Aphid outbreak, mungbean, Cambodia Minimize


February 2011. Cambodia asked how to control and outbreak of aphids on mung bean grown between rows of Jatropha.

Also, there was concern about mealybugs and ladybird beetles on Jatropha plants in another province. The block of Jatropha was established about a year ago and after about 4 months there was a problem with mealybugs which was controlled by EM mixed with garlic, chili and onion. A few months later the mealybugs returned, but so did the ladybird beetles in large numbers.

A report written by the FAO was also distributed on PestNet (below); this pointed out that for Jatropha to meet its 'pro-poor' objectives, international support was needed for research on genetic improvement of varieties, and on cultivation practices, such as water conservation and integrated pest and nutrient management".

Members of PestNet involved in Jatropha production agreed. It is a crop that has only relatively recently been brought into cultivation and there are bound to be problems with its commercialisation.

Unfortunately, yields are far lower than reported in the literature despite the provision of inputs and adequate rainfall for cultivation. In Vietnam, yields of 1.5 t/ha of seed were achieved after 2 years on relatively poor soils and moderate ranfall.

On the question of aphids on the mung bean, the following was suggested:

  • Imidacloprid (but there was concern that it might lead to broad mite attack because of its affect on beneficials).
  • Pymetrozine - very natural enemy-friendly and fits well into IPM strategies; it has anti-feeding activity which means the aphids starve to death, so they remain on the plants for 3-4 days (but they cause no damage because they stop feeding).
  • Overhead irrigation to wash off the aphids.
  • Dimethoate.
  • Do nothing (experience from south India suggests its best to let nature take its course). Ladybird beetles will probably attack the aphids if no chemicals are applied.
  • Collect the ladybeetles on the Jatropha with a sweep net and release on the mung beans. The handle of the sweep net should be about 1 m long, hollow aluminum or wooden. A firm wire frame about 30 cm across for the net is firmly attached to the handle; the fine mesh should be about 40 cm deep - at the worst, use a plastic bag. Sweep the net through the foliage and collect the ladybird beetles, and many other interesting things! Google 'insect sweep net' and you will get a better idea. Then transfer the ladybird beetles to a container that allows air exchange - 100 per 2 litre jar. Some foliage in the container is needed. Keep them in a cool box at say 15 degs., not too cool because they may get caught up in condensation inside the container. When releasing the ladybird beetles, try and end up with at least one per plant. If the ladybird beetles are in egg laying mode so much the better as the larvae are probably more voracious than the adults.
  • A method for raising the mealybug ladybird beetle Cryptolaemus montrouzieri in the lab and distributing the larvae was also mentioned.
It was pointed out that a number of aphids can be found feeding on mung bean. The more commonly found on mung bean, soybean and other legumes are: Aphis craccivora, Aphis glycine, Aphis gossypii, Myzus persicae and sometimes Toxoptera aurantii. As a layman entomologist, not an aphid taxonomist, from the picture you sent it looks like Aphis gossypii Glover. It is light green, polyphagous and normally found in dense colonies. M. persicae looks similar to A. gossypii but it does not congregate to the same extent.

A. craccivora will be dark in color and T. aurantii (normally attacking citrus) is black in color.

The ladybird beetle sent from the Jatropha plantation in Cambodia was identified as Menochilus sexmaculatus (Coleoptera: Coccinellidae), an aphidophagous species. It was known as Chilomenes sexmaculata Mulsant previously. Adults may have variable color patterns on its elytra. It is considered a generalist predator and is one of the most common coccinellids found in tropical Southeast Asia. Both adults and larvae prefer to feed on soft-bodied insects such as aphids. Adult females lay their yellow eggs vertically in small clusters near colonies of its preys. Adults may visit flowers for pollen.

Later (June 2011), the member in Cambodia growing Jatropha asked if there were other methods of encouraging predacious ladybeetles. He had transferred thousands of ladybird beetles from a plantation with a very high number on the Jatropha trees., but they immediately disappeared! 

In reply, a member asked if there was a significant population of mealybugs present on the mung beans? If there was, then do not worry. It will take time for the ladybeetles to breed. The 'disappearance' is common in a large plantation when pradators are introduced to combat a pest problems.

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 Lack of science on Jatropha biofuel Minimize

Lack of science means jatropha biofuel 'could fail poor'

Papiya Bhattacharyya

9 August 2010 | EN 

[BANGALORE] Mass planting of jatropha as a biofuel crop could benefit poor areas as well as combating global warming, but only if a number of scientific and production issues are properly addressed, a review has warned.

Growing jatropha for biofuel on degraded land unsuitable for food and cash crops could help improve the earnings of small farmers and counter poverty, reports the Food and Agriculture Organization (FAO) in the review published last month. 

The plant is an alternative crop for small farmers "particularly in semi-arid, remote areas that have little opportunity for alternative farming strategies, few alternative livelihood options and increasing environmental degradation," notes the FAO. 

And biofuels produced in sufficient volume could make a significant impact on global warming, as it is estimated that transport accounts for a fifth of total greenhouse gas emissions.

But, so far, decisions about jatropha "have been made without the backing of sufficient science-based knowledge," the FAO says in the review, which includes case studies from South Asia and Sub-Saharan Africa. 

For jatropha planting to meet its 'pro-poor' objectives, international support is needed for research on genetic improvement of varieties, and on cultivation practices such as water conservation and integrated pest and nutrient management, the review recommends. 

More research is also needed on oil processing techniques and new oil products to help smallholders reap maximum profits. 

The review also notes that, in India, low yields have been reported despite farmers using a range of seed varieties that are available worldwide. But low yields need not be a barrier if other broader objectives are met, such as reclamation of wasteland, job creation and affordable biofuel for the lighting of homes, for cookers and for operating small milling machines, grinders, irrigation pumps and two-wheeled tractors.

Experts should also ensure that projects to help small farmers grow jatropha can qualify for certification under the clean development mechanism (CDM), which allows organisations to earn credit for reducing emissions of greenhouse gases.

Other jatropha policies could include targeting remote areas with poor transport links and ensuring large-scale plantations do not compete with food crops.

But Balakrishna Gowda, biofuel project coordinator in the southern Indian state of Karnataka, where jatropha is grown, and professor at the University of Agricultural Sciences in Bangalore, said that it would be unrealistic to expect jatropha to reverse poverty "overnight" in developing countries. 

"The plant requires water and nutrition like any other plant [even if it grows on degraded land]," he toldSciDev.Net. "And it takes at least five to seven years for the plants to mature and grow their first fruit. We can rule out expectations of a great 'overnight' yield." 

The full report is available at:
http://www.fao.org/docrep/012/i1219e/i1219e.pdf