Diabrotica beetles

The blossoms of Cucurbitaceae are well known to be highly attractive to many species of Diabrotica beetles. However, the volatile compounds that act as attractants differ in different Diabrotica species. Cinnamaldehyde strongly attracts the spotted cucumber beetle, Diabrotica undecimpunctata hoivardi, whereas 4-methoxycinnamaldehyde is a specific attractant for the western corn rootworm, Diabrotica virgifera virgifera.51 The northern corn rootworm, Diabrotica barberi, and Diabrotica cristata are attracted to eugenol, cinnamyl alcohol, and 2-(4-methoxyphenyl)ethanol. Volatiles of maize, one of the host plants, also attract D. v. virgifera... 

Arthropod defensive secretions may also be sequestered from food plants 68). Thus Ferguson and Metcalf 170) found that four species of Diabrotica beetles sequester cucurbitacins as their defense compounds. 

The Diabrotica spp. com rootworm beetles are specifically attracted to a variety of plant-produced phenylpropanoids, eg, ( )-cinnamaldehyde [14371-10-9] for the southern com rootworm D. undecimpunctata howardr, ( )-cinnamyl alcohol [4407-36-7] for the northern com rootworm D. barberi and indole [120-72-9] for the western com rootworm, D. virgifera virgifera. Especially powerflil lures for these rootworm beetles are 2-(4-methoxyphenyl)ethanol for the northern com rootworm and 4-methoxycinnamaldehyde [71277-11-7] (177) for the western com bootworm. 

Insecticides Vetch aphid (Megoura viciae) bollworm (Helicoverpa zea) army worm (Spodoptera littoralis) diamondback moth (Plutella xylostella) mustard beetle (Phaedon cochleariae) corn rootworm (Diabrotica undecimpunctata) whitefly Bemisia tabaci) red spider mite (Tetranychus urticae). 

Diabrotica undecimpunctata howardi. See Cucumber beetles Southern corn rootworms Diagnosis... 

The compounds were evaluated for insecticidal and acaricidal activity against the following species cabbage looper (Trichoplusia ni [Hubner]), Mexican bean beetle (Epilachna varivestis Muls), southern armyworm (Spodootera eridania [Cram]), pea aphid (Acvrthosiphon pisum [Harris]), twospotted spider mite (Tetranvchus urticae [Koch]) and southern corn rootworm (Diabrotica undecimpunctata Howardi). 

Toxicity of the compounds was examined in four types of insects house fly (Musca domestica), mosquito (Aedes aegypti), corn rootworm beetles (Diabrotica virgifera virgifera and Diabrotica undecimpunctata howardi) and the German cockroach (Blattella... 

Cucurbitacin B evokes chemosensory responses at levels as low as 0.1 uM, probably acting at a different modulatory site than do classical synaptic y-aminobutyric acid (GABA) and glycine receptor-channel complexes. Chyb et al. [83] studied adult western com rootworm (Diabrotica virgifera virgifera, Coleoptera-Chrysomelidae) beetles and reported the possibility that there are peripheral chemosensory receptor sites that may resemble, both functionally and structurally, synaptic receptor sites in the CNS. 

Activity E. and chavicol are attractants for the beetles Diabrotica undecimpunctata and D. virgifera occurring in the South and West USA where they attack corn roots. 

The Egyptian cotton worm (Spodoptera littoralis larva) (left) and banded cucumber beetle (Diabrotica balteata) (right). 

Triterpenes Cucurbitacins (D 6.4) Feeding attractant for Diabrotica undecimpunctata (beetle)... 

Sex pheromone of the banded cucumber beetle Diabrotica balteata (abs. config. of nat. pheromone not yet known). 6R,12Ryform... 

Abscisic acid is a sequiterpene phytohormone that is induced by drought and promotes stomatal closure and seed dormancy. Other sesquiterpenes take part in tritrophic plant-herbivore-parasite interactions (reviewed by Dudareva et al., 2006). In maize infested with lepidopteran larvae, the sesquiterpenes ( )-P-famesene and the ( )-a-bergamotene (Fig. 30) attract the parasitic wasp Cotesia marginiventris (Schnee et al., 2006). Maize roots release ( )-P-caryophyllene (Fig. 30) upon attack of larvae of the beetle Diabrotica virgifera to attract the parasitic nematode Heterorhabditis megidis (Rasmann et al., 2005). 

Another example of partial modification in the insect is found with the beetle Diabrotica speciosa. It feeds normally on plants of the Cucurbita-ceae (cucumbers) which contain bitter triterpenoids (Chapter 7) called cucurbitacins. D. speciosa when fed on [ C]-cucurbitacin B converts it by removing the C-25 acetate and reduces the side-chain double bond to give dihydrocucurbitacin D (Figure 10.17). Other species raised on diets free of cucurbitacins, when fed cucurbitacin D, were able to glycosylate it (at the 2-OH), hydrogenate, desaturate and acetylate it. 

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