CHAPTER ONE

INTRODUCTION

Maize is one the predominant crop of the world that serve for direct human consumption, as animal feed and fuel. But as time passes, it is subjected to pest and disease attacks as a result of the type of practices employed during its cultivation.

Insect pests such as the black maize beetle (Heteronychus aerator) and dusty maize beetle (Gonocephalum simplex) are known to cause damage to agricultural crops but it is unknown to producers if their larvae cause damage.

Due to the concealed and cryptic behavior of these pests, the extent to which they cause damage is undetected hence producers underestimate their importance to subterranean damage to maize.

Therefore, it is important to note that the larvae of both pests are important agricultural pests as they cause very serious damage to crops especially maize.

1.1 Background Study on Black Maize Beetle (Heteronychus aerator) And Dusty Maize Beetle (Gonocephalum simplex)

These are insect pests that attack cultivated crops, especially maize (Zea mays). A pest is any species, strain or biotype of plant, animal or pathogenic agent injurious to plants, animals and plant products, materials or environments and includes vectors of parasites or pathogens of human and animal disease-causing public health nuisance” (Revised 2014: Code of Conduct on Pesticide Management).

Pest species are grouped into primary and secondary pests. A primary pest is known to attack the host directly, while a secondary pest only attacks the host as a result of the primary attack. Black maize beetle attacks the heart directly and is, therefore, a primary pest of maize.

A pest species is further grouped according to which feeding guild it belongs to (Robertson, 2012). Thus, pest species with different modes of feeding such as sucking, biting, and chewing can attack the same plant part. These are grouped together as one feeding guild.

Insect species belonging to the Hemiptera order such as Rhopalosiphum maidis (Fitch) (Hemiptera: Aphididae), commonly known as the maize aphid, is mainly responsible for damage to maize leaves (Robertson, 2012).

Most insect species that belong to Lepidoptera are in the maize stem guild, such as Busseola Fusca (Füller) (Lepidoptera: Noctuidae) commonly known as the maize stalk borer, as well as the maize seedling guild such as Agrotis spp. (Hampson) (Lepidoptera: Noctuidae), commonly known as cutworms (Robertson, 2012).

Most Coleopteran insect pests such as Buphonella nigroviolacea metallica (Jacoby)

(Coleoptera: Chrysomelidae) (maize rootworm), Gonocephalum spp. (Coleoptera:Tenebrionidae) and wireworms (Coleoptera: Elateridae), attack mainly the root and subterranean part of maize (Robertson, 2012).

Heteronychus aerator Fabricius (Coleoptera: Scarabaeidae), commonly known as the black maize beetle, is the most important Coleopteran pest that attacks the subterranean part of maize, especially in South Africa (Taylor, 1951).

This pest is indigenous to South Africa but also occurs in Australia, New Zealand, Zimbabwe, and Zambia (Drinkwater, 1979). According to Ormerod (1889) an epidemic outbreak of Heteronychus aerator occurred in the eastern parts of South Africa from 1881 through to 1885.

During the early summer of 1946, another wave of Heteronychus aerator attack occurred in newly planted maize fields in the Frankfort district of South Africa (Taylor, 1951). After a period of approximately 32 years (from 1946 to 1977), the species again reached epidemic proportions.

This attack surged for five successive planting seasons until 1982 (Drinkwater, 1987).  It is difficult to predict when outbreaks of Heteronychus aerator will occur due to its high injuriousness at low densities, the unpredictability of when it will reach epidemic numbers, the clustered distribution in maize fields, damage that can go undetected due to the concealed and cryptic behavior of this pest and producers underestimating the importance of subterranean damage to maize (Du Toit, 1998).

Adults are known to cause damage to maize but it is unknown if their larvae can cause damage (Du Toit, 1998). Most damage is caused by the overwintering adults that feed on maize seedlings, planted in spring, but newly emerged adults can also cause damage to maize seedlings during late-summer months (Du Toit, 1998).

Late-evenings these adults emerge from the soil and attack nearby maize seedlings by burrowing next to it and feeding on the subterranean parts of the stem (Drinkwater, 1979). Two distinct types of damage symptoms to the plant can be distinguished (Du Toit, 1998).

The first symptom occurs within three weeks after planting where the growth point wilts, resulting in a “dead heart”. If severely attacked this plant usually dies or the seedling forms excessive useless tillers at the base of the plant (Du Toit, 1998).

Gonocephalum simplex is widespread in Africa south of the Sahara, and a wide variety of crops are affected. Economic losses have not been quantified, and this pest also occurs with other soil-dwelling pests (Mlambo 1983).

Severe thinning of stands of sunflower and maize seedlings are recorded in some years in South Africa (Drinkwater, 1992). In one report from India, Gonocephalum sp. Damaged 5% of pods of groundnut in Andhra Pradesh (Reddy et al, 1992).

Adult Gonocephalum simplex destroys emerging seedlings by feeding on the cotyledon leaves or on the growing tips or by ‘ring barking’ the stem at the ground level of maize.

Even seedlings which develop a woody stem, including cotton (Robertson, 1993) and coffee transplants (Mlambo, 1983), can be killed. It appears to cause sporadic damage over most of their distribution. Drinkwater (1999) described it as the most destructive species of Gonocephalum in South Africa.

1.2 Background Study On Maize

Maize is the predominant crop of the world. About 30 percent of world production is used for direct human consumption and as an industrial input, while 70 percent is used as animal feed. . Maize is a cereal crop-producing seeds which are of different colors, the common name for the maize family is Cereals which have other crops such as rice, sorghum, oat, barley, and wheat.

The crop belongs to the Poaceae family and it originated in Central America precisely in Mexico. Maize is a herbaceous plant normally grown as an annual crop. The growth of maize is determinate and has many leaves and it ends up with tassels and has a total of 20-23 leaves through its production cycle and a maximum number of cobs being 2-3.

Maize grows best in a temperature range of 150C-400C or 500C and has an optimal growth temperature of 260C, at least three months of rain and loam soil because of its permeability. Maize has shallow roots and because of its shallow roots, maize is susceptible to droughts, intolerant of nutrient-deficient soils, and prone to be uprooted by severe winds (Monsanto 2008)

Maize is cultivated in the tropical, subtropical, and temperate climatic regions of the world. Land cultivated to maize is divided almost equally between the tropical-subtropical areas and the temperate areas of the world.

CIMMYT (2002) recognizes five mega-environments for maize in the world: lowland tropics (less than 900 meters above sea level), subtropics and mid-altitude tropical zones, tropical highlands, and temperate zones.

Maize may be cultivated in spring-summer and fall-winter growing seasons in the lowland tropics and lowland subtropics whereas in the rest of the mega-environments maize may be cultivated only in the spring-summer season.

Maize shares the more efficient C4 photosynthetic pathway with sorghum and sugar cane, while wheat and rice and most other crops share the C3 photosynthetic pathway.

The examination of the tillage methods of maize ranges from the conventional, high energy need procedures to soil-preserving methods and direct sowing.

There were several classic methods of tillage which are currently neglected, such as the timely application of stubble cleaning, the management of the stubble after cleaning, and even the autumn primary tillage (Győrffy and Szabó, 1979; Rátonyi et al., 2003, 2005; Nagy, 2007; Birkás, 2010).

The proper choice of tillage method with the consideration of maize production level significantly reduces risk (Nagy et al., 2018). KITE Plc. played a pioneering role in applying precision tillage in Hungary by adapting the strip-tillage technology originally developed by the American company Orthman (Jóri, 2016).

Production technological operations have a significant role in the protection of maize. The properly selected cropping sequence may significantly reduce the damage done by soil-borne pests.

Harmonious nutrient replenishment which fits the crop’s needs may increase the tolerance of crops against pathogens and pests, as it reduces the damage of fruit flies, European corn borer and aphids (Bognár et al., 2003; Király, 2005).

The stem strength of maize can be increased by applying the proper dose of phosphorus and potassium as per the crop’s needs. This proper application results in the increased tolerance of maize to stem diseases, e.g. fusarium.

In addition, optimum crop density is an important crop protection factor due to its role in the microclimatic regulation of the crop stand.

High crop density results in higher microclimatic temperature and humidity, which may increase the infestation of European corn borer and aphids, as well as elm-grass root aphid (Glits et al., 1997). The population of leaf aphids and young owlet moth caterpillars is especially reduced by the water applied with sprinkler irrigation.

However, it has a favorable effect on the development of corn rootworms and the spreading of pathogens. The application of the environmentally friendly active ingredient indoxacarb with irrigation technology (especially in the case of sweet maize) also serves as protection against the European corn borer and the cotton bollworm (Glits et al., 1997; Balogh et al., 2004; Balogh and Nádasy, 2005).

1.3 Problem Statement

Maize is one of the crops most produced and consume in the world. With the increasingly growing population of the world, the is a need to improve on different land preparation methods that will increase maize productivity in growth and in yield and also to greatly reduce the unnoticed damage caused by the larva of maize beetles on the seedlings of maize.

1.4 Hypothesis

Null hypothesis:

All land preparation methods will produce the same results on the population density of maize beetles and the growth and yield of maize.

Alternative hypothesis:

Different land preparation methods will produce different results on the population density of maize beetles and the growth and yield of maize.

1.5 Objectives

Main objective;

To see the effects of different land preparation methods on the population density of maize seedlings pests, maize growth, and yield.

Personal objectives;

1. To know the intensity of damage caused by the larva of maize seedlings pests.
2. To be able to differentiate between the larva of the black maize beetle and the larva of the dusty maize beetle