Steinernema puertoricensis n. sp., isolated from sand collected from a coconut plantation, can be distinguished from S. glaseri, its most closely related species, by characteristics of the first generation adults. The female has a greater body length (8.6 mm) and width (375 µm). Males have the excretory pore anteriad or posteriad to the nerve ring. Spicules are arcuate and lack a hook at the ventral side of the spicule tip. Infective third-stage juveniles are over 1 mm in length. This appears to be the first species of Steinernema described from the Caribbean islands and adapted to a hot humid environment.
The effect of several isolates of entomogenous nematodes, Heterohabditis spp., from Puerto Rico was tested under laboratory conditions against larvae of Galleria mellonella, Cylas formicarius, Euscepes postfasciatus, and Cosmopolites sordidus. Five isolates demonstrated their capacity to kill the insect larvae. Isolate 2 was considered highly effective against all insects tested; isolates 14 and 27 caused high mortality rates to larvae of G. mellonella, E. postfasciatus and C. sordidus. Isolate 17 was effective against larvae of C. sordidus; isolate 18 against E. postfasciatus. The rest of the isolates tested varied greatly in their ability to kill the larvae of the insects used.
The entomogenous nematodes Steinernema feltiae Filipjev ( = Neoaplectana carpocapsae Weiser), S. glaseri Steiner, and S. bibionis Bobien (Steinernematidae: Rhabditida) were evaluated as biological control agents against the banana root borer weevil Cosmopolites sordidus. In the grub stage this weevil bore tunnels in the corms of plantains thereby promoting infection and plant decay. In petri-dish trials the three species produced severe mortality at population densities of 4,000 and 40,000 nematodes. Similarly, in greenhouse tests, the three nematode species at rates of 400, 4,000, and 40,000 nematodes/4-month-old plants apparently reduced the number of tunnels produced by the grub. Grub mortality was 100% at nematode populations of 4,000 and 40,000 per plant.
Ten greenhouse experiments tested the effectiveness of the entomophilic nematodes Steinernema feltiae Filipjev, S. glaseri Weiser, and S. bibionis Bobien against larvae of the sugarcane rootstalk borer, Diaprepes abbreviatus (L.). S. feltiae caused mortality to 12- to 16-week-old D. abbreviatus larvae at population densities of 1,000 to 3,000 nematodes/ 300 cm3 of soil. Four hundred S. glaseri or S. bibionis also caused significant mortality of the grubs. An increase of 4,000 to 40,000 S. glaseri/300 cm3 of soil increased mortality of the grubs. S. bibionis infectivity decreased with time, and high rates of mortality of the infective juveniles were recorded under laboratory conditions. When grubs were placed in petri dishes in direct contact with the nematodes before placing the infected grubs in soil, the mortality was independent of the density or nematode species used. These results demonstrated the effectiveness of the entomophilic nematodes and their potential for biocontrol of D. abbreviatus.
In a series of greenhouse tests to determine the susceptibility of the larval stage of the curculionid Diaprepes abbreviatus to the entomogenous nematode Neoaplectana carpocapsae, the nematodes controlled the insect larvae. Grubs 1.5 to 3 months old (smaller than one inch long) were less vulnerable to death than older 3- to 4-month-old grubs. The highest grub mortality, 86.66%, was obtained with the nematode density of 40,000 nematodes per pot. When nematode density was increased from 40,000 to 400,000 nematodes per pot grub mortality did not increase. Grubs placed in direct contact with nematodes in petri plates were equally killed, independently of the nematode density used. Direct nematode inoculation through grub's mouth, anus or a combination of mouth and anus or steeped in water containing nematodes did not increase grub mortality beyond that already obtained in the soil. If similar results are obtained in the field, this method of control could be of great value to reduce D. abbreviatus populations.
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