Insect damage, determinants

Little is known about field contamination by ochratoxin A. Coffee is one of the crops susceptible to ochratoxin, and contamination is often correlated to insect damage. Ochratoxin-producing Penicillium typically infest grain (especially wheat) in temperate zones. Further investigation is required to understand the factors that determine ochratoxin A contamination in coffee and in other susceptible crops. 

Allelochemicals as Determinants of Insect Damage Across the North American Continent... 

SCRIBER ET AL. Determinants of insect Damage in North America... 

The preservation of textiles made from man-made fibers requires attention to similar factors as textiles made from natural fibers—i.e., temperature, humidity, light conditions, and air purity. In some instances, preservation should be easier. Synthetic fibers and cellulose derivative fibers, for example, would be less prone to insect damage than natural fibers. As in the case of the natural fibers, there are well-established techniques for determining the type and extent of damage that has occurred to man-made fibers during use. This will assist in determining cleaning and preservation techniques. 

Volatile compounds emitted from the leaves and stems of agricultural crops during growth may affect plant host-parasite interactions that determine susceptibility or resistance to fungal infections and insect damage (7-9. ... 

Aflatoxins occur both in food crops in the field prior to harvest, and in improperly stored food where mould species have found an opportunity to grow. Fungal growth and aflatoxin contamination are a consequence of an interaction between the mould, the host organic material (i.e. crop, foodstuff) and the environment. The appropriate combination of these factors determines the degree of the colonisation of the substrate, and the type and amoimt of aflatoxin produced. Humidity, temperature and insect damage of the host substrate are major determining environmental factors in mould infestation and toxin production. 

Resistance of plants to herbivorous animals is determined in many cases by the presence in plant tissues of secondary metabolites that may cause feeding deterrence or toxocity to the animal. Insects cause damage to cereals, decreasing grain production. Development of varieties resistant to insects is then desirable for improving cereal productivity. 

One of the major reasons for the interest in insect pheromones is their potential for use to control pests. In one method a large number of traps, baited with small amounts of the sex attractant of the female insect, are used to trap enough males that the breeding of the insects is decreased. In another method that requires fewer traps, a small number of traps are used to monitor the population of the target insect. The best time to apply pesticides can be determined by monitoring these traps. In one case, 10 to 15 applications of a pesticide to control the pink bollworm still resulted in damage to 30% of a cotton crop. This was decreased to almost no damage with only one to two pesticide applications when the ideal times for these applications were determined by the use of traps. 

Only small amounts of sample are required for examination by SEM. Thus, this technique can be used to obtain valuable information that can be of use when characterizing fabrics to determine how they should be conserved or when attempting to elucidate the cause of the damage for historical purposes. The purpose of this chapter then is to describe the potential use of the SEM in such activities. Discussion will be limited to mechanical stress damage. Comparisons are made when possible between fibers damaged in actual use and those fractured under controlled laboratory conditions. Examples are selected from work we have done in our laboratories on some commonly used fibers namely cotton, polyester, and wool. Reports on light (I) and insect (2) damage can be found elsewhere. 

The efficiency of insect resist finishes can be determined by tests that measure the weight loss of the treated fabrics and/or the weight of insect excrement after exposure to insects under controlled conditions. The direct examination of exposed fabrics by microscopic methods to observe fibre damage is also useful. The typical half round bite traces of the moth larvae are observable. Standard methods for evaluating fabrics with insect resist finishes are given in AATCC Test Method 24. Procedures for cultivating the test insects are included in this method. 

Predators and Parasites—Organisms known to attack insert (and insect-like) pests in their native environment can be imported or reared in labomto-ries and released in infested areas. This is done only after the parasites or predators are determined to be harmless to man, animals, plants, and other beneficial organisms. For example, several kinds of parasites and predators of the alfalfa weevil have been imported from Europe and Asia and released in the infested areas in this country. Several species have become established and are helping to reduce pest numbers. However, they do not always prevent serious outbreaks and the resultant damage. 

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