Leaf Surface Characteristics of Selected Malaysian Weed Species of Oil Palm

Laboratory and glasshouse studies were conducted to examine the leaf surface characteristics of selected weed species of oil palm. The broadleaf weeds selected were Asystasia gangetica, Borreria latifolia, Cleome rutidosperma, Clidemia hirta, Diodia ocimifolia and Mikania micrantha, while for the narrow leafs, Axonopus compressus, Cyperus kylingia, Eleusine indica, Paspalum conjugatum and Pennisetum polistachyon were investigated. The weeds were categorized into different types of roughness based on the macroscopic roughness, microscopic roughness and the estimation of three roughness parameters: Ra (arithmetic average height parameter), Rq (root-mean-square roughness parameter, corresponding to Ra), and Rz (average of high peaks and low valleys over the evaluation length). The leaf was examined using scanning electron microscopy (SEM) for the surface roughness, while the epicuticular wax content of the leaf was extracted using chloroform. The amount of wax extracted from the weeds varied between species. For broadleaf plants, Mikania micrantha (44.22 µg/cm2) was identified as the plant that contained the highest quantity of wax. Clidemia hirta (24.03 µg/cm2) and Asystasia gangetica (23.03 µg/cm2) were grouped in the plants with a medium quantity of wax while Cleome rutidosperma (16.52 µg/cm2), Borreria latifolia (14.19 µg/cm2) and Diodia ocimifolia (10.75 µg/cm2) were grouped in the plants with a low quantity of cuticular wax weight. For narrow leaf plants, Eleusine indica (44.23 µg/cm2) and Imperata cylindrica (49.88 µg/cm2) were recognized as the plants that contained a high quantity of wax. Pennisetum polystachion (32.16 µg/cm2) and Cyperus kylingia (22.85 µg/cm2) were categorized under the plants with a medium quantity of wax, whereas Paspalum conjugatum (19.59 µg/cm2) and Axonopus compressus (16.78 µg/cm2) were classified under the plant with a low quantity of wax. The wax on the abaxial surface data of the broadleaf weeds was found to be significantly different when compared to the adaxial surface data. In contrast, the amount of wax on the abaxial and adaxial leaf surface of the narrow leaf weeds was more or less similar. For the leaf surface roughness of the broadleaf species, Borreria latifolia was categorized as the roughest, followed by Clidemia hirta, Diodia ocimifolia, Asystasia gangetica and Cleome rutidosperma. Mikania micrantha had the smoothest leaf surface among the broadleaf species. On the other hand, the narrow leaf of Pennisetum polistachyon was identified as the roughest, followed by Imperata cylindrica and Paspalum conjugatum, while Eleusine indica, Axonopus compressus and Cyperus kylingia were categorized as having the smoothest leaf surface

Efficacy of Exserohilum longirostratum on barnyard grass (Echinochloa crus-galli spp. crusgalli) under field conditions.

An isolate of Exserohilum longirostratum obtained from Rottboelia cochinchinensis in Malaysia was highly pathogenic to barnyardgrass (Echinocloa crus-galli,) a serious weed in rice fields in Malaysia. In glasshouse trials, high levels of barnyardgrass control were achieved when E. longirostratum was applied as a conidial concentration at 105 conidia/mL. This conidial concentration may not be sufficient for field use; therefore, a mini plot trial was carried out to assess the bioherbicidal potential of the fungus and the efficacy of different inoculum types under field conditions. Excellent barnyard grass disease as indicated by Area Under Disease Progress Curve (AUDPC) was achieved with mycelium (AUDPC = 583.8 unit2); mycelium + pretichlaclor (AUDPC = 610.4 unit2) and conidia alone (AUDPC = 468.3 unit2) compared to conidia + pretichlaclor (AUDPC = 395.8 unit2). Although conidia caused lower disease severity on barnyard grass compared to mycelium, this inoculum equally reduced the competition from barnyard grass as indicated by lower mean dry weight and fewer barnyard grass tiller numbers. Positive correlations between AUDPC of rice and its tiller number and AUDPC of rice and its dry weight were recorded while negative correlations were observed for the AUDPC of barnyard grass and its tiller number and AUDPC of barnyard grass and its dry weight. These findings confirmed that E. longirostratum applied either in the form of conidia or mycelium was effective against barnyard grass under field conditions

Growth and development of oriental fruit fly, Bactrocera dorsalis hendel (Diptera: Tephritidae) reared on sweet potatoes (Ipomoea batatas L.) based artificial diet

A study to determine the growth and development of B. dorsalis reared on sweet potatoes-based artificial diet (Ipomoea batatas L.) was conducted under laboratory conditions. Four types of diets used were; orange sweet potato (OSP), purple sweet potato (PSP), white sweet potato (WSP) and wheat germ (WG) as a standard diet. Biological parameters recorded were; number of pupae, pupae weight (mg), pupae and adult survival (%), number of adult emergences, developmental time from eggs to adults’ stage (day), and adult longevity (day). Results showed that among the diet tested, the WG based diet displayed a significant difference (P<0.05) on the growth and development of B. dorsalis particularly on number of pupae, pupa and adult survival and developmental time from egg to adult. However, no significant difference (P>0.05) was shown on pupa weight between WG, OSP, and WSP diet. Adult longevity of B. dorsalis also showed no significant difference (P>0.05) among all the diets. Based on the results obtained, the growth and development of B. dorsalis reared on sweet potatoes based diet was as good as the standard wheat germ-based diet and showed a potential as a main new source of diets for B. dorsalis mass rearing especially in biological control program of the fruit flies