Palo Verde Root Borers

I have seen many Palo Verde (PV) trees impacted by the Palo Verde Root Borer: truck and limbs turning golden brown, leaves drop. All these symptoms develop after the damage has been done. But this year I ran across something I have only ever described after the palo verde begins rapidly declining.

I have always told clients to look for broomstick sized holes in the soil under the tree canopy in the middle of summer if their PV begins turning a golden brown. Well how excited was I when I not only discover it at one client's property, but two properties in the same week! (palms sweating from excitement even as I write about it now!)

When I arrived to a property with a recently declined Mexican PV, I was confident what we were looking at was a death due to the PVRB, but a closer look and there was clear confirmation. The nasty beetle had been there, done damage and fled. So if you suspect your PV has declined due to this spiny-legged critter, take a closer look at the ground and look for these broomstick sized holes.

Unfortunately, often times a Palo Verde Root Borer infestation is a death sentence for the tree. Your best bet is to make sure your trees are healthy, watered appropriately and planted at the correct depth. This pest generally will not attack a healthy tree. It does seem to prefer the Mexican Palo Verde and Palo Brea species for a meal.

Sucessfully Treating the Agave Snout Weevil

As the Agaves begin wilting out there, I am getting more and more questions about the proper treatment for prevention. The first questions is whether or not to treat. Not treating you take a risk of infestation, which may or may not happen this year or even next year. However, if infested, consider the agave a goner. If you have a large number of plants you want to protect, it can be quite costly to treat.

The key to successfully treating agaves is in the timing of your pesticide applications. Your first application of the season needs to be just prior to insect activity in the spring, which is most often dependant on soil temperatures. As temperatures increase in March, activity of the ASW will begin. If using a 'protective' systemic insecticide, you want to make your application before the weevil's activity. Contact insecticides labelled for drenching can also be helpful in killing existing infestations. Make sure both chemicals control Coleoptera insects, otherwise you will waste time and money with your treatments.

Follow-up with a second application of the systemic insecticide just before the residual runs out. Most professional products provide up to 90 days control if used at the high rates. Contact insecticides often only last 1-2 weeks in the high temperatures so don't count on them for control for more than a short period.

If the Agave Snout Weevil does feed on an agave, you won't know it until the rot begins to destruct the agave, most often in the mid to late summer in the Phoenix area. If they are wilting, don't bother treating these plants. Remove the agave along with the soil around the root ball and try not to plant back immediately. When you do replant, treat the new agave with the systemic insecticide for future protection.

If you would like specific chemical recommendations and the proper timing of your applications, please call me for a customized management program. Remember to keep them healthy- careful not to overwater them throughout the year!

Agave Snout Weevil

Every summer, I get calls from landscapers in Phoenix about agaves suddenly wilting and dying. It has to be a fungus, right? Well, sort of, but it is actually a rot that has been caused by the feeding of an insect called the Agave Snout Weevil. The Agave Snout Weevil enters the plant at the base where the larva eats the tissue, inviting decaying organisms also to start working on the agave.

Once the larva has done its damage, the adult- that’s the one with the ‘snout’, will move on to lay eggs on its next victim. The ASW loves the Agave americana, Agave desmentiana and other larger agave species. Though multiple generations per season can sometimes occur, it is best to treat in the fall and again in the late spring when life stages are most susceptible. Preventative treatments are your best bet. If you see wilting, remove the plant and surrounding soil immediately so they don’t move to other nearby agave.

Psyllids

Psyllids begin showing up in the springtime and will hop around on different host plants has temperatures change. They are often confused with aphids due to the fact they are similar in shape, color and cause similar damage. The main noticeable difference between aphids and psyllids is aphids can easily be controlled by hosing off weekly, psyllids are not so easily controlled. They are closer to the leaf, leave crystal-like deposits (excrement) on the foliage that often acts as a protective shield. These barely-visible insects can be very devastating to a host. Arizona and honey mesquites can have new growth deformed for the season and Cascalotes can be defoliated in a matter of weeks if not properly managed. Besides chemical treatments, you can help manage populations by limiting irrigation or trying not to over-water which can promote new succulent growth, which is attractive to the psyllid. Monitor for these little guys starting in February continuing into the summer months. They may go away for the hottest period of the summer (who wants to hang out on a leaf at 110?) but resurface again in the fall.

Spider mites NOT Welcome

Mid-March and already spider mites have made their mark on Italian cypress and oaks. Since we had a warm fall, followed by a mild winter and no rain in March (so far) the Two-spotted spider mite has settled in and started sucking plant juices earlier in this season than expected. At this point in the season, look for copperish leaf discoloration or overall browning and death of a branch. If populations grow, webbing will start to be noticed, usually starting at the base of the petiole and the underside of the leaf and defoliation may be seen. Spider mites love dusty leaves so hose off your cypress, oaks and rosemary regularly to help keep populations low moving into the summer months. If you need help with a spider mite management program for your properties, please send me an email and we can discuss management strategies ideal for your situation.