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Abstract
Potato, Solanum tuberosum L., is considered one of the important vegetable crops in Egypt. This crop is attacked by several insect pests and the potato tuber moth (PTM), Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae) is widely recognized as the most important one. Until recently, the losses due to PTM infestation are increased.
The present study aimed to evaluate five bioinsecticides in addition to the egg parasitoid, Trichogramma evanescens in sole or combined treatments to control PTM in cages or in gunny bags under storage conditions. Also, the effect of the tested bioinsecticides on the biology of the PM was studied.
1. Evaluation of the bioinsecticides against P. operculella in cages.
1.1. Effect on infestation percentage of P. operculella.
Obtained data indicated that the infestation percentages with P. operculella at Neemix, Virotecto suspension, Virotecto dust, Agerin suspension, Agerin dust, Dipel 2x suspension, Dipel 2x dust, Spinosad treatments were 85.00, 71.67, 60, 41.67, 36.67, 5.00, 3.33, 0 %, respectively as compared to the control treatment (90%).
Also, the percentages reduction in tuber infestation at Neemix, VS, VD, AS, AD, DS, DD, Spinosad treatments were 5.79, 18.75, 32.22, 55.93, 60.37, 94.21, 96.06, 0 %, respectively.
1.2. Effect on number of P. operculella recovered pupae.
Obtained data indicated that the number of P. operculella recovered pupae at Neemix, VS, VD, AS, AD, DS, DD, Spinosad treatments were 158.00, 141.33, 73.67, 64.00, 48.67, 14.67, 3.33, 0 pupae, respectively as compared to the control (208.66 pupae).
Also, the percentages of reduction in tuber infestation at Neemix, VS, VD, AS, AD, DS, DD, Spinosad treatments were 24.26, 32.19, 64.60, 69.27, 76.61, 93.01, 98.41, 100 %, respectively.
1.3. Effect on number of P. operculella mines.
Obtained data indicated that the number of P. operculella mines at Neemix, VS, VD, AS, AD, DS, DD, Spinosad treatments were 111.33, 97.00, 53.67, 49.00, 39.33, 15.33, 4.67, 0 tunnels / 20 tubers, respectively) as compared to the control (154.00 tunnels/ 20 tubers).
1.4. Effect on percentage of edible parts.
Obtained data indicated that the percentages of edible part at Neemix, VS, VD, AS, AD, DS, DD, Spinosad treatments were 50.00, 60.00, 68.33, 75.00, 81.67, 95.00, 96.67, 100 %, respectively as compared to the control (48.33%).
2. Integration between bioinsecticides and T. evanescens.
2.1. Effect on infestation percentage by P. operculella.
Data indicated that the infestation percentage of P. operculella at TE only, (Neemix + TE), (VS + TE), (VD + TE), (AS + TE), (AD + TE) treatments were 71.67, 45.00, 41.67, 13.33, 8.33, 3.33 %, respectively as compared to the control (96.67%).
Also, the percentages of reduction in tuber infestation at TE only, (Neemix + TE), (VS + TE), (VD + TE), (AS + TE), (AD + TE) treatments were 26.11, 53.33, 56.48, 86.11, 91.31, 96.48 %, respectively.
2.2. Effect on number of P. operculella recovered pupae.
Data indicated that the numbers of P. operculella recovered pupae at Neemix + TE), (VS + TE), (VD + TE), (AS + TE), (AD + TE) treatments were 62.00, 40.67, 25.33, 17.67, 12.00, 7.67 pupae, respectively as compared to the control (208.67 pupae).
Also, the percentages reduction in tuber infestation at (Neemix + TE), (VS + TE), (VD + TE), (AS + TE), (AD + TE) treatments were 70.38, 80.51, 87.91, 91.51, 94.29, 96.37 %, respectively.
2.3. Effect on number of P. operculella mines.
Obtained data indicated that the numbers of P. operculella mines at (Neemix + TE), (VS + TE), (VD + TE), (AS + TE), (AD + TE) treatments were 51.00, 50.33, 53.33, 20.00, 21.67, 16.67 tunnels / 20 tubers, respectively as compared to the control (154.00 tunnels/ 20 tubers).
2.4. Effect on percentage of edible parts.
Obtained data indicated that the percentages of edible parts at (Neemix + TE), (VS + TE), (VD + TE), (AS + TE), (AD + TE) treatments were 71.67, 76.67, 88.33, 90.00, 95.00, 96.67, respectively as compared to the control (48.33 %).
3. Efficacy of T. evanescens against P. operculella.
3.1. Percentage of parasitism at different distances from release point.
Data revealed that the percentages of parasitism in PTM eggs at different distances (0, 10, 30, 50, 70, 90) cm from parasitoid releasing point were 76.67, 60.00, 23.33, 6.67, 6.67, 0 %, respectively.
3.2. Percentage of parasitism of PTM eggs located at different positions of potato heaps.
Obtained data showed that the rates of parasitism in PTM egg patches placed in different positions from potato heaps were 46.67, 56.67 and 83.33% for the top, middle and the bottom levels of potato heap, respectively.
4. Effect of bioinsecticides on the biology of P. operculella.
4.1. Effect on F1 progeny:
Data indicated that the mean total numbers of formed pupae at Neemix, VS, VD, AS, AD, DS, DD treatments were 42.33, 39.00, 34.00, 27.00, 24.00, 2.00, 1.00 pupae, respectively as compared to the control (74.33 pupae).
Percentages of emerged adult at Neemix, VS, VD, AS, AD, DS, DD treatments were 82.18, 71.92, 75.38, 82.10, 80.09, 61.11, 50.00 %, respectively as compared to the control (97.10%).
Percentages of deformed adults in the respective treatments were 6.91, 0, 3.37, 0, 3.71, 0, 0 %, respectively as compared to the control where no symptoms of deformation were found. Percentages of survival in the respective treatments were 35.00, 28.00, 25.33, 21.33, 18.67, 1.00, 0.67 %, respectively as compared to the control (72.00%).
4.2. Effect on F2 progeny:
Obtained data proved that fecundity at Neemix, VS, VD, AS, AD treatments were 88.80, 109.10, 81.70, 107.20, 77.20 eggs, respectively as compared to the control (124.20 egg).
Mean daily numbers of laid eggs at Neemix, VS, VD, AS, AD treatments were 22.10, 31.12, 20.63, 33.85, 16.24 eggs, respectively as compared to the control (28.82 egg).
Percentages of egg hatching in the respective treatments were 73.81, 48.58, 65.71, 33.70, 42.59 %, respectively as compared to the control (91.59 %).
Percentages of pupation in the respective treatments were 26.15, 35.41, 48.50, 15.52, 41.62 %, respectively as compared to the control (88.25 %).
Percentages of emerged adults at Neemix, VS, VD, AS, AD treatments were 68.29, 63.16, 57.78, 50.33, 55.06 %, respectively as compared to the control (90.62 %).
Percentages of deformed adults in the respective treatments were 10.79, 3.45, 11.78, 0, 9.92 %, respectively as compared to the control treatment where no symptoms of deformation were found.
Percentages of survival in the respective treatments were 14.95, 13.06, 17.38, 6.26, 17.76 %, respectively as compared to the control (74.33 %).
4.3. Effect on ovipositional periods.
Data indicated that the pre-ovipositional period at Neemix, VS, VD, AS, AD treatments were 1.60, 1.10, 1.80, 1.40, 1.40 days, respectively as compared to the control (1.20 days).
Data indicated that the ovipositional period at Neemix, VS, VD, AS, AD treatments were 4.60, 5.10, 5.40, 6.40, 5.50 days, respectively as compared to the control (4.70 days).
Data indicated that the post-ovipositional period at Neemix, VS, VD, AS, AD treatments were 6.20, 5.00, 3.60, 3.90, 3.60 days, respectively as compared to the control (4.30 days).
4.4. Effect on longevity.
4.4.1. Male longevity:
Data showed that the longevity of PTM males at Neemix, VS, VD, AS, AD treatments were 7.50, 6.30, 7.80, 6.80, 6.90 days, respectively as compared to the control (7.60 days).
4.4.2. Female longevity:
Data showed that the longevity of PTM females at Neemix, VS, VD, AS, AD treatments were 12.40, 11.20, 10.50. 11.70, 10.50 days, respectively as compared to the control (10.20 days).
4.5. Effect on development of P. operculella.
Data revealed that egg incubation period of PTM eggs was similar across all treatments. The total developmental period at Neemix, VS, VD, AS, AD treatments were 37.25, 35.95, 36.55, 35.90, 34.25 days, respectively as compared to the control (33.00 days).
4.6. Effect on weight of P. operculella pupae.
Data showed that the weight of PTM pupae at Neemix, VS, VD, AS, AD treatments were 10.15, 9.65, 10.30, 9.10, 8.20, 8.15, 7.15 mg, respectively as compared to the control (10.90 days).
5. Evaluation of the bioinsecticides in gunny sacks.
5.1. Effect on infestation percentage by P. operculella.
Obtained data indicated that the infestation percentage of P. operculella at Neemix, VS, VD, AS, AD, DS, DD, Spinosad treatments were 93.33, 75.00, 57.50, 53.33, 20.00, 4.17, 4.16, 2.50 %, respectively as compared to the control (100%).
Also, the percentages of reductions in tuber infestations at Neemix, VS, VD, AS, AD, DS, DD, Spinosad treatments were 6.67, 25.00, 42.50, 46.67, 80.00, 95.83, 95.83, 97.51 %, respectively.
5.2. Effect on number of P. operculella recovered pupae.
Obtained data indicated that the numbers of P. operculella recovered pupae at Neemix, VS, VD, AS, AD, DS, DD, Spinosad treatments were 2281, 1813, 1335, 2033, 437, 217, 0, 0 pupae, respectively as compared to the control (6891 pupae).
Also, the percentages of reduction in tuber infestation at Neemix, VS, VD, AS, AD, DS, DD, Spinosad treatments were 66.93, 73.71, 80.64, 70.52, 93.67, 96.85, 100, 100 %, respectively.
5.3. Effect on number of P. operculella mines.
Obtained data revealed that the number of P. operculella mines at Neemix, VS, VD, AS, AD, DS, DD, Spinosad treatments were 109.17, 97.50, 23.00, 116.50, 42.00, 16.33, 0.33, 3.00 tunnels / 20 tubers, respectively as compared to the control (118.17 tunnels/ 20 tubers).
5.4. Effect on percentage of edible part.
Obtained data indicated that the percentages of edible parts at Neemix, VS, VD, AS, AD, DS, DD, Spinosad treatments were 0, 20.00, 25.00, 0, 38.00, 48.00, 93.00, 100 %, respectively as compared to the control (0%).