Comparative Biology of Coconut Leaf Beetle (Clb) Brontispa longissimi (Gestro) (Coleoptera: Chrysomelidae) on Selected Coconut Varieties

Comparative biology and development study of B. longissima Gestro was conducted using different coconut varieties namely: Baybay tall (BAYT) green, Baybay tall (BAYT) brown, Malayan Red dwarf (MRD), Malayan Yellow dwarf (MYD), Albuera dwarf (ALD), and Tacunan dwarf (TACD) varieties was investigated in the laboratory. The duration of the developmental period of B. longissimi was influenced by the different coconut varieties used as host plant. Duration from egg laying to hatching of eggs of B. longissima on tall varieties ranged from 3 to 5 days, while on dwarf varieties it took 4 to 5 days. In all varieties, Brontispa beetles underwent 5–6 instars. In addition, it was observed that the fifth and sixth instars took a longer time period compared to other instars. The total mean developmental period of Brontispa on BAYT (green and brown) was shorter in days compared to all dwarf varieties except to ALD. The results generally showed that BAYT (green and brown) seemed to be a preferred variety. There was considerably higher larvae mortality in dwarf variety like MRD (40%) than those reared in the BAYT green and brown (22.21%, 19.12%), respectively. Beetles reared on BAYT (brown) also had the highest fecundity which was statistically different from the rest of the varieties. In addition, results showed that adults reared in both BAYT (green and brown) had the highest longevity observed compared to other varieties

Biology of Red Palm Mite, Raoiella indica, on Different Coconut Varieties

Red palm mite, Raoiella indica Hirst (Acari: Tenuipalpidae), has emerged as a new threat to coconut plantation in Indonesia. To control this mite, understanding on its biology is essential. The effects of three coconut varieties (Salak Dwarf, Local Sumenep Tall, and Hybrid coconuts) on the development and fecundity of R. indica were determined under laboratory conditions at 26−28oC, 80% RH, and photoperiod of 12:12 (L:D). The life cycle of R. indica consisted of the egg, larva, protonymph, deutonymph, and adult stages. Total development time of immature females was significantly influenced by coconut varieties. The shortest immature developmental time occurred at Salak Dwarf variety (26.07 days), whereas no significant difference of development time of immature female on Hybrid and Local Sumenep Tall varieties was found. Moreover, there was also no significant difference on the development time of immature male and on the fecundity of the mite among different coconut varieties. IntisariTungau merah kelapa, Raoiella indica Hirst (Acari: Tenuipalpidae), merupakan ancaman baru bagi perkebunan kelapa di Indonesia. Pemahaman mengenai biologi diperlukan untuk strategi pengendalian tungau tersebut di masa datang. Pengaruh tiga varietas kelapa yang berbeda (Genjah Salak, Lokal Sumenep, dan Hibrida) terhadap perkembangan dan keperidian R. indica diamati pada kondisi laboratorium dengan suhu 26−28oC, kelembapan nisbi 75−85%, serta pencahayaan 12 jam terang dan 12 jam gelap (L:D=12:12). Siklus hidup tungau terdiri dari telur, larva, protonimfa, deutonimfa, dan dewasa. Hasil pengujian menunjukkan bahwa waktu perkembangan betina pradewasa dipengaruhi secara nyata oleh varietas kelapa. Waktu perkembangan paling pendek terdapat pada kelapa Genjah Salak (26,07 hari), sedangkan waktu perkembangan betina pradewasa tidak berbeda nyata pada kelapa Hibrida dan Dalam Lokal Sumenep. Hasil lain pengujian menunjukkan tidak terdapat perbedaan nyata waktu perkembangan jantan pradewasa dan keperidian pada ketiga varietas.

Effects of Short-Day and Gibberellic Acid Treatments on Summer Vegetative Propagation of Napier Grass (Pennisetum purpureumSchumach)

The effects of short-day (SD) and gibberellic acid (GA3) treatments on promoting vegetative propagation during the summer were examined in Napier grass (Pennisetum purpureumSchumach). A dwarf variety of late heading type (DL) Napier grass was exposed to three SD treatments (5, 10, and 20 short days plus a spray of 400 ppm GA3solution following each SD treatment, GASD) or no treatment (control). Additionally, then, a dwarf variety of early heading (DE) and the normal variety of Merkeron (ME) were exposed to 10 days of GA-SD treatment together with nontreated controls. For DL and DE, GA-SD treatments showed the following effects: 10-day GA-SD treatment increased significantly (P<0.05) the length of lateral tiller buds, maintained a high rooting percentage, and increased the diameter of the tiller buds. This resulted in a taller plant, one with enhanced tiller numbers, and thus a greater number of established nursery plants for the two dwarf varieties. In contrast, there was only a limited positive effect of the GA-SD treatments on the normal variety, ME. Thus, 10 days of GA-SD treatment was judged to be the most effective treatment for promoting lateral tiller bud elongation and early maturation in tiller buds for the two dwarf varieties of Napier grass.

Specifics of soil temperature under winter oilseed rape canopy

The aim of this study was to evaluate the course of soil temperature under the winter oilseed rape canopy and to determine relationships between soil temperature, air temperature and partly soil moisture. In addition, the aim was to describe the dependence by means of regression equations usable for pests and pathogens prediction, crop development, and yields models. The measurement of soil and near the ground air temperatures was performed at the experimental field Žabiče (South Moravia, the Czech Republic). The course of temperature was determined under or in the winter oilseed rape canopy during spring growth season in the course of four years (2010 - 2012 and 2014). In all years, the standard varieties (Petrol, Sherpa) were grown, in 2014 the semi-dwarf variety PX104 was added. Automatic soil sensors were positioned at three depths (0.05, 0.10 and 0.20 m) under soil surface, air temperature sensors in 0.05 m above soil surfaces. The course of soil temperature differs significantly between standard (Sherpa and Petrol) and semi-dwarf (PX104) varieties. Results of the cross correlation analysis showed, that the best interrelationships between air and soil temperature were achieved in 2 hours delay for the soil temperature in 0.05 m, 4 hour delay for 0.10 m and 7 hour delay for 0.20 m for standard varieties. For semi-dwarf variety, this delay reached 6 hour for the soil temperature in 0.05 m, 7 hour delay for 0.10 m and 11 hour for 0.20 m. After the time correction, the determination coefficient (R2) reached values from 0.67 to 0.95 for 0.05 m, 0.50 to 0.84 for 0.10 m in variety Sherpa during all experimental years. For variety PX104 this coefficient reached values from 0.51 to 0.72 in 0.05 m depth and from 0.39 to 0.67 in 0.10 m depth in the year 2014. The determination coefficient in the 0.20 m depth was lower for both varieties; its values were from 0.15 to 0.65 in variety Sherpa. In variety PX104 the values of R2 from 0.23 to 0.57 were determined. When using multiple regressions with quadratic spacing (modelling of hourly soil temperature based on the hourly near surface air temperature and hourly soil moisture in the 0.10-0.40 m profile), the difference between the measured and modelled soil temperatures in the depth of 0.05 m was -3.92 to 3.99°C. The regression equation paired with alternative agrometeorological instruments enables relatively accurate modelling of soil temperatures (R2 = 0.95).

COCONUT BISEXUAL FLOWERS AND THEIR SIGNIFICANCE FOR HYBRID SEED GARDENS

Among the tall and dwarf varieties of coconut as well as the hybrids between them, occasionally one comes across hermaphro­dite or bisexual flowers. Some indNridual palms produce a high percentage of hermaphrodite flowers while a great majority of others do not produce any bisexual flower at all. There is clear evidence that coconut flowers at the primordial stage are bisexual with the potential. to develop both stamens and pistils in the same flower. But at a later stage of development, one grows into a female flower whose male organs are reduced to a ring of six staminodes. Another develops into a staminate flower whose pistils are reduced to three pistillodes. However, due to genetic, ecological, physiological or other factors, some unisexual. flowers show an atavistic display of hermaphroditisin. Bisexual flowers are observed among tall. and dwarf variety palms. The negligible percent­age of bisexual flowers that occur in large estates where the fruits are not used as seeds has no major disadvantage. But in seed gardens, especially where inter‑varietal hybrid seeds are produced, hermaphrodite flowers are capable of reducing the percentage of true hybrids. Timely removal of hermaphrodite flowers, therefore, would reduce the occurrence of undesirable true‑to‑mother type progeny and enhance the success of intervarietal hybridization.

Inter-plot competition in variety trials of field beans (Vicia faba L.)

SUMMARYFour trials were carried out to investigate the effect of inter-plot competition on seed yield and plant height of field beans using experimental designs balanced for neighbours. One trial tested four varieties ranging in final height from 25 to 100 cm and sown in four-row plots with 30 cm spacing between rows and one blank row between plots. When grown between plots of a dwarf variety, the plot yield of the tallest variety was increased by 20% compared with its pure stand yield: a complementary reduction in yield was shown by the dwarf variety when grown between plots of the tall. The effect on the yield of the inner rows of the plot was somewhat smaller than that of the outer rows but still significant. Another trial with six commercial varieties differing in final height by less than 15 cm showed no differential effects of inter-varietal competition on yield. In two trials with six varieties of widely differing heights planted with 50 cm spacing between rows, but no gap between plots, plot yield was strongly affected by the neighbouring variety in the trial with single-row plots, while yields from the four-row trial showed a large interaction between variety and inner and outer row position, again indicative of inter-variety competition. The yield response to competition could be described by a common linear regression on the excess height of plot neighbours: there was little evidence of varietal differences in sensitivity or aggressiveness.Plant height showed a positive response to height of plot neighbours in all four trials, whilst in the single-row trial, the ratio of grain yield to total dry-matter production (harvest index) was negatively related to excess height of neighbours.The results suggest that, when testing varieties differing in height by more than 20 cm, at least two buffer rows, e.g. six-row plots with the centre two rows harvested, are required to obtain a true comparison of pure-stand yield. Alternatively, when this procedure would result in an unacceptable use of resources, one of the statistical models adapted in this paper may be used to adjust variety yields for pure stands.