Infestation mechanisms of two woodborer species in the mangrove Sonneratia alba J. Smith in Kenya and co-occurring endophytic fungi

Insect damage on trees can severely affect the quality of timber, reduce the fecundity of the host and render it susceptible to fungal infestation and disease. Such pathology weakens or eventually kills the host. Infestation by two insect woodborer species (a moth and a beetle) is causing mortality of Sonneratia alba, a wide-ranging pioneer mangrove species of the Indo-Pacific. Establishing the infestation mechanism of the two insect woodborer species is an initial and essential step towards understanding their ecological role in the mangroves and in determining sustainable management priorities and options. Our main objectives were to investigate the infestation mechanism employed by the two insect woodborers which infest S. alba trees, to establish the occurrence of secondary infestation by endophytic fungi in the infested S. alba branches, and to explore a control management option to the woodborer infestation. We conducted an external inspection of infested branches in two large embayments in Kenya, Gazi Bay and Mida Creek, and by splitting infested branches we determined the respective internal infestation mechanisms. Infested wood samples from Gazi Bay and Mida Creek were incubated at 28±1°C for 3–5 days to establish the presence of fungi. A survey was conducted in both Gazi Bay and Mida Creek to ascertain the presence of ants on S. alba. The infestation characteristics of the two insect woodborer species were different. It took 6–8 months for the beetle to kill a branch of 150 cm—200 cm long. For the moth to kill a branch, it depended upon several factors including the contribution by multiple species, other than the moth infestation alone. A total of 15 endophytic fungal species were identified. Two ant species Oecophylla longipoda and a Pheidole sp. inhabited 62% and 69% respectively of sampled S. alba trees in Gazi Bay whereas only Pheidole sp. inhabited 17% of the sampled S. alba trees in Mida Creek. In summary, we have documented the time it takes each woodborer species to kill a branch, the infestation mechanism of the two insect woodborers, and we hypothesized on the role of two ant species. The presence of several different fungal species was ascertained, and we discussed their possible role in the infested wood. Our results cannot unambiguously associate the woodborers and identified fungi. We recommend further studies to investigate the presence or absence, and if present, the nature of fungi in the gut of the woodborers.

Pattern recognition-based optical technique for non-destructive detection of Ectomyelois ceratoniae infestation in pomegranates during hidden activity of the larvae

In this research, the feasibility of utilizing visible/near-infrared (Vis/NIR) spectroscopy as an optical non-destructive technique combined with both supervised and unsupervised pattern recognition methods was assessed for detection of Ectomyelois ceratoniae, carob moth, infestation in pomegranates during hidden activity of the larvae. To this end, some fruits were artificially contaminated to the carob moth larvae. Vis/NIR spectra of the blank samples and the contaminated pomegranates without and with external visual symptoms of larvae infestation were analyzed one and two weeks after contaminating the samples as three groups of "Healthy", "Unhealthy-A" and "Unhealthy-B", respectively. Principal component analysis (PCA) as unsupervised pattern recognition method was used to verify the possibility of clustering of the pomegranate samples into the three groups. Discriminant analysis (DA) based on PCA was also used as a powerful supervised pattern recognition method to classify the samples. The calibration models of linear, quadratic and Mahalanobis discriminant analyses were developed based on different spectral pre-processing techniques. The best PCA-DA model was obtained using Mahalanobis distance method and first derivative (D1) pre-processing. The total percentage of correctly classified samples with the best calibration model was 97.9%. The developed model could also predict unknown samples with total percentage of correctly classified samples of 90.6%. It was concluded that Vis/NIR spectroscopy combined with pattern recognition method of PCA-DA can be an appropriate and rapid technology for non-destructively screening the pomegranates for detection of carob moth infestation during hidden activity of the larvae.

Wide Ranging Insect Infestation of the Pioneer Mangrove Sonneratia alba by Two Insect Species along the Kenyan Coast

Insect infestation of mangroves currently threatens mangrove forest health and management. In the Western Indian Ocean region, little is known about insect damage to mangroves despite the fact that numerous infestations have occurred. In Kenya, infestations of Sonneratia alba have persisted for almost two decades, yet the taxonomic identity of the infesting pest(s), the extent of infestation, the pests’ biology, the impacts of infestation on host and the ecosystem, the host’s defensive strategies to the infestation are poorly understood. S. alba is a ubiquitous, pioneer mangrove species of the Indo-Pacific, occurring along the waterfront in a variety of mangrove ecosystem settings. Our main objectives were to identify the pest(s) responsible for the current dieback of S. alba in Kenya, and to determine the extent of infestation. To identify the pests responsible for infestation, we trapped emergent insects and reared larvae in the laboratory. To determine the overall extent of infestation within the S. alba zone, we assessed nine sites along the entire Kenyan coastline for the presence or absence of infested mangroves. Insect infestation in two mangrove embayments (Gazi and Mida) was quantified in depth. Two wood-boring insects were identified: a metarbelid moth (Lepidoptera, Cossoidea) of undescribed genus and the beetle Bottegia rubra (Cerambycidae, Lamiinae).The metarbelid moth infests mangroves in both northern (from Ngomeni to Kiunga) and southern regions (from Vanga to Mtwapa) of the Kenyan coast. B. rubra appeared in low density in Gazi, and in high density in Mida, Kilifi, and Ngomeni, with densities gradually decreasing northward. Insect infestation levels reached 18% in Gazi and 25% of S. alba stands in Mida. Our results indicate that B. rubra has the ability to infest young mangrove trees and expand its range, posing a danger to rehabilitation efforts where plantations have been established. Thus, there is great need for forest managers to address the recent increased levels of infestation in Kenyan mangroves; apart from the ecological interest such plant-herbivore relations bring in this ecosystem.

Assessment of geographic and host-associated population variations of the carob moth, Ectomyelois ceratoniae, on pomegranate, fig, pistachio and walnut, using AFLP markers

The carob moth, Ectomyelois ceratoniae (Zeller 1839) (Lepidoptera: Pyralidae) is the most important pest of pomegranate, Punica granatum L. (Myrtales: Ponicaceae), in Iran. In this study, 6 amplified fragment length polymorphism primer combinations were used to survey the genetic structure of the geographic and putative host-associated populations of this pest in Iran. An AMOVA was performed on test populations. Pairwise differences, Mantel test, multidimensional analysis, cluster analysis and migration rate were calculated for 5 geographic populations of E. ceratoniae sharing the same host, pomegranate. In another part of the study, 3 comparisons were performed on pairwise populations that were collected on different hosts (pomegranate, fig, pistachio and walnut) in same geographic regions. The results showed high within population variation (85.51% of total variation), however geographic populations differed significantly. The Mantel test did not show correlations between genetic and geographic distances. The probable factors that affect genetic distances are discussed. Multidimensional scaling analysis, migration rate and cluster analysis on geographic populations showed that the Arsanjan population was the most different from the others while the Saveh population was more similar to the Sabzevar population. The comparisons didn't show any host fidelity in test populations. It seems that the ability of E. ceratoniae to broaden its host range with no fidelity to hosts can decrease the efficiency of common control methods that are used on pomegranate. The results of this study suggest that in spite of the effects of geographic barriers, high within-population genetic variation, migration rate and gene flow can provide the opportunity for emerging new phenotypes or behaviors in pest populations, such as broadening host range, changing egg lying places, or changing over-wintering sites to adapt to difficult conditions such as those caused by intensive control methods.

Ecology of aphidophagous predators in pomegranate ecosystem in India

The aphid, Aphis punicae Passerini (Homoptera : Aphididae) is a serious pest attacking pomegranate (Punica granatum L.), an important semi arid fruit crop grown widely in most parts of the country. The major predators found preying on A. punicae in pomegranate ecosystem were Cheilomenes sexmaculata (Fabricius), Scymnus sp., Pseudaspidemerus circumflexo (Motsch.), Paragus serratus (Fabricius), Ischiodon scutellaris (Fabricius) and Chrysopa sp. The population dynamics and spatial distribution of these predators in an unsprayed pomegranate ecosystem were studied at Indian Institute of Horticultural Research, Bangalore (12 degrees 58' N; 77 degrees 35'E), India during 2000-2002. The predators were found to be distributed uniformly among different tree quadrants and followed the same distributional pattern of A. punicae during their peak in January and February. The predator density was relatively higher in lower canopies than upper canopies. The spatial distribution of predators showed aggregate distribution pattern at higher mean densities and exhibited regular or under-dispersed distribution at lower mean densities. The temporal distribution of aphidophagous predators on A. punicae showed two peaks one during January - February and second during August - September The population of predators started building up along with aphid population and reached maximum at high aphid densities and declined as the prey availability declined. This indicated that predators followed the same trend of their prey, A. punicae, showing a clear numerical response.

Epizootics of an entomopathogenic fungus Entomophthora aphidis Hoggman on the pomegranate aphid aphispunicae passerini (Homoptera: Aphididae)

Thrips of late are becoming more resurgent in agro-ecosystems especially in India and South Asian countries. One of the reasons attributed is the development of resistance in them to groups of insecticides of organo phosphates, carbamates, synthetic pyrethroids, etc., which form the core of recommendation for thrips management. The chilli thrips, Scirtothrips dorsalis Hood, is no exception and is tending to be an unmanageable pest. In S. dorsalis, besides evidence of resistance, elimination of natural enemies like Orius sp. is evident, which also probably explains the thrips resurgence. Scirtothrips dorsalis is highly polyphagous and of late has become serious on grapes. The damage is manifested as scab on fruit rind, affecting internal and export markets. Fortunately, it does not vector any virus on grapes in India. Farmers have been reporting inefficacy of established chemicals like acephate, dimethoate, monocrotophos, etc. As grapes is an important cash crop of horticulture, management through insecticides, require alternate or new insecticides. So two trials in 2005 on cv. Bangalore Blue following April and October prunings were conducted at the Indian Institute of Horticultural Research (IIHR), Bangalore, S. India to evaluate two doses of a newer molecule viz. Clothianidin [Dantop] on S. dorsalis. Clothianidin 0.006%, Clothianidin 0.008% were compared with monocrotophos 0.05%, dimethoate 0.06% and acephate 0.1125%. There was an untreated check. Each treatment was replicated five times; a vine constituted a replicate. These data were subjected to ANOVA, after arc sine transformation. The critical difference (CD) at p < 0.05 was the test criterion. In the first trial it was found that all the insecticides tried were superior to check and were on par at p < 0.05. However, Clothianidin 0.008% gave the best control with a low mean of 0.26% berry damage/bunch as compared to 4.42% in the unsprayed check. The trend was the same in the second trial also with Clothianidin 0.008% giving the best control with 0.64% berry damage/bunch as compared to 8.49% in the unsprayed check. It was on par with acephate and monocrotophos, but significantly superior to Clothianidin 0.006% and dimethoate.