Good Fruit Grower

October 2012

Issue link:

Contents of this Issue


Page 33 of 47 T o see a video of a female wasp laying its eggs on stinkbug eggs, visit the Web site beneficial native stinkbug species, of which about 25 species are predators themselves rather than plant-feeding pests. Chinese buffet While introducing natural enemies of a foreign pest from the region it came from can be a successful strategy, more often they fail to become established or end up eliminating nontarget native species, Biddinger said. He's hoping nature will provide a faster and surer solution. A number of our exotic fruit pests, such as codling moth and oriental fruit moth in the eastern United States, are mostly attacked by native biocontrol agents that adapted over time to a new food source. "We found at least two wasp predators that were specialized on collecting native stinkbugs to feed their young in under- ground burrows have switched to feeding at the 'Chinese buffet' rather than feeding on the less numerous native bugs as they used to." Already in 2010, Biddinger and his bio- control team began looking for indica- tions that the invasive stinkbug was being attacked by native-born predators. There is some evidence that it is being signifi- cantly attacked by some of the same pred- ators that control native stinkbugs, of which there are more than 300 species. "We have lived with low levels of dam- age in Mid-Atlantic tree fruits from the native brown, dusky, and green stinkbugs for decades now, especially in peaches where they are one of a group of catfacing pests," he said. Their numbers have been kept low enough to live with because of perhaps 20 native predators, including predatory sand wasps, lacewings, lady beetles, spi- ders, ants, assassin bugs, and a dozen species of wasp parasitoids that attack native stinkbug eggs. Biocontrol is essential While the initial reaction to the rise of the brown marmorated stinkbug centered on finding pesticides that would kill them in the orchards, Biddinger—and most other scientists—don't believe spraying is a viable strategy in the long term. There are too many of them ready to invade. The stinkbugs feed on up to 300 differ- ent plants and move throughout the sur- rounding landscape to complete their development. They overwinter in natural areas or buildings outside orchards and spend only a small part of their lifecycle within orchards. For these reasons, Bid- dinger believes the only hope for long- term control of stinkbug pests is through natural regulation of populations by pred- ators, parasites, and diseases outside of the various crops it attacks. Small, white larvae (inset photo above) of the sand wasp, Bicyrtes quadrifasciata, feed on brown marmorated stinkbug nymphs. The sand wasps (at right) collect the nymphs, move them to their burrows, then lay eggs that hatch into larvae that feed on the nymphs. BIOCONTROL VETERANarms for battling brown marmorated stinkbug P ennsylvania State University's Dr. David Biddinger is a veteran in the army battling for better biocon- trol, and it's had its ups and downs. But it has made him confident that patience and diligence can pay off. Over the last ten years, he has been involved in the introduction of a new predatory mite, and it came about in an unusual way. Pennsylvania had become known for a very success- ful integrated pest management program based on bio- logical control of mites in apple orchards by the black lady beetle, Stethorus punctum, he said. It worked from about 1978 to 1998. Then, several new classes of insec- ticides toxic to Stethorus practically eliminated this predator from orchards. But the replacement of one of the older very toxic carbamate insecticides (methomyl) with some of these 34 OCTOBER 2012 GOOD FRUIT GROWER new pesticides allowed the survival of a beneficial mite previously not known in Pennsylvania apple orchards. The new predatory mite, Typhlodromus pyri,was found in 2003 in orchards that were using only reduced-risk insecticides. As it turned out, T. pyri is at least ten times more effective than Stethorus in reducing pest mite injury, he said. It was the perfect replacement. The predatory mite was not widespread, so a pro- gram was set up to allow growers to make spring cut- tings in "seed orchards" on the Penn State research station that had the mite and move them into their own orchards. Once there, they established quickly if not killed by harsh insecticides such as pyrethroids. "Unlike other predatory mite species, T. pyri never leaves the tree, even when pest mite populations decline," Biddinger said. "They are able to subsist on pollen, fungal spores, or nonharmful apple rust mites until the pest mites return." Biddinger would like to be so fortunate dealing with predators of brown marmorated stinkbug. He is survey- ing predators and parasites, and when he finds them, he determines which pesticides are detrimental to them and which food sources they need in order to survive and be available when the first stinkbugs arrive. One key factor is on their side. Because the stinkbugs live outside orchards most of the time, in woodlots and other places where pesticides are not sprayed, much of the biological control fruit growers need can established in safe havens away from the orchards. —R. Lehnert Photos courtesy of DaviD BiDDinger

Articles in this issue

Links on this page

Archives of this issue

view archives of Good Fruit Grower - October 2012