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Who knew they were declining? Well, ecologists Richard "Rick" Karban Mikaela Huntzinger of the UC...

When It Gets Hot, It Gets Confusing

So I got called out to see an orchard that had dieback. Over the phone it sounded like “Dothiorella Leaf Blight” (//ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=10354). This symptom shows up when there has been water stress of some sort, over a period of a few weeks to months. 

It can be a branch or a whole tree. It usually is due to a watering schedule that doesn't meet the needs of the plant.  It is exacerbated by competition from more aggressive plants nearby, like eucalyptus windbreaks.  With increased competition over time, root rot can also start taking its toll because of the stress, as well. Where you see areas cleared of trees, and where there are struggling trees in various stages of survival, it's a good indication of a rough environment.

 

Trees with root rot symptoms may have been stumped previously, and with their weakened root systems are more prone to leaf blight.

In the case of this grove, it was at the top of the hill where it got all the wind and a full day's sun above the typical coastal fog.

So the grower asked about the damage. There was the heat damage from the July heat wave.

Then there was the damage that had showed up earlier, the leaf blight that was associated with the ongoing water stress. In a way, both of these symptoms are of water stress, one very rapid, hence the reddish tint to the leaves. The other a slower collapse, the leaf blight from prolonged water stress. 

Over time, this type of stress had allowed root rot to take hold and trees were stumped in order to help them survive. The trees were also started on a regular phosphonate program.  In general, the rest of the orchard looked good, except for this area near the competitive windbreak trees. The heat damage was mostly in this area, as well. The grower had been forewarned of the impending heat and irrigated the trees prior to the hard weather.

In the case of heat damage or blight, and leaf/stem blight, it's not fatal for mature trees.  Younger trees under two years can be killed.  They usually need whitewashing to prevent sun burn damage. 

But even they can be revived if the watering is improved.

Spotlight on Farming Strawberries Indoors

It looks like even the Wall Street Journal has caught the urban farming bug.  Link to article below out of their "The Future of Everything" series, followed by my comments.

 

https://www.wsj.com/articles/strawberry-jam-urban-farming-startups-tackle-a-problem-crop-1534424400?mod=searchresults&page=1&pos=1

I find it utterly mind-blowing the obsession with pollination indoors.  Strawberries are self-pollinated and do pretty well in the absence of bees, it is even noted in the article towards the end that a grower who spends a lot of time with her plants already doesn't see any issues.

No mention of Botrytis grey mold, which in a windless, less than ideally ventilated space must be a fearsome problem. Ditto mites.  All of this is lost on the obsession with pollination. 

Instead, the indoor growers really should be focusing on light (intensity and length) and temperature, and I'd personally invest some time on seeing responses to different chill times pre-plant.  Would it even be possible to artificially chill plants in the closed environment after fruit production as a form of renovation?  Now THAT would be interesting and possibly yield big dividends, certainly much more than getting one's shorts in a twist about pollination.

Nice quote by Gerald from the CalPoly Strawberry Center, bringing everyone back to reality on what it is going to cost to farm berries like this.  

 

 

When Biocontrol Turns On You

When a biocontrol agent turns on you, it can be painful. Recently a grower called in asking about an insect that had bit him when he picked it up. It caused a fearsome pain and some swelling. This insect is an assassin bug, one of the numerous predators out there that help keep pest insects in control.

Assassin bugs (family Reduviidae) belong to the order Hemiptera and the suborder Heteroptera, the so called “true bugs.”  Altogether, nearly 7,000 species of assassin bugs have been described worldwide, of which about 50 are native to California. All Hemiptera have tubular mouthparts with stylets that help them pierce tissues of plants and other creatures.  The stylets may also help them suck blood.  Indeed, 140 species of assassin bugs are specialized to feed on blood.  Spreaders of Chagas disease, these are the kissing bugs, so named because they frequently bite people on the face around the mouth.

Within insects, they are one of the third biggest groups of predators that mostly feed on other insects. This determines where they are found: many species sit on flowers or leafs, where they stalk or ambush their prey. Others like to hide in special microhabitats, for example, underneath the bark of trees, and feed on insects – such as certain beetle and fly larvae – that live under the bark.

In general, the greatest numbers of assassin bugs are found in wet tropical places around the world, but some also live in subtropical, arid and even temperate places.  About 50 species are native to California and the majority of them also occur in Southern California. In California, you can find different species of these bugs from the low deserts to fairly high elevations in the Sierras.  Altogether, we have fewer than 190 species recorded from the United States and Canada, but as you get into Central and South America, diversity increases and the species numbers go up.

A common species in California is the leafhopper assassin bug that is frequently found even in backyards around Riverside. It is widely distributed from Canada to Central America. Although it is native to this region, it has been introduced and become established in Chile, Greece and Spain. Leafhopper assassin bugs hang out on various plants and are beneficial – as are many other assassin bugs – because they eat pests that can be a nuisance to crops and ornamental plants.

The smallest are about 3 millimeters long.  The largest can be about 1.5 inches in length. As other true bugs, assassin bugs have “divided” wings, meaning that the forewings have a thick leathery texture close to the head and a more membranous structure further back. Assassin bugs can be recognized by the shape of the beak that is typically curved and pretty thick and has three segments.  The bug uses this beak to grab and hold on to its prey.  There is no need to panic when you see an assassin bug, but since they can inflict rather painful bites it is best not to touch them. Kissing bugs are somewhat unusual amongst assassin bugs in having a fairly slender and straight beak. Although their bite is painless in contrast to the bite of other assassin bugs, they are much more dangerous: their saliva can cause allergic reactions, and they can also spread Chagas disease.

The protozoan that causes Chagas disease, Trypanosoma cruzi, is not transmitted when the kissing bug bites you and sucks your blood.  Instead, it is transmitted soon after the kissing bug has stopped feeding blood.  When a kissing bug bites you, you don't feel anything at first because the bug injects an anesthetic and the bite will only get itchy shortly thereafter.  Now, after its blood meal, the kissing bug defecates. The feces contain the Chagas-disease-causing protozoans.  When you scratch, you get the feces into the wound and your blood stream. We have three species of endemic kissing bugs in California. Many of the specimens of our commonest species are to be found in Southern California; about 20-35 percent according to one of our studies, are infected with the protozoan and could serve as carriers. Typically, our native kissing bugs blood-feed on woodrats, but will also try to feed on other vertebrates, given the opportunity. In addition, dogs that sleep outdoors could also get infected with Chagas disease by eating the kissing bugs.

Persons who are bitten should wash and apply antiseptic to the site of the bite. Oral analgesics, such as aspirin or ibuprofen, may be useful to reduce the pain. Treatment by a physician is not usually needed, though Caladryl® or topical corticosteroids may help reduce swelling or itching at the site of the bite. As with any insect sting or bite, the victim should seek medical attention immediately if there is any sign of anaphylactic reaction, such as generalized swelling, itching, hives or difficulty breathing.

What to do with those tough to control perennial weeds in established alfalfa?

The old saying, “Everything's fine until it's not,” comes to mind when dealing with...

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