Ammi visnaga(L.) Lamarck (Apiaceae): Associated Beneficial Insects and Implications for Biological Control, with Emphasis on the Bell-Pepper Agroecosystem

Abstract

Toothpick ammi (Ammi visnaga (L.) Lamarck, Apiaceae), a summer annual of Eurasian origin, commonly occurs along agricultural field margins in the Sacramento Valley of northern California, typically flowering from June to August. Observations during 1979–1984 yielded 65 distinguishable insect taxa attending the flowers, including 60 groups that were at least in part entomophagous. Peak attendances occurred for Braconidae, Ichneumonidae, Sarcophagidae, Sphecidae, Tachinidae, and Vespidae during early morning hours. Hay alfalfa (Medicago sativa L., Fabaceae) was grown in replicated plots with borders of either: (1) toothpick ammi, (2) common knot weed (Polygonum aviculare L., Polygonaceae), (3) prostrate pigweed (Amaranthus graecizans L., Amaranthaceae), or (4) Clean-cultivated edges. Borders of flowering toothpick ammi attracted numerous entomophaga, but had no effect on densities of minute pirate bug (Orius tristicolor [White], Hemiptera: Anthocoridae) occurring in alfalfa. Pepper (Capsicum annuum L., Solanaceae) was grown with borders of either: (1) Vegetative Ammi, from which the flowers were repeatedly clipped, (2) Normally-flowering Ammi; or (3) Clean-cultivated borders (control) to assess impact on abundance of entomophaga. Predator densities and efficiencies within the plots were assessed weekly by: (1) Weekly whole-plant visual inspection; (2) Use of sentinel egg masses of beet armyworm (Spodoptera exigua (Hübner), Lepidoptera: Noctuidae) or omnivorous leafroller (Platynota stultana Walshingham, Lepidoptera: Tortricidae), glued to the apical foliage and later inspected for occupation, or damage, by predators; and (3) Chunks of tuna placed on cards at ground level and later inspected for occupancy by bigeyed bugs (Geocoris spp., Hemiptera: Lygaeidae). Whole-plant visual inspection revealed a complex of generalist predators; those found on sentinel egg masses were in decreasing order of frequency Orius tristicolor, Geocoris pallens Ståi, Lygus spp. (Hemiptera: Miridae), G. atricolor Montandon, Collops vittatus (Say) (Coleoptera: Melyridae), and Nabis sp. (Hemiptera: Nabidae). Weekly inspection of whole pepper plants failed to indicate differences in Orius density due to border regime. Likewise, there were no significant differences among weed regimes in numbers of Orius per sentinel egg mass placed on pepper plants amid the plots. However, another trial indicated that Orius recruitment to egg masses was higher on pepper plants with immediately-adjacent Ammi. Per-plant abundance of Geocoris and predation efficiency (Geocoris per lepidopterous egg mass) were separately regressed against Geocoris per tuna bait. Statistically-significant relationships were obtained when data were assessed across all dates, employing the mean counts for each date. Pending further testing, toothpick ammi should be tolerated in field- and road-side settings, as it is seldom a problem in crops and apparently supplies sustenance to many entomophagous insects.