Virulence of Purpureocillium lilacinum strain ZJPL08 and efficacy of a wettable powder formulation against the Asian citrus psyllid (Diaphorina citri)

Figures & data

Table 1. LC₅₀ of conidial suspension of Purpureocillium lilacinum strain ZJPL08 in Diaphorina citri.

Time (d)	Regression equation	Correlation coefficient (r)	LC50 (conidia/mL)	Log LC50
2	y = 2.164 + 0.266x	0.9957	4.42 × 10^10	10.65
3	y = 2.469 + 0.259x	0.9985	6.06 × 10^9	9.78
4	y = 2.845 + 0.289x	0.9769	2.87 × 10^7	7.46
5	y = 2.948 + 0.369x	0.9599	3.63 × 10^5	5.56
6	y = 2.613 + 0.499x	0.9460	6.10 × 10^4	4.79
7	y = 1.960 + 0.703x	0.9409	2.11 × 10^4	4.32

Table 2. LT₅₀ of conidial suspensions of Purpureocillium lilacinum strain ZJPL08 in Diaphorina citri.

Concentration (conidia/mL)	Regression equation	Correlation coefficient (r)	LT50 (d)	Log LT50
1.0 × 10^4	y = 1.898 + 3.700x	0.9865	6.89	0.84
1.0 × 10^5	y = 2.032 + 4.067x	0.9796	5.37	0.73
1.0 × 10^6	y = 2.187 + 4.340x	0.9703	4.46	0.65
1.0 × 10^7	y = 2.457 + 4.242x	0.9601	3.98	0.60
1.0 × 10^8	y = 2.248 + 5.536x	0.9441	3.14	0.50

Figure 1. Adult D. citri infected with Purpureocillium lilacinum strain ZJPL08 observed under a stereo microscope. (A) Control D. citri. (B − F) Infected D. citri at 12, 24, 36, 48 and 72 h post-inoculation.

Figure 2. Invasion of Purpureocillium lilacinum strain ZJPL08 in D. citri observed under a scanning electron microscopy. (A) Control D. citri. (B − F) Fungal development on the surface of D. citri body at 1, 6, 12, 36 and 48 h post-inoculation. Co: conidia, Gt: germ tubes, Hp: hyphae, Ph: phialides, Cp: conidiophore, Ca: Conidiogenous apparatus.

Figure 3. Invasion of Purpureocillium lilacinum strain ZJPL08 in D. citri observed under a light microscopy. (A) Control D. citri. (B − F) Fungal invasion at 6, 12, 24, 36 and 60 h post-inoculation.

Table 3. Quality index of a wettable powder formulation of Purpureocillium lilacinum strain ZJPL08.

Quality index	Determination results
Conidia content	2.98 × 10^10 conidia/g
Germination rate	92.34%
Moisture content	3.59%
Wetting time	85.32 s
Suspension rate	84.76%
Fineness	96.52% of the preparations passed through a 325-mesh sieve
pH	6.85

Table 4. LC₅₀ of a wettable powder formulation of Purpureocillium lilacinum strain ZJPL08 in Diaphorina citri.

Time (d)	Regression equation	Correlation coefficient (r)	LC50 (conidia/mL)	Log LC50
2	y = 1.979 + 0.336x	0.9901	9.88 × 10^8	8.99
3	y = 2.433 + 0.321x	0.9979	9.67 × 10^7	7.99
4	y = 2.480 + 0.407x	0.9914	1.56 × 10^6	6.19
5	y = 2.788 + 0.439x	0.9921	1.08 × 10^5	5.04
6	y = 1.679 + 0.729x	0.9726	3.57 × 10^4	4.55
7	y = 0.863 + 0.999x	0.9768	1.39 × 10^4	4.14

Table 5. LT₅₀ of a wettable powder formulation of Purpureocillium lilacinum strain ZJPL08 in Diaphorina citri.

Concentration (conidia/mL)	Regression equation	Correlation coefficient (r)	LT50 (d)	Log LT50
1.0 × 10^4	y = 2.034 + 3.755x	0.9874	6.17	0.79
1.0 × 10^5	y = 2.058 + 4.330x	0.9682	4.78	0.68
1.0 × 10^6	y = 1.409 + 6.483x	0.8367	3.58	0.55
1.0 × 10^7	y = 1.256 + 7.588x	0.9279	3.11	0.49
1.0 × 10^8	y = 1.707 + 7.805x	0.8570	2.64	0.42

Table 6. Efficacy of a wettable powder formulation of Purpureocillium lilacinum strain ZJPL08 on Diaphorina citri.

Treatment	Corrected mortality (%) of D. citri
	3 d	7 d	14 d
24.5% abamectin · mineral oil emulsifiable concentrate	98.25 ± 0.31 a	100.00 ± 0.00 a	100.00 ± 0.00 a
10% imidacloprid wettable powder	78.26 ± 1.38 b	94.26 ± 0.87 b	98.83 ± 0.68 b
30% nitenpyram soluable liquid	44.95 ± 1.71 c	58.33 ± 1.12 e	65.19 ± 0.51 d
Conidial suspension of strain ZJPL08	25.32 ± 1.03 d	71.37 ± 1.61 d	93.91 ± 1.60 c
Wettable powder of strain ZJPL08	42.83 ± 1.36 c	86.67 ± 0.92 c	100.00 ± 0.00 a

Different lowercase letters in the same column indicate significant differences at the level of p < .05 determined by Duncan’s new multiple range test (DMRT) using SAS v9.1.