Monday, January 8, 2018

Rats in Fruit Trees

Hollowed out oranges, papaya, bananas and other fruits, whether hanging on the tree or on the ground, are definitely signs of rat feeding.  In Hawaii, there are four rodents that cause economic hardship: the roof or black rat, the Norway or brown rat, the Polynesian or Hawaiian rat, and the house or field mouse. In addition, they are carriers of contagious diseases including plague, murine typhus, leptospirosis, and salmonellosis. Today, most notably, they are part of the disease cycle known as Rat-Lungworm. See  for more information and prevention of this serious condition.

Rodent control is not easy due to their ability to adapt to changes and their capacity to reproduce.

Rats are nocturnal. They have excellent memories and very repetitious habits. They are easily frightened of new things placed in their environment. The roof rat is most pronounced in this tendency. Rats have a keen sense of smell and hearing, and only a fair sense of sight with the ability to see in the dark.

Besides the hollowed out fruits, other common signs of rats are droppings, rubmarks, gnawings, nests, and unpleasant odors.  
                                                         Rat Damage on Oranges - UC IPM

In controlling these pests around the home, the first step is to clean up the environment by removing accesses to food and shelter. Physical barriers such as screens may need to be installed. When only a few rats are involved, trapping can be successful, both live and snap traps. Devices that kill rats by electrocution (e.g., Rat Zapper or Victor Electronic traps) are expensive but effective.

Paraffin-type bait blocks containing anticoagulants are also effective in controlling rats. They appeal to the rats gnawing instinct, especially those blocks with numerous ridges. Baits should be replaced immediately as they are eaten, since a single feeding on the first generation anticoagulants such as diphacinone, will not control rats; multiple doses over several successive days is required. The newer “second-generation” compounds such as brodifacoum, bromadiolone, difenacoum, and difethialone, which can be fatal after a single feeding. Prepackaged, ready-to-use bait stations containing some of these toxicants can be purchased by homeowners. 
Some poisons have a secondary effect which will affect animals that consume dead or nearly dead rodents. Thus, it is imperative that strict safety precautions be used in the placement and disposal of poison baits for rodents.

For more information on rats see the UC IPM website,

Monday, December 18, 2017

Poinsettias are NOT Poisonous

This is the time of year many people buy poinsettias. Yet, some are concerned because they think the plants are poisonous.  Are poinsettias truly poisonous? No, this myth has been around since the early 1900’s. The American Society of Florists has been trying to dispel the myth for a long time. They say that no other commercial plant has been tested for toxicity more than the poinsettia.

According to the American Medical Association’s Handbook of Poisonous and Injurious Plants, ingestion of the poinsettia plant has been found to produce no ill effects except an occasional case of vomiting. According to the POISINDEX information source, a child who weighs 50 lbs. would have to consume over 500 leaves before he reaches a potentially toxic level. Since the taste of poinsettia leaves is reportedly unpleasant, it is unlikely that a child or animal who attempts to eat or chew the leaves, will continue to do so after the first taste. Some people, however, can develop a skin and eye irritation from contact with the milky sap of the plant.
  • Poinsettia plants prefer indirect light, six hours daily is ideal.
  • Poinsettias require daytime temperatures of 60 to 70°F and night time temperatures around 55°F for best growth; high temperatures will shorten the plant’s life.
  • Standing water can be harmful for the plant. Remove any wrappings from around the pot or at least punch holes in the foil so water can drain into a saucer; discard excess water. 

Sunday, November 26, 2017

Dry, Flavorless Citrus?

Overly mature fruit is a major cause of dryness in citrus. In other words, if the fruit is left on the tree too long, drying occurs.  A few other reasons include:
 1) the application of too much nitrogen. 
 2)  At times, dryness may occur when a tree is young; the fruit will improve as the tree ages.  
 3) Trees budded on certain vigorous rootstocks will make the problem of dry fruit worse. 4) For citrus grown in temperate climates, dry fruit is the result of low, freezing temperatures.  
Overall, certain varieties of citrus, especially mandarins, seem to be more susceptible to producing dry fruit. 

In Hawaii and other tropical areas, a further complication is the fact that citrus fruit does not color well. In other climates, such as California, fruit develops a deep orange color due to the great differences between day time and night time temperatures.  And under these conditions, oranges may actually turn color before they are sweet enough to pick. 

In the tropics, however, where there are less temperature fluctuations, the orange coloration does not develop well and therefore is not a good indication of ripeness. In fact, fruit is often sweet but will still show a green coloration; by the time the fruit shows good color, it may have dry segments already forming.

 If you don’t know the harvest season for your particular fruit, I would suggest picking one good sized fruit, even though it may still be greenish in color.  If it is not sweet enough, pick one every 1-3 weeks until it tastes sweet. Fruit will develop more sugar the longer it is held on the tree.