Field evaluation of the long-lasting treated storage bag, deltamethrin incorporated, (ZeroFly^® Storage Bag) as a barrier to insect pest infestation

Highlights

• The ZeroFly^® storage bag was effective in suppressing insect population levels.

• The ZeroFly storage bag reduced insect damaged kernels (IDK) and maize weight loss.

• Percentage IDK in the control increased over time and reached 32% after 6 months.

• The ZeroFly storage bag with insect-free grains could provide long-term storage.

Abstract

The deltamethrin incorporated polypropylene (PP) bag, ZeroFly^® Storage Bag, is a new technology to reduce postharvest losses caused by stored-product insect pests. Maize was pre-fumigated and used for the following treatments: ZeroFly bags filled with untreated maize, PP bags filled with maize treated with Betallic Super (80 g pirimiphos-methyl and 15 g permethrin per liter as an emulsifiable concentrate (EC)), and PP bags filled with untreated maize (control). The experiment was conducted from February–August 2015, at four sites in different locations of the Middle Belt of Ghana. Moisture content (MC), number of live and dead insects, insect damaged kernels (IDK) and maize weight loss data were collected monthly. ZeroFly bags and Betallic treatment significantly reduced insect damage compared to the control treatment. ZeroFly bags were able to keep IDK levels below 5% for 4 months, but the levels increased to 5.2 and 10.2% by 5 and 6 months of storage, respectively. In the control, IDK increased significantly over time and reached 32% after 6 months. The ZeroFly bag was effective against Sitophilus, Tribolium and Cryptolestes species for 4 months. Mean weight loss of ≤3.68% was recorded in ZeroFly bags during 6 months of storage whereas 11.88% weight loss occurred in the PP bags by 6 months of storage. Based on our results, ZeroFly bags were found to have potential for use in the reduction of postharvest grain losses in bagged grains. Maize may still have been infested during bagging hence ZeroFly bags were effective for storage for only 4 months. However, greater benefits of using ZeroFly bags are realized if insect-free grains or legumes are stored in bags.

Introduction

Most of the calorie and protein needs of humans are obtained from cereal grains, grain legumes and oilseeds (Cordain, 1999). Maize (Zea mays L.) is one of the important cereal grains grown widely throughout the world. It is a major staple food in Africa (Food and Agriculture Organization, 2004, Tefera et al., 2011), and significantly contributes to household food security for smallholder farmers (Baoua et al., 2014). From 2008 to 2011, maize was planted on approximately 31.1 million ha of land in sub-Saharan Africa, and the average annual production during this period was 56.7 million tons (AGRA, 2014). However, due to poor storage techniques, maize producers in developing nations experience considerable losses after harvest (Giga et al., 1991, Boxall, 2001, Alonso-Amelot and Avila-Núñez, 2011).

Over the past few decades, postharvest loss estimation and measures to effect mitigation of these losses have been high on the international agenda (Food and Agriculture Organization, 1999, FAO and World Bank, 2011, Abass et al., 2014, Affognon et al., 2015). Despite international focus on postharvest loss issues, farmers in the developing nations still face significant losses. Estimates of postharvest losses vary in literature, and global figures for losses of 9–40% are often quoted (Pimental, 2002, FAO and World Bank, 2011, Parfitt et al., 2010, Tefera, 2012, Hodges et al., 2014). Postharvest losses can arise from inappropriate storage techniques, deterioration by insect pests and rodents, high ambient temperature and high relative humidity (FAO and World Bank, 2011, Anankware et al., 2013, Abass et al., 2014). However, most of the postharvest losses result from damage caused by storage insect pests (Giga et al., 1991, Bett and Nguyo, 2007). Infestation of stored maize by insect pests may produce unpleasant odors, render the grain unfit for consumption, reduce nutritional content and grain quantity thereby leading to low market prices (Hill, 1990, Jood and Kapoor, 1992, Food and Agriculture Organization, 2004, Mboya, 2013). Furthermore, insects can facilitate entry of fungal spores into kernels or seeds by breaking the seed coat; they also disseminate of fungal spores, hence potentially contributing to increased production of mycotoxins that are carcinogenic and immunosuppressive to humans (Khan et al., 2016).

A number of stored-product insect pests, which ultimately cause quantitative and qualitative deterioration (FAO, 2009), can infest stored maize. Of the pests that infest maize, beetles and moths are the most important. Sitophilus oryzae (L.), the rice weevil, Prostephanus truncatus (Horn), the larger grain borer, Tribolium castaneum (Herbst), the red flour beetle, Plodia interpunctella (Hübner), the Indianmeal moth, Sitotroga cerealella (Oliver), the Angoumois grain moth, and Rhyzopertha dominica (F.), the lesser grain borer, are the most important pests of stored maize (USDA (United States Department of Agriculture), 1986, Rees, 2004, Groot, 2004, Hagstrum et al., 2012).

Effective grain storage can reduce pest activity and can help secure food quality and quantity until the next harvest season. For storage of cereal grains and grain legumes, farmers in sub-Saharan Africa predominantly use traditional storage techniques such as open platforms, woven baskets, pots, mud rhombuses, maize cribs, bamboo storage structures, straw roofed storage structures, underground storage, bag storage and warehouses (Food and Agriculture Organization, 1994a, Adejumo and Raji, 2007). Because most of the aforementioned structures are made of locally available materials, smallscale farmers find them economically feasible to construct. Storing cereals in sacks such as jute or polypropylene bags is currently the most common storage technique (Food and Agriculture Organization, 1994a, Koona et al., 2007; De Groote et al. 2013). However, postharvest losses do occur in bagged commodities that are not subjected to insect pest management actions; losses of up to 60% have been reported in maize that is stored using traditional polypropylene bags (Costa, 2014).

Farmers in developed countries use grain protectants and fumigants to control insect pests of stored maize (White, 1995, Arthur, 1996, Zettler and Arthur, 2000). Some challenges to pesticide use are that resource-poor smallholder farmers in developing countries find the cost of pesticides prohibitive, thereby making them unaffordable, and these chemicals have been abused and misused by farmers in ways that pose risks to human health and the environment (Kamanula et al., 2011, Hodges et al., 2014). Additionally, insects develop resistance to chemical insecticides making them less effective (Opit et al., 2012). Therefore, a need exists for the development of reduced-risk approaches for managing insect infestations in bagged grain. Additionally, ways of scaling up reduced risk technologies are needed because farmers in developing countries have been too slow to adopt such technologies (USDA (United States Department of Agriculture), 1986, Kaminski and Christiaensen, 2014).

In rural parts of Ghana, most maize produced by smallholder farmers is traditionally stored in jute or polypropylene bags (Food and Agriculture Organization, 1994a, Akramov and Malek, 2012, Anankware and Bornu-Ire, 2013). These bags often do not protect the grains against insect pests, leading to heavy losses. Reducing postharvest losses in bagged grain could increase smallholder farmers' income and contribute to increased food security. The need for a bag that effectively mitigates infestation of grain stored in it led to the idea of insecticide-containing fabrics for storage bags. Several studies have documented evaluation of bags with insecticide-containing fabrics for the control of stored product pests (Parkin, 1948, Atkins and Greer, 1953, Muthu and Pingale, 1955); but the bags tested were not commercially available then and are still unavailable to date. The concept of insecticide-incorporated textile has been successful in mosquito nets for mosquito control to mitigate malaria (Barlow et al., 2001). Building on the concept of insecticide-containing fabrics for storage bags, Vestergaard SA, Lausanne, Switzerland has developed a deltamethrin incorporated polypropylene bag (ZeroFly^® Storage Bag), which has great potential to reduce postharvest losses of cereal grains and grain legumes stored in it for use in developing countries (Anankware et al., 2014, Costa, 2014). The ZeroFly bag is designed to give protection to commodities by preventing the entry of insect pests, thereby facilitating preservation of cereal grains and grain legumes. However, there is little published data on field trials with the ZeroFly Storage Bag. Therefore, the objective of this study was to determine the effectiveness of the ZeroFly bag to protect maize from infestation by stored-product insect pests under field conditions in Ghana.