Stored-Product Insect Pests Associated with Food Plants

1. Stored-Product Insect PestsAssociated with Food Plants

2. Important Orders • Coleoptera or beetles • Lepidoptera or moths • Psocoptera or book/bark lice

4. Stored-Product Insects • Beetles (50 or more species) • Moths (3 species in U.S.) • Indianmeal moth • Almond moth • Angoumois grain moth • Psocoptera (Liposcelis spp.) Slide 3: The adults of beetles are easily recognized by front pair of wings that are hard (elytra). The second pair of wings are membranous. You have seen several species of beetles in laboratory sessions. The segment behind the head, called the pronotum, is the most prominent thoracic segment that is sometimes used to identify stored product beetles. The larvae of stored product beetles vary depending on the species. The larva of sawtoothed grain beetle or red flour beetle look similar to the larvae shown in Figure B (1). These larvae are dorsoventrally flat and have 3 pair of thoracic legs (true legs). The larva of weevils such as the rice weevil is shown in Figure B (2). This type of larva does not have any legs and is called an apodous larva. As weevil larvae spend all their life within a kernel it is not necessary for them to move around a lot in search of food. The larva of the lesser grain borer is shown in Fugure B (3). It has a “C” shape and 3 pair of true legs. The larva in Figure B (4) is that of a moth, and is called a caterpillar. It has 3 pairs of true legs and 5 pair of false legs or prolegs. These prolegs help in the caterpillar’s movement but are lost in the adult stage. Slide 2: Stored product insects of economic importance to food industry fall into the orders of Coleoptera (beetles), Lepidoptera (moths), and Psocoptera (book lice or psocids). The beetles have hard front wings and membranous hind wings. The moths have scales on their wings and psocids may or may not have wings and the femur of hind pair of legs is enlarged. The psocids are prevalent in developing and developed countries, but in the United States they have been ignored as food industry pests because they were erroneously considered to be pests of bark or books in libraries or museum artifacts. Slide 1: In this lecture we will cover stored product insects associated with food plants. Some basic information about stored product insects will be presented using illustrated material.

5. Proposed Origins • Mostly tropical or subtropical in origin. • Some species were seed feeders; others fed on molds under the tree bark or on rotting animal or plant matter. • Some species still inhabit these areas. • Majority infest habitats provided by humans.

6. Exclusive Seed Feeders • Wild grass seeds • Wild ancestors to currently cultivated crops (Angoumois grain moth) • Seeds stored by rodents • Timber (Lesser grain borer) • Acorns (Rice weevil)

7. Scavengers • Feed on molds • Decaying plant material • Dried plant or animal materials • Bird feathers (dermestids)

8. Sources Created by Humans • Feed • Spilled grain in fields or on farms • Grain residues • Combines • Trucks • Wagon beds • Bins • Under perforated floors

9. Features of Stored-Product Beetles • Adults can live between 2 months and a year • Mate multiple times • Both adults and larvae cause damage • Females lay eggs throughout their adult life

10. Features of Stored-Product Moths • Adults live 6-8 days • Only larvae cause damage • Eggs by females are laid within 6 days • May mate 1-3 times

11. Classification of Stored-Product Insects • Mode of feeding • Food preference

12. Mode of feeding • Internal feeders - remove energy from foods • Rice, Maize, and Granary weevils • Lesser grain borer • Larger grain borer • Angoumois grain moth • External feeders - contaminate food products • All other species, except those listed above

13. Food Preference • Whole grain feeders • Weevils and borers • Broken kernel feeders • Sawtoothed grain beetle, Red flour beetle, Rusty grain beetle, Indianmeal moth larvae • Germ feeders • Indianmeal moth larvae, Rusty and Flat grain beetles, Sawtoothed grain beetles • Flour feeders • Red & Confused flour beetles • Mold feeders • Hairy fungus beetle, foreign grain beetle

14. Damage Caused by Insects • Weight loss • Heating (110oF (43.3oC) or higher) • Increase in moisture • Increase in protein content • Increase in fatty acid content • Increase in uric acid content • Structural damage (Cadelle larvae) • Contamination of raw & processed foods • Excreta, cast skins, eggs, body parts

15. Damage Caused by Insects (continued) • Decrease in seed germination • Distribution of molds from infected to healthy kernels • Penalties or rejection at time of sale • Rejection by customers of infested foods • Indianmeal moth larvae in pop corn • Allergic reactions in sensitive people • Dermestid hairs (hastisetae)

18. Reproductive Potential • Moths mate once or twice during their life time • Beetles mate more than twice • A female, on average, lays 200-400 eggs in her lifetime.

20. Why Are Stored-Product Insects Successful as Pests? • Abundant food of high quality • Insects are protected from extreme climatic changes • Behavioral adaptations (refuge-seeking behavior) • Physiological/biochemical adaptations • Presence of other organisms (molds), broken kernels and grain dust, promotes insect survival, growth, and reproduction

22. Factors Affecting Insect Abundance and Distribution • Grain temperature • Grain moisture • Nutritional quality of food

23. Insects are Cold Blooded • Development changes with temperature • Lower limit for development • Upper limit for development • Optimum temperature for development

30. In the Optimum Temperature Range • Populations increase 5-10 fold per month • Egg-to-adult development takes about 30-40 days

31. Grain Moisture • 12-18% moisture is conducive for insects • Some species can infest 9-10% moisture grain (larger grain borer on corn) • At 15% moisture or higher, molds infect grain