Insect Damage

1. Insect Damage grasshopper spider mites potato beetle aphids

2. This wasp is laying its egg inside an aphid where its young will develop. Parasitoid larvae develop on or inside a host, killing it as they mature. They emerge as adults and continue the cycle. Parasitoids

3. A predator consumes many prey during its lifetime Predators Coccinellids Chrysophids Syrphids

4. Biological Control

5. 1:170 1:70 Syrphid : Aphid Ratios • Temperature dependent aphid population growth • Starvation of syrphids

6. 3.19 2.72 1.06 1.02 1.01 N-isoclines for different growth rates of aphid population Number of Predators Number of Prey (Tenhumberg, Environ Entomol 1995)

7. How many predators do we need? • Aphid density • Aphid population growth rate • Temperature • Host plant (nutritional values) • Predator species • How much do they eat • Temperature • Nutritional value of aphid • How quickly do the find and eat the prey

8. Temperature Metopolophium dirhodum (Dean 1974)

9. Easy estimates Maximum number of aphids consumed during larval phase Episyrphus balteatus

10. Model System Vicia faba Hippodamia convergens (holometabolous) Acyrthosiphon pisum (hemimetabolous)

11. Aphids • 4,400 species of small insects • 250 species are serious pests • Aphids are divided up into 10 families all of which have been extant for 50 - 70 million years Superfamily Aphidoidea Pemphigidae Anoeciidae Hormaphididae Mindaridae Thelaxidae Lachnidae Phloeomyzidae Greenideidae Aphididae Drepanosiphidae 70% of species

12. Aphid Feeding • Specialization • Monophagous: feeding only on 1 species of plant • Polyphagous: feed on hundreds of plant species • How do they feed • Passive feeding on sap of phloem vessels:This sap being kept under high pressure, once a phloem vessel is punctured, it is forced into the food canal. • Active feeding (sucking) from xylem vessels when thirsty • Virus transmission

13. Xylem:conducts water and dissolved minerals from the roots to all the other parts of the plant. Phloem Sieve elements conducts the products of photosynthesis - sugars and amino acids - from the place where they are manufactured (a "source"), e.g., leaves, to the places ("sinks") where they are consumed or stored; Companion cells move sugars and amino acids into and out of the sieve elements. Plant Tissues

14. Excretion of sticky substance known as "honeydew" which usually becomes black with sooty mold.Aphid honeydew is rich on carbohydrates (like melezitose), of which the aphids ingest an excess, being phloem-feeders. Some species of ants "farm" aphids, protecting them on the plant they eat, and eating the honeydew that the aphids secrete; this is a mutualistic relationship. http://en.wikipedia.org/wiki/Aphid Honeydew

15. Migration and Dispersal • Most of the time aphids do not have wings, and in general they move very little, and life consists of feeding and giving birth. • What stimulates movement • death of the host plant • danger • end of season • overpopulation • Short distance dispersal: 1.6 to 3.2 km per hour • Long distance dispersal: >400 km in 9 hours • Fly upwards to get above the planetary boundary layer (1000m above sea level) and are carried by the low level jet streams Winged forms (alatae) appear

16. Reproduction: • Thelytokous parthenogenesis:Obligate parthenogenesis where females give birth only to female offspring • Short generation time (about 10 days on average) • Telescoping of generations:Grandaughters begin developing directly within the daughters which are themselves not yet born

17. Aphid Life Cycles • Alteration of sexual and asexual generations • Holocyclic • Species that produce both sexual and asexual morphs • Cyclical parthenogenesis: Many generations of asexual (parthenogenetic) reproduction (all females), followed by single generation of sexual reproduction • Anholocyclic • Species that produce only asexual morphs • Although many species are either holocyclic or anholocyclic, many other species possess both holocylic and anholocyclic populations • Host plant alternation

18. Viviparous females (winged and unwinged) Fundatrix (usually unwinged) Oviparous female (unwinged) Egg (typically overwintering) Male (winged and unwinged) Holocyclic Species • Asexual and sexual morphs are produced at different times of the year. • Males are present only in one part of the life cycle.

19. Viviparous females (winged and unwinged) Viviparous females (usually overwinter asapterae or nymphs) Anholocyclic Species • No sexual males and females • No direct descendants of the sexual morphs, namely the egg and the fundatrix. • Often no primary host.

20. Host Alternation • Autoecious: single host plant • Heteroecious: alternating between host plants Primary host: Shrub or tree Secondary host: Herbaceous plant

21. Acyrthosiphon pisum • Common name: pea aphid • Pink and green genotypes (polymorphism) • Green morphs suffer higher rates of parasitism than red morphs • Red morphs are more likely to be preyed on by predators than green morphs are • Reproductive rates of both morphs are the same • Aphid defensive behaviour of both morphs is the same.

22. A. pisum Life Cycle

23. Acyrthosiphon pisum • Distribution Throughout the U.S. and Canada • Host Plants Sweet peas, sweet clover, alfalfa, and some leguminous weeds. Vetch and crimson clover are important overwintering hosts

24. Plant Damage • Extract sap from terminal leaves and stems • Feed on pods causing them to curl, shrink, and partially fill. • Feeding can result in deformation, wilting, or plant death • Plants less than 15 cm (6 in) high are easily killed by a few aphids, whereas larger plants are only slightly damaged. • Coated with shiny honeydew • Virus transmission, e.g. pea enation mosaic and yellow bean mosaic viruses. Heavy infestations of pea aphid have caused chlorosis (yellowing) and wilting of plants in this plot of susceptible alfalfa Bean pod damage

25. Vicia faba

26. Lady Beetles(Coleoptera: Coccinellidae) • Over 450 species are found in North America. Some are native and some have been introduced from other countries. • Food: • aphids • mites, small insects, and insect eggs • plants (Mexican bean beetle, Epilachna varivestis, squash beetle, Epilachna borealis) • Low food availability • pollen, nectar • cannibalistic

27. Aposematism • Warning colors: • Most predators associate bright colors (especially orange and black or yellow and black) with poison and other unpleasant properties. • Toxin • toxic to smaller predators, such as lizards and small birds; • Adults are able to reflex-bleed from their leg joints, releasing their oily yellow toxin with a strong repellent smell.

28. Adult Coccinellids • Overwintering • often in aggregations along hedgerows, beneath leaf litter, under rocks and bark, and in other protected places including buildings. • Migration • In spring, the adults disperse in search of prey and suitable egg laying sites.

29. Hippodamia convergens(1-2 generations / year)

30. Predation efficiency(H. convergens) • Activity period: late spring-early fall • Consumption • Cannibalism • Fecundity (no. eggs) and fertility (fertile eggs) • Migration • Pesticide application

31. References • Dixon, A.F.G (1998): Aphid Ecology, Chapman and Hall, London, UK, pp.300 • Hodek, I. and A. Honek (1996): Ecology of Coccinellidae, Kluwer Academic Publishers, The Netherlands, Dordrecht, pp. 464

32. Lab overview • Parameter estimation for aphid model • Developmental time • Survival • Fecundity • Testing predicted aphid population growth rate • How much do predators eat? • Maximum aphid consumption at different developmental stages

33. Aphid Experiments Model

35. H. convergens • Access food • Larva: > 20 aphids/day • Adults: > 50 aphids/day