HP88 Strain Research Articles

Predictability in Biological Control Using Entomopathogenic Nematodes

In an examination of entomopathogenic nematodes used in inundative releases on turfgrass against Japanese beetle larvae, Popillia japonica Newman, 380 treatments from 82 field trials performed from 1984 to 1988 were analyzed using a standard protocol. The results show that most test failures can be explained on the basis of unsuitable nematode strains or environmental conditions. Steinemema carpocapsae (Weiser) appears ill-adapted to parasitize Japanese beetle larvae under any range of conditions. By contrast, the HP88 strain of Heterorhabditis bacteriophora Poinar, produced on solid media, provides control comparable with that by chemical insecticides at the appropriate season (fall), soil temperature (>20°C), soil type (silty clay), irrigation frequency (1-4-d intervals), and thatch depth <10mm). The importance of multiple tests that can be analyzed is discussed. Standardized procedures are recommended for field testing; if widely adopted, they would permit comparisons between trials and the generation of large data sets needed for developing statistical models.

Potential of Entomopathogenic Nematodes as Biological Control Agents of Sweetpotato Weevil (Coleoptera: Curculionidae)

The entomopathogenic nematodes Heterorhabditis bacteriophora Poinar (= H. heliothidis Khan, Brooks, & Hirschmann) (HP88 strain) and Steinernema (=Neoaplectana ) carpocapsae Weiser (All and G-13 strains) were evaluated as biological control agents of the sweet potato weevil, Cylas formicarius elegantulus (Summers). In Petri dish bioassays, all three strains were pathogenic to larvae and pupae of C. f. elegantulus . The LD50 values of C. f. elegantulus larvae were 2.6, 2.9, and 3.4 infective juveniles per insect for ‘All,’ ‘G-13,’ and ‘HP88,’ respectively. The LD50 values of pupae were 4.9, 5.9, and 4.8 infective juveniles per insect for these three nematodes, respectively. Virulence did not differ among strains or between life stages within each strain. Under simulated field conditions, ‘G-13’ was most efficacious at killing weevil larvae within infested sweet potato ( Ipomoea batatas (L.) Lam.) roots followed in decreasing order by ‘HP88’ and ‘All’ nematodes. Efficacy in killing pupae within roots did not differ among the three nematodes or between life stages for each nematode. Field applications of ‘HP88’ and ‘All’ nematodes were more effective than chemical insecticides at reducing weevil densities on plants. ‘HP88’ nematodes were more effective than ‘All’ nematodes and chemical insecticides at reducing weevil damage to fleshy roots.

Laboratory evaluation of steinernematid and heterorhabditid nematodes for control of the beetleMaladera matrida

The potential use of steinernematid and heterorhabditid nematodes against the beetleMaladera matrida Argaman (Coleoptera: Scarabaeidae) was determined under laboratory and greenhouse conditions. Infective juveniles (IJ’s) of the nematodeHeterorhabditis sp., Hp88 strain, mixed with soil at a concentration as low as 50 IJ’s/cm3 soil, resulted in 86% control. No increase in control was obtained with higher nematode concentrations. Soil surface application of the nematodes at concentrations of 160 and 640 IJ’s/cm2 was sufficient to obtain 87% and 86% mortality, respectively, even at a depth of 40 cm below the soil surface. TheHeterorhabditis sp. Hp88 strain was found to be the most pathogenic to the beetle grubs at 25°C. Lower control levels of 30-47% were achieved byHeterorhabditis sp. HL81 strain,S. feltiae ‘All’ strain and 5.bibionis CR strain. The nematodeHeterorhabditis sp. BS strain did not have any effect on insect mortality. However, at a temperature of 16°C, the HL81 strain ofHeterorhabditis sp. was the most effective. Grubs 3-5 wk old were found to be the most susceptible developmental stage of infection ofHeterorhabditis sp. Hp88 strain. Pupae, which were exposed to the nematodes in the same experimental regime, were not affected. The results obtained in the present study suggest thatM. matrida is an attractive candidate for biological control by entomoparasitic nematodes.

Cutworm Control with Entomogenous Nematodes in Hybrid Bermudagrass, 1987

Abstract The study was conducted on a so, farm in Thermal, Calif. Experimental design was a randomized complete block with 4 replications. Individual plot size was 50 sq ft. Two species of entomogenouj nematodes were studied. The first was Neoaplectana carpocapsae (= Steinernema feltiae) the All #25 strain, and the second was Heterorhabditis sp. the Hp88 strain. Nematode solutions were applied with a Solo knapsack sprayer using a hollow-cone nozzle at 32 psi and a spray rate of 4 gal/1000 sq ft. Cutworif larval density was estimated by flooding 2 randomly selected areas of 1 sq yd/plot. After 2-3 min the cutworms emerged to the surface and were countedf Pretreatment larval counts were taken on 28 Aug, after which treatments were applied. There was an average of 0.75 larvae/sq yd pretreatment. Posttreatmenf counts were taken on 1 Sep. Soil texture was sandy loam. Water was pH 7.2. Thatch was negligible (Vw inch). Average temperature during the study wai 95°F. The plots were irrigated daily with 0.1 inch of water during the study.