Field Crops News

Parasitic Wasp Attacking Lygus Bugs in Northeast U.S.

Seven years ago 3,000 Peristenus digoneutis wasps were released into alfalfa fields near the University of New Hampshire - Dunham. The female P. digoneutis lays its eggs in young lygus bug nymphs and the wasp larvae develop internally, killing the bug in about a week.

Tarnished plant bug is very common in alfalfa. When the alfalfa is cut for hay, the bugs fly off to infest nearby fruit and vegetable crops. P. digoneutis is now killing many plant bugs before they leave the alfalfa. At one farm in the town of Strafford, 35% of the tarnished plants bugs were killed by the parasite.

The wasp has now been found in six of new Hampshire's 10 counties. It has survived as far north as the Canadian border near Lake Champlain in New York.

Future studies will determine if P. digoneutis is parasitizing plant bugs infesting other crops, such as strawberries and beans.

Adapted From:

USDA News Release. 1998. Parasitic wasps attack plant bugs. Pest Managment News 9(4): 6 (Winter 1997/1998).

Predators of Green Cloverworm in Soybeans

Predatory nabid bugs and minute pirate bugs are common inhabitants of soybean fields where they prey on a variety of insects, including green cloverworm (GCW). Field experiments have shown that Nabis roseipennis can reduce GCW populations, but similar work had not been done for Orius insidiosus.

Lab experiments showed that Orius fed on eggs and 1st instar GCW, but only fourth instars or adults could handle 2nd instar caterpillars. On potted soybean plants, nabid bugs consumed far more GCW eggs or small larvae than did Orius. Even though predation rates by individual Orius on GCW are quite low compared to N. roseipennis, this bug is still an important predator of GCW because of its sheer numbers; it is frequently the most abundant predaceous species in soybean.

Source:

Clements, D. J. and K. V. Yeargan. 1997. Comparison of Orius insidiosus and Nabis roseipennis as predators of the green cloverworm. Environ. Entomol. 26(6): 1482-1487.


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