2013 Annual Report
In a series of laboratory experiments, we tested the effects of 7 insecticides and 2 fungicides on 8 natural enemy species including adults and immature stages. Just as pesticides kill pest insects or mites, they can also kill beneficial natural enemies. Natural enemies were exposed to each pesticide in three different ways (contact, ingestion, and residue). Our assays showed that the pyrethroid Warrior (lambda-cyhalothrin) was acutely toxic to many natural enemies, such as lacewings, ladybird beetles, spiders, and others. Many pesticides do not kill natural enemies immediately, but they can disrupt their biology in other ways. These so-called “sublethal” effects can result in slow death over longer periods of time. The insect growth regulator Rimon (novaluron) did not kill lacewing adults in our experiments, but it caused nearly 100% of the eggs not to hatch meaning a great reduction of subsequent generations of key predators. Tests also revealed that Exirel (cyantraniliprole), while partially reducing survival of ladybird beetles, had an even stronger negative impact on the number of eggs deposited. Exirel also prolonged the development of convergent ladybird beetle larvae by about 20% which could greatly decrease their effectiveness in pest control. In contrast, we discovered that Altacor (chlorantraniliprole) causes high mortality for lacewing and ladybird beetle adults and larvae after only 48 hours as well as over longer time periods, while it had low effects on other tested natural enemy species including predatory bugs, two spiders and parasitic wasp.
We used traps to determine the time of arrival of benefical insects into orchards and their seasonal phenology. The results show that judicious use of pesticides at particular times of the year may avoid negative effects of pesticides on these beneficial insects.
We tested predator attraction by a variety of plant-based attractants, known as HIPVs (herbivore induced plant volatiles). We discovered useful attractants for lacewings, syrphid flies and some parasitic wasp groups, all important beneficial insects. These technologies will help growers identify when these beneficials are abundant and help them make modifications to pesticide practices thereby enhancing biological control.
We developed a rapid and robust method to evaluate gut contents of predatory arthropods. Over 2400 samples were evaluated to estimate predation rates of likely codling moth predators: Our samples collected from seven apple orchards over a three-year period showed that 9.2% of predators had recently fed on codling moth. We found that a remarkable 95.5% of the total predation of codling moth could be accounted for by three predator groups: ground beetles (Carabidae), the European earwig (Forficula auricularia) and the spider complex (Araneae). Predation rates across orchards generally correspond to management intensity; in orchards with lower management intensity, abundance of ground dwelling predators, particularly carabids, is high. Predation of codling moth on the ground appears to be dominated by predacious ground beetles, while spiders and earwigs are key predators both on the ground and in the canopy.