Population Dynamics of Sugarcane Moth Borers in Indonesian Cane Fields

We conducted monthly monitoring of lepidopterous moth borers in four sugarcane fields in Java, Indonesia, from May 2009 to May 2011. Fields sampled belonged to Pesantren Baru, Jombang Baru, Gondang Baru and Subang sugar factories. Three main moth borer species were found to inflict damage to sugarcane plantations in all regions, and these are the stalk borers Chilo sacchariphagus (Bojer) and Chilo auricilius Dudgeon and the top borer Scirpophaga excerptalis (Walker). Tetramoera (Eucosma) schistaceana (Snellen) was also encountered but only caused minor damage. Borer populations increased with plant age and reached a peak around January – May in most cases, with the onset of rainfall triggering population rise. All borers coexisted in the same plant with no evidence of competition between the two stalk borers (C. sacchariphagus and C. auricilius) over their specific feeding location (internode) or between the two stalk borers and the top borer (S. excerptalis) over the same plant. This suggests that an infestation by one species does not make the plant less desirable to be colonised by another. Parasitism rates by natural enemies were very low which reflects the challenges facing biological control efforts in Java. Knowledge generated through this project will improve our understanding of borer dynamics in South East Asia and will enhance our preparedness for potential introduction by any of these pests into Australia

Yield and Quality of Ratoon Sugarcane Are Improved by Applying Potassium under Irrigation to Potassium Deficient Soils

The current study was carried out at the experimental farm of Rana Sugars Ltd., Buttar Seviyan, Amritsar, Punjab, India, to identify methods to improve the yield and quality of ratoon sugarcane in potassium-deficient soils. The treatments comprised two levels of irrigation, resulting in plants which either received sufficient water (I1) or were water-stressed (I2), and four rates of potassium (K) application: 0 (K1), 40 (K2), 80 (K3) and 120 (K4) kg K2O ha−1. The results showed that the irrigation levels did not influence crop parameters significantly, although all parameters presented higher values for I1-treated plots. Compared to the K1 (i.e., 0 kg ha−1 K fertiliser applied) treatment, the K2, K3 and K4 treatments yielded 11.16, 37.9 and 40.7%, respectively, higher millable canes and 1.25, 5.62 and 13.13% more nodes per plant, respectively. At 280 days after harvest of the first (plant) crop, the I1 treatment provided ratoons which were up to 15.58% higher than those obtained with the I2 treatment, with cane girths up to 7.69% wider and yields up to 7.29% higher than those observed with the I2 treatment. While the number of nodes per plant did not differ significantly between treatments, there were significant differences in other parameters. Quality parameters (with the exception of extraction percentage) were significantly enhanced by the K3 treatment. The benefit-to-cost ratio (B/C) was higher for the I1 treatment than for the I2, due to a reduced productivity associated with the I2 treatment. At both irrigation levels, the K3 treatment resulted in the highest quality parameters. K1-, K2- and K4-treated plots presented more instances of insect infestations than plots receiving the K3 treatment. Relative to the K3 plots, infestation by the early shoot borer (Chilo infuscatellus) was 18.2, 6.0 and 12.2% higher, respectively, in plots that underwent the K1, K2 and K4 treatments, while infestation by the top borer (Scirpophaga excerptalis) was 21.2, 9.21 and 14.0% higher, and that by the stalk borer (Chilo auricilius) was 10.7, 0 and 8.10% higher. Not all infestation differences between treatments were significant. Our research demonstrates that growing sugarcane in potassium-deficient soils with applications of 80 kg K2O ha−1 under irrigation should be recommended to increase yield and quality while minimising insect infestation and to implement sustainable ratoon sugarcane production.

Evaluation of chemical pesticides for the management of Top Borer (Scirpophaga excerptalis Walker) in sugarcane

An experiment was conducted at research field of National Sugarcane Research Program, Jeetpur, Nepal in 2014 and 2016, to evaluate the efficacy of chemical insecticides against sugarcane top borer (Scirpophaga excerptalis Walker). Nine different treatments viz. Chlorantraniliprole 0.4 G, Cartap hydrochloride 4 G, Fipronil 0.3 G, Carbofuran 3 G (standard check) as soil application and foliar spray of Chlorantraniliprole 18.5 SC, Thiodicarp 75 WP, Spinosad 45 SC, Chlorpyrifos 20 EC (standard check) and one untreated check (control) were used in randomized complete block design with three replications. The top borer susceptible genotype, Co 0238 was planted on February and single application of these insecticides was done on July at brood stage against top borers. The lowest 10.65 and 12.43, 13.68, 14.61, 14.15 percentage of top borer damage was found in foliar application of Chlorantraniliprole @ 35g a.i. /ha followed by Spinosad @ 125g a.i. /ha and soil application of Cartap hydrochloride @ 1500g a.i /ha and foliar application of Thiodicarp @ 1500g a.i. /ha and Fipronil @ 100g a.i. /ha. The infestation percentage reduction over control was found highest in Chlorantraniliprole (69.40%) followed by Spinosad (64.29%) treated plots. Furthermore, the cane yield was highest in Chlorantraniliprole (92.30 mt/ha) and Spinosad (90.06 mt/ha) treated plots than that of other insecticide treated plots. The number of millable canes and cane diameter in the plots among the treatment was found non-significant. Based on the infestation reduction rate, foliar application of the chemical insecticide (Chlorantraniliprole 18.5 SC and Spinosad 45 SC) could be better option for chemical management of sugarcane top borer.

Screening of sugarcane genotypes against Top Borer (Scirpophaga exerptalis Walker) infestation

Fourty sugarcane genotypes with different period of maturity were evaluated against top borer (Scirpophaga excerptalis Walker) infestation under natural field condition during 2018 and 2019 at National Sugarcane Research Program, Jeetpur, Nepal. The experiment was conducted in alpha-lattice design under natural condition of infestation using Co 0238 as susceptible check. Based on the incidence, 26 genotypes were categorized as less susceptible, eleven genotypes were found moderately susceptible to S. excerptalis. However, among less susceptible genotypes lowest incidence of 3.11 percent was recorded in genotype CoS 8432. Whereas, highest incidence of 25.24 percent was recorded in highly susceptible genotype, CoSe 98255BD 24. Most of the cane genotypes were found low to moderately susceptible, having 5 to 20% incidence of the pest. Whereas, some of the varieties, namely CoH 160 (21.22%), CoSe 95255 BD 24 (25.24%) and BO 150 (22.02%) were found highly susceptible. The mechanism responsible for host plant resistance against top borer is not studied in this experimentation. The study in these aspects is to be conducted to explore the mechanisms of host plant resistance for using these resistant genotypes for breeding purpose.

A note on parasitisation of top borer by Isotima javensis Rohwer (Hymenoptera: Ichneumonidae)

Isotima javensis is a solitary ecto parasitoid of the sugarcane top borer, S. exceptalis. It attacks the prepupal stage and deposits an egg either on the prepupa or near its vicinity. The extent of parasitisation was observed 2.12%, 4.28%, 7.14%, 5.88% and 5.23 % in I, II, III, IV and V broods of top borer, respectively. The contribution of mortality of pupae of the top borer by parasitisation is high in III and IV broods (Aug-Oct), the time when the brood infestation remains generally very high. The maximum female ratio (59.72%) was observed in III brood of parasitisation followed by 55.20 % in IV brood. In I and II broods, however more or less equal number of males and females can be observed in the field. Equality in the sex ratio at this time ensures fertilisation of almost all the females for retaining the vigour and vitality of the species. The absence of unfertilized parasites naturally removes the chances of parthenogenetic reproduction and thus the number of females gradually rises in the succeeding season. It is concluded that there are several attributes of parasitoid i.e. specific parasite of top borer; its life cycle is much shorter than its host; active throughout the period of activity of the host and even it hibernates under north Indian conditions which make it a good biocontrol agent. It is suggested that parasitoid may be exploited in biological control programme, more detailed study is required for mass multiplication in the laboratory on an alternate host, release technique and survival in the sugarcane field.