2481)||Thaumastocoris peregrinus||South-East Uruguay|||
6. Effect of temperature and humidity on the growth of Lecanicillium spp.
Temperature and humidity are the main factors influencing the growth of the fungus. Effect of different temperature on conidial germination, growth rate, colony size and mycelial growth was discussed and presented in Table 2.
|Water activity (aw)||—||0.985||0.99||0.98||0.975|||
|Strain/isolate||% Conidial germination|
|L. longisporum (Vertalec)||—||—||98||98||28.7||—|
|L. muscarium (Mycotal)||—||20.6||98||98||98||—|
|Mean radial growth rates (mm/day)|
|Strain/isolate||5 °C||10 °C||15 °C||20 °C||25 °C||30 °C|||
|L. longisporum (Vertalec)||0.21||0.66||1.10||1.31||1.86||0.55|
|L. muscarium (Mycotal)||0.22||0.59||1.03||1.59||2.03||0.59|
|Mean colony size (diameter: mm)|
|Strain/isolate||5 °C||10 °C||15 °C||20 °C||25 °C||30 °C|||
Temperature affects the Lecanicillium spp. in different ways by influencing the germination, growth and viability of the fungus in the host insect and environment. High temperature inactivates the fungus before contact with the pest insect or may reduce or accelerate the growth within an insect depending on the temperature requirements of the fungus and the host insect. In contrast, low temperatures reduce or stop the germination and growth. Optimal germination and growth rates of Lecanicillium spp. range between 23°C and 28°C, growth rapidly slows >30°C and ceases at 34 to 37°C. Similarly, conidial germination is adversely affected by temperatures above 30°C. Temperature below 16°C increasingly slows germination and growth and thus affects efficacy in terms of a longer survival of the target population. Lecanicillium strains showed optimum growth at 25°C; the aerial conidia of Lecanicillium strains germinate in a broad temperature range (15–30°C) and L. lecanii 41,185 was the only strain with conidial germination at 35°C .
Effect of different temperature on conidial germination, growth rate, colony size and mycelial growth of L lecanii was discussed and presented in Table 2. At 25°C and 0.975 aw (water activity) conidial germination occurred in all the isolates ranging from 28.7 to 98% whereas isolate PFC 10 no conidial germination had. Per cent germination decreased from highest values at 25°C to the lowest trend at 10°C in Mycotol (20.6°C). Maximum germination of conidia was observed between 15 and 25°C . Most of the isolates showed growth at 5 and 30°C and mean growth rate increased as temperature increased. Optimum growth rate occurred at 25°C (1.64 to 2.07 mm) for all isolates) . Colony size of the fungus was influenced by the temperature, the colony growth is maximum at 25°C (47.3 to 53.6 mm) as compared to the temperature between 5 to 20°C . The optimum temperature for the mycelial growth of L. lacanii CA-1-G was 23°C (37.57 mg/cm2) and 26°C (39.43 mg/cm2) as compared to 20°C (29.43 mg/cm2), 29°C (20.7 mg/cm2) and 32°C (20.63 mg/cm2). Similarly, L. lecanii grew and sporulated over a wide range of temperatures (20–32°C). The optimum temperature for growth was 23°C (46.45 x105 conidia cm−2) or 26°C (33.76 x105 conidia cm−2) for L. lecanii CA-1-G . Virulence of Lecanicillium spp. isolates was evaluated against third instar T. vaporariorum on tomato plants at 23°C. Colony radial growth, conidial production and germination decreased with the reduction in water activity, while 32°C was extremely detrimental for all fungal isolates. However, some isolates were able to grow and produce conidia at low water activity and high temperature . L. muscarium can multiplied in temperature range of 15–30°C but optimum temperature against M. persicae between 20 to 30°C .
Humidity is another important environmental factor affecting the efficacy and survival of Lecanicillium. Spore germination on the insect cuticle and sporulation after outgrowth of the dead host insect require high moisture. Generally high humidity is required for germination of spores under in vitro, insects can become infected at much lower humidity. Under fluctuating humidity, daily saturated humidity requirement of at least 16 h for causing death in Trialeurodes vaporariorum (Westwood) infected with L. lecanii . Several previous studies provided evidence that a threshold time period at high humidity was required for infection. Conidia of L. lecanii required at least 72 h at 100% RH and 20°C before removal to 70% RH to reach >90% infectivity of Myzus persicae (Sulzer) . Similarly, at 25°C temperature and 75% relative humidity (RH), L. lecanii 41,185 showed highly virulent pathogenicity (100%) against M. persicae and Aphis gossypii Glover . Application of L. longisporum against A. gossypii on cucumber in controlled environment (Temperature; 19–26°C and humidity; 80–98%) resulted in 100% mortality [23, 24]. L. muscarium grow at optimum temperature but higher mortality observed against M. persicae between 55 and 90% humidity .
7. Factors influencing the efficacy of Lecanicillium spp. against sucking insect pests
The virulence and pathogenicity of Lecanicillium spp. vary with strain, stage of the insect and dose of the fungus.
Virulence of the Lecanicillium spp. varies with strain to strain or isolate to isolate. The isolate ICAL6 was more virulent (LC50 = 1.05 x 107 conidia mL−1) to nymphs of M. persicae than Macrosiphum euphorbiae (Thomas) (LC50 = 1.26 x 107 conidia mL−1)) and Nasonovia ribisingri (Mosley) (LC50 = 2.78 x 107 conidia mL−1) . The strain Vl 6063 imported from Canada was more virulent to Bemisia tabaci (Gennadius) (2.57 x 105 conidia mL−1)) than the domestic strains V3450 and Vp28 (LC50 = 6.03 x 105 conidia mL−1) . L. lecanii @ 1x107 conidia mL−1 is more effective against nymphs of Plannococcus citri (84% mortality) after six days of treatment as compared to L. longisporum (59% mortality) . L. muscarium isolate FI 2481 @ 1x107 conidia mL−1 was more effective against Thaumastocoris peregrinus (72% mortality) as compared to L. lecanii isolate FI 2482 which reported 50% mortality . Similarly, L. lecanii hybrid strain 2aF4 was more promising (LC50 = 5.3x104 conidia mL−1) for the management of Trialeurodes vaporariorum than L. lecanii 2aF4 (LC50 = 7.8x104 conidia mL−1) .
7.2 Stage of the insect
Stage of host plays important role in the success of Lecanicillium spp. and not all stages of insect life cycle are equally susceptible to fungal infection. So, the fungal application can be successful against the particular pest when it can be done at the condition where the susceptible stage or weaker stages of the particular pest become dominant among population.
First and third instar nymphs of B. tabaci (38 and 65% mortality) were significantly more susceptible to L. muscarium than the fourth instar (15%) in verbena plants. Similarly, first and second instars B. tabaci was more susceptible (50 and 55% mortality) than the third and fourth instar (25 and 20% mortality) on tomato foliage . L. lecanii (ARSEF 7460) showed higher mortality against nymphs of T. vaporariorum followed by L. longisporum (ARSEF 7207) and L. muscarium (ARSEF 74601) @ 1 x 107 conidia mL−1) . The pathogenicity of L. lecanii strains was more in pupae (59–72.5%) than adults (34–52.6%) after 6 days of inoculation . L. lecanii (2.8 x 107 conidia/ml) isolated from Scirtothrips bispinosus (Bagnall) in tea showed higher mortality against larvae (60%) than adults (30%) of S. bispinosus under laboratory at same dose . Mortality of nymphs of Plannococcus citri were more susceptible (84% mortality) after six days of treatment to L. lecanii @ 1x107 conidia mL−1 as compared to adults which showed 40% mortality . L. lecanii hybrid strain 2aF43 @ 1x107 conidia mL−1 showed more efficacy against first instar nymphs of T. vaporariorum (68% mortality) as compared to 4th instar nymphs (30% mortality) and adults (60% mortality). Similarly, L. lecanii hybrid strain 2aF4 is more effective against first instar nymphs (46% mortality) as compared to 4th instar nymphs (30% mortality) .
7.3 Dose/inoculums level
Fungal inoculum level is the important factor which affects the performance. It is general trend that the higher fungal inoculum level gives higher insect mortality. However, sufficient inoculum level should be worked out for the particular pest to prevent the over inoculum wastage and to achieve higher mortality. Higher dose of L. lecanii (1.2 x 109 conidia ha−1) was caused 92.30 and 80.93% mortality of Brevicoryne brassicae Linnaeus and Aleurodicus disperses (Russell) respectively at 10 days after treatment in the laboratory, whereas in field conditions L. lecanii (Vl3) at 2 x 1012 conidia ha −1) causing 61.16% and 66.50% mortality of B. brassicae and A. craccivora respectively .
8. Efficacy of Lecanicillium spp. against sucking pests under laboratory/greenhouse/field
Efficacy of Lecanicillium spp., against aphids, whiteflies, thrips, scales and mealy bugs in the laboratory/greenhouse/field conditions
|Strain/isolate||Conditions (Lab, GH, F)||Pest||Mortality/LC50 /LT50||Temperature (°C)||Humidity (%)||References|
|Lecanicillium lecanii||Lab||Bemisia argentifolii||95–98%||20–25||100|||
|L. lecanii (HRI 1.72)||Lab||A. fabae||LT50 (2.79 d)||10–23|||
|L. lecanii (HRI 1.72)||Lab||M. persicae||LT50 (3.39 d)||23|||
|L. lecanii (Vl6063)||Lab||B. tabaci||(94.9%) LC50 = 2.57 x 105 Conidia mL−1||25||95|||
|L. lecanii (V3450)||Lab||B. tabaci||86.9 (LC50 = 6.03 x 105 conidia mL−1)||25||95|||
|L. longisporum||M. persice, Macrosiphum euphorbiae, Aulacorthum solani||(LT50 = 2.4;1.8; 2.0 d) 100% mortality||25||95|||
|L. longisporum (HRI 1.72)||Lab||M. persicae, A. fabae, Acrithosiphon pisum, Sitobion avenae||LT50 = 74–78 h|||
|L. longisporum||Cucumber||A. gossypii||100% (LT50 = 6.9 d)||25.8||80.6|||
|L. longisporum or L. muscarium||Lab||Frankliniella occidentalis||95%||20||70%|||
|L. lecanii||Lab||A. craccivora||(LC50 = 2.5 x 104 spores mL−1) (LT50 = 3.9 x 108 spores mL−1)|||
|L. muscarium (1x107 spores/ml||Verbana, tomato (GH)||B. tabaci||65 and 55% mortality||20||95|||
|L. muscarium (1x107 conidia/ml)||Verbana, tomato (GH)||B. tabaci||85 and 80%||20||85|||
|L. longisporum||Cucumber (GH)||A. gossypii||100%||19.0||80.2|||
|L. lecanii||Tea (F)||S. bispinosus||30–60%||—||—|||
|L. attenuatum ZJLSP07 and L. psalliotae ZJLA08||Lab||Diaphorina citri||100% (1x108 conidia/ml)||25||90|||
|L. attenuatum (SD-16, SDMP1 and 2)||Lab||M. persicae||100%||25||>90|||
|L. lecanii||Lab||M. persicae, A. gossypii||100% (1x108 conidia/ml)||20||>90|||
|L. lecanii (JMC-01)||Lab||B. tabaci||82.2% (1x108 conidia/ml)||25||70|||
|L. lecanii (FI 2482) and L. muscarium (FI 2481)||Lab||Thaumastocoris peregrinus||50 and 72%||25||65|||
|L. lecanii 2aF4 3 and 2aF4||Lab||T. vaporariorum||83% (LC50 = 5.3x104 conidia/ml) and 84% (LC50 = 7.8 x104 conidia/ml)||23||99.6|||
9. Substrates used for mass production of Lecanicillium spp.
Lecanicillium spp. can be mass multiplied by solid state fermentation (SSF) and liquid state fermentation (LSF) using different growth media. In SSF, different grains, agars and non-synthetic solid media were used for mass production of Lecanicillium spp. (Table 4).
|Sabaroud dextrose agar||2.87 x 107 conidia cm −2|||
|Malt extract agar||5.23 x 107 conidia cm −2|
|Nutrient agar||1.07 x 107 conidia cm −2|
|Corn meal agar||0.09 x 107 conidia cm −2|
|Yeast peptone dextrose agar||4.58 x 107 conidia cm −2|
|Potato dextrose agar||2.91 x 107 conidia cm −2|
|Rice||8.43 x 108 spores g −1|||
|Wheat||9.13 x 108 spores g −1|
|Sorghum||11.31 x 108 spores g −1|
|Pearl millet||10.17 x 108 spores g −1|
|Finger millet||9.76 x 108 spores g −1|
|Maize||7.54 x 108 spores g −1|
|Rice||1.97 x 109 spores g −1|||
|Sorghum||1.90 x 109 spores g −1|
|Finger millet||1.66 x 109 spores g −1|
|Wheat||1.65 x 109 spores g −1|
|Corn||1.84 x 109 spores g −1|
|Polished rice||5.7 x 108 conidia g −1|||
|Cooked rice||1.5 x 109 conidia g −1|
|Rice bran||1.4 x 109 conidia g −1|
|Crushed bajra +1% yeast extract (YE)||17.49 x 108 conidia g −1|||
|Crushed sorghum +1% YE||10.34 x 108 conidia g −1|
|Crushed navane +1% YE||3.52 x 108 conidia g −1|
|Crushed maize +1% YE||4.80 x 108 conidia g −1|
|Crushed rice +1% YE||24.59 x 108 conidia g −1|
|Crushed wheat +1% YE||3.54 x 108 conidia g −1|
|Rice bran||24 x 107 conidia g −1|||
|Crushed maize cobs +10% molasses||10.07 x 104 conidia/g −1|||
|Wheat bran +10% molasses||18.76 x 104 conidia g −1|
|Rice bran +10% molasses||30.86 x 104 conidia g −1|
|Baggase +10% molasses||10.88 x 104 conidia g −1|
|Press mud +10% molasses||7.90 x 104 conidia g −1|
|Sugarcane molasses 3%||8.35 x 108 spores ml −1|||
|Sugarcane molasses 4%||8.56 x 108 spores ml −1|
|Sugarcane molasses 5%||8.42 x 108 spores ml −1|
|Non synthetic solid media|
|Carrot||2.17 x 108 spores g −1|||
|Jack seeds||4.11 x 108 spores g −1|
|Ladies finger||3.12 x 108 spores g −1|
|Rice husk||1.27 x 108 spores g −1|
|Saw dust||0.69 x 108 spores g −1|
|Beet pulp||23 x 107 conidia g −1|||
|Non synthetic liquid media|
|Coconut water||5.27 x 108 spores g −1|||
|Rice cooked water||2.11 x 108 spores g −1|
|Rice wash water||3.12 x 108 spores g −1|
|Wheat wash water||1.21 x 108 spores g −1|
|Potato carrot broth||6.50 x 107spores mL −1|||
|Potato dextrose broth||3.95 x 107spores mL −1|
|Potato sucrose broth||6.30 x 107 spores mL −1|
|Jaggery yeast broth||2.45 x 107 spores mL −1|
|Sucrose yeast broth||2.50 x 107 spores mL −1|
|Molasses yeast broth||8.33 x 107 spores mL −1|
Among grains, rice is most suitable substrates for mass production (1.97 x 109 spores g−1) followed by sorghum (1.90 x 109 spores g−1) as compared to finger millet, wheat and corn (1.6–1.80 x 109 spores g−1) . Similarly, crushed rice +1% yeast extract recorded higher spore yield (24.59 x 108 conidia g−1) followed by crushed bajra +1% yeast extract (17.49 x 108 spores g−1) as compared to crushed sorghum, maize and wheat .
Among different agro wastes used for multiplication of L. lecanii, the growth and sporulation were found to be better on rice bran +10% molasses (30.86 x 104 conidia g −1) followed by wheat bran +10% molasses (18.76 x 104 conidia g−1) and rice bran (15.98 x 104 conidia g−1). Complete inhibition of growth and reproduction of the fungus was noticed on bagasse and pressmud with 1 per cent yeast extract alone. However, growth was recorded when bagasse and press mud was supplemented with 10% molasses (10.88 and 7.90 conidia g−1 respectively) . Among agars, malt extract agar (MEA) yields high conidia production (5.23 x 107 conidia cm−2) followed yeast peptone dextrose agar (4.58 x107 conidia cm−2) as compared to potato dextrose agar and sabaroud dextrose agar (2.91 and 2.87 x 107 conidia cm−2 respectively) . In non-synthetic media, jack seeds produced high spore yield (4.11 x 108 spores g−1) followed by ladies’ finger (3.12 x 108 spores g−1), carrot (2.17 x 108 spores g−1) and rice husk (1.27 x 108 spores g−1) .
In LSF, molasses yeast broth (MYB) supported maximum spore production of L. lecanii (8.33 x 107 spores ml−1) followed by potato carrot broth (6.5 x 107 spores/ml) and potato sucrose broth (6.3 x 107 spores ml−1) as compared to Sucrose yeast broth, Jaggery yeast broth and Potato dextrose broth (2.45–3.95 x 107 spores mL−1). Among non-synthetic liquid media, coconut water produced higher spores (5.27 x 107 spore’s g−1) and biomass production than rice wash water (3.12 x 107 spore’s g−1) as compared to rice cooked water and wheat wash water (1.21–2.11 x 107 spores g−1) . The growth of L. longisporum conidial spores are higher in rice bran [24 x 107 conidia g−1] as compared to beet pulp [23 x 107 conidia g−1] .
10. Safety of Lecanicillium spp. to parasitoids/predators/pollinators
The safety of any bio control agent to parasitoids/predators/pollinators is the important aspect which should be studied thoroughly before its commercialization to avoid the hazards and disturbance of ecological balance. Effect of L. lecanii on aphid parasitoid Aphidius colemani (Viereck) which showed the normal development (approximately 90% adult emergence) when its cotton aphid, A. gossypii host was treated with L. lecanii conidia 5 or 7 days after parasitization. Fungus exposure 1 day before or up to 3 days after parasitization, however, reduced Aphidius colemani (Viereck) emergence from 0 to 10%. They suggested that the parasitoid and fungus may be used together for aphid bio control . L. lecanii showed pathogenicity against predatory mite, Phytoseiulus persimilis Athias-Henriot but its effect was lower than that of spider mite, Tetranychus urticae (Koch) . L. lecanii is safer to predatory coccinellid, Coccinella septempunctata Linnaeus and predatory mites, Amblyseius ovalis (Evans) and Amblyseius longispinosus (Evans) under field conditions . The fungus L. lecanii was not pathogenic to Chrysoperla carnea (Stephens), Coccinella septempunctata (Linnaeus), Episyrphus balteatus (De Geer) and Samia cynthia ricini (Boisduval), but was found to be pathogenic to Bombyx mori (Linnaeus). Parasitism, adult emergence and adult longevity of Trichogramma chilonis (Ishii) were affected by fungal treatments. Aphid mummification and Diaeretiella rapae adult emergence were affected by the fungus. Results suggest that L. lecanii is compatible with natural enemies of cabbage aphid, T. chilonis and is harmless to silk worm . L. muscarium at 106 and 107 spores mL−1 was safer to predatory mite P. persimilis . Number of parasitized larvae of Eretmocerus sp. nr. furuhashii survival decreased with increasing concentrations of L. muscarium and only 29% emergence of pupae was observed at a conidial concentration of 1 × 108 conidia mL−1. Similarly, 67% emergence of adult E. sp. nr. Furuhashii was observed . Parasitoid (Diaeretiella rapae) emergence was affected by application of L. longisporum before or after parasitism and longevity decreased in female F1 populations . In the laboratory conditions, application of L. muscarium (1 x 108 conidia/ml) against A. colemani had not affected longevity and fertility of the female A. colemani. The combination of Aphidius colemani with L. muscarium reduced the aphid infestation in the semi field conditions as compared to A. colemani alone .
The Lecanicillium spp. is not harmful to humans during handling in the laboratory and field for the control of pests.
11. Compatibility of Lecanicillium spp. with agro chemicals
Chemical pesticides may have antagonistic or synergistic effect on the potentiality of Lecanicillium spp. and may disrupt natural epizootic. Under such epizootic condition, it is expected to enhance effectiveness through joint action of pathogen and compatible insecticides, which would reduce not only the cost of protection but also reduce the contamination of the environment. The literature on compatibility of Lecanicillium spp. with agrochemicals is lacking.
Among different insecticides studied for their effect on L. lecanii under in-vitro, malathion was significantly detrimental (69.18% inhibition) than all other insecticides except quinalphos (66.76%). Conversely, endosulfon and chlorpyriphos were significantly safer (37.31 to 44.37%), followed by oxydemeton methyl and dimethoate (45.33 to 48.27% inhibition) . Similarly, endosulfan completely inhibited the germination of conidia and hyphal growth. In contrast, diafenthiuron, thiamethoxam, imidacloprid, thiodicarb, primicarb, omethoate, acetamiprid, and pymetrozine were compatible with L. lecanii in planta . Imidacloprid and cyromazine were compatible with L. lecanii in terms of vegetative growth, sporulation, conidial viability and pathogenicity against T. urticae. At the recommended concentration, the fungicides carbendazim, chlorothalonil, propiconazole, mancozeb and wettable sulphur completely inhibited the germination of candida (100%) except iprodione and triadimefom allowed 37.38 and 41.62% conidia to germinate respectively .
12. Commercial formulations
The commercial formulations based on Lecaniillium spp. are available in India and other countries are presented in Table 5. Number of manufacturers based on Lecanicillium spp. products is more in India however; the production is very low and not available to the farmers/stakeholders/growers on time as compared to synthetics due to dominant in pesticides market and lack of awareness to farmers/growers about biopesticides. In India, the efficacy of Lecanicillium spp., based products was less due to high temperature and low humidity as compared to temperate countries, even though in India, these products were used as one of the components in IPM and also used for the management of sucking pests of flowers and vegetables in greenhouse.
|Country||Trade Name||Target pest||Country||Source|
|Honduras, El Salvador, Nicaragua, Jamaica||Verzam||Whiteflies, aphids, thrips, mites||Escuela Agrícola Panamericana Honduras||—|
|Uruguay||Lecafol||Whiteflies||Lage y Cía. S.A., Uruguay|
|Denmark, Finland, Italy, UK, Netherlands, Italy, Turkey, Switzerland, Japan, France, India||Mycotal||Whiteflies, thrips||Koppert Biological Systems, Netherlands|
|India||Bio-Catch||Whitefly, Aphids, Thrips, Mealy bugs||M/s T. Stanes & Company, India|
|Multiplex Varsha||aphids, thrips, mealy bug, whitefly, scales mites||Multiplex Biotech Pvt. Ltd., Bengaluru, Karnataka, India|
|Verti Guard||---Do--||Lokmangal Bio Tech Maharashtra, India|
|Sun Bio Verti||---Do--||Sonkul Agro Industries Pvt. Ltd. Maharashtra, India|
|Vertisterk||Scales, mealy bugs||Vijaya Agro Industries, Maharashtra, India|
|Green Basivert||Aphids, thrips, whitefly, mealy bug, scales||Greentech Biotech Laboratory, Tamil Nadu, India|
|Vertocoz-P||whitefly, mealy bug||Utkarsh Agrochem Pvt. Ltd., Surat, India|
Lecanicillium spp. is promising biocontrol agent and can be used as one of the components of integrated pest management under green house and field conditions against sucking insect pests. Lecanicillium is multiplying on commercially available media (potato dextrose agar and broth etc.) till date but it can be mass multiplied at cheaper rate on solid grain media of sorghum and rice; liquid media of sugar cane molasses. It can be used effectively in conjunction with other natural enemies and compatible pesticides.
Author is grateful to Director, Institute of Himalayan Bioresource Technology (Council of Scientific and Industrial Research, New Delhi), Ministry of Science and Technology, Government of India, Palampur, Himachal Pradesh, India for encouragement and support.
Conflict of interest
Author declares that no conflict of interest is reported.