Stem Boers In Longan/Lamyi Trees

[fredge45]

This year I am experiencing attacks of stem boers in some of my longan trees. The larvae seem to start at the small end of a limb and eat their way down.

The limb will die as the larvae progress. Even if it doesn't die it is weakened and won't support much fruit without breaking.

In that most of the affected limbs are well up in the trees, climbing around to find the tell-tale holes just isn't very feasible. Attempting to apply any insecticide to kill the larvae isn't an option right now with the fruit on the tree and the, seemingly, impossibility of getting anything inside to do the killing.

We have been cutting the affected limbs as we see them, cutting further down the limb until we can no longer find the hole inside.

I do not know what forms the rest of the life cycle of these bugs may be nor when the adults may be around to lay eggs. I would like to spray with a soluble oil to smother the eggs and/or knock out the adults.

Any suggestion or directions are more than welcome.

Edited May 21, 2011 by fredge45

[WatersEdge]

The adult is likely a very large brown beetle with fearsome looking jaws.

Similar to the Sugar Cane fighting beetle that's so popular as a school kid's show and tell,

but not the same species

We had such a beast in North Carolina,

with habits exactly as you describe.

A few days ago my sons were playing with one that appeared on our porch here in Mae Sot.

They wanted to know what it was, was it poisonous, all the questions a fascinated boy has.

I told them it's not poisonous and you can play with it all you like, just don't hazard your fingers in those jaws.

He won't give you lasting damage but it won't feel good for the moment.

The thing was finally annoyed enough to fly off into the nearest Tamarind tree.

I recognized the similarity immediately, so am fairly confident to connect the dots.

I'm not the bug expert around here, just a layman's observation of known patterns.

[drtreelove]

I don't know this specific borer. Have you seen an adult? It is probably a beetle as WE indicated, but could be a clear-wing moth (looks like a wasp). If you can identify the adult you can find out more about life cycle and vunerable timing for controls."Emergence" is when adults emerge from pupation and fly to the same or nearby trees to bore and lay eggs again. Timing a barrier spray just before emergence is when you can prevent a new generation of activity. A barrier spray can be something like permethrin (a pyrethroid) which binds to the bark and prevents new boring activity; more practical for trunk borers than crown. Some borers have one emergence a year, but some have two or more.

Some borers spread fungus diseases which spead and kill tree tissues. This one looks big enough to do damage all by itself from the feeding activity. I don't have time to follow up on this for you, but you can send picutures and description to "Pisuth EK-AMNUAY" insectzoos at hotmail. He's the author of the pest and disease book that I reviewed last year on this forum. Run it by the Plants, Pets and Vets forum too, there are some very knowlegeable biologists there, and some don't read this farming forum. If you are near an agricultural university, you can walk in with your samples to the entomology or plant protection department, or pomology dept (fruit trees), There are extension services but I've never used them. The Thailand Dept of Agriculture has a biological control division where I've received some good information in the past.

Unless you are an organic farmer , non-systemic contact sprays are not so bad for lamyai, because the skin is removed before consumption. But spraying is not usually effective for borers like it can be with sucking and foliage chewing insect pests, unless you can pin down the life-cycle and vulnerable stage; it is complicated because the larva that does the damage is inside the wood where contact sprays cannot get to it. Eggs may not be on the plant surfaces where oil sprays could be effective like with surface feeding pests; beetle borers usually lay eggs inside galleries that they bore in the stem. Moth eggs are layed in cracks and crevices and may also not be exposed for contact spray or oil.

You are doing the right thing to prune out the active/damaged branches as soon as possible; and be sure to burn, chip/grind or remove from the site.

Prevention is the key in dealing with borers. Adequate soil moisture is usually a key element; drought stressed trees are move vulnerable to attack; so be sure to consider your irrigation program. Don't overfertiilze, especially with high nitrogen fertilizers or manure. Soil fertility, organic matter content and mineral nutrient content and balance are important in builiding resistance to pests and disease. Also, not using broad spectrum pesticides that kill off the beneficial/predatory critters is important. Biological control can come from birds, mini-wasps, bats, ants, and others.

Please post your results/experience with this. Good luck, don

Edited May 22, 2011 by drtreelove

[drtreelove]

Another point in pest prevention is not to do radical pruning. Heavy pruning creates a response of rapid shoot growth that is susceptible to pest infestation. Don't prune more than 25% of the foliage in any one year period.

[fredge45]

Came across this copy of an article by Eric Danell of Dokmai Garden which appeared in the Chiangmai Mail last year.

I also understand that there is another suspect in the form of a nocturnal moth... I'll post what I can find on that.

My thanks for the input by the responders... Don is an important and knowledgeable member of this board and I really appreciate his input.

Boring beetles.doc