December 2022

In early July, I wrote a post titled “Considering Conifers”, where I discussed a few pests, diseases, and abiotic issues that conifers face here in New England. Some mentioned in that post included witches’ broom, root rot disease, and bagworm feeding. With the holiday season upon us, I figured now would be a good time to continue that post by discussing a few additional pests and diseases.

One category of pests briefly mentioned in the previous conifer post was scales. Scales are slow-moving insects in the order Hemiptera with a protective covering, making management with insecticides alone more difficult. An integrated pest management (IPM) approach, using a combination of low-impact approaches, is usually the most effective approach for homeowners and commercial growers alike.

Targeting scales with insecticides is most successful when applying the product in the spring and early summer during the scales’ “crawler”, or immature, stage when they are more likely to come in contact with the insecticide. Be sure to apply the product following the instructions on the label and following any specific timeline established for the species of scale in question. Two common scale pests one might encounter on conifers include wooly hemlock adelgid (you might see these when decorating your hemlock outside) and cryptomeria scale (these are more likely to be on your cut Christmas tree, like Canaan fir or Fraser fir).

Cryptomeria scales are often called “fried egg scale” due to their appearance. They are found exclusively on the underside of needles. The photo above shows some previous beetle predation of the scales. Photo credit: Nick Goltz, DPM

Scout for pests like scales routinely during the growing season. If you notice scales on your cut Christmas tree, don’t worry – they are harmless to humas and don’t survive off the plant. If you notice scales on your conifers, you may want to introduce a biological control agent, like the twice-stabbed ladybird beetle (Chilocorus stigma) in early summer, particularly if you would prefer to use minimal insecticides. Be careful to not apply insecticides, especially products containing pyrethroids or bifenthrin, when the ladybird beetles are active as these products will kill them as well as the scale pest. For Christmas tree growers, trees that have heavy scale infestations should be removed when observed to prevent spread to healthy trees nearby.

Beyond insect pests, conifers are prone to fungal diseases as well. Some fungal pathogens cause needle drop, such as fungi in the genera Pestalotiopsis, Rhizosphaera, Cyclaneusma, Dothiostroma, Lecanosticta, and others. These pathogens tend to produce copious numbers of spores and spread to new trees vi wind and rain. Needles, usually beginning with the outer needles, will become discolored before falling off the tree.  Other fungi cause cankers and blight, such as those in the genera Neonectria, Caliciopsis, Diplodia, Seiridium, Fusarium, and others. These pathogens are more serious as they destroy vascular (cambium) tissue, resulting in reduced water movement, trunk lesions, and often an untimely death for the tree. Minimizing unnecessary wounding (such as through excessive or off-season pruning) and environmental stress (drought, freezing, etc.) will reduce the likelihood of canker diseases appearing.

Pestalotiopsis (shown above) and other needle drop fungi produce abundant spores, especially after rain during the growing season. Prune away and tissue that appears to be diseased. Either submit it to a diagnostic lab for identification, burn it, or throw it in refuse/compost off-site. Photo credit: Nick Goltz, DPM.

While some fungal diseases, such as Armillaria root rot, cubical brown rot/ crumbly rot, and others produce large fruiting bodies (shelf mushrooms) on the trunk/base of the tree, making identification of the cause of decline easier, other diseases can be complicated to diagnose without culturing in a lab. If you’re ever unsure what could be wrong with your plant, consider contacting the UConn Home and Garden Education Center at to discuss your plant’s health and inquire about submitting a sample to the UConn Plant Diagnostic Laboratory. The UConn PDL is funded, in part, by the state of Connecticut and the USDA through IPM Extension Implementation and National Plant Diagnostic Network grants.

If you plan to submit a sample, be sure to do so BEFORE applying any fungicides for the season, or the pathogen may not be able to be cultured.

Wishing you and your loved ones a joyous holiday season and a safe and prosperous new year.


There are a few animal species that cause people tremendous amounts of economic damage, loss of time, and good old-fashioned frustration. Two of the most despised warm furries are rats and mice. There is nothing worse than having a great harvest, only to find out later that your bounty has been ruined by one or both of these creatures. They literally are ever present, but seldom seen. They carry a number of diseases, and you really want to make sure you do not get bitten by one of these. A disease, like rabies, is fatal if untreated, but according to the CDC is not usually seen in mice and rats. Even so, if the animals don’t actually cause the disease themselves, they can carry the vector that does. Mice host deer ticks that carry Lyme disease, and rats carry the fleas that caused the Black Plague many years ago. My barn had a big rat infestation this past summer, and I can tell you the fleas were the worst part. The rats would run on the rafters above me and the fleas would drop down onto me and bite. It took me a while to figure out how and why I had fleas on me at a certain time of the day!

An ounce of prevention is worth a pound of cure when it comes to both rodents, but especially the rats. If you let the rats get a foothold, and they start reproducing, it can get very hard to get rid of the colony. They are one of the smartest vertebrate creatures on the planet, which is what makes them so difficult to eradicate. From my experience over the years, it generally starts with one that shows up. It seems to take them a while (up to six months) before they start having babies, but it can happen much, much sooner. Next thing you know, you are overrun. No place is safe from them, so don’t think it could not happen in your basement, barn, garage, etc. We once had a rat show up in our basement. My wife had left some Halloween candy down there because she did not want the kids eating it all and rotting their teeth. Apparently, a rat showed up and found her stash sometime between the beginning of November and the end of December. He carried it to the opposite corner of the basement. There were wrappers and rat feces everywhere, but hidden from plain sight.  Because there was only one, I was able to use a jaw trap. I baited it with a Gummy bear candy (apparently his favorite), and that ended the problem. A little while later, I found this rat was living in my root cellar. He ripped out a bunch of the fiberglass insulation, mounded it up into a nice nest, and covered it in his own excrement.

For the gardener, seed stores are most vulnerable to rats and mice. I had my seeds, stored in my cool basement, raided by some mice recently. They spilled some I had drying and ate some others. Like many gardeners, I start seeds each spring. Last year, four flats of pepper seedlings were nibbled down to the soil surface. First it was the leaves, then on another day, the stems. It continued until they were all gone. By the time I figured out the culprit, it was too late – my plants were gone. I also had larger bags of agricultural pasture seed in my woodshed. I missed the fall planting and was going to opt for the spring. Over the winter, the mice chewed through the bag and were eating my seed. In the barn, I had some bags of cracked corn for my poultry.  The rats went to the underside of the pallet and chewed holes in the bottom layer of bags. This made it impossible to get to the bags to seal them up. The amount of time and money I, and others, have lost to these creatures is incredible. 

Getting rid of vermin can be tricky. You have to out-think them. Mice are not very bright, but rats are geniuses. As I said before, an ounce of prevention is worth a pound of cure. Try your best not to give them food. That is the number one thing that attracts them. Be careful where you store your seeds, your harvest, and your animal feed. Monitor the areas closely and nip it in the bud when one of these animals arrives. As far as your seed or your animal feed, if you can store that in metal garbage cans with a tight-fitting lid, it will prevent the animals from accessing the food. Be careful not to spill feed or seed when you are using the materials, as this can invite trouble.

Four “snap traps.” From left to right, a covered mouse trap, a plastic pedal mouse trap, a plastic pedal rat trap, and a jaw-style rat trap. Photo by mrl2022.

 So, what do you do if you find yourself with a pest problem? Well it is by no means a simple answer, and it will depend on whether you are talking about mice, rats, or both. Looking at the scat the animals leave is your best way of identifying which creature you have. The second thing you can do is try and remove their food source. For example, a neighbor once was inundated with rats in her horse barn. She moved her feed from the barn to her garage. Once the rats had no food, they left. She solved her problem. Unfortunately for me, the colony decided to move into my chicken coop. What an experience that was! Anyway, there is a bit of a lag time between removing the food and the animals moving on. Up until the point you removed the food, the location was like paradise. You will need a little time for them to get hungry enough to relocate.  You also want to tidy up as much as possible. Try not to leave them good places to live, although I know this can be difficult. The time it takes to get rid of rats or mice will depend on the population size. You must be diligent though. Once you begin measures to get rid of them, do not stop until they are all gone. Both species are active mostly at night. A mouse scratching or chewing the inside of your wall when you are trying to sleep is a nice exercise in frustration.

Fortunately for us, mice are relatively easy to get rid of. Simple snap traps are quite effective, but you will have to dispose of the dead mouse and reset the trap at least once a day. There are some disposable options if you cannot stomach the thought, but these probably are not very good for the environment, and unless you only have one or two mice, it will get rather expensive. For mice, I really like the pedal-style snap traps. They have what looks like a piece of cheese for a trigger. You do not even need to bait them.  ust place them against the wall and as the mice run along it, they will step into the trap.

The next trap is one of my favorites, but the success with it seems to vary by location (I have not figured out why yet). It is called the rolling log trap. You can make your own or buy one on line.  It consists of a five-gallon bucket with a stick or wire going across it. In the middle of that stick, you put a can or similar container. On the container, you put peanut butter. A board going from the floor to the rim of the bucket provides access. The mouse walks out to get the food, and the can spins and the mouse drops into the bucket. The advantage to this style of trap is that it repeats. You can catch a number of mice in one night. You also have the option to make it a lethal trap or a catch-and-release. For the former, fill the bucket halfway with water. This will cause the mice to drown. For the latter, leave the bucket empty. I would recommend you check with local wildlife laws on the legality of releasing animals. This also presents an additional danger of being near/handling live wild animals. There are many variations on these traps. For many years I used to use a plain bucket with nothing, and the mice would drop in to get some feed I scattered on the bottom.      

Best suited for mice, a rolling-log style bucket trap made by the author. Photo by mrl2022.

For rats, things are much more complicated. As I stated above, they are extremely smart. Rats are very shy of anything new in their environment. They will not explore new traps or food. In addition, the older reproductive rats will let the younger individuals try the new food first. The use of snap traps should be reserved for the first few or the last few. Otherwise, if a rat sees one in the trap, it will not go near it ever again. You may need to bait any trap you do use. Meat or sweets generally work the best. I never had any luck with peanut butter for rats, but it works great with mice. It will be virtually impossible to eradicate a colony of rats without eliminating their food source. When I had the infestation in my chicken coop years ago, I found I needed to feed the chickens in the morning as opposed to the evening. The rats were eating the food all night and the chickens did not have much to eat! Eliminating the food altogether was not an option – the chickens needed to eat. However, by switching to the morning, I removed the rats’ food source. Any uneaten chicken feed was taken in the garage at the end of the day so the rats literally had nothing left to eat.

For the remainder of the article, I wanted to comment on some traps or techniques that could apply to both species. The first are glue boards. These are plastic trays filled with extremely sticky glue. The idea is that the mouse or rat walks onto it and sticks. They eventually die due to lack of water. The whole board is then thrown away. I generally do not like these. You will have to place them in an area frequented by the rodents and hope they walk onto them. Ideally, you place them in a runway. Mice are more easily caught by these. I have never been able to catch a rat as they are too dirty and oily (they walk right off). There is also a risk of little kids, pets, or larger wildlife having the trap get stuck to them. You also may be putting yourself at risk of contact with a live animal capable of biting, and/or exposing yourself to disease. Save your money and opt for a better remedy. 

If you do have a barn or similar outbuilding, barn cats may be a solution. These are generally either hard-to-adopt animals that need a home, or animals in need of adoption due to crowding at the shelter. Being that these are more work animals and not companions, they can be highly effective. Recently, my barn cats took out eight mice in one night. This was during the latest cold night, which drove the rodents inside to seek shelter. The cats have not really done much with the rats. I am not sure why that is the case. Barn cats may also go after other mammalian farm pests, like voles, so they can be a real asset. On the down side, if they are good hunters, they may take out songbirds or other beneficial organisms. 

There is a special breed of dog, called a Rat Terrier, that can be useful. This is an American breed that was bred to go after farm pests like rats and rabbits. They can be highly energetic.  There are numerous videos of them in action on the internet. Before you get too excited and go out and buy one, these fell out of favor in the mid-1900s when poisons became widely available (more on them in a minute).   

There is a new product on the market that is made of pellets that are supposedly pet and wildlife safe. They work by the rodent ingesting them, which coats their digestive tract. The rodent does not drink as they do not feel thirsty, and then they die in a few days due to dehydration. The trouble I had with this product was the rats are not consuming it!  It was also very expensive for the small amount that came in the bag. Either way, every individual would have to eat this to wipe out the colony, but that is not how rats behave. As such, I would not recommend those products. There are also recipes on the internet for how to mix either plaster of pairs with cocoa powder or baking soda and cocoa powder. The former hardens in the rodent’s stomach and eventually kills them, while the latter forms gas. Rats cannot belch so they end up dying. All the times I have tried these concoctions, the animals would not eat it. 

The last option is poison, but they are not recommended by our Center. Although there are different ingredients that can be used, they are generally anticoagulants. After ingestion, they cause the rodents to bleed and die. There is a great risk to pets, farm animals, and wildlife if you  use these. If any animal ingests them, it will be the same outcome – death. Rats generally only nibble on a new food source. As such, the poisons are fairly concentrated so a little nibble is enough to kill the animal. There are bait boxes that restrict access to all animals except for rodents. These can be screwed shut to prevent non-target animals and/or children from accessing the poison. The problem is, if predators normally feeding on these rodents eat one that has been poisoned, it is highly likely they will die themselves. There are some baits that claim they are less concentrated and therefore less likely to do this, but because the outcome cannot be controlled, we advise against using these. In addition, I have heard stories of rats ending up in house walls and bleeding right through them. How unsightly! Even if they didn’t bleed into your living space, the stench from a rotting rat in the wall would be very unpleasant, and would usually be followed by a fly infestation.

Rodent problems should not be taken lightly. They cause losses of time and money, and can carry diseases that you, your pets, and your livestock may acquire. It is best to be vigilant and prevent these situations from ever happening in the first place. Store your seeds, feed, and food in metal containers, and monitor the areas for rodent scat frequently. If you have a problem, eliminate the food source first before attempting to eliminate the organisms. Overall, the choice of how to deal with these pests is yours. You will have to assess your situation, your surroundings, and your family. Please don’t forget to consider wildlife with whatever you choose. Prompt action at the first sign of vermin with snap traps/jaw traps can prevent most problems.       

Matt Lisy