Tag Archives: rice fields

In Greece, Spraying Mosquitos Makes Life Bearable

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mosqueto

Mosquito Biting Human

Greece has a long history of mosquito-borne diseases (malaria, dengue fever) and there is scientific evidence that some inhabitants have contracted West Nile virus. Especially in Northern Greece where the majority of wetlands and rice fields are located, inhabitants and visitors suffer from an unbearable mosquito nuisance every year for more than 5 months (May – September) and counts of 150-200 mosquito bites per 15 minutes are not unusual. A large-scale mosquito insecticide spray program makes life bearable.

“Wide area mosquito control projects involve survey and applications in natural, agricultural, periurban and urban environment.

A total of about 8,000 sampling stations are established every summer period and checked weekly for larval activity. In addition more than 25,000 private properties (houses and tourist installations) are visited and checked for breeding sites.

The main spraying applications (larviciding) are conducted by four Hiller UE-12E helicopter, and an Ultra Light Motorized (ULM) aircraft. Minor applications are conducted by 15 conventional spraying units, mounted on 4×4 trucks and one low volume fan sprayer unit mounted on a Unimog 4×4 vehicle. For various spot treatments mainly in urban and periurban environment, knapsack sprayers and granule applicators were used.

In total a mean of 100,000 ha are sprayed with larvicides every year. About 80% of this surface is aerially treated. Spraying frequency of rice fields varies considerably from one to five times while this of the natural systems rarely exceeds two times per season.

The positive results of the project are clearly reflected in surveys in the form of questionnaires the company has conducted in 1999 and 2006 in a sample of 1000 inhabitants in 15 communities of the Thessaloniki plain: In 1999 100% of the people considered the mosquito problem unbearable before the beginning of the control project, while 68% considered it medium, small or non-existent after its implementation. In 2006 the results were 48% and 84% respectively.”

Authors: Iatrou, G. and S. Mourelatos.
Affiliation: Ecodevelopment S.A.
Title: Mosquito control in Greece.
Source: International Pest Control. 2007. May/June:66-69.

Sustaining Water Resources in Asia Means Rice Growers Must Use Herbicides

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Rice Fields

Rice Fields

Flooding rice fields prevents certain weed species from developing and rice fields in Asia are major users of water resources. However, a looming water shortage in Asia means that rice growers will have to cut back on water use. Herbicides are being tested as a replacement for flooding for weed control in rice fields.

Currently, sustainability of water resources is of major concern, and declining water availability threatens the sustainability of traditional flood-irrigated rice ecosystems. In Asia, it is predicted that 17 million ha of irrigated rice areas may have “physical water scarcity” and 22 million ha areas may be subject to “economic water scarcity” by 2025. It is, therefore, no longer feasible to flood rice fields for better crop establishment and weed control.

“Aerobic rice, growing rice in non-saturated and non-puddled aerobic soil, is a promising water-wise technique of rice cultivation under the context of ever-mounting water scarcity. But weed menace continues to be a severe problem in aerobic rice systems resulting in up to 90% reduction in grain yield. When direct seeded, rice seeds germinate simultaneously with weed seeds without any “head start” over germinating weed seeds, and the initial flush of weeds is not suppressed by flooding. …Therefore, effective weed management in aerobic rice has become a serious challenge for researchers and farmers.

Eight commercial herbicide products were applied singly or as tank-mix or in sequence to evaluate their efficacy, rice selectivity and cost-effectiveness in aerobic rice. …Most of the herbicide treatments provided excellent weed control, and produced much higher net benefit than weedy or weed-free check. …Among the herbicide treatments, sequential application of Cyhalofop-butyl + Bensulfuron at early growth stage followed by Bentazon/MCPA at mid growth stage provided the highest weed control efficiency, productivity and net benefit. …Since manual weeding was not economic, herbicide rotation using the above chemicals may be recommended for effective weed management in aerobic rice.

In the present study, cost of different herbicide treatments ranged from RM 167 to RM 469 ha-1 depending upon the price and rate of application, while manual weed control required a high investment of RM 2500 ha-1 for season-long weed-free checks.

In our study, the net benefit of the herbicidal weed control was two to three times higher than that obtained from manual weed control. Hence, manual weeding is less remunerative than herbicidal control, and keeping aerobic rice field weed-free manually throughout the season is a losing concern, confirmed by many others.”

Authors: Anwar, P., et al.
Affiliation: Institute of Tropical Agriculture, Universiti Putra Malaysia
Title: Efficacy, phytotoxicity and economics of different herbicides in aerobic rice.
Source: Acta Agriculturae Scandinavica Section B – Soil and Plant Science. 2012. 62:604-615.

A floating Fungus Would Destroy Much of the World’s Rice Crop Without Fungicide Sprays

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Rice Field With Sheath Blight

Rice Field With Sheath Blight

Sheath blight is a disease of rice plants which is caused by a fungus that lives in the soil. When rice fields are flooded, the fungus floats to the top of the water and contacts rice plants; the fungus grows out and moves into the rice leaf. The fungus spreads across the water to adjacent plants. The fungus grows across touching plant parts. The flow of water and nutrients in the rice plant is interrupted and the leaf dies, reducing rice yield. Development of resistant cultivars has been slow, because resistance is linked to undesirable traits such as tall plant stature, late maturity, and poor milling quality. Research has shown that a single application of a fungicide provides almost season-long control of sheath blight.

“Sheath blight of rice, caused by the fungus Rhizoctonia solani, is an economically important rice disease that is occurring throughout the rice-producing areas in the world, including the southern United States. Significant losses in grain quality and yield may occur in severely infected rice fields. Despite its economic importance, there are no completely resistant rice cultivars against this fungal rice disease and control methods for sheath blight are limited to heavy usage of fungicides.”

Authors: Shrestha, B. K., et al.
Affiliation: Louisiana State University Agricultural Center, Baton Rouge
Title: Suppression of sheath blight development in rice and sclerotia germination of Rhizoctonia solani by rice-associated strains of Bacillus spp.
Source: Phytopathology. 2013. 103(Supplement 1)(5):S1.9