The avocado is an amazing fruit. It grows on a tree and comes to maturity, reaches certain oil content and a stage at which it will ripen, but it does not ripen on the tree. It needs to be removed from the tree before it will soften. If the fruit is removed before it has reached maturity it will not soften, and will remain rubbery and inedible. One of the problems is that the fruit will hang on the tree for an extended period of time and it is hard to know when they are mature. Avocados are not like apricots where you have about 2 weeks to get the fruit off before it falls off. As the fruit stays on the tree in gradually develops more and more oil content and has a richer flavor.

If the fruit stays on the tree too long, the oil can develop and almost rancid flavor, however. So it is good to know when the best, acceptable flavor is. Avocado varieties fall into general seasonal periods when they are mature, such as Fuerte' and ‘Bacon” in winter, ‘Hass' in spring/summer, ‘Lamb-Hass' in summer/fall. 

To assess maturity, take an unripe stage cut the fruit in half.  Look at the seed coat.  If the seed coat (the covering of the seed that separates it from the flesh) is white and thick, it is definitely not ready to pick.  If it is whitish brown and getting thinner, then if you are desperate, you can try ripening the fruit and taste.  If the seed coat is thin and brown, then usually this will mean that the fruit is ready to pick.  If the seed has germinated already in the fruit then normally the fruit is over the hill. Some green skin varieties skin will begin to crack when the fruit are very mature on the tree.  This will tell you when you have reached the end of the useful tree life of the fruit.

For ripening, pick the fruit and without any help, the fruit will typically be ripe in 7 to 10 days.  If you want to speed things along a bit you can take 3 or 4 avocados and place them in a loosely closed paper bag with 2 – 3 Red or Golden Delicious apples or ripe kiwifruit.  The purpose of the apples or kiwifruit is that these fruit produce a natural plant hormone, ethylene that will help stimulate the avocado to produce its own ethylene.  Apples and kiwifruit are known to produce lots of ethylene.  The Delicious apples are varieties that produce more ethylene than other apple varieties.  You can keep them even after they are shriveled and they will be producing ethylene.  Don't use a plastic bag unless you keep it opened since the fruit need to breathe during this process.  Just keep the fruit on your kitchen counter or in a warm place.  68F is the ideal temperature.  Lower and higher temperatures both actually slow the process.

The roof rat (Rattus rattus), sometimes called the black rat, is a common vertebrate pest in citrus, avocado and other yummy tree orchards. It builds leaf and twig nests in fruit trees or nearby trees, or it can nest in debris piles or thick mulch on the ground. This agile, sleek rat has a pointed muzzle, and a tail that is longer than the body and head combined.

Be sure to identify the species of rat present to avoid killing nontarget or protected species. Be aware that endangered native kangaroo rats (Dipodomys spp.) and the riparian woodrat (Neotoma fuscipes riparia) resemble pest rats, but are protected by law. Unlike the hairless, scale-covered tail of roof rats, the tails of kangaroo rats and the riparian woodrat are covered with fur. The riparian woodrat is active mostly during the day, and its tail is somewhat shorter than the combined length of its body and head. A kangaroo rat's tail is noticeably longer than its body and head combined. Kangaroo rats are nocturnal, but unlike Norway rats and roof rats, which move on all four legs, kangaroo rats hold their front legs off the ground and travel by hopping on their hind legs.

Rats gnaw on electrical wires, wooden structures, and fruit on trees. After harvest, they damage fruit in bins, chewing on the bins and leaving excrement. Rats are active throughout the year, and mostly at night.

To help manage rats, reduce shelter and nesting sites of rats. Eliminate debris and wood piles. Store materials neatly and off the ground. Thin and separate non-crop vegetation around orchards where feasible. Exclude rats from nearby structures by properly sealing entry ways.

Baits and rat-sized snap traps placed in trees are the most effective control measures. Rats are wary, tending to avoid baits and traps for at least a few days after their initial placement. Fasten traps to limbs and bait them with sweet fruit or nut meats, but do not set the traps until after bait is readily eaten. Secure anticoagulant wax blocks in a bait station before placing in trees on limbs 6 feet or more above the ground. Placing the wax blocks in a bait station will prevent chunks of the anticoagulant wax from dropping to the ground and creating a hazard.

Be aware that certain types of single-dose rat baits for use inside buildings are not labeled for use outdoors in orchards; these are hazardous to wildlife and should not be used.

For more on the subject see:

http://icwdm.org/handbook/allPDF/RO_B125.PDF

http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn74106.html

and another blog:

http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=16880

Using organic herbicides in production fields and non-crop areas.

The forecasts call for rainy winter and that means a lot of weeds. During dry times perennial weeds tend to grow better than annual weeds, since perennial structures such as underground rhizomes or tubers can support them and give competitive advantage. Seed of annual weeds in dry soil may have been losing viability, senescing or eaten during this time, but many have remained dormant and look forward to the wet winter us much as the rest of us.

Controlling weeds ‘organically' is always an extra challenge whether you are in a certified field or in an area where synthetic herbicides are not desired. Hand-weeding, already expensive, is even a greater burden with limited labor availability, and frankly not much fun either. Of course sanitation and prevention, mechanical and cultural management are essential in organic systems. That requires time and commitment and can quickly become your not-so-favorite pastime.

Organic herbicides have traditionally been contact materials with no systemic activity. This means that they only affect tissue that they contact and do not translocate through the plant like most synthetic herbicides. Thus, good coverage is critical for these contact materials. Many years ago the first herbicides were sulfuric acid and diesel fuel, current organic materials are often acids or oils too, although a lot more benign.

Recent trials by the University of California weed scientists showed that several organic herbicides provided decent control of easy to control pigweed and nightshade when they were small. When weeds were 12 days old, a mixture of 45% clove and 45% cinnamon oil, 20%-acetic acid and d-limonene gave 61-89% control; however only d-limonene controlled 19-day old weeds and none was effective on one-month old ones. As weeds get bigger they also develop a protective cuticle that minimizes efficacy of these herbicides.

This year we conducted trials with a recently OMRI approved herbicide for row crops, trees and vines that is a mix of caprylic and capric acids. It disrupts cell membranes of plans and causes the contents to leak and plants to desiccate. It worked well at 6 to 9% by volume mixture with water and gave 90% control of little mallow and >95% of annual sowthistle compared to untreated checks. We have also tested it in organic strawberry furrows before planting the crop to prevent potential injury from drift. Furrow cultivation does not get close to the plastic mulch that covers the beds to prevent tears, so the weeds in that zone are good target for the herbicide. This fatty acid herbicide provided excellent control of common lambsquarter, reduced the growth of common purslane but didn't do much for yellow nutsedge - one of our notoriously difficult to control perennial weeds (Figure). The bigger weeds need higher rates (9% is the maximum labeled rate) and better coverage. When you have multiple layers of weed leaf canopy and diverse architecture some plants or their parts may be protected by others that intercept the deposition of the herbicide. When on target, this contact material acts fast – you can see results within 2-3 days, however, it does nothing to weed propagules in soil and has no residual activity against wind-dispersed weed seed that fly in after application. This means the control does not last and you will need additional applications or other control measures. Repeated application is not a problem in a non-crop area and is a great way to deplete your weed seedbank, but crop protection from drift, such as shielded sprayers, is necessary to avoid off target plant injury.

Figure. Weed control in strawberry furrows prior to planting with 9% by volume of fatty acid herbicide (top) and weeds in untreated check (bottom)

Of the many known varieties, they fall into three broad categories based on whether they are of the Mexican, Guatemalan or West Indian races of Persea americana, the avocado specie and the crosses that occur between these races. For example, ‘Hass' has the thick skin of the Guatemalan but turns black like a Mexican. Generally speaking, California varieties have been the result of crossing between the Mexican and Guatemalan races. West Indian race varieties are not common here because of their generally lower cold tolerance. There are lots of factors approaching the identification of an avocado and its origins, and here is a brief run down on those that need to be considered.

Grafted?

Is it a grafted tree, or is it a known variety with known characteristics which the tree can be compared to? Look for the change in bark texture at the base of the tree where the graft was made.

Leaf characteristics

When you crush the leaf, does it have an anise smell (Mexican) or not?

Is the leaf edger smooth (Hass) or wavy (Zutano)?

Is the color of the new leaves red and turn green (Mexican) or are green (Guatemalan)?

Canopy shape

Is it columnar (Bacon, Reed) or umbrella (Hass)?

Is the mature tree big (Hass) or under 20 feet in height (Holiday, Littlecado, Gwen)?

Fruit

Is the fruit round (Nabal), pear shaped (Fuerte), thin necked (Pinkerton) or broad shouldered (Lamb-Hass)

Is it thick skinned (Guatemalan) or thin skinned (Mexican)?

Is it green when ripe (Guatemalan) or black (Mexican)?

Is it big (more than 16 ounces; Daily 11 is 5 pounds) or small (Mexicola is 5 ounces)?

When is fruit maturity; winter, spring, summer or fall?

The combination of all these factors go into describing a variety and distinguishes it from other varieties. When varieties have mixed parentage, they will take on those characteristics of each parent, so often the lines of either Mexican or Guatemalan get blurred.