Coccinellid species associated with different host-aphid plant combination
Four coccinellid species were recorded in this study. Only Menochilus sexmaculatus Fab and Brumus suturalis Fab were recorded on calotropis and oleander and the number of M. sexmaculatus was significantly greater on these plants (caloptropis: F3, 21=89.98, P = 0.0001; 2010 and 2011) (oleander: F3, 21=137.84, P = 0.0001; 2013 and 2014) compared to other systems. The numbers of Coccinella septempunctata L. were significantly higher than those of other ladybeetles on mustard (F3, 21=44.21, P = 0.0001; 2010 and 2011). Safflower significantly affected the the number sof different species of coccinellids recorded (F3, 21=24.22, P = 0.0001; 2010 and 2011) and the highest numbers of C. undecimpunctata L. were recorded on this plant. There were significant differences in abundance among species on barley (F3, 21= 11.89, P = 0.0001; 2010 and 2011), with B. suturalis most abundant on this host. The numbers of C. septempunctata were significantly higher on rocket than on other host plants (F3, 21=3.71, P = 0.027; 2013 and 2014). The populations of all coccinellid predators were significantly higher during 2010 compared with 2011 which may be due to differences in climatic conditions.
Records Of Larval Mortality
The mortality of ladybird beetle larvae collected from different host plants due to diseases and unknown causes did not vary significantly within years (F3, 33 =0.48, P = 0.7005, 2010; F3, 9= 0.87, P = 0.49, 2011; F2, 6= 0.09, P = 0.9155, 2013, and F2, 6=0.12, P = 0.8847, 2014) and ranged between 5 ± 2.2 and 31 ± 3.8% (mean ± SE). However, mortality varied significantly among years (Table 2). The lowest and the highest coccinellid larval mortality were recorded on barley and calotropis plants, respectively (Table 2). Coccinellid larval mortality caused by the gregarious larval parasitoid, Homalotylus flaminius Dalman (Hymenoptera: Encyrtidae), on different host plant-aphid combinations was not significantly different within years (F3,33=0.48, P = 0.689, 2010; F3,9=0.06, P = 0.978, 2011; F2,6= 3.27, P = 0.1097, 2013; F2,6=1.08, P = 0.399, 2014) and ranged from 9.6 ± 1.98 to 36.3 ± 2.7% in larvae collected from mustard and safflower, respectively. The number of adult parasitoids emerging from single host larvae collected from different host plants varied significantly (F3, 72 = 12.9, P = 0.0001, 2010; F3, 56= 15.7, P = 0.0001, 2011; F2, 32=5.59, P = 0.0083, 2013; F2, 34=10.73, P = 0.0002, 2014) and ranged from 2.2 ± 0.11 on oleander to 7.1 ± 0. on safflower (Table 3).
Table 2
Percent mortality (Mean ± SE) of entomophagous coccinellids collected from different plant systems during 2010, 2011, 2013 and 2014 and reared on aphids feeding on Calotropis procera, Brassica campestris, Carthamus tinctorius, Hordeum vulgare, Eurica sativa, and Nerium oleander due to natural (& unknown) causes, and larval and pupal mortality due to parasitoids. The SE are calculated over time (collections)
Host plant | Natural mortality | Larval mortality | Pupal mortality | Total (n) |
2010 | | | | |
Calotropis procera & Aphis nerii | 7.5 ± 2.5 | 13.8 ± 5.0ab | 25.4 ± 11.3 | 46.7 (240) |
Brassica campestris & Lipaphis erysimi | 6.2 ± 2.5 | 9.6 ± 2.0b | 30.0 ± 11.9 | 45.8 (240) |
Carthamus tinctorius & Uroleucon compositae | 6.3 ± 1.3 | 15.8 ± 8.9ab | 28.3 ± 10.1 | 50.4 (240) |
Hordeum vulgare & Diuraphis noxia | 5.0 ± 2.16 ns | 17.1 ± 10.8a | 27.1 ± 15.0 ns | 49.1(240) |
2011 | | | | |
Calotropis procera & Aphis nerii | 36.3 ± 2.7 | 22.5 ± 2.1 | 31.3 ± 2.5 | 90.1 (80) |
Brassica campestris & Lipaphis erysimi | 41.25 ± 2.9 | 23.8 ± 2.2 | 27.5 ± 2.3 | 92.5 (80) |
Carthamus tinctorius & Uroleucon compositae | 33.8 ± 2.6 | 23.8 ± 2.2 | 36.3 ± 2.7 | 93.9 (80) |
Hordeum vulgare & Diuraphis noxia | 31.2 ± 2.5 ns | 25.0 ± 2.2 ns | 32.5 ± 2.5 ns | 88.7 (80) |
2013 | | | | |
Calotropis procera & Aphis nerii | 21.3 ± 2.9 | 21.3 ± 2.9 | 16.8 ± 2.7b | 59.4 (160) |
Nerium oleander & Aphis nerii | 21.3 ± 3.2 ns | 21.3 ± 8.8 ns | 24.4 ± 2.7a | 67 (160) |
Eurica sativa & Lipaphis erysimi | 20.0 ± 2.7 | 23.8 ± 3.0 | 21.9 ± 2.8ab | 71.9 (160) |
2014 | | | | |
Calotropis procera & Aphis nerii | 31.3 ± 3.8 | 20.0 ± 3.5 | 23.8 ± 2.4 | 75.1 (80) |
Nerium oleander & Aphis nerii | 25.0 ± 3.5 ns | 16.3 ± 3.2 ns | 22.5 ± 4.0 ns | 63.8 (80) |
Eurica sativa & Lipaphis erysimi | 26.3 ± 5.5 | 22.5 ± 4.3 | 23.8 ± 5.5 | 72.6 (80) |
Means ± SE followed by same letter in a vertical column are not significantly (P < 0.05) different from each other by LSD test. ns = non-significant. The ANOVA for each year was done separately. |
Table 3
Summary of larval and pupal parasitoid load and pupal weight of entomophagous coccinellids collected from different plant systems during 2010, 2011, 2013 and 2014.
Treatments | Year | No: of Larval parasitoids/Larva | Pupal weight(mg) | No: of Pupal parasitoids/ Pupa |
Calotropis (Calotropis procera) | 2010 2011 2013 2014 | 3.3 ± 0.1c 4.1 ± 0.1c 3.3 ± 0.5ab 3.6 ± 0.1b | 6.1 ± 5.7c 5.1 ± 0.1d 2.9 ± 01.9b 4.9 ± 1.8b | 11.5 ± 1.2c 7.61 ± 0.4d 8.4 ± 9.0b 17.8 ± 0.5b |
Oleander (Nerium oleander) | 2013 2014 | 2.5 ± 0.8b 3.3 ± 0.4c | 5.2 ± 1.8c 3.4 ± 1.2c | 18.5 ± 5.9a 12.4 ± 0.4c |
Mustard (Brassica campestris) | 2010 2011 | 4.3 ± 0.1a 5.7 ± 0.4b | 9.15 ± 0.7b 7.6 ± 0.1b | 23.0 ± 0.2b 18.3 ± 0.7b |
Rocket (Eurica sativa) | 2013 2014 | 4.1 ± 0.7a 3.9 ± 0.4a | 3.7 ± 1.8b 7.2 ± .8a | 10.4 ± 1.2b 30.8 ± 0.6a |
Safflower (Carthamus tinctorius) | 2010 2011 | 3.9 ± 0.1b 7.3 ± 0.8a | 11.2 ± 0.9a 8.4 ± 0.1a | 29 ± 2.1a 27.8 ± 0.7a |
Barley (Hordeum vulgare) | 2010 2011 | 3.3 ± 0.1c 3.8 ± 0.5c | 6.8 ± 0.3c 5.6 ± 0.2c | 13.9 ± 1.1c 10.7 ± 0.5c |
Means ± SE followed by same letter in a vertical column are not significantly (P < 0.05) different from each other by LSD test. The ANOVA for each year was done separately. |
Coccinellid Pupal Weights
The weight of coccinellid pupae reared on different host plant-aphid combinations varied significantly (F3, 125=15.9, P = 0.0001, 2010; F3, 72=12.9, P = 0.0001, 2011; F 2,108=15.38, P = 0.0001, 2013; and F2, 36=25.31, P = 0.0001 2014) and ranged from 2.9 ± 01.91 on calotropis to 11.20 ± 0.90 mg on safflower. Mortality caused by the gregarious pupal parasitoid, Oomyzus scaposus (Thomson) (Hymenoptera: Eulophidae), on different host plants did not differ significantly within years (F3, 33=1.82, P = 0.698, 2010; F3, 9= 0.65, P = 0.601 2011; F2, 6=4.67, P = 0.0599, 2013; F2, 6=0.04, P = 0.963, 2014) and ranged between 16.8 ± 2.7 on calotropis to 41.3 ± 2.9% on mustard. The number of adult O. scaposus emerging from each pupa varied significantly (F3, 125=26.4, P = 0.0001, 2010; F3,100=247.0, P = 0.0001, 2011; F2,108=23.5 P = 0.0001, 2013; F2, 36=18.78, P = 0.0001, 2014) and ranged from 7.6 ± 0.4 parasitoids per pupa on calotropis to 30.8 ± 0.6 on rocket. The relationship between pupal weight and number of parasitoids per coccinellid pupa was significant in most cases and larger pupae typically supported more parasitoids than smaller pupae (Table 4). In 2010, a single Dinocampus coccinellae Schrank (Hymenoptera: Braconidae) was reared from a coccinellid collected on safflower.
Table 4
Linear regression equations of coccinellid pupal weight (x) and number of parasitoids/ pupa (Y) for Calotropis procera, Brassica compestris, Carthamus tinctorius, Hordeum vulgare, Eurica sativa, and Nerium oleander when used as host plant of Aphis nerii, Lipaphis erysimi, Uroleucon compositae and Diuraphis noxia. All regressions are significant (at P < 0.05) except for C. procera in 2014.
Relation between pupal weight and No. of parasitoids per pupa | Linear regression equations | Determination coefficients |
Calotropis procera | 2010 | Y = 4.3273x − 14.417 | R2 = 0.7713 |
2011 | y = 2.3098x − 4.0581 | R² = 0.8714 |
2013 | y = 2.5776x − 5.4522 | R² = 0.8102 |
2014 | y = -0.0351x + 18.193 | R² = 0.0005 |
Brassica campestris | 2010 | y = 2.2059x + 4.8161 | R² = 0.7486 |
2011 | y = 4.8663x − 18.711 | R² = 0.8501 |
Carthamus tinctorius | 2010 | y = 3.8717x − 12.356 | R² = 0.8474 |
2011 | y = 4.589x − 10.805 | R² = 0.7587 |
Hordeum vulgare | 2010 | y = 3.8717x − 12.356 | R² = 0.8474 |
2011 | y = 2.8692x − 5.4169 | R² = 0.7926 |
Eurica sativa | 2013 | y = 4.3863x − 5.3811 | R² = 0.7904 |
2014 | y = 5.2347x − 7.1736 | R² = 0.5927 |
Nerium oleander | 2013 | y = 4.9366x − 5.3362 | R² = 0.7486 |
2014 | y = 3.1201x + 1.9747 | R² = 0.8736 |
Table 5
Influence of host plant- prey combination on adult weight (mg) of coccinellids
Coccinellids | Brassica compestris | Eurica sativa | Hordeum vulgare | Nerium oleander | Calotropis procera |
Menochilus sexmaculatus F. | 11.0 ± 0.5c | 9.9 ± 0.8c | 7.5 ± 0.6d | 18.4 ± 0.7a | 14.7 ± 0.4b |
Coccinella septempunctata L. | 27.1 ± 0.7a | 21.2 ± 0.8b | 19.9 ± 1.0b | | |
Coccinella undecimpunctata L. | 32.4 ± 1.0a | 24.9 ± 0.5b | 26.2 ± 1.5b | | |
Brumus suturais F. | 5.0 ± 0.5a | | 4.2 ± 0.3a | | |
Means ± SE followed by same letter in horizontal rows are not significantly (P < 0.05) different from each other by LSD test. |
|
|
Coccinellid Adult Weights
Significant differences in adult weights were recorded, depending on the host plant-aphid combination. At eclosion, M. sexmaculatus adults fed with aphids from Nerium oleander were significantly (F4, 45=43.8, P = 0.0001) larger than those fed with aphids from other host plants. Cocinella septempunctata adults fed on aphids from Brassica campestris were significantly (F2, 27= 19.5, P = 0.0001) heavier than other host plant-aphid combinations. Adults of C. undecimpunctata reared on B. campestris were significantly (F2, 27=9.04, P = 0.001) larger than adults reared on other aphid-host plant combinations. There was no significant (F1, 18=2.19, P = 0.1565) difference in adult weight of B. suturalis fed with aphids reared on either B. campestris or H. vulgare.