Willow trees , Salixspp . , are deciduous trees worthy for cultivation in USDA Hardiness Zones 4 to 9 .
They make imposing landscape specimens with heights from 20 to 140 foot and spreads of 30 to 60 groundwork , reckon on the variety .
ethnic necessary include full sunlight to part shade , moderate to high wet , and well - draining , loamy soil .
A sawfly larva,Pontaniaspp., parasitizes a willow. Photo credit: Whitney Cranshaw, Colorado State University, Bugwood.org
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Sometimes , you may notice galls – warty bulge on the leave or growths that look like short pine cone shape at the ending of the branch , or even unearthly swelling on the trunk .
There may be few or many , and like me , you may get them fascinating .
A sawfly larva,Pontaniaspp., parasitizes a willow. Photo credit: Whitney Cranshaw, Colorado State University, Bugwood.org
In ourguide to growing willow tree treeswe cater all you demand to know to cultivate these cosmetic shade trees in your outdoor bread and butter outer space .
This article discusses galls usual to tree diagram in theSalixgenus and suggests proactive steps you may take to avoid them .
Here ’s what we ’ll cover :
What You’ll Learn
What Are Willow Galls ?
Common campaign
Management and Proactive Measures
Let ’s start .
willow tree saddle sore are tumorous or wart - similar growths that appear on the leaves , stem , and/or branches .
They can be do by bacteria , fungi , insects , mites , nematodes , and viruses that release growth - modulate chemicals into emerging or young willow tree tissue .
Older foliation is not normally vulnerable to these parasitical organisms .
The chemicals cause increase hormone yield and abnormal cadre sectionalisation in the plant tissue paper , resulting in tumor - comparable abnormalities .
In some cases , the galls nourish , protect , and shelter the progeny of the pests that caused them .
Let ’s hash out some of the causative agents that can result in strange growths on willow tree .
Bacteria
Rhizobium radiobacter , antecedently known asAgrobacterium tumefaciens , is a soilborne bacterium that causes crown gall , tumorous growth on the crown , where the bole and rootage run across , and on the roots .
The bacterium go into damage plant tissue , causing hormonal changes and atypical cell division .
These change produce galls or nodules that facilitate the housing and eating of the parasitic bacteria at the tree diagram ’s disbursal .
Symptoms let in boss on willow branches , root word , and trunk . When the knobs join and deaden a trunk , an senior tree may outlast , but a younger one may die from impaired water and nutrient ingestion .
Fungi
Melampsora caprearum , or rust fungus fungus , causes rancour formation .
symptom let in white-livered discoloration and vein anomalousness on willow leaf topside and lift , powdery , orangey bumps on the undersides .
Midges, Mites, and Sawflies
In addition to bacteria , parasitic midge , mite , and sawflies cause tumors on willow trees , generally on the stem turn and foliage .
Midges are flyspeck unfeigned fly . Over 100 species in theRabdophagagenus can produce abnormalities at or near the branch tips with their feeding , includingR.rosaria , R. strobilina , andR. strobiloides .
Different species within the genus may be “ inquilines ” or cohabitants of an individual increment or gall .
Females pierce the foliage and lay their egg inside it . When a tree reacts to the midge ’s growth - determine internal secretion , it creates precisely what the sponger necessitate to lift their young – protective shelters full of eatable industrial plant tissue .
The orchis concoct , and the larvae provender and mature to pupae before emerging as adult .
There is one generation of midges per growing season . After wintering over in the soil , adult resurface in the springiness to start the cycle again .
Here are a few species you may encounter :
R. rosariamidges cause tip foliation to contain grow stem and instead produce layer of leaves like those of an globe artichoke at the ship’s boat limb tips .
As they age , they dry out and resemble withered roses .
R. salicisproduces smooth , spindle - shaped increment on attendant stems . These galls resemble lilliputian Raphanus sativus with top foliage still attached .
The stem canker - style tumor ofR. strobilinaare marvelous and cabbage - similar and appear at the growing tips of the outgrowth .
R. strobiloidescreates dwellings that resemble pine cone with many layers of leaf tissue paper making a thickset barrier to protect the young from predators .
You ’ll incur them at the terminal ends of the branches where the leave-taking are untested .
The willow leaf insolence hint , Aculopstetanothrix , is a tiny , insect - similar pest with two ramification . It is an arachnid rather than an worm and is a penis of the Eriophyidae family of parasitic mites .
With their chewing mouthparts , the pinch feed on the foliage , producing warty bumps along the leaf nervure on the upper and/or undersides of the leafage that set forth unripe and eventually shade to redness .
Leaf drop may occur in the case of extensive hurt .
The willow tree red gall sawfly , Euura proxima , akaPontania proximais not a true tent flap but a miniature wasp - like louse .
female lie their eggs in dustup along the central leaf vena or midrib .
The growths formed are smooth and green , shade to red , and may be on the upper and/or undersides of the leaf and on the stems or petioles . As the larvae grow , so do the galls .
pupa come forth and dangle to the ground , where they overwinter in plant debris and emerge as adult the keep an eye on spring . There may be several generations in one farm season .
Nematodes
Unlikebeneficial nematode worm , root - knot roundworm ( RKN),Meloidogynespp . , are “ endozoan ” that bottom injured plant tissue and live in roots beneath the stain , create swollen insolence and suppress piddle and nutrient uptake .
M. incognitauses willows and many other landscape flora as its server .
While the galls produced by root - grayback roundworm are n’t the ones you see on the leaf and staunch , they would be visible if you were to dig down and examine the roots .
seeable aboveground symptom admit chlorosis , or leaf yellowing and foliar disfiguration . Below ground , the root acquire fierce and crack .
Parasitic nematodes are not very likely to pose a threat in colder regions because temperature below 64 ° degree Fahrenheit inhibit their ability to overrun the roots .
You canlearn more about theme - knot roundworm in our guidebook .
Viruses
Viral causes of willow tree crust are not as well understood as other agents discourse here .
What is certain is that sapsucking louse likeaphidsare likely vectors or transmitters of infections that may leave in growth anomalies on the stems , leaves , or ament , the pendant clump of flowers .
It is important to handle midge , mite , sawfly , and other pest populations to suppress disease transmission .
There are no organic or chemical treatments for crown gall – it is incurable .
Once an transmission is confirm , you have to ruin affected trees and replant the field with a resistant species , like catalpa , golden rain tree , ormagnolia .
bar measures let in buy tree diagram certify to be disease - free and hygienize all pruning equipment before and after use .
For Foliar Abnormalities
If your trees display telltale hump , cones , and/or wart - like growths , there is nothing you could do to control it during the current season .
If they are not all-encompassing , you’re able to prune off the damaged sprig or leaves .
To do this , sanitize your pruning shear or a saw with rubbing alcohol or a 10 percentage blanching agent - to - pee solution ( one part bleaching agent to nine section water ) and ignore off affected foliation and stems , disposing of septic plant material in the chicken feed . Sanitize equipment again after use .
Proactive avoidance measure include :
Heterorhabditis bacteriaphoranematodes are microscopical roundworm that parasitize a number of pest including gall midge .
Apply these living organisms as soon as the temperature is consistently above 42 ° F in the spring . The challenge is to have them in place before the midges result their winter homes in the grunge .
NemaSeek Pro Hb Beneficial Nematodes ™ are easy to mix with water and spray over the ground per parcel instructions .
NemaSeek Pro Hb Beneficial Nematodes
NemaSeek Pro Hb Beneficial Nematodes ™ areavailable from Arbico Organics .
Introducing host - specific parasitoid white Anglo-Saxon Protestant may prove effective , however , the type of dirt ball choose must be a natural predator that parasitizes the eggs of midges , mites , or sawflies that use willow as their legion .
late research march that a leechlike wasp in theSynopeasgenus , S. uttermost , quarry upon soy gall midges .
Future findings may determine which specie is appropriate for willow tree gall midge .
Finally , not all sawfly induct galls , so products targeting sawfly in oecumenical may be ineffective against those that scathe willow tree .
A Galling Problem
It ’s pesky to have foliage covered with unsightly bump and no easy way to demolish the perpetrators .
Take meat in know that the damage is most often cosmetic and unconvincing to undermine the wellness of your darling willow tree .
Take the proactive beat discussed to disembarrass the ground of widow’s weeds and other pace debris that may otherwise harbor offending midges , mites , and sawflies .
Try an early - season program program of good nematodes to curb gadfly reemergence in the give .
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Nan Schiller
