Predators beneficial insects

Beneficial insects associated with fruit orchards show different responses to diflubenzuron treatment (Broadbent and Pree 1984). Lacewings (Chrysopa oculata) in contact with leaves containing 300 mg/kg DW had reduced survival and inhibited molting of first instar larvae, but the assassin bug (Acholla multispinosa) was not affected by contact with treated leaves. Lacewings and other beneficial predator insects fed diflubenzuron-treated, two-spotted spider mites (Tetrany-chus urticae) for 3 days showed no adverse effects after 14 days (Broadbent and Pree 1984). 

Some gardeners purchase and release various beneficial insects into their garden to control harmful insects. A variety of companies sell beneficial insects. Extension factsheet SP290-Z, Commercial Sources for Predators and Parasites, lists several such companies. 

Schuster, M. F. and Calderon, M. (1986). Interactions of host plant resistant genotypes and beneficial insects in cotton ecosystems. In Interactions of Plant Resistance and Parasitoids and Predators of Insects, eds. D. J. Boethel and R. D. Eikenbary, pp. 84-97. New York John Wiley Sons. 

The best-known recent aphid damage is that of Russian Wheat aphid, Diuraphis noxia which was first discovered in Texas in 1986 but has now spread to 16 million of the total of 59 milhon wheat and small grain acres in the Great Plains states causing 37,000,000 annual crop loss (5). Due to the widespread use of synthetic pyrethroids killing beneficial insect predators, aphids are becoming increasingly important on cotton. 

Many insects are predators of crop pests. For example a hoverfly larva can eat 400 aphids in its life time. Some insecticide treatments are not very specific so can affect the beneficial insects as well as the pests. Beneficial insects can be encouraged on the farm by ensuring that there are suitable diverse habitats as encouraged by many of the options available in the current enviromnental stewardship schemes. 

Mainly a pest of spring beans. It also attacks sugar beet and mangels. Populations of aphids and amount of colonisation and predation by beneficial insects vary each year. Warning systems are available. The threshold for treatment is 5% of plants infected in headland on windward side of field pre-floweiing to 2.5% infected across field and colonies spreading onto pods. 

The specificity of the viruses can be either an advantage or a disadvantage. Because the viruses are host specific, they will not kill beneficial insects such as honey bees or parasitic insects. Therefore, using viruses does not remove the natural pressures on the target insect or on other potential pests controlled by parasites or predators and lead to increased need for chemical control. They will not harm plants or vertebrates nor will they accumulate in other organisms in the food chain as do some chemicals. Because of their specificity and the fact that they can multiply in the field after application, no tolerance levels are established for viruses thus, there is no residue problem. 

Some of DDT s effects seemed counterproductive, too. It actually encouraged some citrus-fruit pests by destroying their predators. It killed all the insects in an area, even beneficial ones, so birds and other small creatures that depended on insects for food also died. 

Many species of the Ladybug family (Coccinellidae) play a beneficial role in controlling populations of harmful insects such as aphids, mealy bugs and scale insects (70MI30800). Ladybugs have few natural enemies. When disturbed they emit droplets of a fluid from their joints which serve as an efficient deterrent to would-be predators. 

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