Several species of armyworms can be found in the Midwest every year. However, the development of economically damaging populations depends on a number of factors such as; cropping practices, insect migration patterns, parasites and predators, weather conditions, etc. For example, several weeks of cool wet weather in the spring favor armyworm development and reduce the normal activity of parasites and predators, thus influencing the growth of armyworm populations.
Infestations usually first develop in fields of small grains or in other grass cover crops. In conventional tillage systems, partially-grown larvae can migrate into corn fields from grassy waterways or wheat fields. Damage is usually first noticeable around the field margins adjacent to these areas. The name armyworm derives from its behavior of migrating in large numbers into fields similar to invading armies. In no-till or reduced tillage systems, infestation may cover the entire field. In these systems, eggs may be laid on grasses within the field prior to planting and herbicides may force armyworms to feed on corn as the weeds or cover crop dies. Cool, wet, spring weather usually favors armyworm development.
One of main target crop of army worm is corn. Armyworm feeding gives corn a ragged appearance, with defoliation occurring from the leaf edge toward the midrib. Damage may be so extensive that most of the plant, except leaf midribs and the stalk, is consumed. Such a highly damaged plant may recover, however, if the growing point has not been destroyed. It is regarded as a pest and can wreak havoc with crops if left to multiply. Its name is derived from its feeding habits. They will eat everything in an area and once the food supply is exhausted the entire “army” will move to the next available food source.
The larvae feed primarily on grain crops and grasses, attacking other plants only when preferred foods are not available. Infestations usually develop in grass pastures, fence rows, roadsides and in small grain fields where crops have lodged or are matted against the ground. Once the larvae have consumed the readily available food, or small grains mature, they move into other crops, most notably corn. This usually happens during May and early June. An exception to this pattern may develop in no-till corn fields where cover crops are used, or in corn fields with many grassy-type weeds. Armyworm moths are attracted to the grasses in these fields for oviposition. When the larvae hatch in these fields, they can immediately cause damage throughout the field. This is in contrast to their appearance along the edges of tilled corn fields.
Some species of army worms like the African armyworm Spodoptera exempta (Walker) (Lepidoptera: Noctuidae), also called okalombo or Kommandowurm or nutgrass armyworm are highly dangerous. It is a very deleterious pest, capable of destroying entire crops in a matter of weeks. The larvae feed on all types of grasses early stages of cereal crops (e.g., corn, wheat, coconut etc.) The armyworm gets its name from its habit of “marching” in large numbers from grasslands into crops. They tend to occur at very high densities during the rainy season, especially after periods of prolonged drought.
These vile species are known for their ability to cause large scale destructions. Recently, it was reported that outbreak of armyworms in South Africa may lead to starvation condition. Let’s take a look at the article in detail;
Crop-eating pests plague southern African farmers
Army worms can destroy entire crops in a matter of weeks
HARARE/JOHANNESBURG, 7 February 2014 (IRIN) – The rainy season, always welcome in often dry southern Africa, has brought with it favourable breeding conditions for army worms and red locusts. The crop-eating pests are contributing to the woes of subsistence farmers already struggling to recover from setbacks in the last farming cycle.
In Zimbabwe, where the World Food Programme (WFP) estimates that 2.2 million people now require food assistance, more than 800 hectares of cereal grain crops and 300 hectares of pasture have been destroyed by outbreaks of army worms.
Godfrey Chikwenhere, Deputy Director of the Department of Research and Specialist Services in the Ministry of Agriculture, told IRIN that the damage caused by the army worms, which are in fact moth larvae, was significant and would impact the food security of households in the affected areas.
He said the army worm originated in East Africa and the Horn of Africa. Between October and November, moist winds carried the moths into Zimbabwe and deposited them in northern Zimbabwe’s Mashonaland Central Province, from where they spread across the country. A similar pattern of movement occurred in 2013
“Some crops were completely destroyed, forcing some farmers to replant when we are way into the farming season, and this will result in reduced yields,” Chikwenhere said. “The effect will also be felt among livestock producers because of the destruction of pastures, especially in the cattle-producing provinces of Matabeleland North and South.”
Spraying pesticides to destroy the caterpillars could only be done on crops because the spraying of pastures and game parks could expose animals to toxic chemicals, he noted. As a result, the army worms had been able to reproduce unhindered in some areas.
Although his department initially had adequate supplies of carbaryl – the chemical used to contain the pest – Chikwenhere said stocks were running out fast and there was a shortage of vehicles to monitor outbreaks and distribute the pesticide.
“Because of the almost daily high rainfall being recorded in many parts of the country, some farmers are having to respray, as the rains dilute the effect of the chemical,” he added.
Recent torrential rains and flooding in several of Zimbabwe’s southern provinces have destroyed crops as well as homes and infrastructure, according to local news report
In its monthly report for January, Chikwenhere’s department predicted that: “Fresh outbreaks emanating from secondary generation army worm are likely to hit most parts of the country up to May 2014, if current weather conditions persist.”
He said there was a need to train farmers on prevention and early reporting. “A lot of our farmers are well versed on spraying pests… but they need to be trained on how to identify army worm at an early stage, so that intervention mechanisms are implemented before any damage is done.”
Army worm outbreaks have also been reported in Mozambique, eastern Zambia and Malawi, where 2,600 hectares of crops were affected, over 500 hectares of which were totally destroyed according to reports from the Ministry of Agriculture.
Food shortages in Malawi are already afflicting 1.85 million people, according to the Malawi Vulnerability Assessment Committee (MVAC). Now the country is also experiencing outbreaks of red locusts, mainly around Lake Chiuta and Lake Chilwa near the border with Mozambique in the southeast.
A January migratory pest report by the International Red Locust Control Organisation for Central and Southern Africa (IRLCO-CSA) notes that the locusts bred in January and their eggs have now produced hoppers.
“Hoppers will fledge and adults are expected to appear in March/April,” reads the report. “These swarms, if not controlled, will migrate and threaten food security in most countries in the region.”
Strong steps have to be adopted to prevent such precarious outcomes. The crops can be protected from the attack of army worms by using the solution provided by C Tech Corporation.
Termirepel™, a product of C Tech Corporation is an ideal solution to combat the pest problem as it is extremely low toxic in nature, works effectively and efficiently against the pests and have very low environmental implications. It works on the mechanism of repellence and does not harm target or non-target species. In masterbatch form it can be incorporated in agriculture films, mulches, tarpaulins to protect the crops from the vile pests. It can also be incorporated in storage bags to protect the produce. In coating form in can be coated near the storage areas to make them pests free. It is high time that we adopt the use of safe measures to fight the problem of pests.