Finding effective natural enemies is only one of the challenges to implementing an augmentative biological control program. Delivering the natural enemy to the crop introduces new challenges. One of the reasons for interest in entomophagous nematodes is that they can be readily delivered using standard pesticide spray equipment. Developing ways to transfer parasitoids and predators with modified spray equipment could greatly enhance adoption of some augmentative procedures. Use of acrylamide sticky gels and seed drills to deliver eggs is only one of the new promising techniques of natural enemy delivery. Using aqueous suspensions to deliver natural enemies could also be quite attractive to potential biological control practitioners because of its compatibility with spray systems.
Research conducted with eggs of the green lacewing Chrysoperla rufilabris and Trichrogramma pretiosum in the eggs of it insectary host Ephestia kuhniella suggests that aqueous delivery systems could work rather well for these natural enemies. Eggs of C. rufilabris remained viable when submerged for 3 hours in water, or when agitated for up to 60 minutes and sprayed out of a compressed air sprayer with a FloodJet TK3 spray nozzle. Likewise, rate of T. pretiosum emergence from the similarly treated eggs of parasitized E. kuhniella was no different from that of unhandled control eggs. Development of these efficacious delivery techniques could greatly simplify delivery of natural enemies to a wide variety of cropping systems.
Source: Gardner, J. and K. Giles 1997. Mechanical distribution of Chrysoperla rufilabris and Trichogramma pretiosum: Survival and uniformity of discharge after spray dispersal in and aqueous suspension. Biological Control 8: 138-142.
Nematodes Control Black Vine Weevil
The black vine weevil is a serious pest of nursery and landscaping plants throughout much of the country. The larvae feed on roots and girdle stems near the soil surface; the adults chew holes in foliage. When population levels are high, the larvae can do substantial damage. Damage frequently occurs in urban landscape settings, including small beds of mixed shrubs and containerized plantings. Such areas may be in home gardens, parks, or in commercial settings such as shopping areas and restaurants. Although commercial insecticides are available for controlling black vine weevil, in some situations where people congregate, biological control may be a more preferred option.
California workers have evaluated insect parasitic nematodes against this pest in planters in an area of commercial buildings in San Francisco. The nematodes evaluated were two commercially available species, Steinernema feltiae (rate of 327 nematodes per square inch) and Heterorhabditis bacteriophora (474 nematodes per square inch). Applications were made with a Hudson sprayer. One year later the planters were sampled for results. The untreated planters averaged 19-24 black vine weevil larvae and pupae whereas with both species of nematodes the black vine weevil populations had decreased to about 1-5 per planter. Both species of nematode were still present at the end of the experiment, indicating that they had successfully reproduced throughout the year.
Although the long-term survival in similar situations has not been evaluated in the harsh winter climate of the Upper Midwest, it is likely that early-season applications of nematodes will infect black vine weevil, if applications are made when larvae are present.
Source: Burlando, T. M., H. K. Kaya, and P. Timper. 1993. Insect-parasitic nematodes are effective against black vine weevil. California Agriculture 47 (3):16-18.
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