Archive for the ‘Grain storage pests’ Category

How Insect Saliva is Helping Crops Protect Against Pest Damage

Cowpea is one of Africa’s most important cash crop, and has been found to detect larvae and reduce feeding damage (Image by Toby Hudson)

A new study has unlocked the hidden ways in which important cash crops such as cowpea (Vigna unguiculata) tackle localised pest invasion and damage using natural defence mechanisms. Insights such as these are key for the future protection of our global agricultural production in the light of increasing pest outbreaks and crop damage.

Scientists have published research in which they have found an immune receptor in cowpea cells that can detect the saliva of caterpillars feeding on their leaves, causing a series of natural defence responses such as the release of chemicals that limit the rapid growth capabilities of the larvae. An example of such a defence mechanism is found when the bean pod borer (Maruca vitrata) larvae feed on cowpea, causing the release of a pheromone which attracts parasites to then feed on the larvae.

“Despite chemical controls, crop yield losses to pests and diseases generally range from 20 to 30 percent worldwide. Yet many varieties are naturally resistant or immune to specific pests,” explains biologist Adam Steinbrenner from the University of Washington. “Our findings are the first to identify an immune recognition mechanism that sounds the alarm against chewing insects.”

As of yet, very little is known about how plants are able to identify and combat pest threats, however this new study which is built on previous research by the same team has found that certain peptides known as inceptins are found in the saliva of the larval pests such as the beet armyworm (Spodoptera exigua) larvae – which is one of greatest threats to cowpea crops across Asia and North America. The beet armyworm is native to Southeast Asia and has colonised parts of America since the late 1800s. This pest is extremely damaging to crop foliage, with larvae being found to consume more than other major crop pests such as the diamondback moth (Plutella xylostella).  

Beet armyworm larvae (Image by Russ Ottens, University of Georgia)

The inceptins are the spark that causes the cowpea defence mechanisms against feeding pests, ultimately resulting in larval damage or death. The research found inceptin receptors (INRs) on cowpea plant calls specifically. Unfortunately, there are limited ways to study cowpea crops, resulting in the team having to use tobacco plants to test how the INRs work in practice.

By inserting the gene for INR production into tobacco crops, the team were able to test what would happen in the presence of armyworm larvae. It was found that the INRs were triggered in response to the presence of certain protein fragments in the saliva of feeding caterpillars, as well as in response to direct feeding damage on leaves. The fragments of saliva protein that caused the defence response was found to be pieces of cowpea proteins that were broken down by the caterpillar during feeding. In the tobacco test crops, the presence of these proteins triggered the release of a plant hormone that is known to occur when under threat, resulting in the suppression of insect growth.

“Like many plant immune receptors, this receptor is encoded only by certain plant species but can be transferred across families to confer new signalling and defence functions,” the author wrote.

With the genomic techniques used in this study, the team were able to discover hidden information about plants natural defence mechanisms against pest damage. With the increasing global demand for food as well as more prevalent agricultural pest outbreaks, such studies must be conducted on numerous important food crops and a variety of environmental climates so we can better prepare for and mitigate future threats.

If you would like to read more on this subject, please see the links below:

armywormbeet armywormcowpeaAgriculture and International DevelopmentCrop healthFood and nutrition securityPlant Sciences

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post harvest

Zimbabwean man harvests maize from a field outside Harare. Reuters/Philimon Bulawayo

What constitutes post-harvest losses?

The loss of harvested maize and other food commodities can be qualitative or quantitative. Quantitative losses are easy to determine and report since they constitute a physical reduction in the marketable volume and can be easily measured. Globally, quantitative grain losses are estimated to be 10–20% of the total volumes.

Qualitative losses refer to deterioration of nutritional quality, safety or grade. Qualitative loss data is hardly ever reported. But it’s a loss that must concern everyone. For example the levels of qualitative losses due to aflatoxin contamination, although not reported, have dire long-term effects on health. Chronic dietary exposure to low doses of aflatoxins is a known risk factor for liver cancer and other health-related issues.

How serious is the problem of post-harvest losses in Africa?

According to the Food and Agriculture Organisation of the United Nations, 30% of food produced for human consumption is lost or wasted along the supply chain every year. This is a whopping 1.3 billion metric tons of food that doesn’t ever reach the consumer. Some reports have estimated that this lost or wasted food could be used to feed 1.6 billion people every year.

In Africa, the losses are even higher: between 30% and 50%. They occur mainly downstream, between the production and retail stages of the supply chain. Fruit and vegetable losses are estimated to be 50% or more. This estimate is cumulative because losses occur at every stage of the supply chain – from production to the consumption. Losses at the farm level can be attributed to poor harvest practices and poor handling.

Generally, any loss of produce translates to lost production resources, mainly land, water, energy and inputs. It is also lost income for the various actors in the supply chain. A 2011 World Bank study estimated the value of African grain losses alone at USD$4 billion for grains alone in Africa. This could feed 1.6 billion people each year.

This study further showed that 470 million smallholder farmers suffer a decline of 15% income, while 25% of fresh water and 20% of farmland is wasted on unconsumed food. These figures are alarming. But they’re important in highlighting the seriousness and impact of post-harvest losses.

The world’s population is projected to reach 9 billion people by 2050, with Africa contributing more than half of that increase. To feed these people, production must increase by up to 70%. However production resources – land, water, energy and so on – are limited and inelastic. Instead of producing more, we could increase the amount of food available by ensuring that most of the food produced for human consumption reaches the end user.

Quantitative and qualitative losses negatively impact on all aspects of food security – access, availability, utilisation and stability. There can be no sustainable food systems when 30% of food produced using limited production resources is lost or wasted along the supply chains.

What are the main drivers of Africa’s post-harvest losses?

Losses occur at all stages between production at the farm level through to consumption. There are unique challenges at each stage depending on specific commodities and value chains as well as context. The causes are complex and interrelated; actions or lack of action at one stage of the supply chain could be the driver of post-harvest loss at a different stage.

Qualitative and quantitative losses are driven by poor or wrong harvest practices and poor handling. This includes poor storage or packaging, mode of transport, processing practices, lack or poor access to markets and poor coordination among the actors in the supply chains. There are other broader factors such as poor infrastructure and lack of policies that have a direct impact on post-harvest issues.

** What are the latest interventions to reduce post-harvest losses and what are the limitations or prospects of success?**

Many technologies and innovations have been developed to address the various causes of food losses. However, some of these have either not reached the targeted user or have not had the desired result. This is partly because people aren’t aware of them or can’t afford them. Some technologies are also unsuitable for the African context.

Creating awareness about the applicable technologies and demonstrating their benefits is one way to yield results. This strategy has been used in promoting hermetic storage bags for grains. Hermetic storage is a proven solution for the threat of storage pests like weevils which attack stored grain. Its adoption has risen because of stakeholders’ concerted efforts.

The same aggressive campaign should be adopted for other technologies that are useful for smallholder farmers. Forums such as the one held in Nairobi, Kenya earlier this year provide an opportunity to showcase new technologies and innovations from all over the world. Such forums should be encouraged as a way of creating awareness about food losses and available solutions.

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Connect!: PICS Bags: How you can get your hands… | AgTechXChange

A simple storage solution, NO CHEMICALS NEEDED- The Purdue Improved Crop Storage (PICS) bags!

PICS bags are triple-layer hermetic bags designed to store grains without using chemical. PICS is a simple, fully commercialized technology that benefit smallholder farmers the world over. PICS are effective at stopping insect damages after harvest on several grains including cowpea, common bean, chickpea, pigeon pea, mung bean, maize, rice, sorghum, millet, bambara groundnut, peanut, hibiscus seed, and sesame.

With PICS bags you will:

  • Keep grain clean and free of insects.
  • Increase income
  • Increase food security
  • Store seed for planting
  • Stop aflatoxin contamination in stored grain

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Interested in partnering, click here!

PICS is composed of three distinct plastic bags, one placed in the other, and hand-tied to create a hermetic seal. PICS transfers its licensing for manufacture and distribution to a local company, increasing distribution and availability, for smallholder farmers at the very low price of under $3.00 for a 90 kg bag in Rwanda or Kenya, for example. All of these qualities set PICS a part for commercial potential when Feed the Future Partnering for Innovation first partners with Purdue University to take the technology from the research lab to the market. The commercialization started in 2013 and now in 2017 PICS bags are widely available: click the link above or here for finding where and how to purchase the bags.

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