I see the best way to prevent harm to aphids - use a trap crop (winter pear, for instance) strip planted around the edges of your experimental plots (if it is a spring-seeded pea). The trap crop can be treated regularly by pesticide to kill the beetle. In theory, any contact insecticide should kill the beetle but not aphids... but I am not sure that it will not influence their immigration and settlement. Most of Bacillus thuringiensis -based biocontrol agents will not harm aphids.

I see the best way to prevent harm to aphids - use a trap crop (winter pear, for instance) strip planted around the edges of your experimental plots (if it is a spring-seeded pea). The trap crop can be treated regularly by pesticide to kill the beetle. In theory, any contact insecticide should kill the beetle but not aphids... but I am not sure that it will not influence their immigration and settlement. Most of Bacillus thuringiensis -based biocontrol agents will not harm aphids.

Do the weevils arrive before the aphids, especially when the peas are young? If so, a broad spectrum short acting OP like phosmet is an answer. Regular scouting and good husbandry is always a good idea. BT products, whilst exhibiting low aphid toxicity, do have long term effects. http://aem.asm.org/content/75/14/4897.full

Good luck, A. pisum is a delight to work with.

In potato Bt products were used by us to control CPB to keep aphids alive for virus transmission. But Bt products may not be effective to control Sitona spp.

In the last years we used Alverde (metaflumizone) to control CPB because it has a better and more reliable efficacy on CPB. Aphids seem not to be affected. But I do not know if Sitona is controlled by this active. In contrast to CPB where larvae often are exposed, for Sitona adults are exposed.

You can use a contact insecticide with short residual life like malathion. You can develop further on similar lines.

have you considered to use a toxic baits specific for your beetles? Dr. Robert Metcalf launched a very successful toxic baits program for corn rootworm beetles control in Illinois.

Though, i am not an entomologist but i would like to submit that for beetles contact herbicides are used and for aphids systemic herbicides are used as both of them have different mouth type i.e. Biting & chewing and sucking type, respectively.

Therefore, any contact insecticide would kill those insects which have biting and chewing type mouth parts as beetles in your case. And sorry i wrote insecticide as herbicide in previous post.

There is an aggregation pheromone for this species. You can try trapping them by aggregation using males if synthetic pheromone is not available as a lure. If you are not able to eliminate all of them al least probably you can reduce enough its populations to go on with your studies.

"Male-produced aggregation pheromone in pea and bean weevil, Sitona lineatus" Journal of Chemical Ecology. Volume 13, Issue 4, pp 733-739.

If you are interested in additional collaboration regarding synthetic pheromone I will be glad.

You can use specific microbial enthomopathogen as Beauveria bassiana or Metharrizium sp, first is most specific to beetles. And chemicals, you should know that aphids are insects that have greater resistance range to a huge list of more than 54 molecules of conventional pesticides, is a matter of seeking to degrade easier but at the same time, be effective against weevils.

I was told thatThere are some Baccillus spp. specificy in control of beetles.

As many mentioned above Bacillus thuringiensis ssp. tenebrionis has a coleopteran specificity however I do not know its efficiency againts Sitona spp. Sitona spp. generally are early pests so control against them is necessary merely in the beginning of the growing season.

You can use some biological control method. Above they already told you to try to use B.t. ssp. tenebrionis, Beauveria bassiana. You can also use some parasitoids such as Microctonus aethiopoides (Hymenoptera: Braconidae), also Bembidion quadrimaculatum L. (Coleoptera: Carabidae) consumed S. lineatus eggs (http://www.collectionscanada.gc.ca/obj/thesescanada/vol2/AEU/TC-AEU-29454.pdf )

Halofenozide is best insecticide to kill coreopteran, but not aphid.

The organophosphate insecticide phosmet would kill most beetles but not the aphids as would possibly lower doses of the carbamate carabaryl. The ecdysone agonist IGR halofenozide would be more selective but slower as it would mostly kill larvae and cause sublethal reproductive effects. The first two products would also kill most predators and parasitoids though which would release your aphids from biocontrol and affect their population growth.

There are strains of BT, among which the ssp tenebrionis, that kill selectively some coleoptera (not all. See precisely what beetles you want to kill). BT was largely employed against the colorado leaf beetle and the adequate strain is efficient against most chrysomelids (just to complete the suggestion of Slobodan). The advantage of BT is that it is really harmless for aphids. The suggestion of Takao is good also, but I doubt that halofenozide is completely harmless for aphids. Look at the toxicologic spreadsheet of rhe molecule to be sure.

I worked for 8 years as R&D for Rohm & Haas Co. before going back to the university. Guy Smagghe and I worked on edysone agonist IGRs for our PhD work and after, mostly with tebufenozide and methoxyfenozide, but also RH-5849 which was halofenozide. This class of IGRs works as ecdysone agonists and it selectivity toward particular orders of insects is based on the configuration and transport of the product in the haemolymph of the insect. Tebufenozide and methoxyfenozide are some of the most selective pesticides with little if any effects on non-target hymenoptera or coleopteran because of differences in the ecdysone receptors of those orders. There is some effect on primitive Nematoceran Diptera which are more closely related. Halofenozide was somewhat less specific as it worked best on Coleoptera, but to a lesser extent on Lepidoptera. It never showed activity on Heteroptera in many lab and field trials both with the company and with universities. Just slow to kill the larvae because they begin molting to a new instar prematurely and bleed or starve due to abnormalities in the cuticle. Stop feeding quickly though. Treated adults have reduced fecundity and fertility. Guy Smagghe has most of the papers on this compound and its selectivity. He is on research gate as well as are many of his papers. Since we both worked on it as an experimental compound initially it would be under the RH-5849 designation.

Hi - I agree with most of the above - ideally it would be good to lure, trap and kill the beetles as an application of any insecticide could affect your apids in some way. Hvae you looked into entomopathogens (fungi and nematodes). I see halofenozide mentioned - this is prefered to methoyx- and tebufenozide as it has better beetle activity the others are more lep focussed. Another possibility are the spinosyns (spinosad and spinetoram) - these are active mostly on chewing pests (like beetles, leps and thrips) but have virtually no activity on aphids - depending on where you live both or one are considered as organic. Good luck!

depending on crop. In potatoes cyfluthrin, deltamethrin, permethrin, cypermetrin are poor for aphid control, excellent controlling beetles; esfelerate, same. BUT, biological control is compromised. My two cents

Recalling previous message:

There is an aggregation pheromone for this species. You can try trapping them by aggregation using males if synthetic pheromone is not available as a lure. If you are not able to eliminate all of them al least probably you can reduce enough its populations to go on with your studies.

"Male-produced aggregation pheromone in pea and bean weevil, Sitona lineatus" Journal of Chemical Ecology. Volume 13, Issue 4, pp 733-739.

Entomopathogenic nematodes (e. g. Heterorhabditis bacteriophora) are highly effective against Curculionidae. You would just need to treat the soil during the larval development of Sitona. If you have 2 generations a year than you may repeat the treatment. Steinernema feltiae or krausei (if available) are more effective at lower temperatures and may allow treatments already during or before sowing. Soil temperatures should not below 8°C. At summertime H. bacteriophora or S. carpocapsae are the best choices for a treatment. The nematodes are not effective against adult beetles.

Good luck

Olaf

Instead of endorsing one substance or another, why don't you simply have a look at http://ec.europa.eu/sanco_pesticides/public/?event=activesubstance.selection

http://ec.europa.eu/sanco_pesticides/public/?event=activesubstance.selection

ist not very helpful if you don't have any idea about the mode of action and specificity of the listed substances. You don't want to check each listed substance.

Furthermore, the questioner comes from the USA and not from the EU. So he would need to look at http://iaspub.epa.gov/apex/pesticides/f?p=chemicalsearch:1, but same problem.

If you are doing community studies, you'll want to affect the non-target organisms as little as possible. There are several generalist predators, such as ground beetles, that will affect aphid populations, so if you use an insecticide that is specific to beetles, you will kill those too. Some insecticides can be applied as a seed treatment or a drench, however, you'll have to make sure these chemicals won't affect the aphids (like you say in your question). Adult pea leaf beetles only cause a bit of feeding damage, but it is the larvae feeding on the roots that cause the biggest damage. If you can tolerate some adults, I would recommend controlling the larvae using entomopathogenic nematodes. As suggested above, the adults then might be kept away from your peas by trap cropping or pheromone traps.

Good luck!

Some strains of Beauveria bassiana may be specific for Coleoptera, and B. brongniartii can be more specific.

Try to use biological insecticide on the basis of Bacillus thuringiensis var. tenebrionis (or var. san diego) , because they are efficient for some Coleoptera, but they are safe for Aphids.

Agreed with Slobodan suggestion. Bt is target-specific and not affecting non-target organisms. Besides, u can also follow-up the treatment via pheromone trapping using female beetles or pheromone specific to beetles.

The entomopathogenic nematodes as suggested by Olaf would be a good choice. They would effectively control the root feeding grubs. Adults could be picked using a portable vacuum.

I have a strain of Beauveria which I Isolated from Rhinozerus beetle and it is especially pathogenic to beetles but unable to cause significant mortality of many other insects I have tested it on. You may want to try this, but the ethics of cross boarder transfer of strains? I also want to properly identify the strain genetically to make it useful for scientific reports. I wouldn't mind sending you if quarantine problems are not there.

Bacillus thuringiensis galleriae is now on the market in the United States, it only targets beetles. 

Here https://pnwhandbooks.org/insect/legume-grass-field-seed/pea/dry-edible-seed-pea-pea-leaf-weevil you can find some chemical products. Check if you can use it in your county, country. Read label carefully.