Effect of Abiotic Factors on the Incidence of African Rice Gall Midge, Orseolia oryzivora and its Parasitism by Platygaster diplosisae and Aprostocetus procerae

African rice gall midge (AfRGM), Orseolia oryzivora is one of the most damaging insect pests of lowland rice in Nigeria in the recent time, and could result in total crop failure in endemic areas. Of all the control measures adopted so far biological control is the most promising. Two parasitoids (Platygaster diplosisae, Hym: Platygastridae and Aprostocetus procerae, Hym: Eulophidae) have been identified with the potential to suppressed AfRGM population. In the current study, we evaluated the effect of abiotic factors (rainfall, relative humidity and temperature) in two eco-sites for two years on the incidence of AfRGM, and on the efficiency of the two parasotioids in the management of AfRGM. The incidence of AfRGM was significantly influenced by abiotic factors (rainfall, relative humidity and temperature). The percentage infestation increased with increase in rainfall and relative humidity. The trend was similar at both locations with the highest infestation recorded in October, and decreased in November. At both locations, percentage tiller infestation was greater in the rainy season of 2006 with more frequent rains than in 2007, with highest infestation recorded at Edozhigi in both years. Percentage parasitisms by the two parasitoids were found to have significant correlation with the abiotic factors. Heavy rains and high humidity significantly reduced the efficiency of the two parasitoids. On the contrast, the population and efficiency of the parasitoids were observed to increase with reducing rainfall, RH, but increasing temperature thus increasing the efficiency of the parasitoids later in the season with up to 70% parasitism when combined, with P. diplosisae dominating the field. The results suggest that abiotic factors played significant role on the incidence of AfRGM and the efficiency of these parasitoids and should be considered in the adoption of these parasitoids as bio-control agents of AfRGM. Keywords: Orseolia oryzivora, Platygaster diplosisae, Aprostocetus procerae, abiotic factor

Comparative studies of drying methods on the seed quality of interspecific NERICA rice varieties (Oryza glaberrima x Oryza sativa) and their parents

Seed moisture content (MC) is a key component that determines storability of germplasm conserved in seed genebanks. The purpose of this research was to compare the efficiency of sun-, shade-, silica geland conventional room drying in terms of rice seed MC and viability using seeds of two interspecific progenies (NERICA 1 and NERICA 3) and their parents Oryza glaberrima and O. sativa varietiesharvested 15 days before, at and 15 days after mass maturity. Sun drying most significantly reduced MC (4-5%) and was comparable with silica gel drying regardless of the variety tested and the maturity stageat harvest. Likewise, sun drying gave the best germination percentages followed by silica gel. Shade and room drying did not significantly lower MC and led to poor germination, especially when rice washarvested prematurely. Except for the sativa variety, harvesting prematurely resulted in no germination. In contrast, the initial germination percentages in all tested varieties improved as rice was harvested at or after mass maturity rather than 15 days earlier. Though comparable to sun drying, silica gel may not be readily available and affordable for resource-limited seed storage facilities. In this case sun drying was found an effective and affordable method for short-term storage, especially farm-saved seeds

A simple head cage technique for monitoring sorghum midge (Diptera: Cecidomyiidae)

A head cage technique for monitoring populations of Stenodiplosis sorghicola, a variant of the type previously described for screening sorghum genotypes for resistance, was developed. The technique was effective and efficient in collecting adults from flowering sorghum panicles under field conditions in Andhra Pradesh, India. Adults emerged over 2-3 weeks during the 1992-93 post-rainy and 1-2 weeks during the 1993 rainy season. The activity (density) of S. sorghicola was higher during the rainy than during the post-rainy seaso

Tritrophic interactions in sorghum, midge (Stenodiplosis sorghicola) and its parasitoid (Aprostocetus spp.)

Studies were conducted on tritrophic interactions involving sorghum genotypes, Stenodiplosis sorghicola and the predominant parasitoids (Aprostocetus spp.) in Patancheru, Andhra Pradesh, India, using three midge resistant (ICSV 745, ICSV 89058 and IS 10712) and three susceptible (Swarna, CSH 9 and ICSV 112) genotypes during the post-rainy (1992/93) and rainy (1993) seasons. A. coimbatorensis, the predominant parasitoid during post-rainy season, preferred mid-late midge larvae for parasitization, while A. gala, which was predominant during the rainy season, preferred early-mid larval stages. Variations in the preference of A. coimbatorensis and A. gala for the developmental stage of their host larvae indicated good prospects for the biological control of sorghum midge populations. There were significant differences in parasitization level of midge by Aprostocetus spp. between resistant and susceptible sorghum genotypes, and season. Higher parasitization was observed on susceptible genotypes than on resistant ones during both post-rainy and rainy seasons. However, the level of parasitization was greater in post-rainy than in rainy seasons. There was also evidence of higher midge infestation in rainy than in post-rainy seasons. Susceptible genotypes attracted more parasitoids because of high levels of midge infestations. Low parasitoid density in midge resistant sorghum under glasshouse and field conditions was associated with low midge infestations in these genotypes. However, parasitoids were always associated with their host in spite of low midge densities in resistant genotypes. The present study revealed that the interaction between host plant resistance and parasitoids of sorghum midge would thus be synergistic and complementary and could result in successful integration of these two important pest management tactics

Emergence pattern of sorghum midge and its major parasitoids on midge-resistant and susceptible genotypes

Studies were conducted on the species composition of parasitoids of Stenodiplosis sorghicola, emergence pattern and level of parasitism. The studies were carried out in Andhra Pradesh, India, with three midge-resistant (ICSV 745, ICSV 89058 and IS 10712) and three susceptible (Swarna, CSH 9 and ICSV 112) sorghum genotypes during the 1992-93 post-rainy and 1993 rainy seasons. The species of parasitoids collected were Aprostocetus gala, A. coimbatorensis and Eupelmus spp. The species composition varied with the season, but was unaffected by varietal resistance and susceptibility to the midge. Although both species of Aprostocetus were present in rainy and post-rainy seasons, A. gala was predominant during the rainy season whereas A. Coimbatorensis was predominant in the post-rainy season. There was no significant difference in the pattern of parasitoid emergence or the level of midge parasitization between resistant and susceptible genotypes. These results indicate that resistance to midge in the genotypes studied was not antagonistic to parasitoid activity, and that there is potential to interface biological control with host-plant resistance in the management of this insect

Effects of biofertilizer containing N-fixer, P and K solubilizers and AM fungi on maize growth: A greenhouse trial.

An in vitro study was undertaken to evaluate the compatibility of indigenous plant growth promoting rhizobacteria (PGPR) with commonly used inorganic and organic sources of fertilizers in tea plantations. The nitrogenous, phosphatic and potash fertilizers used for this study were urea, rock phosphate and muriate of potash, respectively. The organic sources of fertilizers neem cake, composted coir pith and vermicompost were also used. PGPRs such as nitrogen fixer; Azospirillum lipoferum, Phosphate Solubilizing Bacteria (PSB); Pseudomonas putida, Potassium Solubilizing Bacteria (KSB); Burkholderia cepacia and Pseudomonas putida were used for compatibility study. Results were indicated that PGPRs preferred the coir pith and they proved their higher colony establishment in the formulation except Azospirillum spp. that preferred vermicompost for their establishment. The optimum dose of neem cake powder

Fecundity and Diurnal Oviposition Behaviour of Sorghum Shoot Fly, Atherigona soccata Rondani (Diptera: Muscidae)

The fecundity and diurnal oviposition behaviour of Atherigona soccata was studied on CSH 5, a susceptible sorghum genotype, under greenhouse conditions. The fecundity of females deprived of 10-day-old sorghum seedlings was drastically reduced, and no fertile eggs were laid after 11 days of host deprivation. However, when the females were provided with host plants, egg production was prolonged, and fell considerably after the flies reached 22 days of age. There were three distinct peaks (6-7, 13-14 and 18-19 days of age) in egg-laying activity. Further studies with flies of three age groups (7, 13 and 19 days old) did not show significant differences in diurnal oviposition pattern with age. However, most eggs (60%) were laid between 08.00 and 12.00 h. It was evident from the present study that the prolonged egg-laying capacity of female A. soccata when provided with a susceptible host may partly account for the dramatic increase in damage as the crop season advances, since there would be a geometric increase in active females with every new generation of flies

Effect of Beauveria bassiana and Metarhizium anisopliae on the adult African rice gall midge (AfRGM – Orseolia oryzivora)

Published online: 06 Nov 2019Rice is an important staple crop whose production is limited by array of insect pests and diseases. African rice gall midge (AfRGM) Orseolia oryzivora Harris & Gagné (Diptera: Cecidomyiidae) is a major insect pest of lowland rice ecology in Africa. Heavy yield losses have been recorded in many farmers’ rice fields. Use of synthetic insecticides has fostered environmental and human health concern that initiates a search for alternative control measures such as Entomopathogenic fungi (EPF) – Beauveria bassiana and Metarhizium anisopliae. The experiment was laid out on completely randomised design (CRD) with three replications. The study showed M. anisopliae IC30 had the greatest control effect on adult AfRGM with 90.58% of non-infested tillers. The percentage of non-infested tiller advantage over the control followed the same trend with M. anisopliae IC30 having the greatest value of 50.72%. Tiller infestation had significant negative correlation with chlorophyll content, leaf breadth and grain number