The present study revealed that the EPF, I. fumosorosea (ICAR-NBAIR Pfu-5), had significant virulence and fungal mycelia development on RSW eggs, nymphs and adults. I. fumosorosea infection affects egg hatching, and nymphal mortality especially fourth-instar nymph (pupae), which led to a severe reduction in adult emergence and further perpetuation of RSW population. Substantial mycosis and deformation were seen in newly emerging adults from I. fumosorosea-treated nymphs, which led to a drastic reduction of adult emergence that may result in less perpetuation of the pest in the coconut ecosystem (Fig. 1). Further, the combination of I. fumosorosea (ICAR-NBAIR Pfu-5) @ 5 ml /l sublethal dose of profenophos 50 EC@ 2 ml/l was superior to all other treatments after 7 and 15 days, with significantly lower RSW population on coconut palms.
Aleurodicus rugioperculatus: a–d Healthy life stages; e–h Isaria fumosorosea infested life stages after spraying
Infestation of RSW per palm (%)
Pre-treatment per cent infestation was uniform in all the treatments as indicated by non-significant differences, ranging from 43.44 to 51.99% (Fig. 2). However, after 7 days of topical application, I. fumosorosea (ICAR-NBAIR Pfu-5) @ 5 ml/l + profenophos 50 EC @ 2 ml/l (T7) showed the lowest infestation (13.84%), followed by I. fumosorosea (ICAR-NBAIR Pfu-5) @ 5 ml/l + buprofezin 25% SC @ 1.25 ml/l (T3) with (16.72%), I. fumosorosea (ICAR-NBAIR Pfu-5) @ 5 ml/l + azadirachtin10000 ppm @ 2 ml/l (T6) with (18.47%) and I. fumosorosea (ICAR-NBAIR Pfu-5) @ 5 ml/l + buprofezin 25% SC @ 0.6 ml/l (T2) with (24.53%) over I. fumosorosea (ICAR-NBAIR Pfu-5) @ 5 ml/l alone (T1) with (26.74%), while the highest RSW infestation was recorded in I. fumosorosea (ICAR-NBAIR Pfu-5) @ 5 ml/l + pongamia soap @10 g/l (T4) with (29.60%) followed by I. fumosorosea (ICAR-NBAIR Pfu-5) @ 5 ml/l + fish oil rosin soap @ 2 ml/l (T5) with (28.89%), whereas untreated control, (T8) with (49.90%) infestation (Fig. 2).
Efficacy of Isaria fumosorosea alone and in combination with selected insecticides and biopesticides on per cent infestation of RSW on coconut in summer (first and second spray pooled data). Means followed by the same letter do not differ significantly by DMRT (P = 0.05); DBS = day before spray; DAS = day after spray; RSW = rugose spiraling whitefly; infestation of RSW/palm (%): (number of fronds infested by RSW/total fronds per palm) × 100
Similarly, after 15 days, T7 dominated all other treatments with the lowest infestation (4.95%), followed by T3 with (6.06%), T6 with (8.75%) and T2 with (13.35%) over I. fumosorosea (ICAR-NBAIR Pfu-5) alone (T1) with (14.16%), while the highest RSW infestation was recorded in T4 with (18.77%) followed by T5 with (17.98%), whereas untreated control, T8 with (60.44%) infestation (Fig. 2).
However, after topical application of T7 showed the lowest mean infestation (9.40%), followed by T3 with (11.39%) and T6 with (13.61%) over I. fumosorosea (ICAR-NBAIR Pfu-5) alone (T1) with (20.45%), while the highest RSW infestation was recorded in T4 (24.18%) followed by T5 (23.43%), whereas untreated control, T8 with 55.17% infestation (Fig. 2).
The application of T7 resulted in the highest reduction of RSW infestation (82.97%) over I. fumosorosea (ICAR-NBAIR Pfu-5) alone, T1 with (62.93%) and untreated control. Following that, T3 with (79.35%) and T6 with (75.33%) (Fig. 2).
Intensity of RSW infestation (%)
Pre-treatment RSW intensity was uniform across all treatments, as evidenced by non-significant differences ranging from 47.32 to 59.79% (Fig. 3). After applying I. fumosorosea (ICAR-NBAIR Pfu-5) @ 5 ml/l + profenophos 50 EC @ 2 ml/l (T7), the percentage intensity of RSW was drastically reduced.
Efficacy of Isaria fumosorosea alone and in combination with selected insecticides and biopesticides on per cent intensity of RSW on coconut in summer (first and second spray pooled data). Means followed by the same letter do not differ significantly by DMRT (P = 0.05); DBS = day before spray; DAS = day after spray; RSW = rugose spiraling whitefly; intensity of RSW (%): (number of leaflets infested by RSW/total leaflets per frond) × 100
After 7 days of topical application, T7 showed the lowest (16.64%) intensity, followed by T3 with (20.39%), T6 with (23.37%) and T2 with (24.97%) over I. fumosorosea (ICAR-NBAIR Pfu-5) alone (T1) with (27.88%), while the highest RSW intensity (30.59%) was recorded in T4 followed by T5 with (30.01%), whereas untreated control, T8 with (51.35%) intensity (Fig. 3).
Similarly, after 15 days, T7 showed the lowest (4.05%) intensity, followed by T3 with (6.34%), T6 with (7.30%) and T2 with (10.60%) over I. fumosorosea (ICAR-NBAIR Pfu-5) alone (T1) with (11.84%), while the highest RSW intensity was recorded in T4 with (15.62%) followed by T5 with (14.08%), whereas untreated control, T8 with (54.71%) intensity (Fig. 3).
Palms treated with T7 surpassed all other treatments with the lowest (10.34%) mean per cent intensity followed by T3 with (13.37%) and T6 with (15.33%) over I. fumosorosea (ICAR-NBAIR Pfu-5) alone, T1 with (19.86%). While RSW intensity in T5 with (22.04%) and T4 with (23.11%) was recorded. Whereas, untreated control T8 with (53.03%) intensity (Fig. 3).
The treatment of T7 resulted in the greatest reduction (80.49%) of RSW intensity over I. fumosorosea (ICAR-NBAIR Pfu-5) alone, T7 with (62.55%) and untreated control. The next best treatments are T3 with (74.79%) and T6 with (71.09%) (Fig. 3).
Mean live colonies of RSW/leaflet
The pre-treatment mean live colonies of RSW were uniform in all the treatments as indicated by non-significant differences, ranging from 11.92 to 12.56 colonies/ leaflet (Fig. 4). The RSW mean live colonies were drastically reduced after palms were treated with I. fumosorosea (ICAR-NBAIR Pfu-5) @ 5 ml/l + profenophos 50 EC @ 2 ml/l.
Efficacy of Isaria fumosorosea alone and in combination with selected insecticides and biopesticides on mean live colonies of RSW on coconut in summer (first and second spray pooled data). Means followed by the same letter do not differ significantly by DMRT (P = 0.05); DBS = day before spray; DAS = day after spray; RSW = rugose spiraling whitefly; mean number of whitefly live colonies/leaflet: (ten leaflets from each palm)
After 7 days, T7 showed the lowest (4.25 mean live colonies/leaflet), followed by T3 with (5.04 mean live colonies/leaflet), T6 with (5.60 mean live colonies/leaflet) and T2 with (5.88 mean live colonies/leaflet) over I. fumosorosea (ICAR-NBAIR Pfu-5) alone (T1) with (6.15 mean live colonies/leaflet). However, the highest RSW mean live colonies/leaflet were recorded in T4 with (6.80 mean live colonies/leaflet) followed by T5 with (6.48 mean live colonies/leaflet), whereas untreated control, T8 with 12.84 mean live colonies/leaflet (Fig. 4).
After 15 days, T7 showed the lowest (1.23 mean live colonies/leaflet) followed by T3 with (1.91 mean live colonies/leaflet), T6 with (2.40 mean live colonies/leaflet) and T2 with (2.78 mean live colonies/leaflet) over I. fumosorosea (ICAR-NBAIR Pfu-5) alone (T1) with (3.23 mean live colonies/leaflet), while the highest RSW mean live colonies were recorded in T4 with (4.11 mean live colonies/leaflet) followed by T5 with (3.80 mean live colonies/leaflet) and, however, untreated control T8 with 14.10 mean live colonies/leaflet (Fig. 4).
Palms treated with T7 were significantly superior to all other treatments with the lowest (2.74 overall mean live colonies/leaflet) followed by T3 with (3.48 mean live colonies/leaflet), T6 with (4.00 mean live colonies/leaflet) over I. fumosorosea (ICAR-NBAIR Pfu-5) alone (T1) with (4.69 mean live colonies/leaflet), while T5 with (5.14 mean live colonies/leaflet) and T4 with (5.38 mean live colonies/leaflet) were recorded and, however, untreated control (T8) with 13.47mean live colonies/leaflet (Fig. 4).
In general, palms treated with T7 showed the greatest reduction (79.68%) mean number of RSW live colonies over I. fumosorosea (ICAR-NBAIR Pfu-5) alone (T1) with (65.20%) and untreated control. This was followed by T3 with (74.20%) and T6 with (70.30%) reduction (Fig. 4).
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